set up, mini ram with 5858 cea. MV-S 8.7pound spring. 3" downpipe 1.75" dumptube.

i was on the dyno yesterday tuning my car when i ran into a weird boost spike issue. about 7300rpm boost would shoot up from 11 to 15.8 pounds once i got to 8500.

this is running a straight vacuum line from turbo to wastegate. Also tried straight from manifold to wastegate. Also tried using hondata boost control with duty cycle per rpm per gear to try to stop it. forum wont let me upload a log.

 

Sounds like a boost creep issue if vacuum lines are ran correctly. This is why wastegates need to be tear dropped if running a single gate, but at those kinds of rpms at least a MVR 44mm gate should be used. Just reciculate the gate back into the downpipe and it should solve your issue.

 

Is 11psi your target or 8.7?

Is boost steady and level before it begins to spike?
Did you 0 out the boost controller duty above 7000rpm?

 

That and the fact that the MAC Solenoids are notorious for that condition even over the tear drop design of the manifold. Tear drop helps, but more than likely the solenoid

 

You dont think that has to do with most ebc setups using a quick spool or 100% duty cycle until target boost is reached? If you reduce the duty cycle slightly before target boost is reached, in theory should be able to round that spike down.

 

Nope. Because we use a lot of Gain in boost response on the GReddy and AVCR Solenoids ( even the AVCRs that use the boost by rom feature). It's strictly the way the solenoid was designed. I can use 100% duty right up to target boost and still not creep past the target.

 

This is why wastegates need to be tear dropped if running a single gate

 

That's only a small part of the problem. There are plenty of manifolds that don't have the tear drop fabrication. Again. it helps to have it, but isn't the pure root of the issue. But hell, WTF do I know, anymore.