tjsierra1500

Hey everybody I'm having a problem with my sidemount whipple only bulding 4psi in my gmc sierra. It's mounted on an untouched 2001 lq4. From what I've read these old whipple sidemounts are a pain in the ***. I have the whipple electronics deleted, and running a custom tune with 42lb injectors. Pulley is a 4in whipple pulley with the stock crank pulley. My crank is not pinned but I know the pulley is not spinning(I've checked it many times with a paint marker just to see if it was shifting at all).I've replaced the belt. Checked and made sure the bypass actuator with a vaccum pump and it works fine. It used to build 8psi but slowly started to build less and less until it got all the way down to 2 psi and nothing more. At that point I pulled the supercharger and sent it out to get rebuilt. It is now making 4 psi. And I don't know whereally to go from here.
any help on this would be greatly appreciated.
thanks to everyone ahead of time

03sierraslt

iTrader: (22)

Is the bypass vacuum operated?

Mike1992

I'm running one of these as well on my truck and hit 4-6 psi same size pulley on a 5.3l

03sierraslt

iTrader: (22)

I am surprised it's making 4psi with a 4" pulley.

dirt track racer 81

iTrader: (45)

It made 8psi on that motor or another one?

tjsierra1500

It made 8 psi on this motor. I've been playing with a vaccum pump attached to the actuator. I've noticed that it doesn't matter if I hold the bypass open or all the way closed with the actuator, either way I only build 4 psi.
I've read up about other people deleting the whipple electronics and are having this problem. They are blaming it on the whipple bypass solenoid. But I don't understand why they would need it if they delete the electronics because it would then just be vacuum controled. When I got this whipple rebuilt I removed this solenoid(figured it wasn't doing anything anymore) could this be my problem?? Can someone explain the solenoid working without the electronics hooked up to me please???

03sierraslt

iTrader: (22)

Is is vacuum controlled now?

tjsierra1500

Yes it is. I have just a vacuum line coming from the pressure side of the blower to the port on the actuator that will have the bypass opened under vacuum and under boost it will hold the bypass closed by pushing on the actuator

Mike1992

I have the top nipple of my actuator hooked up to the inlet side of my whipple and I'm getting 6 psi. The bottom nipple on the actuator is vented and the pressure side nipple is plugged on the whipple.

James B.

iTrader: (1)

Something seems odd. The bypass valve should be normally closed. Meaning that with no vacuum lines attached the valve is closed. Vacuum should open the valve.

The real purpose of the bypass valve is prevent blower surge at idle and low throttle positions. Watch any video of a pro-street engine with a 6 or 871 on it and you'll see RPM surging up and down - that is blower surge. It only takes a servo actuator with one vacuum port to provide this functionality. In later iterations of Whipple's electronics they added double-sided servo so that they could employ the bypass valve to also limit boost. Gen-III engines have weak ring lands and do not withstand any pre-iginition. Also, the truck manifolds will lean out 8 and 7 from a ram-air effect down the center of the manifold causing a lean condition and again pre-ignition.

You've omitted the Whippletronics, so here's what you need to do:
- Confirm the servo normally holds the bypass valve tightly closed as atmospheric pressure. You can confirm this holding it in your hand.
- Figure out which vacuum port opens the bypass valve and connect that port to a vacuum port between the throttle body and the compressor intake, NOT the pressure side of the compressor or the intake manifold/plumbing. (Second vacuum port remains open and unconnected.) The servo should not require pressure to close the bypass valve, it's the absence of vacuum that should close it. If your valve doesn't work that way then post up your findings.