What is the stock boost pressure (PSI) for a stock 3800SC?

When (RPM) should you see, or typically see full boost?

I am just curious and want to make sure my engine is boosting properly.

I actually tested the engine in the donor car, and the LED guage jump all the way over. I have boost but I just want to make sure I have no belt slip or other issues.

Also, pulley swaps -- how much more boost would I see?

i would like to know what the stock boost pressure is as well. the L67 and L32 both have a different psi right? as for the pulleys, every .1 inch you go down is another psi. i believe that is right.

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My 2000 Buick regal gs makes 10psi at wot. I have seen 12 before I have a 4" jmb intake on it and exhaust but that is it.

Im not sure the exact boost, but if I remember scale on my 97 bonnie ssei i believe the boost read from -10 to +10, so that probably means about 8-9 psi. My 02 gp gtp only has the corny digitar bar gauge in the DIC so I dont know what that is truly registering but I can't imagine it is any different. RPM really doesnt change the boost levels very much since superchargers tend to have full boost in very low rpms, but full boost is maxed out early in the RPMs. Turbo charges on the other hand tend to have a little lag but can create higher in in higher rpms thus usually making higher powered engines. The boost on supercharges are usually held back by a bypass valve that works in conjunction with throttle position. When at WOT the boost is very high, even when in a higher gear and lower rpms. Infact if you floor the throttle the boost will maxout but as soon as the auto tranny drops a gear the rpms climb and the boost is dropped. THis is because the supercharger becomes less efective at the higher rpms.

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The M90 is positive displacement blower. It doesn't compress the air, just moves it. If you have a very free flowing intake with a crappy exhaust, you will see more boost than someone with a basic intake and a very free flowing exhaust. The easier the air can get out of the engine, the less boost you will see. The blower will still move the same amount of air, and that's whats important. With everything being equal, a car with headers will see less boost than the identical one without them, but it will make more power, for example.

Whether or not the supercharger is a blower, or a compressor (like newer some superchargers), the point is that it's positive displacement (not talking centrifugal). In both cases, the mass air flow rate is dependent on the intake air density, and the supercharger's speed.

That's true about the ability to move air, and the exhaust acting as an obstruction. I remember when I had my rotrex SC, when I removed my cat I actually dropped about 2psi. So I am running a 3inch exhaust with a camaro muffler, I expect to see anywhere from 6-8psi?

I dont think stock these things push 10-12, unless there is a pulley upgrade.

I'm not sure what kind of problems you expect.

If the belt is slipping you'll probably hear it.

If you have a boost leak (which will be a vacuum leak when idling), then you'll most likely get a trouble code because even with the IAC fully closed, the idle RPM will still be too high.

quote Originally posted by pmbrunelle: I'm not sure what kind of problems you expect.

Well, my 3800SC has 80K. It may be new to my Fiero but it has been around the block so to speak. It apears to run great, but at 80K it is no spring chicken!!!

quote Originally posted by RotrexFiero: Well, my 3800SC has 80K. It may be new to my Fiero but it has been around the block so to speak. It apears to run great, but at 80K it is no spring chicken!!!

Its not even broken in yet!

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Just my 2 cents here, but on my 3800SC swap with a stock pully, I get 12psi at full throttle. I have a flowmaster 80 series muffler with single 3" in, dual 2.5" outs with no cats.

hmm.. so 12psi, and 1# every .1" smaller on the pulleys... stock is a 3.8"... drop down say a 3.2, thats 6#'s more of boost putting you at 18psi. and i think the SC3 is rated at maybe a bit more boost... man im gonna have fun stompin ricers and loosing to TT Vipers and TT Ford GT's. haha

Wow, that's a lot!