Whipple 3.4L Belt Slip?

[aCiD]

Alright, built a brand new engine, Whipple 3.4 on top, aftermarket dual BB idlers, stock caged lower, RR manual tensioner, RR 4" upper. I have tried both Gates green belts, and Gatorbacks.

I can't get consistent, not-dropping off boost to save my life.

Either it peaks to 18psi, and RAPIDLY drops off to 9 or 10, or it starts at 10 and goes to 9. That's all with the 4" RR upper.

Then I put the 3.5" Whipple upper on just to rule out any weird surface issues with that, and same thing starts at 10psi, immediately falls to 9psi.

I put a small fortune into this thing and I haven't even been able to do a full 18psi pass yet (aiming to be doing 20psi once I get this sorted) and I'm starting to get pretty pissed off.

As for the manual tensioner, I'm putting WAY more tension on it than I feel safe just to rule that out. Video that kinda demonstrates tension level (I'm pushing/twisting pretty hard): https://www.youtube.com/watch?v=l-ZQ76Ocg9s I do intend to switch to a manual spring assist tensioner.

Picture of engine being mocked up: https://fbcdn-sphotos-b-a.akamaihd....7_10100768522312731_2323012308845009776_o.jpg

 

[aCiD]

Could it be bypass valve related?

 

[Vr4me]

Yon need an auxiliary pulley.

 

[aCiD]

Yon need an auxiliary pulley.

You can't even fit one with a 4" upper. I have one, it's not even close to fitting. As well Whipple themselves have said there should be no need for that with a 4" upper.

 

[aCiD]

ok, very disappointed in this thread so far

Did this last night, didn't make a goddamn difference. Using the regular size pulley it actually crushes the belt against the pulley, waaay too close. So I used this other OEM pulley I had around that was slightly smaller, but still a good size.

Next thing I'm doing it putting an optical tach on the belt and pulley with a gopro and doing pulls to calculate belt and pulley speeds and find where the differential lays. Any other simpler ideas before I order a new optical tach?

 

[03redfirevert.]

hooked the bypass valve up wrong

 

[Vr4me]

Have you ruled out the tensioner? I had a issue trying to run #26. It hit the target boost but rapidly dropped off at 4500 rpms. The tensioner hit the stop and couldnt travel anymore under the load. I had a very tight belt at the time.

 

[T-Pain808]

Good suggestion
4 inch upper with slip, I would be wtf too.

 

[Blueline]

It Sounds like your bypass valve is not working correctly....