Questions about my cobalt's performance
03-14-2012, 01:06 PM
#30
Senior Member
You got it backwards. An open exhaust system will cause boost to drop. Since there's less restriction on the hot side, the blower doesn't build as much pressure. Freeing up the intake side (pre-blower), however, will cause boost to go up. Think of it as trying to blow through a straw (a lot of restriction) then trying to blow through a piece of PVC (virtually no restriction). Pressure inside the PVC is a lot lower than inside the straw. Same principle applies here.
OP: If you're boosting to 20psi, you are either running a 2.7 or smaller ( I saw 17psi on my 2.7 before the belt blew up), or you have a massively clogged cat causing serious restriction and therefore uber boost
OP: If you're boosting to 20psi, you are either running a 2.7 or smaller ( I saw 17psi on my 2.7 before the belt blew up), or you have a massively clogged cat causing serious restriction and therefore uber boost
Yes
M62 = Air Pump
Pump = Create flow
Restriction = Create Pressure
Naturally the harder and engine works the more resistance there is, thus higher intake manifold pressures. If you never modify the engine, and always run it at the same RPM you could use your boost gauge as a measurment of howh ard the engine is working.
Free up the exhaust, the engine doesnt have to work as hard to expell the exhaust, your boost levels go down...
When I got my ZZP Header/Downpipe installed I boosted 17PSI (2.85" Pulley) With stock exhaust, and 15-16 PSI with the ZZP exhaust. Also went from 232 whp to 239 whp just adding the ZZP Long tube header/downpipe combo.
Only ever went to the track once, and I hit 18 PSI on the track, that was after the ZZP Exhaust. Seeing as everything ealse was the same, even RPM (Ran to 7K) I can comfortable say that my car put down more HP on the track then it did to the dyno. Not sure why that happens, Guess thats why people say real numbers come from the track insteadof the dyno.
03-14-2012, 10:29 PM
#39
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There is a strong Cobalt community in Chicago, with a couple guys who know these things inside and out.
Join facebook.com/ChicagoEcotec
Post up, they can help you out. Will probably even offer to come check the car out in person and really see what is up with it.
Join facebook.com/ChicagoEcotec
Post up, they can help you out. Will probably even offer to come check the car out in person and really see what is up with it.
03-14-2012, 10:30 PM
#40
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Kinda far-fetched but what if there's a damper installed it could cause him to be boosting higher on a s2 pulley. I'm not real familiar on how they work or I'd offer more info, but I know ZZP advertises that the "GM ECOTEC Super Damper" will effectively drop a pulley size without dropping a pulley size. That would be about right.....
3.0"-->2.8" = 15#-->20#
3.0"-->2.8" = 15#-->20#
03-14-2012, 10:49 PM
#41
well considering a 2.4 and a 2.6 pully on a m62 only makes 12lbs of boost but this guys problem is something is pluged either the cat or the muffler
you are way off dropping 1 size isent gonna give 5lbs or so increase and i would bet that it still has the stock dampner
nice wheels and a good idea
Kinda far-fetched but what if there's a damper installed it could cause him to be boosting higher on a s2 pulley. I'm not real familiar on how they work or I'd offer more info, but I know ZZP advertises that the "GM ECOTEC Super Damper" will effectively drop a pulley size without dropping a pulley size. That would be about right.....
3.0"-->2.8" = 15#-->20#
3.0"-->2.8" = 15#-->20#
nice wheels and a good idea
Last edited by mrbelvedere; 03-14-2012 at 10:49 PM. Reason: Automerged Doublepost
03-14-2012, 11:06 PM
#42
Premium Member
Get the rest of the parts you need to be just turbo or sell them.
03-14-2012, 11:27 PM
#43
Yes
M62 = Air Pump
Pump = Create flow
Restriction = Create Pressure
Naturally the harder and engine works the more resistance there is, thus higher intake manifold pressures. If you never modify the engine, and always run it at the same RPM you could use your boost gauge as a measurment of howh ard the engine is working.
Free up the exhaust, the engine doesnt have to work as hard to expell the exhaust, your boost levels go down...
When I got my ZZP Header/Downpipe installed I boosted 17PSI (2.85" Pulley) With stock exhaust, and 15-16 PSI with the ZZP exhaust. Also went from 232 whp to 239 whp just adding the ZZP Long tube header/downpipe combo.
Only ever went to the track once, and I hit 18 PSI on the track, that was after the ZZP Exhaust. Seeing as everything ealse was the same, even RPM (Ran to 7K) I can comfortable say that my car put down more HP on the track then it did to the dyno. Not sure why that happens, Guess thats why people say real numbers come from the track insteadof the dyno.
M62 = Air Pump
Pump = Create flow
Restriction = Create Pressure
Naturally the harder and engine works the more resistance there is, thus higher intake manifold pressures. If you never modify the engine, and always run it at the same RPM you could use your boost gauge as a measurment of howh ard the engine is working.
Free up the exhaust, the engine doesnt have to work as hard to expell the exhaust, your boost levels go down...
When I got my ZZP Header/Downpipe installed I boosted 17PSI (2.85" Pulley) With stock exhaust, and 15-16 PSI with the ZZP exhaust. Also went from 232 whp to 239 whp just adding the ZZP Long tube header/downpipe combo.
Only ever went to the track once, and I hit 18 PSI on the track, that was after the ZZP Exhaust. Seeing as everything ealse was the same, even RPM (Ran to 7K) I can comfortable say that my car put down more HP on the track then it did to the dyno. Not sure why that happens, Guess thats why people say real numbers come from the track insteadof the dyno.
03-15-2012, 07:41 AM
#46
https://www.youtube.com/watch?v=BGle...e_gdata_player
not the greatest video quality but it'll give you an idea
not the greatest video quality but it'll give you an idea
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