Boost? What Boost?
08-03-2010, 07:55 PM
#1
Staging Lane
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Boost? What Boost? So the mods are below in the sig and its pretty much the way I bought the car. I noticed immediately that the autometer gauge on the a-pillar wasn't showing positive boost pressure, only vac and 0 psi under load at WOT. I did the following:
- Checked all T connectors on the vac and replaced 2 that were leaking under pressure
- Replaced the cheap-o Bosch diaphragm bypass valve with an adjustable brass piston replacement.
- Replaced PCV valve found to be leaking under pressure
- Replaced EGR gasket found to be leaking under pressure. It still leaks above 6 psi because it's a 98 LS1 intake manifold and only has 1 bolt instead of 2 so it rocks, but is able to hold 6 psi and below (at least while the engine is off and being pressurized externally).
- Checked all couplers for proper fit, adjusted and tightened.
- Replaced Procharger standard 2-core fmic with a Mishimoto G series because the Procharger was found to be leaking under pressure test.
- Verified the supercharger is producing > 11 psi when tested at the supercharger outlet on even less then a full dyno pull
- Manually pressureized the system by taking the pipe off the supercharger outlet, capping it off, and adding air pressure to the entire system including the motor to verify there were no leaks (other than through open exhaust valves).
- Verified the gauge inside the car is working via manually pressurization.
STILL
No boost on the road under load at 5-6k RPM at WOT. I can maybe squeak a piece past 0 psi, but not enough to confidently call it 2 psi, maybe 1. The blower pulley appears to be a 3". Also note the shorter gears and the non-stock cam. Additionally, the piping is 2.5" and I know most run 3", although I can't see how this would cause a pressure loss.
What am I missing here?
- Checked all T connectors on the vac and replaced 2 that were leaking under pressure
- Replaced the cheap-o Bosch diaphragm bypass valve with an adjustable brass piston replacement.
- Replaced PCV valve found to be leaking under pressure
- Replaced EGR gasket found to be leaking under pressure. It still leaks above 6 psi because it's a 98 LS1 intake manifold and only has 1 bolt instead of 2 so it rocks, but is able to hold 6 psi and below (at least while the engine is off and being pressurized externally).
- Checked all couplers for proper fit, adjusted and tightened.
- Replaced Procharger standard 2-core fmic with a Mishimoto G series because the Procharger was found to be leaking under pressure test.
- Verified the supercharger is producing > 11 psi when tested at the supercharger outlet on even less then a full dyno pull
- Manually pressureized the system by taking the pipe off the supercharger outlet, capping it off, and adding air pressure to the entire system including the motor to verify there were no leaks (other than through open exhaust valves).
- Verified the gauge inside the car is working via manually pressurization.
STILL
No boost on the road under load at 5-6k RPM at WOT. I can maybe squeak a piece past 0 psi, but not enough to confidently call it 2 psi, maybe 1. The blower pulley appears to be a 3". Also note the shorter gears and the non-stock cam. Additionally, the piping is 2.5" and I know most run 3", although I can't see how this would cause a pressure loss.
What am I missing here?
08-03-2010, 11:37 PM
#5
Teching In
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I have a 2.75" pulley if you are interested. The 9 pound pulley that comes with the kit is a 3.12" I believe. So with the cam, long tubes, and a 3.5" pulley that very well may be your problem
08-04-2010, 06:54 AM
#6
That could definately be your problem. When I first installed my gtrim I had a 3.13 or 3.33 and was hardly getting any boost. I put a 2.75 on and got 7lbs, then I put a 2.50 and got 9lbs
08-04-2010, 12:40 PM
#7
Staging Lane
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Are there differences in how various places measure them? For example, at Summit Racing I see a 2.87 and 2.62 6-rib, but not a 2.75 and 2.50. I'm guessing overall diameter vs. top of rib to top of rib? These are all 6-rib, are our cars 6 or 8?
Last edited by rjparth; 08-04-2010 at 12:46 PM.
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08-04-2010, 06:35 PM
#10
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the charger itself is bad i bet...had a buddy with the same problem, the impeller looks worn but not bad but only builds 2 psi. he had it rebuilt and now has 10...