Boost bypass getting stuck/slow to open

[cheetohead04]

Car is a 2011. Built motor, jdm cams, fuel system etc etc. I’m running a l&m low vacuum bypass. When you drive the car at low rpms and try to get on it it stumbles/hesitates then will continue to rev fine. Then when you do a full pull to 7k rpms or higher the valve will actually get stuck open during shifts and the car will not build boost in the next gear. It doesn’t do it if I shift around 6500. Vacuum lines are good. The bypass is working. Any other ideas? I’m going to pull the blower in a few days to check and make sure the shaft/valve isn’t in some sort of bind. I’m not sure what else it could be. Kind of lost at this point.

 

[Catmonkey]

If you're pulling the supercharger, you want to make sure the by-pass is adjusted so that it snaps shut. Using a mighty vac can also help you determine how much vacuum it takes to open it. Just the fact that it opens the by pass at lower vacuum than the stock by pass, you know it has a fairly weak spring in it closing the by pass. Playing around with a stock by pass, they generally open in the 12-15 inhg range of vacuum.

If your car is stumbling and hesitating at low rpm, that's more a characteristic of the cam with a lot of overlap. You're going to need to keep the revs up because that cam probably will experience conniption fits at ranges under 2,000 rpm. I'm running a moderate cam profile and my car doesn't like to cruise at anything less than 1,600 rpm. You may even need more gear. Based on my in-town driving thus far, I'm considering going to 4.10s, but I'm going to give it more time.