guys...need some help....i rebuild a 00 SI engine to lower compression 9:1, the car is supercharged with Jakson racing....before they install the V-AFC the car was boosting 8psi, but when the dyno came out, only 135 HP on wheel....and the gage show onlr 4-5 psi....the shop said is due to lower compression engine..is it true?

 

there is no reason why lowering your compression would lower your boost. you either have a problem with your charger or your pulley. but the shop is crazy to think lowering your comp. would lower your boost!

 

Actually it's quite possible with a JRSC. They are steady-state type forced induction. As in your boost is always at the same level. If your engine breathes more as in lower compression with forced induction you have to push more air than normal. Which means you need to change pullies to up your boost.
That's one of the reason's people go with turbo. Instead, you can just turn the ****.

 

only 135 to the wheel = shop fucked up

 

Check your vaccum lines. I have had problems reading boost in the past because of the vaccum lines.