Hey all
Question for all you guys,I have a Whipple on my c3 with 44lb. injectors and wester's tune. The bypass valve is vacuum operated and the vacuum source is on the blower inlet, I moved the vacuum hose to the outlet side of the blower so that when it is under boost the valve stays closed and it gave me almost 2lbs. of extra boost. So I was thinking that with it on the inlet side when the blower was sucking the air in it was opening the bypass valve through the vacuum hose. More boost is great BUT now I have about 7* of knock retard at WOT and almost 10lbs of boost. Dose anyone think that this bypass set up is a problem and I think that I can tune for the extra boost with more fuel. Any help wound be great.
Thanks Chris

 

interesting...do you feel more power or is it possible only a relative pressure increase right near where your guage inlet is and it is only showing 2psi more, but the engine is not really seeing it. ... I would imagine not...but the KR may also be coming from higher IAT's.
Good Luck!

 

sounds to me like the bypass is not adjusted properly. The diaphram is not designed to see pressure, so that could be a potential issue in the future. The 7* of knock retard is obviously from the 2 psi of added boost, I think a dyno tune is in order.

 

Thats not a good setup. It needs to see vacuum to operate, but not boost. Its purpose is to allow air to flow past the rotors at low throttle positions. By moving the reference source after the rotors, its not getting a true reading. I think its very likely that the bypass will close up on you much sooner and be slow in closing. I suspect that under much lower throttle positions you are seeing some boost, which is causing your KR. This would only be slightly better than having no bypass at all. I bet you see higher IATs during normal driving too.

 

Big Tex
I think that you are right, but my theroy was that when referencing vacuum on the inlet side when the blower in pulling in air it is causing a small amount of vacuum and opening the bypass valve slightly.And then with it on the outlet side i have vacuum at light throttle and under boost it keeps the valve closed, I just did not know how the valve would stand up to the boost.
Thanks for the advise
Chris

 

Glad you understand whats its doing. I'd say under any fair amount of throttle the bypass will close and you'd see boost. In my situation with the radix, I fight KR at low rpms when I'm lightly accellerating anyway. I would expect that to be worse with going into boost earlier. That doesn't even account for the higher IATs.

If you really want to keep it that way, you can buy a check valve to go inline on the bypass hose. That would let vacuum pressure pull on the bypass valve, but would not allow boost pressure to reverse back through the hose.