still getting low boost

x182dan

Registered User
My sc is still getting low boost even with my new supercharger and a 5% pulley. The car has tbird88 manifolds, scp exhaust, deleted mufflers. The gauge still says slightly over 10psi. Idle is around 20vac and going 60ish the vac is at 25. Now I just put the supercharger in so I am pretty sure there aren't any leaks on the ic tubes. I used high temp rvt for the supercharger, top and I have tbird88 reuseable gaskets for the tubes. What gives how come the boost is so low?
 
When you open up the exhaust the Psi will register lower because the exhaust is more effecient.

You're still making the psi it's just flowing through the engine faster.
 
Blk89TBSC said:
When you open up the exhaust the Psi will register lower because the exhaust is more effecient.

You're still making the psi it's just flowing through the engine faster.

I know that buy 10 is extremly low
 
Dan, with a 5% pulley on my stock exhaust, I had 12 psi, so with the way yours is opened up, 10% should be about right. You might go with a 5% jackshaft for more boost. That could put you around 12 psi.
 
RadiumSC said:
Dan, with a 5% pulley on my stock exhaust, I had 12 psi, so with the way yours is opened up, 10% should be about right. You might go with a 5% jackshaft for more boost. That could put you around 12 psi.

yes I know I SHOULD have gone with a 10% but I am being very careful with this car
 
Boost is directly proporational to back pressure

x182dan said:
yes I know I SHOULD have gone with a 10% but I am being very careful with this car
Dan,
I have almost the same exhaust setup as you do on my 90 except I have the Flowmaster Force II after the res. With a 10% pulley and at WOT I get 12-13psi. When I had my stock pulley installed I was lucky to see 9psi. When I had my stock exhaust installed I use to get 12psi. The less back pressure you have the less psi your blower creates.
 
Dan,

Check to make sure the bypass valve is closing all the way. Sometimes the linkage gets hung up on the back side of the supercharger top.

David
 
Blk89TBSC said:
When you open up the exhaust the Psi will register lower because the exhaust is more effecient.

You're still making the psi it's just flowing through the engine faster.
not to be nit-picking.....aw hell who am i kidding, thats exactly what i am being.

You are clearly not creating the same PSI...the gauge plainly states you're making 2 less PSI, you are moving the same CFM, but because it's able to flow more freely, you are in turn seeing lower PSI.
 
91supacoop said:
not to be nit-picking.....aw hell who am i kidding, thats exactly what i am being.

You are clearly not creating the same PSI...the gauge plainly states you're making 2 less PSI, you are moving the same CFM, but because it's able to flow more freely, you are in turn seeing lower PSI.

Well, if ya REALLY wanna be nit-picking.... with reduced restrictions in the exhaust, it's quite likely that it is actually moving MORE CFM through the engine even at lower PSI. Probably not a LOT more but more is more. :p :D
 
I should have done 10% but I didn't cause its my daily and I don't want to blow the hgs AGAIN. Maybe I will buy the 10% so when I take it to the track I could put it on
 
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