4.8 2007 classic Silverado. Installed blower 10 months ago, been daily driving since and worked flawless! Kit was about 3-4 years old. Usually makes 8-9psi, multiple runs and lots of miles working perfectly.

Today, during a spirited 2 gear pull everything was fine. Right after that, I lost all boost. The truck runs flawless, no noises, no CEL, just wont build boost. Once the engine gets to boost operating range, it just falls flat on its face.

No detectable vacuum leaks(sprayed it all down with brake cleaner). The bypass valve is connected. Used a vaccum pump and applied 15psi to bypass valve, valve stays open and does not leak down.

Pulled TB off, and both lobes are spinning perfectly fine.

WTF is going on here?

 

What does it do with the vac line to the bypass valve disconnected? The bypass does not close with pressure. Its naturally closed and vac holds it open, 3-4" should open it. So with the vac ref unhooked the valve should be closed and not bypass any air.

 

Vacuum line off its slams shut(flap closed in blower). When vacuum is applied the valve opens the flap in the blower

 

If for some reason you have a large inlet restriction it will not allow the valve to close at WO. For testing purposes Ive driven mine briefly to test with the vac line unhooked. (Bypass disabled) Just don't go far, I pulled it and tested something real quick and then pulled over and put it back on. With it off long it can heat the blower up too much so keep that in mind.

 

Well in park when you rev the truck up, the valve drops out and shuts, which would lead me to believe its working under load also. The3 boost gauge in the trucks reads vaccumm, and when you rev it it builds boost on gauge. But you drive it, and it just falls flat

 

You load and airflow in park is not going to be enough for a restriction to show up. Unless its horrible. I done a lot of inlet vac testing on mine.

 

Just guessing if this is possible- Coupler break? Just free spinning? I'm not sure on the full design on the tvs style-

didnt the Lsa blowers have issues like this?

 

And when you drive it, and it falls flat, the boost gauge reads 0? (No boost, no vacuum)

 

What is the pre TB setup, any large rubber couplers?Also sounds like an inlet restriction to me under load..

 

Ok. TVS has no jack shaft, and both lobes are spinning therefore there is no mechanical break.

No CEL. Found p171,174 and a knock sensor code in a deep code scan with Snbp on verus. Cleared all codes, everything is now fine and i cant get it to fail. Gonna see what comes back. Found Air filter(bottom) very dirty and small pieces of poo on Maf(its my dads truck and he is a bit of a savage). I figure it ran a bit lean, detected a biut of knock, and put it in like a Half limp mode.

I will report back if something comes back