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Compressor Surge :-(
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Posted by SQRSaab (more from SQRSaab) on Thu, 8 Dec 2005 20:02:33 Share Post by Email
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It's been awhile since I posted, let me re-introduce myself. For those that know me, hello. For the others, I've got a 1999 93 that's fully modified (brakes need more work :-) I've been modding this car for over 6 years (making many mistakes along the way) and tested many GT's (1)25 (3)28 & (1) 30. Currently running with a 3" Stainless intake, GT2871R, 7K Redline, KJ intercooler, 2.5" stainless piping to TB, GG Injectors, 3" DP, all pipes ceramic coated. Poly bush all the way around, BBS, OG VRK, Koni/Eibach, Upgraded clutch/tranny,...................Anyway hello!

Anyone have any ideas how to solve my compressor surge?
I've eliminated a funny 3" aluminum intake elbow on my GT2871R compressor housing. Thoughts were, this was causing the surge. The new intake is much smoother, 3" with a 7 degree taper down to a 2.5" elbow straight into the Compressor housing.

I have horrible surge in gears 3-5, but none in gears 1 & 2. Usually surges ~1.5 Bar and ~5500 RPM. I just installed the new compressor housing on Saturday (Dec 3.) On Monday I noticed I had my base boost at .9 BAR.....Oops! Funny cause 3rd gear was starting to surge at ~1.0 Bar. So I've since played with the base boost. If it was lower than ~.5 Bar the car ran pretty good but at ~4800 RPM surges ~1.3 Bar. If I turned up base boost ~ .7 Bar I'd get surge later ~ 1.5 Bar. If Base boost dropped beneath ~.3 Bar the car would never really boost at all. (Probably due to the extra short wastegate arm)

I've also noticed surge as soon as I let off the gas, regardless of boost level. What is the best way to find out what is causing this?

FYI the ECU tune was custom done at sea level on 93 Octane, I'm at 6000 Ft. elevation and the best gas I can get is 91 Octane........Can this be related? I'd think this would cause spikes misfires, not surge!

Anyone got any ideas? Would specific data loggings help anyone? TIA

posted by 67.162.154...

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