I just did a Lsa supercharger install on my l96. My issue is no boost under load at part throttle. Cruising I'm showing 10-12inhg, I can tip into the throttle and it builds 2-3psi and then almost immediately goes back into vacuum. If I tip into the throttle further it will do it again, but it will not stay into boost. If I try to stall it up at a stop it won't build boost. If I go wfo it makes 6psi and holds it. Any ideas as to why this is? Is this normal? I am new to boosted applications and not sure how it should act.

 

72 views and no response... This was either a stupid question or a really difficult question

 

bypass valve issue?

 

I checked the valve with a mitty-vac and it works properly. I also ran it off of 2 different ports and it does the same thing on each port

 

When you say back into vacuum do you mean 0 boost, or some amount of vacuum? Is it possible to adjust the bypass valve position any?

 

It goes back into vacuum... 5in maybe and as the rpms rise so does the vacuum. Then when it shifts gears it will see a little boost ( 1-2lbs) and repeat the process. Yes there is a small amount of adjustment.

 

You have to keep adding load (pressing the throttle more) to keep it in boost. If it's in vac, then there isn't enough load to keep the bypass closed and in boost. You shouldn't see much boost at just part throttle unless your pulling a trailer or trying to accelerate hard.

Doesn't sound like you have a problem to me.

 

Is there a spring in that actuator or is it positioned only by the pressure balance on each side of the diaphragm so that the PCM can regulate boost? On a Maggie kit the valve is closed by the spring when there is no or low vacuum, so that if you removed the vacuum line you would have full time boost.

 

This is what I was thinking also.

 

Yup, this. As you pulley down it will build more boost at part throttle. Id guess this is at a lower speed and therefore in a lower gear where rpm increases faster. As rpm increases the engine sucks more air and creates more vacuum behind the TB therefore opening the internal bypass. The bypass will only let you build boost as you need it. It shouldn't necesaariyl feel like power is dropping off even as boost decreases, does it?