Any advantages in removing the cat

[Miguelito]

Yo!

has anyone (especially UK/AU/NZ guys with EJ20 engines) ever tried
removing the catalyzator (how do you write that word?) and measured
(=dyno) the gain in hp?
I was offered a complete 2,5" exhaust, all the way from the turbo,
made almost entirely in stainless steel, but without the cat. Since
the cat obviously is a must here, one would have to switch pipes at
least once a year for the yearly inspection, but if there where two
complete sets of pipes it wouldn't be that big a task... They said
that the downpipe was made as it is on '98 rallycars, but I can't say
anything to that.
One more thing, the pipe was on a "sedan" and I have a wagon, I guess
it has to be the same car at least up to the rear axle, but is the
wagon a bit longer from there on?

I was just wondering if it's worth while. So do you have ANY ideas
how much one could imagine to gain out of this, or any PROs/NEEs at
all?

Miguelito

PS. the price was ~ 150USD...


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[Dave aka DLC/dackampf]

Removing the cat will make the exhaust a tiny bit less restrictive so
you should see a small gain, but nothing dramatic unless your present
one is clogged up or something.

The Sedan and Wagon are the EXACT same length.

--- In BC-BFLegacyWorks@egroups.com, "Miguelito " <awdturbodude@y...>
wrote:
> Yo!
>
> has anyone (especially UK/AU/NZ guys with EJ20 engines) ever tried
> removing the catalyzator (how do you write that word?) and measured
> (=dyno) the gain in hp?
> I was offered a complete 2,5" exhaust, all the way from the turbo,
> made almost entirely in stainless steel, but without the cat. Since
> the cat obviously is a must here, one would have to switch pipes at
> least once a year for the yearly inspection, but if there where two
> complete sets of pipes it wouldn't be that big a task... They said
> that the downpipe was made as it is on '98 rallycars, but I can't
say
> anything to that.
> One more thing, the pipe was on a "sedan" and I have a wagon, I
guess
> it has to be the same car at least up to the rear axle, but is the
> wagon a bit longer from there on?
>
> I was just wondering if it's worth while. So do you have ANY ideas
> how much one could imagine to gain out of this, or any PROs/NEEs at
> all?
>
> Miguelito
>
> PS. the price was ~ 150USD...


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[Miguelito]

Thanks Dave,
now I know at least that the pipe will fit 100%...

cheers,

Miguelito



--- In BC-BFLegacyWorks@egroups.com, "Dave aka DLC/dackampf"
<legacycentral@y...> wrote:
> Removing the cat will make the exhaust a tiny bit less restrictive
so
> you should see a small gain, but nothing dramatic unless your
present
> one is clogged up or something.
>
> The Sedan and Wagon are the EXACT same length.
>
> --- In BC-BFLegacyWorks@egroups.com, "Miguelito "
<awdturbodude@y...>
> wrote:
> > Yo!
> >
> > has anyone (especially UK/AU/NZ guys with EJ20 engines) ever
tried
> > removing the catalyzator (how do you write that word?) and
measured
> > (=dyno) the gain in hp?
> > I was offered a complete 2,5" exhaust, all the way from the
turbo,
> > made almost entirely in stainless steel, but without the cat.
Since
> > the cat obviously is a must here, one would have to switch pipes
at
> > least once a year for the yearly inspection, but if there where
two
> > complete sets of pipes it wouldn't be that big a task... They
said
> > that the downpipe was made as it is on '98 rallycars, but I can't
> say
> > anything to that.
> > One more thing, the pipe was on a "sedan" and I have a wagon, I
> guess
> > it has to be the same car at least up to the rear axle, but is
the
> > wagon a bit longer from there on?
> >
> > I was just wondering if it's worth while. So do you have ANY
ideas
> > how much one could imagine to gain out of this, or any PROs/NEEs
at
> > all?
> >
> > Miguelito
> >
> > PS. the price was ~ 150USD...


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[Josh Colombo]

Just a quick question? This isn't a twin turbo 2.0 is it? If it is, what I've heard is that the primary turbo is small and is easily over-spun. So removing the cat on the primary turbo is NOT a good idea. If it's just a single turbo, then by all means i'd do it, and like dave said, hp gains will prob vary. I know one thing also with N/A cars, if you go to a larger exhaust diameter, too big that is, you can sacrafice low end torque and power, because of no back pressure. I don't know if this is a concern with the turbos.

Josh

-----Original Message-----
From: Miguelito
Sent: Wed 11/22/2000 1:59 PM
To: BC-BFLegacyWorks@egroups.com
Cc:
Subject: [BC-BFLegacyWorks] Any advantages in removing the cat



Yo!

has anyone (especially UK/AU/NZ guys with EJ20 engines) ever tried
removing the catalyzator (how do you write that word?) and measured
(=dyno) the gain in hp?
I was offered a complete 2,5" exhaust, all the way from the turbo,
made almost entirely in stainless steel, but without the cat. Since
the cat obviously is a must here, one would have to switch pipes at
least once a year for the yearly inspection, but if there where two
complete sets of pipes it wouldn't be that big a task... They said
that the downpipe was made as it is on '98 rallycars, but I can't say
anything to that.
One more thing, the pipe was on a "sedan" and I have a wagon, I guess
it has to be the same car at least up to the rear axle, but is the
wagon a bit longer from there on?

I was just wondering if it's worth while. So do you have ANY ideas
how much one could imagine to gain out of this, or any PROs/NEEs at
all?

Miguelito

PS. the price was ~ 150USD...


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[awdturbodude@yahoo.com]

It's a single turbo, but yes, I've also heard that by mounting too
big an exhaust, you could sacrafice low end torque and power. I don't
think, however, that this is a problem with 2,5".

cheers,

Miguelito


--- In BC-BFLegacyWorks@egroups.com, "Josh Colombo" <jcc189@p...>
wrote:
> Just a quick question? This isn't a twin turbo 2.0 is it? If it
is,
> what I've heard is that the primary turbo is small and is easily
> over-spun. So removing the cat on the primary turbo is NOT a good
idea.
> If it's just a single turbo, then by all means i'd do it, and like
dave
> said, hp gains will prob vary. I know one thing also with N/A
cars, if
> you go to a larger exhaust diameter, too big that is, you can
sacrafice
> low end torque and power, because of no back pressure. I don't
know if
> this is a concern with the turbos.
>
> Josh
>
> -----Original Message-----
> From: Miguelito
> Sent: Wed 11/22/2000 1:59 PM
> To: BC-BFLegacyWorks@egroups.com
> Cc:
> Subject: [BC-BFLegacyWorks] Any advantages in removing the cat
>
>
>
> Yo!
>
> has anyone (especially UK/AU/NZ guys with EJ20 engines) ever
> tried
> removing the catalyzator (how do you write that word?) and
> measured
> (=dyno) the gain in hp?
> I was offered a complete 2,5" exhaust, all the way from the
> turbo,
> made almost entirely in stainless steel, but without the cat.
> Since
> the cat obviously is a must here, one would have to switch
pipes
> at
> least once a year for the yearly inspection, but if there
where
> two
> complete sets of pipes it wouldn't be that big a task... They
> said
> that the downpipe was made as it is on '98 rallycars, but I
> can't say
> anything to that.
> One more thing, the pipe was on a "sedan" and I have a wagon,
I
> guess
> it has to be the same car at least up to the rear axle, but is
> the
> wagon a bit longer from there on?
>
> I was just wondering if it's worth while. So do you have ANY
> ideas
> how much one could imagine to gain out of this, or any
PROs/NEEs
> at
> all?
>
> Miguelito
>
> PS. the price was ~ 150USD...
>
>
> -------------------------- eGroups Sponsor
> -------------------------~-~>
> eGroups eLerts
> It's Easy. It's Fun. Best of All, it's Free!
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[JohnnyG]

I am a qualifying Kiwi!

2.5" is ideal for an EJ20 in the 250-350hp range... 3" for any greater hp
ambitions. Using 3" for less than 300hp is actually a backward step for a
turbo.

Rip the cat off... damn the greenies! It is restrictive if you have goals
over 250hp. With that provocation stated... Yes, you will be polluting the
environment with aromatics such as benzine and tolulene and the other crap
that they stick in todays fuel... but your engine will be higher performance
/ more efficient, and you will be conserving the world's dwindling supply of
fossil fuels... so there!

The shape of the downpipe is critical... bit hard to describe, but the best
is a "bell mouth" design, that is made of two separate tube sections
"siamese" welded together that provide smooth duct-like exits for both the
turbo exhaust and wastegate. Between each of these "siamese ducts", there
should be a short "tang" extending into the union of the two ducts and also
extending iand butting into the wall of the turbo exhaust outlet... the
purpose of which is to provide extend the separation of the turbo and
wastegate exhaust flows further into the downpipe and away from the turbo.

All the above is valid for a single turbo EJ20... the twin turbo is a
completely different can of worms.

The BC-BF through to BG use the exact same floor pan on sedans and wagons...
no difference in length.

John Gillon

----- Original Message -----
From: Miguelito <awdturbodude@yahoo.com>
To: <BC-BFLegacyWorks@egroups.com>
Sent: Thursday, November 23, 2000 7:59 AM
Subject: [BC-BFLegacyWorks] Any advantages in removing the cat


> Yo!
>
> has anyone (especially UK/AU/NZ guys with EJ20 engines) ever tried
> removing the catalyzator (how do you write that word?) and measured
> (=dyno) the gain in hp?
> I was offered a complete 2,5" exhaust, all the way from the turbo,
> made almost entirely in stainless steel, but without the cat. Since
> the cat obviously is a must here, one would have to switch pipes at
> least once a year for the yearly inspection, but if there where two
> complete sets of pipes it wouldn't be that big a task... They said
> that the downpipe was made as it is on '98 rallycars, but I can't say
> anything to that.
> One more thing, the pipe was on a "sedan" and I have a wagon, I guess
> it has to be the same car at least up to the rear axle, but is the
> wagon a bit longer from there on?
>
> I was just wondering if it's worth while. So do you have ANY ideas
> how much one could imagine to gain out of this, or any PROs/NEEs at
> all?
>
> Miguelito
>
> PS. the price was ~ 150USD...
>
>
>
> To unsubscribe from this group, send an email to:
> BC-BFLegacyWorks-unsubscribe@egroups.com
>
>
>
>


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[JohnnyG]

You're abolutely correct Josh...

The twins are a lot more tricky in maintaing a balance of the turbo's A/Rs
accross the engine rev range.

..and you are correct about exhaust diameter as it applied to turbos also.
It is all about selecting the appropriate velocity of thermal expansion for
exhaust energy for a given turbo AR for a target rpm/hp, ....meaning that
bigger is not necessarily better. A 2.5" inch exhaust is quite satisfactory
for a 250-350hp target and typical street turbo Sub vehicle rpm.

...and ditch the cat.

John Gillon


----- Original Message -----
From: Josh Colombo <jcc189@psu.edu>
To: <BC-BFLegacyWorks@egroups.com>
Sent: Thursday, November 23, 2000 5:39 PM
Subject: RE: [BC-BFLegacyWorks] Any advantages in removing the cat


> Just a quick question? This isn't a twin turbo 2.0 is it? If it is,
> what I've heard is that the primary turbo is small and is easily
> over-spun. So removing the cat on the primary turbo is NOT a good idea.
> If it's just a single turbo, then by all means i'd do it, and like dave
> said, hp gains will prob vary. I know one thing also with N/A cars, if
> you go to a larger exhaust diameter, too big that is, you can sacrafice
> low end torque and power, because of no back pressure. I don't know if
> this is a concern with the turbos.
>
> Josh
>
> -----Original Message-----
> From: Miguelito
> Sent: Wed 11/22/2000 1:59 PM
> To: BC-BFLegacyWorks@egroups.com
> Cc:
> Subject: [BC-BFLegacyWorks] Any advantages in removing the cat
>
>
>
> Yo!
>
> has anyone (especially UK/AU/NZ guys with EJ20 engines) ever
> tried
> removing the catalyzator (how do you write that word?) and
> measured
> (=dyno) the gain in hp?
> I was offered a complete 2,5" exhaust, all the way from the
> turbo,
> made almost entirely in stainless steel, but without the cat.
> Since
> the cat obviously is a must here, one would have to switch pipes
> at
> least once a year for the yearly inspection, but if there where
> two
> complete sets of pipes it wouldn't be that big a task... They
> said
> that the downpipe was made as it is on '98 rallycars, but I
> can't say
> anything to that.
> One more thing, the pipe was on a "sedan" and I have a wagon, I
> guess
> it has to be the same car at least up to the rear axle, but is
> the
> wagon a bit longer from there on?
>
> I was just wondering if it's worth while. So do you have ANY
> ideas
> how much one could imagine to gain out of this, or any PROs/NEEs
> at
> all?
>
> Miguelito
>
> PS. the price was ~ 150USD...
>
>
> -------------------------- eGroups Sponsor
>
> To unsubscribe from this group, send an email to:
> BC-BFLegacyWorks-unsubscribe@egroups.com
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>
>
>
>
>
>
> To unsubscribe from this group, send an email to:
> BC-BFLegacyWorks-unsubscribe@egroups.com
>
>
>


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[Matt Scicchitano]

--- In BC-BFLegacyWorks@egroups.com, "JohnnyG" <grilla@i...> wrote:
> I am a qualifying Kiwi!
>
> 2.5" is ideal for an EJ20 in the 250-350hp range... 3" for any
greater hp
> ambitions. Using 3" for less than 300hp is actually a backward step
for a
> turbo.


John, if you can explain more on the "backward step" bit. I run a
full 3" from the turbo back to an Apex-i N1 muffler and to be honest
I can't think of one disadvantage to it. I run usually around 12psi
so I doubt my car makes more then, say, 220hp if that. Absolutely
everything improved, spool up time, throttle response, boost stability
(mostly due to the downpipe though), even "off boost" performance
which was a big surprise to me. And although I don't have a dyno
sheet, I would feel quite safe to say that torque is up throughout
the entire rev range. The only thing I can think of that is a bit of
a downer with 3 inch pipe is the price.

Personally, I would put a 3" system on any turbo car. Is it
absolutely needed in lower output cars, probably not, but my
experience with turbo's is that it surely will not hurt.


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[JohnnyG]

Well Matt,

We may have to agree to disagree... but maybe we have a misunderstanding?

My statement applies to BC-BF EJ20 Japanese version, that in stock form
produces from 220hp at about 12lb boost.... with no cat and a free-flow
style muffler, using stock turbos, only basic other modifications to intake,
engine management, etc

I can reference same opinion from owners, performance shops, exhaust
manufacturers.

John Gillon

----- Original Message -----
From: Matt Scicchitano <nzwrc1@sunlink.net>
To: <BC-BFLegacyWorks@egroups.com>
Sent: Friday, November 24, 2000 2:35 AM
Subject: [BC-BFLegacyWorks] Re: Any advantages in removing the cat


> --- In BC-BFLegacyWorks@egroups.com, "JohnnyG" <grilla@i...> wrote:
> > I am a qualifying Kiwi!
> >
> > 2.5" is ideal for an EJ20 in the 250-350hp range... 3" for any
> greater hp
> > ambitions. Using 3" for less than 300hp is actually a backward step
> for a
> > turbo.
>
>
> John, if you can explain more on the "backward step" bit. I run a
> full 3" from the turbo back to an Apex-i N1 muffler and to be honest
> I can't think of one disadvantage to it. I run usually around 12psi
> so I doubt my car makes more then, say, 220hp if that. Absolutely
> everything improved, spool up time, throttle response, boost stability
> (mostly due to the downpipe though), even "off boost" performance
> which was a big surprise to me. And although I don't have a dyno
> sheet, I would feel quite safe to say that torque is up throughout
> the entire rev range. The only thing I can think of that is a bit of
> a downer with 3 inch pipe is the price.
>
> Personally, I would put a 3" system on any turbo car. Is it
> absolutely needed in lower output cars, probably not, but my
> experience with turbo's is that it surely will not hurt.
>
>
>
> To unsubscribe from this group, send an email to:
> BC-BFLegacyWorks-unsubscribe@egroups.com
>
>
>
>


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[Matt Scicchitano]

--- In BC-BFLegacyWorks@egroups.com, "JohnnyG" <grilla@i...> wrote:
> Well Matt,
>
> We may have to agree to disagree... but maybe we have a
misunderstanding?
>
> My statement applies to BC-BF EJ20 Japanese version, that in stock
form
> produces from 220hp at about 12lb boost.... with no cat and a free-
flow
> style muffler, using stock turbos, only basic other modifications
to intake,
> engine management, etc
>


I'm not disagreeing with you really, I just was curious as to why a
3" system on a car making less then 300hp was a step backwards. My
car fits your discription perfectly(besides the fact that it has an
EJ22T and the stock ECU) so I don't think it's like comparing apples
to oranges.

I am speaking in my experiences only so opinions will surely varry,
but all the tuners I have talked to and just about everything I had
ever read in my years with messing with turbos is that the biggest
exhaust you can fit to a turbo car is the exhaust you should go with(
providing your ears and wallet can manage it). And the reasoning
behind it is that ANY backpressure will hamper ANY turbo's
ability to spool. I can possibly see the reasoning that some
backpressure may be good for a turbo when you are off boost, but as I
said earlier, in my case, this simply wasn't true.

I do agree that on many low-output turbo cars, switching from a free
flow 2.5" system to a free flow 3" system may only produce more noise
then anything, so it may indeed be a total waste of money for someone
to do so, but I can't see how it would be a step "backwards" in
performance terms.

-Matt


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[penty]

Can I join ?

Lets say having a huge 2" exhaust on a turbo'd 250 cc engine (just an example) then that would make it a gutless high revver, you should be able to apply the same to a turbo engine aswell so sticking a.... for example 3 " exhaust onto a turbo ScoobyDoo may have the same although not as drastic effect.

So in the above case with the 250cc how could "bigger is always better apply"

I think there must be a size on all engines that if you pass it results in not enough back pressure and poor high revving power.


I'm probably talking poo but in my head it seems to make sense

cheers

John


----- Original Message -----
From: Matt <mailto:nzwrc1@sunlink.net> Scicchitano
To: BC-BFLegacyWorks@egroups.com
Sent: Thursday, November 23, 2000 2:26 PM
Subject: [BC-BFLegacyWorks] Re: Any advantages in removing the cat

--- In BC-BFLegacyWorks@egroups.com, "JohnnyG" < grilla@i...> wrote:
> Well Matt,
>
> We may have to agree to disagree... but maybe we have a
misunderstanding?
>
> My statement applies to BC-BF EJ20 Japanese version, that in stock
form
> produces from 220hp at about 12lb boost.... with no cat and a free-
flow
> style muffler, using stock turbos, only basic other modifications
to intake,
> engine management, etc
>


I'm not disagreeing with you really, I just was curious as to why a
3" system on a car making less then 300hp was a step backwards. My
car fits your discription perfectly(besides the fact that it has an
EJ22T and the stock ECU) so I don't think it's like comparing apples
to oranges.

I am speaking in my experiences only so opinions will surely varry,
but all the tuners I have talked to and just about everything I had
ever read in my years with messing with turbos is that the biggest
exhaust you can fit to a turbo car is the exhaust you should go with(
providing your ears and wallet can manage it). And the reasoning
behind it is that ANY backpressure will hamper ANY turbo's
ability to spool. I can possibly see the reasoning that some
backpressure may be good for a turbo when you are off boost, but as I
said earlier, in my case, this simply wasn't true.

I do agree that on many low-output turbo cars, switching from a free
flow 2.5" system to a free flow 3" system may only produce more noise
then anything, so it may indeed be a total waste of money for someone
to do so, but I can't see how it would be a step "backwards" in
performance terms.

-Matt


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[Nigel White]

I believe that this idea of backpressure being good for low end power is an unfortunate myth. How can something that restricts the flow of exhaust gases be good? I think what we should really be talking about is exhaust gas velocity. Long, narrow pipes are critical for obtaining the exhaust gas velocity necessary for low rpm combustion chamber scavenging (drawing exhaust gases out to make room for intake charge). The increased backpressure due to a smaller pipe, at low rpm is outweighed by the advantage of higher exhaust gas velocity. Unfortunately, it seems that people have associated this increased backpressure as being responsible for for better low end power, instead of increased gas velocity.

Now, with a turbo engine, scavenging is not an issue because you have a compressor to force the intake charge into the chamber and push the exhaust gases out. Consequently, you want as little restriction as possible for the exhaust gases so the turbine can be spun as efficiently as possible. The best exhaust for a turbocharged engine is no exhaust!


Nigel


penty wrote:


Can I join ? Lets say having a huge 2" exhaust on a turbo'd 250 cc engine (just an example) then that would make it a gutless high revver, you should be able to apply the same to a turbo engine aswell so sticking a.... for example 3 " exhaust onto a turbo ScoobyDoo may have the same although not as drastic effect. So in the above case with the 250cc how could "bigger is always better apply" I think there must be a size on all engines that if you pass it results in not enough back pressure and poor high revving power. I'm probably talking poo but in my head it seems to make sense cheers John

----- Original Message -----
From: Matt Scicchitano <mailto:nzwrc1@sunlink.net>
To: BC-BFLegacyWorks@egroups.com
Sent: Thursday, November 23, 2000 2:26 PM
Subject: [BC-BFLegacyWorks] Re: Any advantages in removing the cat
--- In BC-BFLegacyWorks@egroups.com, "JohnnyG" < grilla@i...> wrote:
> Well Matt,
>
> We may have to agree to disagree... but maybe we have a
misunderstanding?
>
> My statement applies to BC-BF EJ20 Japanese version, that in stock
form
> produces from 220hp at about 12lb boost.... with no cat and a free-
flow
> style muffler, using stock turbos, only basic other modifications
to intake,
> engine management, etc
>


I'm not disagreeing with you really, I just was curious as to why a
3" system on a car making less then 300hp was a step backwards. My
car fits your discription perfectly(besides the fact that it has an
EJ22T and the stock ECU) so I don't think it's like comparing apples
to oranges.


I am speaking in my experiences only so opinions will surely varry,
but all the tuners I have talked to and just about everything I had
ever read in my years with messing with turbos is that the biggest
exhaust you can fit to a turbo car is the exhaust you should go with(
providing your ears and wallet can manage it). And the reasoning
behind it is that ANY backpressure will hamper ANY turbo's
ability to spool. I can possibly see the reasoning that some
backpressure may be good for a turbo when you are off boost, but as I
said earlier, in my case, this simply wasn't true.


I do agree that on many low-output turbo cars, switching from a free
flow 2.5" system to a free flow 3" system may only produce more noise
then anything, so it may indeed be a total waste of money for someone
to do so, but I can't see how it would be a step "backwards" in
performance terms.


-Matt



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[josh]

Nigel, I'm not an expert, but I still do think either back pressure or something is needed. I know on my 90 legacy N/A when I put the intake on, I did notice a SLIGHT decrease in the lower end. I wouldn't say it was much if any, just different, but she screams at the top end. I know this is the other side of the engine, but the theory is somewhat similar, and is probably different with turbos. But I'm pretty sure N/A engines need a little backpressure.

Josh

-----Original Message-----
From: Nigel White [mailto:nigelw@worldwise.ca]
Sent: Thursday, November 23, 2000 1:55 PM
To: BC-BFLegacyWorks@egroups.com
Subject: Re: [BC-BFLegacyWorks] Re: Any advantages in removing the cat


I believe that this idea of backpressure being good for low end power is an unfortunate myth. How can something that restricts the flow of exhaust gases be good? I think what we should really be talking about is exhaust gas velocity. Long, narrow pipes are critical for obtaining the exhaust gas velocity necessary for low rpm combustion chamber scavenging (drawing exhaust gases out to make room for intake charge). The increased backpressure due to a smaller pipe, at low rpm is outweighed by the advantage of higher exhaust gas velocity. Unfortunately, it seems that people have associated this increased backpressure as being responsible for for better low end power, instead of increased gas velocity.

Now, with a turbo engine, scavenging is not an issue because you have a compressor to force the intake charge into the chamber and push the exhaust gases out. Consequently, you want as little restriction as possible for the exhaust gases so the turbine can be spun as efficiently as possible. The best exhaust for a turbocharged engine is no exhaust!


Nigel


penty wrote:


Can I join ? Lets say having a huge 2" exhaust on a turbo'd 250 cc engine (just an example) then that would make it a gutless high revver, you should be able to apply the same to a turbo engine aswell so sticking a.... for example 3 " exhaust onto a turbo ScoobyDoo may have the same although not as drastic effect. So in the above case with the 250cc how could "bigger is always better apply" I think there must be a size on all engines that if you pass it results in not enough back pressure and poor high revving power. I'm probably talking poo but in my head it seems to make sense cheers John

----- Original Message -----
From: Matt <mailto:nzwrc1@sunlink.net> Scicchitano
To: BC-BFLegacyWorks@egroups.com
Sent: Thursday, November 23, 2000 2:26 PM
Subject: [BC-BFLegacyWorks] Re: Any advantages in removing the cat
--- In BC-BFLegacyWorks@egroups.com, "JohnnyG" < grilla@i...> wrote:
> Well Matt,
>
> We may have to agree to disagree... but maybe we have a
misunderstanding?
>
> My statement applies to BC-BF EJ20 Japanese version, that in stock
form
> produces from 220hp at about 12lb boost.... with no cat and a free-
flow
> style muffler, using stock turbos, only basic other modifications
to intake,
> engine management, etc
>


I'm not disagreeing with you really, I just was curious as to why a
3" system on a car making less then 300hp was a step backwards. My
car fits your discription perfectly(besides the fact that it has an
EJ22T and the stock ECU) so I don't think it's like comparing apples
to oranges.


I am speaking in my experiences only so opinions will surely varry,
but all the tuners I have talked to and just about everything I had
ever read in my years with messing with turbos is that the biggest
exhaust you can fit to a turbo car is the exhaust you should go with(
providing your ears and wallet can manage it). And the reasoning
behind it is that ANY backpressure will hamper ANY turbo's
ability to spool. I can possibly see the reasoning that some
backpressure may be good for a turbo when you are off boost, but as I
said earlier, in my case, this simply wasn't true.


I do agree that on many low-output turbo cars, switching from a free
flow 2.5" system to a free flow 3" system may only produce more noise
then anything, so it may indeed be a total waste of money for someone
to do so, but I can't see how it would be a step "backwards" in
performance terms.


-Matt



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[Nigel White]

Like exhaust gases, the velocity of intake gasses is also an issue,
but not backpressure. A long narrow intake system is going to result
in higher intake gas velocity, which is helpfull for low rpm power.
This introduces backpressure. But again, this is outweighed by the
improved gas velocity. A wider, shorter intake will flow better at
high rpm, because there is less restriction and the gasses need less
assistance to maintain velocity.

Remember, an engine is basicaly an air pump. Whatever you can do to
keep air moving through it as quickly as possible is the goal.
Anything that restricts this process is bad, and that includes
backpressure. In a normaly aspirated high performance engine, this
means that you want the valves open for as long as possible with wide,
short intake and exhaust plumbing to keep the gases moving. But, at
low rpm, this means that the gases just can't keep up the momentum.
This is why a high performance engine can barely maintain an idle if
at all. So, for street engines, we compromise with less valve
duration and overlap, and longer, narower intake and exhaust plumbing
to help build some gas velocity at low rpm.

I'm sure you've noticed that many car makers today have been trying to
develop systems that alow an engine to function at both ends of the
spectrum, with technologies like variable valve timing and variable
length intake runners to name two. Of course, with a turbo or
supercharger, all of this is not so much of an issue because you have
an aditional pump to keep the air moving.

This being said, I'm no expert myself. But I think my reasoning is
sound, and I can back it up with scientific principles, as best as I
understand them. If anyone can dispute my claims, I welcome that!

That's all for tonight!

Cheers

Nigel

--- In BC-BFLegacyWorks@egroups.com, "josh" <jcc189@p...> wrote:
> Nigel, I'm not an expert, but I still do think either back pressure
or
> something is needed. I know on my 90 legacy N/A when I put the
intake on, I
> did notice a SLIGHT decrease in the lower end. I wouldn't say it
was much
> if any, just different, but she screams at the top end. I know this
is the
> other side of the engine, but the theory is somewhat similar, and is
> probably different with turbos. But I'm pretty sure N/A engines
need a
> little backpressure.
>
> Josh
> -----Original Message-----
> From: Nigel White [mailto:nigelw@w...]
> Sent: Thursday, November 23, 2000 1:55 PM
> To: BC-BFLegacyWorks@egroups.com
> Subject: Re: [BC-BFLegacyWorks] Re: Any advantages in removing the
cat
>
>


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[JohnnyG]

Matt, I can't remember exactly what model / size turbo you have, but
generally speaking if you...

- develop around 220hp
- use your car as street driver

...you are probably a bit big in your exhaust system

A guy called Corky Bell has written a book on the subject, and one of his
graphs is referenced here...
http://members.fortunecity.com/spasmodi ... xhaust.htm
You can reference further information on the subject from...
http://www.speed.org.nz/garage/common_m ... urbos.html

Too large a diameter pipe does not have any exhaust velocity or extractor
effect until very high rpm. Removing all the backpressure from a system will
allow the turbo to breathe more efficiently once it is on boost, but it will
generally delay the turbo from coming on boost. The Catch-22 here is that
the engine off boost needs a certain amount of backpressure to develop the
exhaust flow that will allow the Turbo to spool-up. You need to compromise
with an exhaust size that will allow the car to run correctly over its
entire RPM range. In the case of a street and strip EJ20 that size is 2.5"
with or without a Cat. If you have a huge Turbo and just want to make
monster boost and HP and don't give a crap about driveability or performance
below 4000 rpm, hey, go for it. 3" pipe is the answer. In an unlimited
situation where max power and flow is the consideration and driveability is
no issue than a bigger free flow system is the answer.

An efficient turbo set up will have somewhere near a 2:1 pressure
differential across the engine. In other words, if your making 10 lbs. of
boost, you'll have about 20 lbs. of exhaust gas pressure before the turbo.
Some good full race set ups can get things closer to a 1.5:1, but this takes
a lot of research and testing, if you can get close to 2:1 on a street turbo
set up, you're doing good. But it is all about balance... bigger is not
necessarily better, depending on your application and driving style.

John Gillon

----- Original Message -----
From: Matt Scicchitano <nzwrc1@sunlink.net>
To: <BC-BFLegacyWorks@egroups.com>
Sent: Friday, November 24, 2000 2:35 AM
Subject: [BC-BFLegacyWorks] Re: Any advantages in removing the cat


> --- In BC-BFLegacyWorks@egroups.com, "JohnnyG" <grilla@i...> wrote:
> > I am a qualifying Kiwi!
> >
> > 2.5" is ideal for an EJ20 in the 250-350hp range... 3" for any
> greater hp
> > ambitions. Using 3" for less than 300hp is actually a backward step
> for a
> > turbo.
>
>
> John, if you can explain more on the "backward step" bit. I run a
> full 3" from the turbo back to an Apex-i N1 muffler and to be honest
> I can't think of one disadvantage to it. I run usually around 12psi
> so I doubt my car makes more then, say, 220hp if that. Absolutely
> everything improved, spool up time, throttle response, boost stability
> (mostly due to the downpipe though), even "off boost" performance
> which was a big surprise to me. And although I don't have a dyno
> sheet, I would feel quite safe to say that torque is up throughout
> the entire rev range. The only thing I can think of that is a bit of
> a downer with 3 inch pipe is the price.
>
> Personally, I would put a 3" system on any turbo car. Is it
> absolutely needed in lower output cars, probably not, but my
> experience with turbo's is that it surely will not hurt.
>
>
>
> To unsubscribe from this group, send an email to:
> BC-BFLegacyWorks-unsubscribe@egroups.com
>
>
>
>


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[JohnnyG]

Well we can debate the point Matt, 8^p

> I'm not disagreeing with you really, I just was curious as to why a
> 3" system on a car making less then 300hp was a step backwards. My
> car fits your discription perfectly(besides the fact that it has an
> EJ22T and the stock ECU) so I don't think it's like comparing apples
> to oranges.

I am unfamiliar with the EJ22T as the USA was the only market, but as I
understand them, they originally had a low-boost setup and would it be true
that the turbo is even smaller than an EJ20? ...if so, my argument is more
correct.


> I am speaking in my experiences only so opinions will surely varry,
> but all the tuners I have talked to and just about everything I had
> ever read in my years with messing with turbos is that the biggest
> exhaust you can fit to a turbo car is the exhaust you should go
h(
> providing your ears and wallet can manage it).

A fallacy... for wide rev range and street application. True if you working in the upper rev range most of the time.

> behind it is that ANY backpressure will hamper ANY turbo's
> ability to spool. I can possibly see the reasoning that some
> backpressure may be good for a turbo when you are off boost, but as I
> said earlier, in my case, this simply wasn't true.

A ":little" back pressure is desirable for street applications.

> I do agree that on many low-output turbo cars, switching from a free
> flow 2.5" system to a free flow 3" system may only produce more noise
> then anything, so it may indeed be a total waste of money for someone
> to do so, but I can't see how it would be a step "backwards" in
> performance terms.

OK, in all-out performance terms ... Yes, you are correct.... but sacrificing off-boost / lower rev range and drivability.

John Gillon




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[JohnnyG]

Nigel,

All true for peak performance in the high rev range... but your off-boost / low rev performance in street use suffers. It is a compromise....

John Gillon

----- Original Message -----
From: Nigel White <mailto:nigelw@worldwise.ca>
To: BC-BFLegacyWorks@egroups.com
Sent: Friday, November 24, 2000 7:55 AM
Subject: Re: [BC-BFLegacyWorks] Re: Any advantages in removing the cat

I believe that this idea of backpressure being good for low end power is an unfortunate myth. How can something that restricts the flow of exhaust gases be good? I think what we should really be talking about is exhaust gas velocity. Long, narrow pipes are critical for obtaining the exhaust gas velocity necessary for low rpm combustion chamber scavenging (drawing exhaust gases out to make room for intake charge). The increased backpressure due to a smaller pipe, at low rpm is outweighed by the advantage of higher exhaust gas velocity. Unfortunately, it seems that people have associated this increased backpressure as being responsible for for better low end power, instead of increased gas velocity.

Now, with a turbo engine, scavenging is not an issue because you have a compressor to force the intake charge into the chamber and push the exhaust gases out. Consequently, you want as little restriction as possible for the exhaust gases so the turbine can be spun as efficiently as possible. The best exhaust for a turbocharged engine is no exhaust!


Nigel


penty wrote:


Can I join ? Lets say having a huge 2" exhaust on a turbo'd 250 cc engine (just an example) then that would make it a gutless high revver, you should be able to apply the same to a turbo engine aswell so sticking a.... for example 3 " exhaust onto a turbo ScoobyDoo may have the same although not as drastic effect. So in the above case with the 250cc how could "bigger is always better apply" I think there must be a size on all engines that if you pass it results in not enough back pressure and poor high revving power. I'm probably talking poo but in my head it seems to make sense cheers John

----- Original Message -----
From: Matt <mailto:nzwrc1@sunlink.net> Scicchitano
To: BC-BFLegacyWorks@egroups.com
Sent: Thursday, November 23, 2000 2:26 PM
Subject: [BC-BFLegacyWorks] Re: Any advantages in removing the cat
--- In BC-BFLegacyWorks@egroups.com, "JohnnyG" < grilla@i...> wrote:
> Well Matt,
>
> We may have to agree to disagree... but maybe we have a
misunderstanding?
>
> My statement applies to BC-BF EJ20 Japanese version, that in stock
form
> produces from 220hp at about 12lb boost.... with no cat and a free-
flow
> style muffler, using stock turbos, only basic other modifications
to intake,
> engine management, etc
>


I'm not disagreeing with you really, I just was curious as to why a
3" system on a car making less then 300hp was a step backwards. My
car fits your discription perfectly(besides the fact that it has an
EJ22T and the stock ECU) so I don't think it's like comparing apples
to oranges.


I am speaking in my experiences only so opinions will surely varry,
but all the tuners I have talked to and just about everything I had
ever read in my years with messing with turbos is that the biggest
exhaust you can fit to a turbo car is the exhaust you should go with(
providing your ears and wallet can manage it). And the reasoning
behind it is that ANY backpressure will hamper ANY turbo's
ability to spool. I can possibly see the reasoning that some
backpressure may be good for a turbo when you are off boost, but as I
said earlier, in my case, this simply wasn't true.


I do agree that on many low-output turbo cars, switching from a free
flow 2.5" system to a free flow 3" system may only produce more noise
then anything, so it may indeed be a total waste of money for someone
to do so, but I can't see how it would be a step "backwards" in
performance terms.


-Matt



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[Rod]

i don't want to get into a huge debate over which theory is correct but the
biggest difference i noticed when upgrading from 2.5" system with std rear
muffler to a full 3"system from MRT, here in Australia, is driveability at
low rpm. the car is much better to drive in stop start traffic. it also
spools up quicker than before and the boost seems to come on more smoothly
than in a rush. HP increase is but one advantage, debateable here, but the
other advantages make a huge difference.
regards, rod.
----- Original Message -----
From: "JohnnyG" <grilla@ihug.co.nz>
To: <BC-BFLegacyWorks@egroups.com>
Sent: Saturday, November 25, 2000 7:29 PM
Subject: Re: [BC-BFLegacyWorks] Re: Any advantages in removing the cat


>
> Well we can debate the point Matt, 8^p
>
> > I'm not disagreeing with you really, I just was curious as to why a
> > 3" system on a car making less then 300hp was a step backwards. My
> > car fits your discription perfectly(besides the fact that it has an
> > EJ22T and the stock ECU) so I don't think it's like comparing apples
> > to oranges.
>
> I am unfamiliar with the EJ22T as the USA was the only market, but as I
> understand them, they originally had a low-boost setup and would it be
true
> that the turbo is even smaller than an EJ20? ...if so, my argument is more
> correct.
>
>
> > I am speaking in my experiences only so opinions will surely varry,
> > but all the tuners I have talked to and just about everything I had
> > ever read in my years with messing with turbos is that the biggest
> > exhaust you can fit to a turbo car is the exhaust you should go
>

> > providing your ears and wallet can manage it).
>
> A fallacy... for wide rev range and street application. True if you
working in the upper rev range most of the time.
>
> > behind it is that ANY backpressure will hamper ANY turbo's
> > ability to spool. I can possibly see the reasoning that some
> > backpressure may be good for a turbo when you are off boost, but as I
> > said earlier, in my case, this simply wasn't true.
>
> A ":little" back pressure is desirable for street applications.
>
> > I do agree that on many low-output turbo cars, switching from a free
> > flow 2.5" system to a free flow 3" system may only produce more noise
> > then anything, so it may indeed be a total waste of money for someone
> > to do so, but I can't see how it would be a step "backwards" in
> > performance terms.
>
> OK, in all-out performance terms ... Yes, you are correct.... but
sacrificing off-boost / lower rev range and drivability.
>
> John Gillon
>
>
>
>
>
> To unsubscribe from this group, send an email to:
> BC-BFLegacyWorks-unsubscribe@egroups.com
>
>
>


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[Matt Scicchitano]

>
> OK, in all-out performance terms ... Yes, you are correct.... but
sacrificing off-boost / lower rev range and drivability.
>
> John Gillon


John, this is exactly what I (and Rod) said DIDN'T happen, again, "in
my experience", . Off-boost performance IMPROVED making it much nicer
in the lower rev range around town.This was probably the biggest
shocker to me since I figured going to a full 3" system with nothing
but an N1, I thought surely what little lower end I had would
disappear...Absolutley positively not true. And as far as the turbo
spooling, it nows spools instantly, and I do mean instantly and
overall throttle response has improved greatly. I would guess that
although the exhaust AFTER the turbo does help somewhat in making the
turbo spool( not LETTING it spool more freely which is the exhaust's
main objective), the headers have much much more effect on building
the adequet pressure to spool the turbine. And yes I do agree that in
getting the turbo to spin, the size, shape, etc. of the headers play
and absolutely vital role in doing so, and in that case, bigger is in
no way, shape, or form, better.

I am not disputing your findings or Corky Bell's knowledge of turbos(
which in recent years have been debated, but that's another story).
What I am doing is telling you what worked for me on my Legacy Turbo.
Not theories or assumtions, but what actually happened. Basically you
said that in going with a 3" system on a low-output turbo car( under
300hp), the turbo will take longer to spool and low-end driveability
will be sacrificed. I'm saying that those things did not happen when
I installed my 3" system, and actually everything improved. Granted,
I did not go from an identical 2.5" system to my 3" system( mandrel
bent, no cats, Apex-i N1), BUT, as fast as my turbo now spools up and
as much as my off-boost and lower-end and throttle response improved
compared to my old 2.5" system, I can't see how down-grading to an
indetical 2.5" system will net better results, nor will I ever find
out. But, if someone were to ask " should I go with a 2.5" or 3"
exhaust on my Legacy Turbo?", again, going on my experience, I would
recommend a 3" every time, no matter what Mr. Bell says ;^)

-Matt


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[JohnnyG]

OK Matt,

All I'm saying is if we were to make a fairer comparison of an 2.5" system
"equivalent" to your 3" system, your off-boost performance would be even
better, and with you current power output, you would notice any impact on
top range rpm.

My beliefs are based on many other local Sub enthusiasts, and a local
manufacturer of exhaust systems... that all support this.

...if it works for you ...be happy

John Gillon

----- Original Message -----
From: Matt Scicchitano <nzwrc1@sunlink.net>
To: <BC-BFLegacyWorks@egroups.com>
Sent: Sunday, November 26, 2000 11:53 AM
Subject: [BC-BFLegacyWorks] Re: Any advantages in removing the cat


>
> >
> > OK, in all-out performance terms ... Yes, you are correct.... but
> sacrificing off-boost / lower rev range and drivability.
> >
> > John Gillon
>
>
> John, this is exactly what I (and Rod) said DIDN'T happen, again, "in
> my experience", . Off-boost performance IMPROVED making it much nicer
> in the lower rev range around town.This was probably the biggest
> shocker to me since I figured going to a full 3" system with nothing
> but an N1, I thought surely what little lower end I had would
> disappear...Absolutley positively not true. And as far as the turbo
> spooling, it nows spools instantly, and I do mean instantly and
> overall throttle response has improved greatly. I would guess that
> although the exhaust AFTER the turbo does help somewhat in making the
> turbo spool( not LETTING it spool more freely which is the exhaust's
> main objective), the headers have much much more effect on building
> the adequet pressure to spool the turbine. And yes I do agree that in
> getting the turbo to spin, the size, shape, etc. of the headers play
> and absolutely vital role in doing so, and in that case, bigger is in
> no way, shape, or form, better.
>
> I am not disputing your findings or Corky Bell's knowledge of
bos(
> which in recent years have been debated, but that's another story).
> What I am doing is
telling you what worked for me on my Legacy Turbo.
> Not theories or assumtions, but what actually happened. Basically you
> said that in going with a 3" system on a low-output turbo car( under
> 300hp), the turbo will take longer to spool and low-end driveability
> will be sacrificed. I'm saying that those things did not happen when
> I installed my 3" system, and actually everything improved. Granted,
> I did not go from an identical 2.5" system to my 3" system( mandrel
> bent, no cats, Apex-i N1), BUT, as fast as my turbo now spools up and
> as much as my off-boost and lower-end and throttle response improved
> compared to my old 2.5" system, I can't see how down-grading to an
> indetical 2.5" system will net better results, nor will I ever find
> out. But, if someone were to ask " should I go with a 2.5" or 3"
> exhaust on my Legacy Turbo?", again, going on my experience, I would
> recommend a 3" every time, no matter what Mr. Bell says ;^)
>
> -Matt
>
>
>
> To unsubscribe from this group, send an email to:
> BC-BFLegacyWorks-unsubscribe@egroups.com
>
>
>
>



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[Matt Scicchitano]

.
>
> ...if it works for you ...be happy


Fair enough John. Just to be clear, I do respect your opinions on the
whole exhaust diameter issue, but as you said in the end, I couldn't
be happier with my current set-up, and I'm sure you feel the same
with yours, so we'll leave it at that

-Matt


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