I've been spending some more time in the car lately, and for a brief period, I ran a helper spring on the wastegate. I stopped because when at 60%< throttle in third, around 25-700rpm, it would boost to ~22psi and then make the unmistakable "shhhhhchchchchchchchchc" of compressor surge (I think). If you don't know what that sounds like, look up a youtube video of "real compressor surge".
I removed the spring, and have resumed running just OE wastegate load and the T7 BPV valve. It still does it though, and still boosts pretty hard and early. However, I do not remember--ever-- a time when it did that. The BPV moves freely, and blows off, around idle with a slight blip. The T7 valve also clicks away merrily. So, from the maps I've seen, it doesn't seem likely that I'd surge the turbo at this pressure ratio/flow. The only thing that has changed is that my intake manifold holds pressure a little better than it used to and the tune has gotten better with regard to fuel and ignition. I've seen a lot of tunes with this same or similar turbo's and they run right up to 30 psi with no surge. Weird thing is that it seems to make plenty of boost (~25psi) in 4th, with no surge...that I can hear. What gives!
-Cm
I removed the spring, and have resumed running just OE wastegate load and the T7 BPV valve. It still does it though, and still boosts pretty hard and early. However, I do not remember--ever-- a time when it did that. The BPV moves freely, and blows off, around idle with a slight blip. The T7 valve also clicks away merrily. So, from the maps I've seen, it doesn't seem likely that I'd surge the turbo at this pressure ratio/flow. The only thing that has changed is that my intake manifold holds pressure a little better than it used to and the tune has gotten better with regard to fuel and ignition. I've seen a lot of tunes with this same or similar turbo's and they run right up to 30 psi with no surge. Weird thing is that it seems to make plenty of boost (~25psi) in 4th, with no surge...that I can hear. What gives!
-Cm
Over break I ran the spring on it and it would hold 25psi all the way to the end of the revs, but it didn't run "well". Afr was fine and it knocked here and there. I took the boost down and it ran better. I never took it past 30 or so psi, so I can't imagine I broke anything turbo wise...
