Supercharger boots/Vac

DGernmann

Registered User
I have a 94 Sc, I am new to the supercharger thing. My boost gauge reads 0 when the car is idling, when I drive the gauge reads 20 Vac. Sometimes the boost gauge when I give it some gas reads about 10-12, but a little gas gives me about 5-8 of boost. Is this right? The car feels fast but not too fast....

Thanks for all the help!
 
Our superchargers have a bypass valve that allows the SC load on the engine to be reduced when it's just not needed. The bypass valve runs some of the intake air back through the supercharger to keep it from having to build up when power is called for.

So when you don't have your foot into the gas, the engine acts like a normally aspirated vehicle by running at vacuum (less than zero on the boost gauge) when just cruisng around.

you should be below zero at idle as well, but not a smuch as when you are crusing faster. But when you crack the throttle, the bypass valve closes and the boost starts to build. WOT should see 12-15psi depending on the exhaust on the car. Other throttle positions will see something less, but should be greater than zero if accelerating.

As far as feeling of quickness. high boost doesn't mean high power. On a fairly stock car it is often a sign of restricted exhaust. Also keep in mind that it takes considerable additional HP to make our cars feel "quick". They can feel Fast easy, but "Quick" implies light on their feet. At around 2 tons, our cars take serious HP to feel "quick". If they ever really do.
 
I definitely defer to mike 8675 on the SC subject ..but 5 to 8 lbs with little throttle? and 10 to 12 with "some gas" My exhaust is open and it's an AOD but i have to try harder than that to get my car into boost and keep slammin to climb into the 10-12 range !!!
Boost guage sounds wonky ,but i have not driven a 5 spd either!
Just my .02
Mike??
 
i have a 5 speed and i too have to try really hard just to get to the 12 ibs of boost, something is up with your gauge or sensor
 
PULLEY Maybe

I have a 10% on my car with an open exhaust and in the mountains i could always hit 12-13 PSI with ease. But down here in the flats of Delaware my gauge pegs again like it did before putting on the bigger exhaust. So it could be ok, but you could also have a wacky gauge.
 
Same here i have a 94 and with the snap of the throttle my gauge climbs to 5-6 psi almost instantly. I have an open exhaust as well and at full throttle the gauge reads 12-14 psi just my 2 pennies

Victor
 
I haven't driven my car in like 3 months now so it's a little foggy.

Max boost could be hit for me with WOT at around 4000rpm.

1/2 to 3/4 throttle would pop above 5psi of boost. From there it would build with RPM.

Our SC is a positive displacment unit. It compresses a specific amount for every rotation. Rotate it faster, more air is compressed. It takes higher revs to pack the air into the intake tract to hit max boost.

A 5 speed and an Auto should be no difference when looking at engine RPM.
 
porting will affect your boost readings too. stock heads wont flow as much as ported heads but stock heads will have higher boost pressure due to the fact they dont flow as well as ported heads.
 
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