well first of all if you have a stock valve or one like the APS that recirculates 50% (more at low boost) then it does not go into the pipes, it goes right into the intake manifold via the return line. If you source your MBC from this line it will work fine at WOT when the whole system is charged with the same psi of air, but if you are at partial throttle you will get surging as the airflow is different before and after the partially opened/closed throttle body (without getting further into that) and air will be forced back to your turbo. This backpressure is a surge.

 

I get this when I am boosting at low speed and then don't let off the throttle all the way.

Sometimes I get what I think is compressor surge though. When I floor it on the highway sometimes the intake doesn't sound smooth, more like pssspssspsspssspssspssspssspssp it sounds like the boost pressure is pulsing...then when I let off and get back on it sounds normal....i dunno these cars make all kinds of weird noises....

 

What you are describing that happens to you on the highway is exactly what my car used to do and now doesnt. My guess is you have a MBC hooked up to your BOV line?

well lunch is over. there is a TON of info on this stuff on here guys so you will be just fine. Back to work for me.

 

^thanks for the info.

 

I experience not constant flutter but something that feels like surge (4th & 5th) as described. My MBC is not hooked up to the BOV line. I removed the lines from the stock solenoid and removed them from the turbo completely. I then installed the new lines where the old lines were removed. The MBC install worked perfect.

 

So you are sourcing boost off of your stock licp nipple, have the other MBC line to your WGA, and capped off your boost solenoid. Well that is correct. I guess my follow up question would be do you experience this surge when leaving off the gas slightly after a sustained load in say 5th gear for example? Because I think the partial throttle "flutter" is something many guys experience and can be eliminated by hooking the MBC boost source up pre-TB whereas the "surge" problem that happens only in very specific circumstances like going up a steep hill in 5th like I described seems to be a characteristic of the stock turbo and cannot be helped. Although I must say I very rarely experience this. I only get it in the situation I described and if it gets to that point, I downshift. I mean you shouldnt be going up a hill in 5th gear at like 2000 RPM at 10psi of boost sustained anyway. Part of the problem I think is guys getting used to driving turbo cars. Just my thoughts....