No boost at part throttle
09-08-2015, 07:10 PM
#1
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No boost at part throttle
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.
09-09-2015, 03:29 PM
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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.
Last edited by 2500ZL1; 09-09-2015 at 04:46 PM.
09-09-2015, 03:59 PM
#7
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.
Doesn't sound like you have a problem to me.
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09-09-2015, 05:09 PM
#8
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.
09-09-2015, 06:27 PM
#9
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.
Doesn't sound like you have a problem to me.
09-09-2015, 10:28 PM
#10
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.
Doesn't sound like you have a problem to me.
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?