I am happy to see the discussion turning to exhaust sizing and the responses
that are coming in. It gives me an excuse to stir the pot with one of my
long winded discussions, which is intended to promote some overlooked
considerations and provoke additional attention and response. With a
potential group buy at stake, I would like to present information which
could be useful in the decision of whether to go group or solo. I have acquired
some serious reservations about a 3 inch system that I need to resolve.
Reading time is about 5 minutes, so hang with me
A very good question was asked; "Where can I get an exhaust system and what
size should it be?"
And we got some interesting responses; "3 inch", "Anything bigger than
stock", 2-1/2 to 3 inch", nothing smaller than 2-1/2 inch, the bigger the
better for a turbo motor.
I have been investigating the configuration of available systems on the
market, and studying reference material to try and determine what would be
best for me. In doing so, I believe it is important to pass along the
information for your consideration. Plus, I'm still looking for the answer.
There is no - " BEST " - size.
3 inch is popular, I think, because it is used a lot in competition motors,
so it must be good. Also, if one were to choose a most correct answer size,
3 inch is a safe bet to be LARGE enough for most any 2 liter application.
I believe those reasons are only partially correct, much too big is better
than much too small, but a little too small can be better than a little too
big, depending on where you're looking for a performance improvement.
It may well be true that all of the answers we have seen so far would
provide better engine performance than the stock system for most people with
enhanced engine configurations.
*B*U*T*, what's best for a competition engine, with a hundred horsepower
more than I expect to develop, is not necessarily the BEST thing for me.
Better than stock does not mean BEST.
>From Hugh Macinnes' "Turbochargers", Corky Bell's "Maximum Boost", Headers
by Ed's reference material, communication with MRT, calculations, charts,
everything I can find... 3 inch is not an optimum size for my expected
application, which is in the 300 horsepower ballpark.
There is a tendency to look at exhaust system size in half inch increments.
When you really start looking closely at available information, you will
find that size differentials, up or down, of one-eighth of an inch (1/8" - 3
mm) in pipe diameter can result in SIGNIFICANT power gain or loss. What's
significant? I think in science class 40 years ago it was 2%. I am
concerned with numbers of twice that magnitude, which in the 300 HP range
represent 10 or 12 HP.
This is because the change in cross sectional area is proportional to the square
of the change in radius. So a 3 inch system is 9.2% larger than a 2-7/8 system,
and 19.7% larger than a 2-3/4 inch system. So if your optimum system size is 2-3/4,
and you're off by a quarter of an inch, you're off by about 20%! Significant.
If one examines engine parameters such as displacement, compression, speed,
volumetric efficiency, valve duration and lift, desired peak power and/or
torque location, and on, and on...to determine OPTIMUM exhaust size, choice
answers for a particular engine will likely be something like 2-1/2" vs
2-5/8", or 2-3/4" vs 2-7/8", not a spread like 2-1/2" vs 3". So if I'm
going to change out my exhaust system, I am hoping to zero in on a size that
will provide a 4 or 5 percent gain of 10 or 12 horsepower, IN THE POWER BAND
WHERE I EXPECT TO OPERATE rather than a 2 percent gain of 5 or 6 horsepower
...maybe...hopefully, or a gain at the top and a loss at the bottom.
But peak horsepower is only part of the story and not even the most
important part. Proper exhaust sizing also determines where in the engine
RPM range the peak horsepower is generated, and where the peak torque is
generated, and more importantly for my street driven application, how flat
the torque curve remains or becomes. A 10 horsepower gain at 6000 RPM is no
good to me if I sacrifice 8 to 10 from 2500 to 5000, and end up going slower
most of the time because my system is too large. A system which is too
large can also permit exhaust gasses to expand so quickly that at low engine
speeds where you may need it most, turbo response suffers. And whatever you
do, a restrictive muffler or cat, can nullify what you spent on your fancy system.
So I submit to all, there is more out there to what size exhaust should I
get than first meets the nose. The answer is like the answer for a lot of
other hot rod stuff. What is your goal? Circle track? Drag strip? World
Rally Championship? Daily driver? Stock or near stock power levels? 50%
power gain? 100% power gain? The answer is different for all those combos.
The stock exhaust system is more restrictive than it needs to be. Almost
any aftermarket system will be less restrictive, but depending on where you
are now, and where you want to go, it is possible to wind up with a system
designed for a racing application that is too much less restrictive for a street
driven application, and performance could remain unimproved or even degrade,
especially at low RPM, where you're likely to notice it most.
That's all for now. I think it's enough. Now I need feedback.
Larry Witherspoon
ssspoon@aol.com
To unsubscribe from this group, please send an email to:
BC-BFLegacyWorks-unsubscribe@egroups.com
zZz <http://docs.yahoo.com/info/terms/> .
Where can I get an exhaust system and what size should it be
Moderators: Helpinators, Moderators
-
Samuel Barrett
Where can I get an exhaust system and what size should it be
Another fantastic Larry Witherspoon essay.
My question: You did not actually mention what you thought the optimal dimension would be for your particular application. Can you briefly expand on what your goal for your exhaust replacement would be? You stated:
I am hoping to zero in on a size that will provide a 4 or 5 percent gain of 10 or 12 horsepower, IN THE POWER BAND WHERE I EXPECT TO OPERATE rather than a 2 percent gain of 5 or 6 horsepower.
What is *your* application? Where is that power band?
I know you are always focused on improving performance without sacrificing operational excellence. In light of that, what about material composition? Steel? Stainless?
-Sambo
-----Original Message-----
From: ssspoon@aol.com [mailto:ssspoon@aol.com]
Sent: Friday, April 05, 2002 8:42 PM
To: BC-BFLegacyWorks@yahoogroups.com
Subject: [BC-BFLegacyWorks] Where can I get an exhaust system and what size should it be?
I am happy to see the discussion turning to exhaust sizing and the responses
that are coming in. It gives me an excuse to stir the pot with one of my
long winded discussions, which is intended to promote some overlooked
considerations and provoke additional attention and response. With a
potential group buy at stake, I would like to present information which
could be useful in the decision of whether to go group or solo. I have acquired
some serious reservations about a 3 inch system that I need to resolve.
Reading time is about 5 minutes, so hang with me
A very good question was asked; "Where can I get an exhaust system and what
size should it be?"
And we got some interesting responses; "3 inch", "Anything bigger than
stock", 2-1/2 to 3 inch", nothing smaller than 2-1/2 inch, the bigger the
better for a turbo motor.
I have been investigating the configuration of available systems on the
market, and studying reference material to try and determine what would be
best for me. In doing so, I believe it is important to pass along the
information for your consideration. Plus, I'm still looking for the answer.
There is no - " BEST " - size.
3 inch is popular, I think, because it is used a lot in competition motors,
so it must be good. Also, if one were to choose a most correct answer size,
3 inch is a safe bet to be LARGE enough for most any 2 liter application.
I believe those reasons are only partially correct, much too big is better
than much too small, but a little too small can be better than a little too
big, depending on where you're looking for a performance improvement.
It may well be true that all of the answers we have seen so far would
provide better engine performance than the stock system for most people with
enhanced engine configurations.
*B*U*T*, what's best for a competition engine, with a hundred horsepower
more than I expect to develop, is not necessarily the BEST thing for me.
Better than stock does not mean BEST.
From Hugh Macinnes' "Turbochargers", Corky Bell's "Maximum Boost", Headers
by Ed's reference material, communication with MRT, calculations, charts,
everything I can find... 3 inch is not an optimum size for my expected
application, which is in the 300 horsepower ballpark.
There is a tendency to look at exhaust system size in half inch increments.
When you really start looking closely at available information, you will
find that size differentials, up or down, of one-eighth of an inch (1/8" - 3
mm) in pipe diameter can result in SIGNIFICANT power gain or loss. What's
significant? I think in science class 40 years ago it was 2%. I am
concerned with numbers of twice that magnitude, which in the 300 HP range
represent 10 or 12 HP.
This is because the change in cross sectional area is proportional to the square
of the change in radius. So a 3 inch system is 9.2% larger than a 2-7/8 system,
and 19.7% larger than a 2-3/4 inch system. So if your optimum system size is 2-3/4,
and you're off by a quarter of an inch, you're off by about 20%! Significant.
If one examines engine parameters such as displacement, compression, speed,
volumetric efficiency, valve duration and lift, desired peak power and/or
torque location, and on, and on...to determine OPTIMUM exhaust size, choice
answers for a particular engine will likely be something like 2-1/2" vs
2-5/8", or 2-3/4" vs 2-7/8", not a spread like 2-1/2" vs 3". So if I'm
going to change out my exhaust system, I am hoping to zero in on a size that
will provide a 4 or 5 percent gain of 10 or 12 horsepower, IN THE POWER BAND
WHERE I EXPECT TO OPERATE rather than a 2 percent gain of 5 or 6 horsepower
...maybe...hopefully, or a gain at the top and a loss at the bottom.
But peak horsepower is only part of the story and not even the most
important part. Proper exhaust sizing also determines where in the engine
RPM range the peak horsepower is generated, and where the peak torque is
generated, and more importantly for my street driven application, how flat
the torque curve remains or becomes. A 10 horsepower gain at 6000 RPM is no
good to me if I sacrifice 8 to 10 from 2500 to 5000, and end up going slower
most of the time because my system is too large. A system which is too
large can also permit exhaust gasses to expand so quickly that at low engine
speeds where you may need it most, turbo response suffers. And whatever you
do, a restrictive muffler or cat, can nullify what you spent on your fancy system.
So I submit to all, there is more out there to what size exhaust should I
get than first meets the nose. The answer is like the answer for a lot of
other hot rod stuff. What is your goal? Circle track? Drag strip? World
Rally Championship? Daily driver? Stock or near stock power levels? 50%
power gain? 100% power gain? The answer is different for all those combos.
The stock exhaust system is more restrictive than it needs to be. Almost
any aftermarket system will be less restrictive, but depending on where you
are now, and where you want to go, it is possible to wind up with a system
designed for a racing application that is too much less restrictive for a street
driven application, and performance could remain unimproved or even degrade,
especially at low RPM, where you're likely to notice it most.
That's all for now. I think it's enough. Now I need feedback.
Larry Witherspoon
ssspoon@aol.com
To unsubscribe from this group, please send an email to:
BC-BFLegacyWorks-unsubscribe@egroups.com
zZz <http://docs.yahoo.com/info/terms/> .
ADVERTISEMENT
<http://rd.yahoo.com/M=215002.1990895.34 ... 000239/R=1>
<http://us.adserver.yahoo.com/l?M=215002 ... =754206583>
To unsubscribe from this group, please send an email to:
BC-BFLegacyWorks-unsubscribe@egroups.com
zZz <http://docs.yahoo.com/info/terms/> .
My question: You did not actually mention what you thought the optimal dimension would be for your particular application. Can you briefly expand on what your goal for your exhaust replacement would be? You stated:
I am hoping to zero in on a size that will provide a 4 or 5 percent gain of 10 or 12 horsepower, IN THE POWER BAND WHERE I EXPECT TO OPERATE rather than a 2 percent gain of 5 or 6 horsepower.
What is *your* application? Where is that power band?
I know you are always focused on improving performance without sacrificing operational excellence. In light of that, what about material composition? Steel? Stainless?
-Sambo
-----Original Message-----
From: ssspoon@aol.com [mailto:ssspoon@aol.com]
Sent: Friday, April 05, 2002 8:42 PM
To: BC-BFLegacyWorks@yahoogroups.com
Subject: [BC-BFLegacyWorks] Where can I get an exhaust system and what size should it be?
I am happy to see the discussion turning to exhaust sizing and the responses
that are coming in. It gives me an excuse to stir the pot with one of my
long winded discussions, which is intended to promote some overlooked
considerations and provoke additional attention and response. With a
potential group buy at stake, I would like to present information which
could be useful in the decision of whether to go group or solo. I have acquired
some serious reservations about a 3 inch system that I need to resolve.
Reading time is about 5 minutes, so hang with me
A very good question was asked; "Where can I get an exhaust system and what
size should it be?"
And we got some interesting responses; "3 inch", "Anything bigger than
stock", 2-1/2 to 3 inch", nothing smaller than 2-1/2 inch, the bigger the
better for a turbo motor.
I have been investigating the configuration of available systems on the
market, and studying reference material to try and determine what would be
best for me. In doing so, I believe it is important to pass along the
information for your consideration. Plus, I'm still looking for the answer.
There is no - " BEST " - size.
3 inch is popular, I think, because it is used a lot in competition motors,
so it must be good. Also, if one were to choose a most correct answer size,
3 inch is a safe bet to be LARGE enough for most any 2 liter application.
I believe those reasons are only partially correct, much too big is better
than much too small, but a little too small can be better than a little too
big, depending on where you're looking for a performance improvement.
It may well be true that all of the answers we have seen so far would
provide better engine performance than the stock system for most people with
enhanced engine configurations.
*B*U*T*, what's best for a competition engine, with a hundred horsepower
more than I expect to develop, is not necessarily the BEST thing for me.
Better than stock does not mean BEST.
From Hugh Macinnes' "Turbochargers", Corky Bell's "Maximum Boost", Headers
by Ed's reference material, communication with MRT, calculations, charts,
everything I can find... 3 inch is not an optimum size for my expected
application, which is in the 300 horsepower ballpark.
There is a tendency to look at exhaust system size in half inch increments.
When you really start looking closely at available information, you will
find that size differentials, up or down, of one-eighth of an inch (1/8" - 3
mm) in pipe diameter can result in SIGNIFICANT power gain or loss. What's
significant? I think in science class 40 years ago it was 2%. I am
concerned with numbers of twice that magnitude, which in the 300 HP range
represent 10 or 12 HP.
This is because the change in cross sectional area is proportional to the square
of the change in radius. So a 3 inch system is 9.2% larger than a 2-7/8 system,
and 19.7% larger than a 2-3/4 inch system. So if your optimum system size is 2-3/4,
and you're off by a quarter of an inch, you're off by about 20%! Significant.
If one examines engine parameters such as displacement, compression, speed,
volumetric efficiency, valve duration and lift, desired peak power and/or
torque location, and on, and on...to determine OPTIMUM exhaust size, choice
answers for a particular engine will likely be something like 2-1/2" vs
2-5/8", or 2-3/4" vs 2-7/8", not a spread like 2-1/2" vs 3". So if I'm
going to change out my exhaust system, I am hoping to zero in on a size that
will provide a 4 or 5 percent gain of 10 or 12 horsepower, IN THE POWER BAND
WHERE I EXPECT TO OPERATE rather than a 2 percent gain of 5 or 6 horsepower
...maybe...hopefully, or a gain at the top and a loss at the bottom.
But peak horsepower is only part of the story and not even the most
important part. Proper exhaust sizing also determines where in the engine
RPM range the peak horsepower is generated, and where the peak torque is
generated, and more importantly for my street driven application, how flat
the torque curve remains or becomes. A 10 horsepower gain at 6000 RPM is no
good to me if I sacrifice 8 to 10 from 2500 to 5000, and end up going slower
most of the time because my system is too large. A system which is too
large can also permit exhaust gasses to expand so quickly that at low engine
speeds where you may need it most, turbo response suffers. And whatever you
do, a restrictive muffler or cat, can nullify what you spent on your fancy system.
So I submit to all, there is more out there to what size exhaust should I
get than first meets the nose. The answer is like the answer for a lot of
other hot rod stuff. What is your goal? Circle track? Drag strip? World
Rally Championship? Daily driver? Stock or near stock power levels? 50%
power gain? 100% power gain? The answer is different for all those combos.
The stock exhaust system is more restrictive than it needs to be. Almost
any aftermarket system will be less restrictive, but depending on where you
are now, and where you want to go, it is possible to wind up with a system
designed for a racing application that is too much less restrictive for a street
driven application, and performance could remain unimproved or even degrade,
especially at low RPM, where you're likely to notice it most.
That's all for now. I think it's enough. Now I need feedback.
Larry Witherspoon
ssspoon@aol.com
To unsubscribe from this group, please send an email to:
BC-BFLegacyWorks-unsubscribe@egroups.com
zZz <http://docs.yahoo.com/info/terms/> .
ADVERTISEMENT
<http://rd.yahoo.com/M=215002.1990895.34 ... 000239/R=1>
<http://us.adserver.yahoo.com/l?M=215002 ... =754206583>
To unsubscribe from this group, please send an email to:
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-
Josh Colombo
Where can I get an exhaust system and what size should it be
Hey Larry,
Just curious.....where are doing your research on exhaust sizing and such? Any particular person.....I should talk to.
Thanks
Josh
************************************
Josh Colombo
<mailto:Josh@surrealmirage.com> Josh@surrealmirage.com **NEW**
"Life, an ever-changing melody
of beats and rhythm" - ME
************************************
-----Original Message-----
From: ssspoon@aol.com [mailto:ssspoon@aol.com]
Sent: Friday, April 05, 2002 10:42 PM
To: BC-BFLegacyWorks@yahoogroups.com
Subject: [BC-BFLegacyWorks] Where can I get an exhaust system and what size should it be?
I am happy to see the discussion turning to exhaust sizing and the responses
that are coming in. It gives me an excuse to stir the pot with one of my
long winded discussions, which is intended to promote some overlooked
considerations and provoke additional attention and response. With a
potential group buy at stake, I would like to present information which
could be useful in the decision of whether to go group or solo. I have acquired
some serious reservations about a 3 inch system that I need to resolve.
Reading time is about 5 minutes, so hang with me
A very good question was asked; "Where can I get an exhaust system and what
size should it be?"
And we got some interesting responses; "3 inch", "Anything bigger than
stock", 2-1/2 to 3 inch", nothing smaller than 2-1/2 inch, the bigger the
better for a turbo motor.
I have been investigating the configuration of available systems on the
market, and studying reference material to try and determine what would be
best for me. In doing so, I believe it is important to pass along the
information for your consideration. Plus, I'm still looking for the answer.
There is no - " BEST " - size.
3 inch is popular, I think, because it is used a lot in competition motors,
so it must be good. Also, if one were to choose a most correct answer size,
3 inch is a safe bet to be LARGE enough for most any 2 liter application.
I believe those reasons are only partially correct, much too big is better
than much too small, but a little too small can be better than a little too
big, depending on where you're looking for a performance improvement.
It may well be true that all of the answers we have seen so far would
provide better engine performance than the stock system for most people with
enhanced engine configurations.
*B*U*T*, what's best for a competition engine, with a hundred horsepower
more than I expect to develop, is not necessarily the BEST thing for me.
Better than stock does not mean BEST.
>From Hugh Macinnes' "Turbochargers", Corky Bell's "Maximum Boost", Headers
by Ed's reference material, communication with MRT, calculations, charts,
everything I can find... 3 inch is not an optimum size for my expected
application, which is in the 300 horsepower ballpark.
There is a tendency to look at exhaust system size in half inch increments.
When you really start looking closely at available information, you will
find that size differentials, up or down, of one-eighth of an inch (1/8" - 3
mm) in pipe diameter can result in SIGNIFICANT power gain or loss. What's
significant? I think in science class 40 years ago it was 2%. I am
concerned with numbers of twice that magnitude, which in the 300 HP range
represent 10 or 12 HP.
This is because the change in cross sectional area is proportional to the square
of the change in radius. So a 3 inch system is 9.2% larger than a 2-7/8 system,
and 19.7% larger than a 2-3/4 inch system. So if your optimum system size is 2-3/4,
and you're off by a quarter of an inch, you're off by about 20%! Significant.
If one examines engine parameters such as displacement, compression, speed,
volumetric efficiency, valve duration and lift, desired peak power and/or
torque location, and on, and on...to determine OPTIMUM exhaust size, choice
answers for a particular engine will likely be something like 2-1/2" vs
2-5/8", or 2-3/4" vs 2-7/8", not a spread like 2-1/2" vs 3". So if I'm
going to change out my exhaust system, I am hoping to zero in on a size that
will provide a 4 or 5 percent gain of 10 or 12 horsepower, IN THE POWER BAND
WHERE I EXPECT TO OPERATE rather than a 2 percent gain of 5 or 6 horsepower
...maybe...hopefully, or a gain at the top and a loss at the bottom.
But peak horsepower is only part of the story and not even the most
important part. Proper exhaust sizing also determines where in the engine
RPM range the peak horsepower is generated, and where the peak torque is
generated, and more importantly for my street driven application, how flat
the torque curve remains or becomes. A 10 horsepower gain at 6000 RPM is no
good to me if I sacrifice 8 to 10 from 2500 to 5000, and end up going slower
most of the time because my system is too large. A system which is too
large can also permit exhaust gasses to expand so quickly that at low engine
speeds where you may need it most, turbo response suffers. And whatever you
do, a restrictive muffler or cat, can nullify what you spent on your fancy system.
So I submit to all, there is more out there to what size exhaust should I
get than first meets the nose. The answer is like the answer for a lot of
other hot rod stuff. What is your goal? Circle track? Drag strip? World
Rally Championship? Daily driver? Stock or near stock power levels? 50%
power gain? 100% power gain? The answer is different for all those combos.
The stock exhaust system is more restrictive than it needs to be. Almost
any aftermarket system will be less restrictive, but depending on where you
are now, and where you want to go, it is possible to wind up with a system
designed for a racing application that is too much less restrictive for a street
driven application, and performance could remain unimproved or even degrade,
especially at low RPM, where you're likely to notice it most.
That's all for now. I think it's enough. Now I need feedback.
Larry Witherspoon
ssspoon@aol.com
To unsubscribe from this group, please send an email to:
BC-BFLegacyWorks-unsubscribe@egroups.com
zZz <http://docs.yahoo.com/info/terms/> .
ADVERTISEMENT
<http://rd.yahoo.com/M=215002.1990895.34 ... 000239/R=1>
<http://us.adserver.yahoo.com/l?M=215002 ... =509786083>
To unsubscribe from this group, please send an email to:
BC-BFLegacyWorks-unsubscribe@egroups.com
zZz <http://docs.yahoo.com/info/terms/> .
Just curious.....where are doing your research on exhaust sizing and such? Any particular person.....I should talk to.
Thanks
Josh
************************************
Josh Colombo
<mailto:Josh@surrealmirage.com> Josh@surrealmirage.com **NEW**
"Life, an ever-changing melody
of beats and rhythm" - ME
************************************
-----Original Message-----
From: ssspoon@aol.com [mailto:ssspoon@aol.com]
Sent: Friday, April 05, 2002 10:42 PM
To: BC-BFLegacyWorks@yahoogroups.com
Subject: [BC-BFLegacyWorks] Where can I get an exhaust system and what size should it be?
I am happy to see the discussion turning to exhaust sizing and the responses
that are coming in. It gives me an excuse to stir the pot with one of my
long winded discussions, which is intended to promote some overlooked
considerations and provoke additional attention and response. With a
potential group buy at stake, I would like to present information which
could be useful in the decision of whether to go group or solo. I have acquired
some serious reservations about a 3 inch system that I need to resolve.
Reading time is about 5 minutes, so hang with me
A very good question was asked; "Where can I get an exhaust system and what
size should it be?"
And we got some interesting responses; "3 inch", "Anything bigger than
stock", 2-1/2 to 3 inch", nothing smaller than 2-1/2 inch, the bigger the
better for a turbo motor.
I have been investigating the configuration of available systems on the
market, and studying reference material to try and determine what would be
best for me. In doing so, I believe it is important to pass along the
information for your consideration. Plus, I'm still looking for the answer.
There is no - " BEST " - size.
3 inch is popular, I think, because it is used a lot in competition motors,
so it must be good. Also, if one were to choose a most correct answer size,
3 inch is a safe bet to be LARGE enough for most any 2 liter application.
I believe those reasons are only partially correct, much too big is better
than much too small, but a little too small can be better than a little too
big, depending on where you're looking for a performance improvement.
It may well be true that all of the answers we have seen so far would
provide better engine performance than the stock system for most people with
enhanced engine configurations.
*B*U*T*, what's best for a competition engine, with a hundred horsepower
more than I expect to develop, is not necessarily the BEST thing for me.
Better than stock does not mean BEST.
>From Hugh Macinnes' "Turbochargers", Corky Bell's "Maximum Boost", Headers
by Ed's reference material, communication with MRT, calculations, charts,
everything I can find... 3 inch is not an optimum size for my expected
application, which is in the 300 horsepower ballpark.
There is a tendency to look at exhaust system size in half inch increments.
When you really start looking closely at available information, you will
find that size differentials, up or down, of one-eighth of an inch (1/8" - 3
mm) in pipe diameter can result in SIGNIFICANT power gain or loss. What's
significant? I think in science class 40 years ago it was 2%. I am
concerned with numbers of twice that magnitude, which in the 300 HP range
represent 10 or 12 HP.
This is because the change in cross sectional area is proportional to the square
of the change in radius. So a 3 inch system is 9.2% larger than a 2-7/8 system,
and 19.7% larger than a 2-3/4 inch system. So if your optimum system size is 2-3/4,
and you're off by a quarter of an inch, you're off by about 20%! Significant.
If one examines engine parameters such as displacement, compression, speed,
volumetric efficiency, valve duration and lift, desired peak power and/or
torque location, and on, and on...to determine OPTIMUM exhaust size, choice
answers for a particular engine will likely be something like 2-1/2" vs
2-5/8", or 2-3/4" vs 2-7/8", not a spread like 2-1/2" vs 3". So if I'm
going to change out my exhaust system, I am hoping to zero in on a size that
will provide a 4 or 5 percent gain of 10 or 12 horsepower, IN THE POWER BAND
WHERE I EXPECT TO OPERATE rather than a 2 percent gain of 5 or 6 horsepower
...maybe...hopefully, or a gain at the top and a loss at the bottom.
But peak horsepower is only part of the story and not even the most
important part. Proper exhaust sizing also determines where in the engine
RPM range the peak horsepower is generated, and where the peak torque is
generated, and more importantly for my street driven application, how flat
the torque curve remains or becomes. A 10 horsepower gain at 6000 RPM is no
good to me if I sacrifice 8 to 10 from 2500 to 5000, and end up going slower
most of the time because my system is too large. A system which is too
large can also permit exhaust gasses to expand so quickly that at low engine
speeds where you may need it most, turbo response suffers. And whatever you
do, a restrictive muffler or cat, can nullify what you spent on your fancy system.
So I submit to all, there is more out there to what size exhaust should I
get than first meets the nose. The answer is like the answer for a lot of
other hot rod stuff. What is your goal? Circle track? Drag strip? World
Rally Championship? Daily driver? Stock or near stock power levels? 50%
power gain? 100% power gain? The answer is different for all those combos.
The stock exhaust system is more restrictive than it needs to be. Almost
any aftermarket system will be less restrictive, but depending on where you
are now, and where you want to go, it is possible to wind up with a system
designed for a racing application that is too much less restrictive for a street
driven application, and performance could remain unimproved or even degrade,
especially at low RPM, where you're likely to notice it most.
That's all for now. I think it's enough. Now I need feedback.
Larry Witherspoon
ssspoon@aol.com
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ssspoon@aol.com
Where can I get an exhaust system and what size should it be
Josh Colombo" <josh@surrealmirage.com> wants more details on Where can I get an exhaust system and what size should it be?
Hey Larry,
Just curious.....where are doing your research on exhaust sizing and such? Any particular person.....I should talk to.
Thanks
Josh
Hi Josh, I've got several sources, that give similar, but not identical resultant figures, hence my "uncertainty range"
I should fess up and admit to possibly falling into the "theorist" trap of overanalyzing to death. Sometimes you have to shoot the engineer and build the plane!
My "essay" may have been too heavy-handed on the side of perfection, when in reality, the difference in the optimum system and one that is appreciably better than stock, may only be a small number. From a practical standpoint, that small number may only be apparent in a speed contest that will be decided by a small time interval.
However, since I have the material available, and since I don't know the details of any research done with the engine I am using, I'm trying to use independent sources to narrow my range of uncertainty. Because I don't know if that number may not be so small after all, if I'm too far off.
See the thing is, when a stock system is changed out for an aftermarket system that's a lot bigger, and we get an improvement, it's easy to jump to the conclusion that we did the right thing. But we could only be partially right. It's not a scientifically valid conclusion because too many variables were changed. It could be that the stock system size is correct, or nearly correct, and the improvement came from trashing the restrictive mufflers and cats for better ones with the new larger system. It could be that if the mufflers and cats were changed out and the rest left unchanged, that the improvement would be even better than going to the larger system ! ! ! Or that a still better result could be obtained by going larger but not SO much larger. That's where I'm coming from.
My first hint was when inquiring to MRT about their "Head to Turbo Extractors". To their credit, I was advised that unless my engine was highly modified, I might not realize any performance advantage with them.
I pulled out my references;
"Turbochargers", by Hugh Macinnes, published by HP Books, a division of Price Stern Sloan, Los Angeles, CA, 1984
"Maximum Boost", by Corky Bell, published by Robert Bentley Automotive Publishers, Cambridge, MA, 1997
I went over all the formulas, charts, and graphs plugging in whatever I could for my engine
I was surfing the web for "engine headers" and found the "Headers By Ed" site, and recalled my buddy, a lifelong hotrodder, and close to retirement as a master mechanic for the Los Angeles Police Department, intended to use Headers By Ed on a rod he is building. I read everything on Ed's extensive website and sent for his full Info Pak. This is what really opened my eyes to the importance of proper sizing, which I only touched on earlier, because the discussion really started out looking at turbo back exhaust systems, and I kind of segued over into headers too.
Trouble is, Ed specializes in "old school" musclecars, so I'm trying to integrate the info from the textbooks on turbocharging with the extensive research Ed has published. Variables in header design that affect power and torque, are tube length, variation in length between tubes, tube diameter, collector length, collector diameter, collector taper, and tube to collector interface.
I believe exhaust system size after the turbo can be considered as an extension of collector diameter.
Check out "Headers By Ed" at http://www.headersbyed.com/
Advanced word from a reliable source has indicated my suspicions have been confirmed by header testing underway as we speak.
If anyone would be kind enough to help me with this research, I would please like to know for the USA version EJ22T engine, the following cam specs for both the intake and exhaust valves, preferably at 0.050" lift, or ___________(whatever available);
1) Intake Valve Duration
2) Intake Valve Lift
3) Intake Open Degrees BTDC
4) Intake Close Degrees ABDC
5) Exhaust Valve Duration
6) Exhaust Valve Lift
7) Exhaust Open Degrees BBDC
Exhaust Close Degrees ATDC
9) Valve Overlap Degrees
10) Centerline Degrees
And
11) Intake Valve Size
12) Exhaust Valve Size
13) Rocker Arm Ratio
Thank you for your indulgence
Larry Witherspoon
ssspoon@aol.com
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Hey Larry,
Just curious.....where are doing your research on exhaust sizing and such? Any particular person.....I should talk to.
Thanks
Josh
Hi Josh, I've got several sources, that give similar, but not identical resultant figures, hence my "uncertainty range"
I should fess up and admit to possibly falling into the "theorist" trap of overanalyzing to death. Sometimes you have to shoot the engineer and build the plane!
My "essay" may have been too heavy-handed on the side of perfection, when in reality, the difference in the optimum system and one that is appreciably better than stock, may only be a small number. From a practical standpoint, that small number may only be apparent in a speed contest that will be decided by a small time interval.
However, since I have the material available, and since I don't know the details of any research done with the engine I am using, I'm trying to use independent sources to narrow my range of uncertainty. Because I don't know if that number may not be so small after all, if I'm too far off.
See the thing is, when a stock system is changed out for an aftermarket system that's a lot bigger, and we get an improvement, it's easy to jump to the conclusion that we did the right thing. But we could only be partially right. It's not a scientifically valid conclusion because too many variables were changed. It could be that the stock system size is correct, or nearly correct, and the improvement came from trashing the restrictive mufflers and cats for better ones with the new larger system. It could be that if the mufflers and cats were changed out and the rest left unchanged, that the improvement would be even better than going to the larger system ! ! ! Or that a still better result could be obtained by going larger but not SO much larger. That's where I'm coming from.
My first hint was when inquiring to MRT about their "Head to Turbo Extractors". To their credit, I was advised that unless my engine was highly modified, I might not realize any performance advantage with them.
I pulled out my references;
"Turbochargers", by Hugh Macinnes, published by HP Books, a division of Price Stern Sloan, Los Angeles, CA, 1984
"Maximum Boost", by Corky Bell, published by Robert Bentley Automotive Publishers, Cambridge, MA, 1997
I went over all the formulas, charts, and graphs plugging in whatever I could for my engine
I was surfing the web for "engine headers" and found the "Headers By Ed" site, and recalled my buddy, a lifelong hotrodder, and close to retirement as a master mechanic for the Los Angeles Police Department, intended to use Headers By Ed on a rod he is building. I read everything on Ed's extensive website and sent for his full Info Pak. This is what really opened my eyes to the importance of proper sizing, which I only touched on earlier, because the discussion really started out looking at turbo back exhaust systems, and I kind of segued over into headers too.
Trouble is, Ed specializes in "old school" musclecars, so I'm trying to integrate the info from the textbooks on turbocharging with the extensive research Ed has published. Variables in header design that affect power and torque, are tube length, variation in length between tubes, tube diameter, collector length, collector diameter, collector taper, and tube to collector interface.
I believe exhaust system size after the turbo can be considered as an extension of collector diameter.
Check out "Headers By Ed" at http://www.headersbyed.com/
Advanced word from a reliable source has indicated my suspicions have been confirmed by header testing underway as we speak.
If anyone would be kind enough to help me with this research, I would please like to know for the USA version EJ22T engine, the following cam specs for both the intake and exhaust valves, preferably at 0.050" lift, or ___________(whatever available);
1) Intake Valve Duration
2) Intake Valve Lift
3) Intake Open Degrees BTDC
4) Intake Close Degrees ABDC
5) Exhaust Valve Duration
6) Exhaust Valve Lift
7) Exhaust Open Degrees BBDC
Exhaust Close Degrees ATDC9) Valve Overlap Degrees
10) Centerline Degrees
And
11) Intake Valve Size
12) Exhaust Valve Size
13) Rocker Arm Ratio
Thank you for your indulgence
Larry Witherspoon
ssspoon@aol.com
ADVERTISEMENT
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rodeddy
Where can I get an exhaust system and what size should it be
At the end of the day most power is achieved by getting the turbo on
boost ASAP and holding peak boost right through the rev range.
To get the turbo on boost ASAP the exhaust needs to be as least
restrictive as possible with no backpressure so the turbo can spin
freeling and quickly. Another important issue is to have a 'splitter'
in the turbo outlet so that wastegate gases don't interfere with the
flow.
Once you have a free flowing exhaust the next question to ask is what
type of turbo is required? One thats gets on boost real quick in the
lower rev range but often runs out of puff up high, or one that comes
on boost a little later in the rev range but keeps a strong boost
right through to redline. If you are only wanting good driveability
and quick low down response go the 'smaller' turbo but if you don't
mind a little more lag and want good mid to high end power go
a 'bigger' turbo. This is where the question of how you drive and
want you want the car to do becomes and endless search of comprimise.
Still, it doesn't matter which turbo you go for, getting the turbo
spinning and on boost ASAP is best achieved with the best free
flowing exhaust you can get. Then comes the issue of noise. The best
free flowing exhaust can be noisy....it's all comprimise and what you
are finally trying to achive.
cheers, Rod... in Oz
--- In BC-BFLegacyWorks@y..., ssspoon@a... wrote:
> Josh Colombo" <josh@s...> wants more details on Where can I get
> an exhaust system and what size should it be?
>
> Hey Larry,
>
> Just curious.....where are doing your research on exhaust sizing
and such?
> Any particular person.....I should talk to.
>
> Thanks
>
> Josh
>
> Hi Josh, I've got several sources, that give similar, but not
identical
> resultant figures, hence my "uncertainty range"
>
> I should fess up and admit to possibly falling into the "theorist"
trap of
> overanalyzing to death. Sometimes you have to shoot the engineer
and build
> the plane!
> My "essay" may have been too heavy-handed on the side of
perfection, when in
> reality, the difference in the optimum system and one that is
appreciably
> better than stock, may only be a small number. From a practical
standpoint,
> that small number may only be apparent in a speed contest that will
be
> decided by a small time interval.
>
> However, since I have the material available, and since I don't
know the
> details of any research done with the engine I am using, I'm trying
to use
> independent sources to narrow my range of uncertainty. Because I
don't know
> if that number may not be so small after all, if I'm too far off.
>
> See the thing is, when a stock system is changed out for an
aftermarket
> system that's a lot bigger, and we get an improvement, it's easy to
jump to
> the conclusion that we did the right thing. But we could only be
partially
> right. It's not a scientifically valid conclusion because too many
variables
> were changed. It could be that the stock system size is correct,
or nearly
> correct, and the improvement came from trashing the restrictive
mufflers and
> cats for better ones with the new larger system. It could be that
if the
> mufflers and cats were changed out and the rest left unchanged,
that the
> improvement would be even better than going to the larger
system ! ! ! Or
> that a still better result could be obtained by going larger but
not SO much
> larger. That's where I'm coming from.
>
> My first hint was when inquiring to MRT about their "Head to Turbo
> Extractors". To their credit, I was advised that unless my engine
was highly
> modified, I might not realize any performance advantage with them.
>
> I pulled out my references;
>
> "Turbochargers", by Hugh Macinnes, published by HP Books, a
division of Price
> Stern Sloan, Los Angeles, CA, 1984
>
> "Maximum Boost", by Corky Bell, published by Robert Bentley
Automotive
> Publishers, Cambridge, MA, 1997
>
> I went over all the formulas, charts, and graphs plugging in
whatever I could
> for my engine
>
> I was surfing the web for "engine headers" and found the "Headers
By Ed"
> site, and recalled my buddy, a lifelong hotrodder, and close to
retirement as
> a master mechanic for the Los Angeles Police Department, intended
to use
> Headers By Ed on a rod he is building. I read everything on Ed's
extensive
> website and sent for his full Info Pak. This is what really opened
my eyes
> to the importance of proper sizing, which I only touched on
earlier, because
> the discussion really started out looking at turbo back exhaust
systems, and
> I kind of segued over into headers too.
>
> Trouble is, Ed specializes in "old school" musclecars, so I'm
trying to
> integrate the info from the textbooks on turbocharging with the
extensive
> research Ed has published. Variables in header design that affect
power and
> torque, are tube length, variation in length between tubes, tube
diameter,
> collector length, collector diameter, collector taper, and tube to
collector
> interface.
>
> I believe exhaust system size after the turbo can be considered as
an
> extension of collector diameter.
>
> Check out "Headers By Ed" at http://www.headersbyed.com/
>
> Advanced word from a reliable source has indicated my suspicions
have been
> confirmed by header testing underway as we speak.
>
> If anyone would be kind enough to help me with this research, I
would please
> like to know for the USA version EJ22T engine, the following cam
specs for
> both the intake and exhaust valves, preferably at 0.050" lift, or
> ___________(whatever available);
>
> 1) Intake Valve Duration
> 2) Intake Valve Lift
> 3) Intake Open Degrees BTDC
> 4) Intake Close Degrees ABDC
>
> 5) Exhaust Valve Duration
> 6) Exhaust Valve Lift
> 7) Exhaust Open Degrees BBDC
> Exhaust Close Degrees ATDC
>
> 9) Valve Overlap Degrees
> 10) Centerline Degrees
>
> And
>
> 11) Intake Valve Size
> 12) Exhaust Valve Size
> 13) Rocker Arm Ratio
>
> Thank you for your indulgence
>
> Larry Witherspoon
> ssspoon@a...
------------------------ ---------------------~-->
Buy Stock for $4
and no minimums.
FREE Money 2002.
http://us.click.yahoo.com/k6cvND/n97DAA ... /XoTolB/TM
---------------------------------------------------------------------~->
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boost ASAP and holding peak boost right through the rev range.
To get the turbo on boost ASAP the exhaust needs to be as least
restrictive as possible with no backpressure so the turbo can spin
freeling and quickly. Another important issue is to have a 'splitter'
in the turbo outlet so that wastegate gases don't interfere with the
flow.
Once you have a free flowing exhaust the next question to ask is what
type of turbo is required? One thats gets on boost real quick in the
lower rev range but often runs out of puff up high, or one that comes
on boost a little later in the rev range but keeps a strong boost
right through to redline. If you are only wanting good driveability
and quick low down response go the 'smaller' turbo but if you don't
mind a little more lag and want good mid to high end power go
a 'bigger' turbo. This is where the question of how you drive and
want you want the car to do becomes and endless search of comprimise.
Still, it doesn't matter which turbo you go for, getting the turbo
spinning and on boost ASAP is best achieved with the best free
flowing exhaust you can get. Then comes the issue of noise. The best
free flowing exhaust can be noisy....it's all comprimise and what you
are finally trying to achive.
cheers, Rod... in Oz
--- In BC-BFLegacyWorks@y..., ssspoon@a... wrote:
> Josh Colombo" <josh@s...> wants more details on Where can I get
> an exhaust system and what size should it be?
>
> Hey Larry,
>
> Just curious.....where are doing your research on exhaust sizing
and such?
> Any particular person.....I should talk to.
>
> Thanks
>
> Josh
>
> Hi Josh, I've got several sources, that give similar, but not
identical
> resultant figures, hence my "uncertainty range"
>
> I should fess up and admit to possibly falling into the "theorist"
trap of
> overanalyzing to death. Sometimes you have to shoot the engineer
and build
> the plane!
> My "essay" may have been too heavy-handed on the side of
perfection, when in
> reality, the difference in the optimum system and one that is
appreciably
> better than stock, may only be a small number. From a practical
standpoint,
> that small number may only be apparent in a speed contest that will
be
> decided by a small time interval.
>
> However, since I have the material available, and since I don't
know the
> details of any research done with the engine I am using, I'm trying
to use
> independent sources to narrow my range of uncertainty. Because I
don't know
> if that number may not be so small after all, if I'm too far off.
>
> See the thing is, when a stock system is changed out for an
aftermarket
> system that's a lot bigger, and we get an improvement, it's easy to
jump to
> the conclusion that we did the right thing. But we could only be
partially
> right. It's not a scientifically valid conclusion because too many
variables
> were changed. It could be that the stock system size is correct,
or nearly
> correct, and the improvement came from trashing the restrictive
mufflers and
> cats for better ones with the new larger system. It could be that
if the
> mufflers and cats were changed out and the rest left unchanged,
that the
> improvement would be even better than going to the larger
system ! ! ! Or
> that a still better result could be obtained by going larger but
not SO much
> larger. That's where I'm coming from.
>
> My first hint was when inquiring to MRT about their "Head to Turbo
> Extractors". To their credit, I was advised that unless my engine
was highly
> modified, I might not realize any performance advantage with them.
>
> I pulled out my references;
>
> "Turbochargers", by Hugh Macinnes, published by HP Books, a
division of Price
> Stern Sloan, Los Angeles, CA, 1984
>
> "Maximum Boost", by Corky Bell, published by Robert Bentley
Automotive
> Publishers, Cambridge, MA, 1997
>
> I went over all the formulas, charts, and graphs plugging in
whatever I could
> for my engine
>
> I was surfing the web for "engine headers" and found the "Headers
By Ed"
> site, and recalled my buddy, a lifelong hotrodder, and close to
retirement as
> a master mechanic for the Los Angeles Police Department, intended
to use
> Headers By Ed on a rod he is building. I read everything on Ed's
extensive
> website and sent for his full Info Pak. This is what really opened
my eyes
> to the importance of proper sizing, which I only touched on
earlier, because
> the discussion really started out looking at turbo back exhaust
systems, and
> I kind of segued over into headers too.
>
> Trouble is, Ed specializes in "old school" musclecars, so I'm
trying to
> integrate the info from the textbooks on turbocharging with the
extensive
> research Ed has published. Variables in header design that affect
power and
> torque, are tube length, variation in length between tubes, tube
diameter,
> collector length, collector diameter, collector taper, and tube to
collector
> interface.
>
> I believe exhaust system size after the turbo can be considered as
an
> extension of collector diameter.
>
> Check out "Headers By Ed" at http://www.headersbyed.com/
>
> Advanced word from a reliable source has indicated my suspicions
have been
> confirmed by header testing underway as we speak.
>
> If anyone would be kind enough to help me with this research, I
would please
> like to know for the USA version EJ22T engine, the following cam
specs for
> both the intake and exhaust valves, preferably at 0.050" lift, or
> ___________(whatever available);
>
> 1) Intake Valve Duration
> 2) Intake Valve Lift
> 3) Intake Open Degrees BTDC
> 4) Intake Close Degrees ABDC
>
> 5) Exhaust Valve Duration
> 6) Exhaust Valve Lift
> 7) Exhaust Open Degrees BBDC
>
Exhaust Close Degrees ATDC>
> 9) Valve Overlap Degrees
> 10) Centerline Degrees
>
> And
>
> 11) Intake Valve Size
> 12) Exhaust Valve Size
> 13) Rocker Arm Ratio
>
> Thank you for your indulgence
>
> Larry Witherspoon
> ssspoon@a...
------------------------ ---------------------~-->
Buy Stock for $4
and no minimums.
FREE Money 2002.
http://us.click.yahoo.com/k6cvND/n97DAA ... /XoTolB/TM
---------------------------------------------------------------------~->
To unsubscribe from this group, please send an email to:
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-
ssspoon@aol.com
Where can I get an exhaust system and what size should it be
Rod in Oz, "rodeddy" <melrod@optusnet.com.au> writes;
At the end of the day most power is achieved by getting the turbo on
boost ASAP and holding peak boost right through the rev range.
To get the turbo on boost ASAP the exhaust needs to be as least
restrictive as possible with no backpressure so the turbo can spin
freely and quickly.
Hey Rod, I would like to add some fuel to that fire. I keep running into info, which even seems to conflict within the same book, that bigger is not necessarily better, within a few paragraphs that says something like all back pressure is bad. I have even written to one author to try and reconcile the disparity, but no answer so far.
I have read theory that says turbo response is the result of the pressure differential across the turbine wheel, which at first seems like the largest or least restrictive, or even no exhaust pipe is preferable.
I have also read theory that says an ADEQUATE size is necessary to permit unrestricted flow, but small enough to maintain a high gas velocity, also necessary for the response we would like. It may be that too large of an exhaust pipe is not the same as no pipe until you get some crazy size like 6 or 8 inches. It may be that too large of an exhaust can allow the gas to expand, cool, and slow too soon after the turbine, then not be able to get out of its' own way, causing turbo response to suffer.
The recurring reference to a "proper size" indicates to me that there is a size for each engine configuration, and power output, which is small enough to promote the desired high gas velocity, but still large enough to do it without acting as a restriction.
I know, it may seem contradictory, but I think you CAN be too big. In all the published stuff I've seen, nobody says get the biggest exhaust you can find, but they might say something like, keep the restriction to a minimum, but keep the gas velocity up. I believe the proper size is a balance that needs to be found for each engine, and that might not necessarily mean the biggest.
Larry Witherspoon
ssspoon at AOL
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To unsubscribe from this group, please send an email to:
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At the end of the day most power is achieved by getting the turbo on
boost ASAP and holding peak boost right through the rev range.
To get the turbo on boost ASAP the exhaust needs to be as least
restrictive as possible with no backpressure so the turbo can spin
freely and quickly.
Hey Rod, I would like to add some fuel to that fire. I keep running into info, which even seems to conflict within the same book, that bigger is not necessarily better, within a few paragraphs that says something like all back pressure is bad. I have even written to one author to try and reconcile the disparity, but no answer so far.
I have read theory that says turbo response is the result of the pressure differential across the turbine wheel, which at first seems like the largest or least restrictive, or even no exhaust pipe is preferable.
I have also read theory that says an ADEQUATE size is necessary to permit unrestricted flow, but small enough to maintain a high gas velocity, also necessary for the response we would like. It may be that too large of an exhaust pipe is not the same as no pipe until you get some crazy size like 6 or 8 inches. It may be that too large of an exhaust can allow the gas to expand, cool, and slow too soon after the turbine, then not be able to get out of its' own way, causing turbo response to suffer.
The recurring reference to a "proper size" indicates to me that there is a size for each engine configuration, and power output, which is small enough to promote the desired high gas velocity, but still large enough to do it without acting as a restriction.
I know, it may seem contradictory, but I think you CAN be too big. In all the published stuff I've seen, nobody says get the biggest exhaust you can find, but they might say something like, keep the restriction to a minimum, but keep the gas velocity up. I believe the proper size is a balance that needs to be found for each engine, and that might not necessarily mean the biggest.
Larry Witherspoon
ssspoon at AOL
ADVERTISEMENT
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-
Josh Colombo
Where can I get an exhaust system and what size should it be
Larry,
I've got some more fuel for the fire......
I was goin to wait to post this till I got all the rest of the information, but I'll give you a precurser.
You mentioned you read that turbo response is the result of the pressure differential across the turbine wheel.
I had a class on engines last week....one of the things I picked up, which I still have yet to settle in my head was that the turbine is driven mainly with heat.....not pressure, as one would intuitively think. In fact the pressure drop across the turbine is not that great.
Like I said, I do not have all my info sorted and such yet. I need to get some turbo charger books from the library or something. I haven't really found anything on the net, nothing was technical enough.
I have talked with one of the engineers at work, he has told me it is related to Boyle's law. With a large increase in temperature, you result in a large volume increase, or large flow rate.
So if we take that temp thing into account.....one would want headers that would maintain as much heat as possible before the turbo, then....as you pointed out Larry....have an exhaust that is big enough to remove exhaust gasses without too much restriction....yet have it small enough to keep velocities up.
I will hopefully find out more information today about the turbo and heat.......I believe that the temp thing is correct......I just need to see some formulas and such to prove it to myself and see how it works........only bad thing is I think my engineer buddy said it's like a 3 1/2 page differential equation to prove it........yuck....
I'll let ya know what i find out.
Josh
-----Original Message-----
From: ssspoon@aol.com [mailto:ssspoon@aol.com]
Sent: Tue 4/9/2002 3:26 AM
To: BC-BFLegacyWorks@yahoogroups.com
Cc:
Subject: [BC-BFLegacyWorks] Where can I get an exhaust system and what size should it be?
Rod in Oz, "rodeddy" <melrod@optusnet.com.au> writes;
At the end of the day most power is achieved by getting the turbo on
boost ASAP and holding peak boost right through the rev range.
To get the turbo on boost ASAP the exhaust needs to be as least
restrictive as possible with no backpressure so the turbo can spin
freely and quickly.
Hey Rod, I would like to add some fuel to that fire. I keep running into info, which even seems to conflict within the same book, that bigger is not necessarily better, within a few paragraphs that says something like all back pressure is bad. I have even written to one author to try and reconcile the disparity, but no answer so far.
I have read theory that says turbo response is the result of the pressure differential across the turbine wheel, which at first seems like the largest or least restrictive, or even no exhaust pipe is preferable.
I have also read theory that says an ADEQUATE size is necessary to permit unrestricted flow, but small enough to maintain a high gas velocity, also necessary for the response we would like. It may be that too large of an exhaust pipe is not the same as no pipe until you get some crazy size like 6 or 8 inches. It may be that too large of an exhaust can allow the gas to expand, cool, and slow too soon after the turbine, then not be able to get out of its' own way, causing turbo response to suffer.
The recurring reference to a "proper size" indicates to me that there is a size for each engine configuration, and power output, which is small enough to promote the desired high gas velocity, but still large enough to do it without acting as a restriction.
I know, it may seem contradictory, but I think you CAN be too big. In all the published stuff I've seen, nobody says get the biggest exhaust you can find, but they might say something like, keep the restriction to a minimum, but keep the gas velocity up. I believe the proper size is a balance that needs to be found for each engine, and that might not necessarily mean the biggest.
Larry Witherspoon
ssspoon at AOL
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I've got some more fuel for the fire......
I was goin to wait to post this till I got all the rest of the information, but I'll give you a precurser.
You mentioned you read that turbo response is the result of the pressure differential across the turbine wheel.
I had a class on engines last week....one of the things I picked up, which I still have yet to settle in my head was that the turbine is driven mainly with heat.....not pressure, as one would intuitively think. In fact the pressure drop across the turbine is not that great.
Like I said, I do not have all my info sorted and such yet. I need to get some turbo charger books from the library or something. I haven't really found anything on the net, nothing was technical enough.
I have talked with one of the engineers at work, he has told me it is related to Boyle's law. With a large increase in temperature, you result in a large volume increase, or large flow rate.
So if we take that temp thing into account.....one would want headers that would maintain as much heat as possible before the turbo, then....as you pointed out Larry....have an exhaust that is big enough to remove exhaust gasses without too much restriction....yet have it small enough to keep velocities up.
I will hopefully find out more information today about the turbo and heat.......I believe that the temp thing is correct......I just need to see some formulas and such to prove it to myself and see how it works........only bad thing is I think my engineer buddy said it's like a 3 1/2 page differential equation to prove it........yuck....
I'll let ya know what i find out.
Josh
-----Original Message-----
From: ssspoon@aol.com [mailto:ssspoon@aol.com]
Sent: Tue 4/9/2002 3:26 AM
To: BC-BFLegacyWorks@yahoogroups.com
Cc:
Subject: [BC-BFLegacyWorks] Where can I get an exhaust system and what size should it be?
Rod in Oz, "rodeddy" <melrod@optusnet.com.au> writes;
At the end of the day most power is achieved by getting the turbo on
boost ASAP and holding peak boost right through the rev range.
To get the turbo on boost ASAP the exhaust needs to be as least
restrictive as possible with no backpressure so the turbo can spin
freely and quickly.
Hey Rod, I would like to add some fuel to that fire. I keep running into info, which even seems to conflict within the same book, that bigger is not necessarily better, within a few paragraphs that says something like all back pressure is bad. I have even written to one author to try and reconcile the disparity, but no answer so far.
I have read theory that says turbo response is the result of the pressure differential across the turbine wheel, which at first seems like the largest or least restrictive, or even no exhaust pipe is preferable.
I have also read theory that says an ADEQUATE size is necessary to permit unrestricted flow, but small enough to maintain a high gas velocity, also necessary for the response we would like. It may be that too large of an exhaust pipe is not the same as no pipe until you get some crazy size like 6 or 8 inches. It may be that too large of an exhaust can allow the gas to expand, cool, and slow too soon after the turbine, then not be able to get out of its' own way, causing turbo response to suffer.
The recurring reference to a "proper size" indicates to me that there is a size for each engine configuration, and power output, which is small enough to promote the desired high gas velocity, but still large enough to do it without acting as a restriction.
I know, it may seem contradictory, but I think you CAN be too big. In all the published stuff I've seen, nobody says get the biggest exhaust you can find, but they might say something like, keep the restriction to a minimum, but keep the gas velocity up. I believe the proper size is a balance that needs to be found for each engine, and that might not necessarily mean the biggest.
Larry Witherspoon
ssspoon at AOL
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rodeddy
Where can I get an exhaust system and what size should it be
i agree with you with the high gas velocity, (to the turbo)which as
you say may better be achieved by smaller pipe, though only from the
heads to the turbo, after the turbo i still consider larger is better
cheers, rod-
-- In BC-BFLegacyWorks@y..., ssspoon@a... wrote:
> Rod in Oz, "rodeddy" <melrod@o...> writes;
>
> > At the end of the day most power is achieved by getting the turbo
on
> > boost ASAP and holding peak boost right through the rev range.
> > To get the turbo on boost ASAP the exhaust needs to be as least
> > restrictive as possible with no backpressure so the turbo can
spin
> > freely and quickly.
>
> Hey Rod, I would like to add some fuel to that fire. I keep
running into
> info, which even seems to conflict within the same book, that
bigger is not
> necessarily better, within a few paragraphs that says something
like all back
> pressure is bad. I have even written to one author to try and
reconcile the
> disparity, but no answer so far.
>
> I have read theory that says turbo response is the result of the
pressure
> differential across the turbine wheel, which at first seems like
the largest
> or least restrictive, or even no exhaust pipe is preferable.
>
> I have also read theory that says an ADEQUATE size is necessary to
permit
> unrestricted flow, but small enough to maintain a high gas
velocity, also
> necessary for the response we would like. It may be that too large
of an
> exhaust pipe is not the same as no pipe until you get some crazy
size like 6
> or 8 inches. It may be that too large of an exhaust can allow the
gas to
> expand, cool, and slow too soon after the turbine, then not be able
to get
> out of its' own way, causing turbo response to suffer.
>
> The recurring reference to a "proper size" indicates to me that
there is a
> size for each engine configuration, and power output, which is
small enough
> to promote the desired high gas velocity, but still large enough to
do it
> without acting as a restriction.
>
> I know, it may seem contradictory, but I think you CAN be too big.
In all
> the published stuff I've seen, nobody says get the biggest exhaust
you can
> find, but they might say something like, keep the restriction to a
minimum,
> but keep the gas velocity up. I believe the proper size is a
balance that
> needs to be found for each engine, and that might not necessarily
mean the
> biggest.
>
> Larry Witherspoon
> ssspoon at AOL
------------------------ ---------------------~-->
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and no minimums.
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you say may better be achieved by smaller pipe, though only from the
heads to the turbo, after the turbo i still consider larger is better
cheers, rod-
-- In BC-BFLegacyWorks@y..., ssspoon@a... wrote:
> Rod in Oz, "rodeddy" <melrod@o...> writes;
>
> > At the end of the day most power is achieved by getting the turbo
on
> > boost ASAP and holding peak boost right through the rev range.
> > To get the turbo on boost ASAP the exhaust needs to be as least
> > restrictive as possible with no backpressure so the turbo can
spin
> > freely and quickly.
>
> Hey Rod, I would like to add some fuel to that fire. I keep
running into
> info, which even seems to conflict within the same book, that
bigger is not
> necessarily better, within a few paragraphs that says something
like all back
> pressure is bad. I have even written to one author to try and
reconcile the
> disparity, but no answer so far.
>
> I have read theory that says turbo response is the result of the
pressure
> differential across the turbine wheel, which at first seems like
the largest
> or least restrictive, or even no exhaust pipe is preferable.
>
> I have also read theory that says an ADEQUATE size is necessary to
permit
> unrestricted flow, but small enough to maintain a high gas
velocity, also
> necessary for the response we would like. It may be that too large
of an
> exhaust pipe is not the same as no pipe until you get some crazy
size like 6
> or 8 inches. It may be that too large of an exhaust can allow the
gas to
> expand, cool, and slow too soon after the turbine, then not be able
to get
> out of its' own way, causing turbo response to suffer.
>
> The recurring reference to a "proper size" indicates to me that
there is a
> size for each engine configuration, and power output, which is
small enough
> to promote the desired high gas velocity, but still large enough to
do it
> without acting as a restriction.
>
> I know, it may seem contradictory, but I think you CAN be too big.
In all
> the published stuff I've seen, nobody says get the biggest exhaust
you can
> find, but they might say something like, keep the restriction to a
minimum,
> but keep the gas velocity up. I believe the proper size is a
balance that
> needs to be found for each engine, and that might not necessarily
mean the
> biggest.
>
> Larry Witherspoon
> ssspoon at AOL
------------------------ ---------------------~-->
Buy Stock for $4
and no minimums.
FREE Money 2002.
http://us.click.yahoo.com/k6cvND/n97DAA ... /XoTolB/TM
---------------------------------------------------------------------~->
To unsubscribe from this group, please send an email to:
BC-BFLegacyWorks-unsubscribe@egroups.com