BOV
Posted: Mon Nov 27, 2000 1:48 pm
Subaru uses a small cheap plastic compressor bypass valve. When the
throttle plate is closed (such as when you are shifting) and there is
boost trapped between the turbo and the throttle plate, it caused the
turbo to bog and when you touch the throttle again, this trapped boost
causes an unpleasant bucking and surge. I have heard this called
"trailering" because it feels amazing like what you experience when
pulling a trailer that is trying to be in control of your car. A CBV
opens when there is vacuum on the engine side of the throttle plate and
pressure on the air cleaner side. It routs the boost back to just
upstream of your turbo so the turbo keeps spinning and doesn't bog. The
need for a CBV or a BOV increases as boost increases. You can get away
without one under about 5psi, but they are absolutely essential above
10psi. When your CBV is blowing open from too much pressure, it sounds
like someone blowing across a jug. A failing CBV causes the car to
surge at high boost. I added a bigger spring to mine and glued it back
together, with mixed results.
I like to use Blow-off Valve (BOV) to describe one that dumps to
atmosphere and Compressor Bypass Valve (CBV) to describe one that routs
back upstream. Onve air has passed my Mass Airflow Sensor (MAF), then I
want it accounted for all the way out the exhaust pipe. I don't want my
ECU to get confused by "inventory shrinkage" i.e. air that was there at
the MAF, but not part of the air/fuel mixture, so I am a CBV man. They
are identical valves, just plumbed differently. In BOV mode, they make
a wierd prprprprprpr "bird call" noise when you back off. I have a
$200, big purple adjustable TURBO-XS model from Oz. The cheapest
reasonable alternative is to get one from a Diamond Star triplet
(Mitsubishi Eclipse, Talon, Laser). The old aluminum ones are slightly
better than the new plastic ones, but both are considerably more robust
than Subarus. A stock EJ20G CBV is identical to a stock EJ22T CBV.
Both are shit.
Love
Bill Robinson
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throttle plate is closed (such as when you are shifting) and there is
boost trapped between the turbo and the throttle plate, it caused the
turbo to bog and when you touch the throttle again, this trapped boost
causes an unpleasant bucking and surge. I have heard this called
"trailering" because it feels amazing like what you experience when
pulling a trailer that is trying to be in control of your car. A CBV
opens when there is vacuum on the engine side of the throttle plate and
pressure on the air cleaner side. It routs the boost back to just
upstream of your turbo so the turbo keeps spinning and doesn't bog. The
need for a CBV or a BOV increases as boost increases. You can get away
without one under about 5psi, but they are absolutely essential above
10psi. When your CBV is blowing open from too much pressure, it sounds
like someone blowing across a jug. A failing CBV causes the car to
surge at high boost. I added a bigger spring to mine and glued it back
together, with mixed results.
I like to use Blow-off Valve (BOV) to describe one that dumps to
atmosphere and Compressor Bypass Valve (CBV) to describe one that routs
back upstream. Onve air has passed my Mass Airflow Sensor (MAF), then I
want it accounted for all the way out the exhaust pipe. I don't want my
ECU to get confused by "inventory shrinkage" i.e. air that was there at
the MAF, but not part of the air/fuel mixture, so I am a CBV man. They
are identical valves, just plumbed differently. In BOV mode, they make
a wierd prprprprprpr "bird call" noise when you back off. I have a
$200, big purple adjustable TURBO-XS model from Oz. The cheapest
reasonable alternative is to get one from a Diamond Star triplet
(Mitsubishi Eclipse, Talon, Laser). The old aluminum ones are slightly
better than the new plastic ones, but both are considerably more robust
than Subarus. A stock EJ20G CBV is identical to a stock EJ22T CBV.
Both are shit.
Love
Bill Robinson
-------------------------- eGroups Sponsor -------------------------~-~>
eGroups eLerts
It's Easy. It's Fun. Best of All, it's Free!
http://click.egroups.com/1/9698/1/_/_/_/975348706/
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BC-BFLegacyWorks-unsubscribe@egroups.com
