Part throttle stutter 100-180 load ranges <3100rpm. I am having a part throttle studder in that range. Mods are HKS 272's, Walbro pump, stock injectors, Silicone intake, stock maf, tbe, and a mildy tuned 88590015 rom.

I can post the ROM if anyone thinks its worth a look at. Driving at part throttle cruise is an impossible feat. Looking for suggestions. When the stutter happens the in car wideband drops suddenly to 10 or maybe lower if it displayed that.

I cannot log wideband 02 yet, working on a solution.

 

Since Nobody else is helping you Ill try to, I am an amateur and I have just started reading about how Evo ECUs work and tuning them. I do have a solid grasp of Engine management systems though. I have experience using Evoscan and ECUFlash. I have done plenty of datalogging and tinkering with my own evo but I haven't tackled tuning it yet. So don't freak out if I say something stupid or incorrect.

First off as always Just for the sake of asking is your maintenance up to par. You have good Spark plugs that aren't fouled and the plug wires are in good condition.

Next Can you post a log, with knock sum logged. If the ECU detects knock it will switch to the Low octane fuel map I think and thats usually richer that the High octane map. Also are all three of you maps the same?

The more info thats provided the better chances there are to finding a soulition

 

is your DV connected and working propperly..?

to me sounds like blocked DV..

 

If there was an issue with the Bypass Valve you would be likely to experience quite a large amount of compressor surge. Compressor surge sounds like a loud chopping sound kind of. Type in into you tube and look up a video, its distinct. It will cause the car to stutter but I don't think that kind of issue would only be present only under 3100 revs. you would experience it anytime you boost. But my car does surge a little when its cold out and the revs are low and I stomp on the throttle then lift. As far as I can tell thats normal though..

 

Possibly the TB closing and no air going in causing it to be rich. Whats your TPS during this?

If you give more gas does it fix itself?

 

with Stock bov and stock boost control system ?

 

I have a log, there is zero knock . My thoughts were nor enough vac and too much boost at low rpm to reliably operate the bpv. Stock except for a hallman.. tps is constant when this happens , opening the throttle more cures the problem. Also related is letting off the throttle lightly to trim speed for a corner, it shudders and has a hard time settling. Very unpredictable car behavior when coming in at the limit. I'm going to try to reverse the bpv and see any change. Didn't think anyone would be.in tune on this issue . I will get a log and post it. ASAP

 

I ordered a 4 bar map sensor, so I will wait till I get that in to post more informative data.

I wanna try a different , lighter spring bpv, my stock 9 one OS crushed which I think is.adding tor my trouble

 

Crushed valve does have some stutter when letting off the throttle at low boost. Mine will even start to surge a bit when pulling a hill in 4th or 5th low boost, even with constant throttle.

Its annoying but its part of the tradeoff if you want to run high boost on the stock BPV.

 

It's not a trade off for me because I am going to fix the problem. Sooner or later. I flipped the bypass valve around tonight and it definitely made the studder harder to get locked into but still existed. Pretty sure ill have a synapse very soon to try

 

i had the same problem on evo 8 with the 9 turbo gm 3port psi boost control- the synapse dv help on it but never solve it.Also I tuned the boost settings too in the ecu. Maybe the Synapse bov with the c port can be better but i put in the orignal metal oem bov and works fine.
I believe the best will be the same 3D boost control tables as in the Evo X for every gear. RPM TPS based wgdc for every gear. Tephra is it possible ?

 

well you cant stop it from building this little boost with a wastegate spring stock @ 10-11 psi. There is something seriously funky with my setup. Its just getting retarded. I tried to drive 700 miles yesterday and it was studdering the entire way, any time I tried to let off the throttle a little to trim speed up a hill, it just put your face on the DASHboard. I sort of expected this as I cruised at 3500-4000 rpms most of the way, it wouldnt get stuck in the low rpm studder, instead it got stuck in the endless compressor surge/bpv surge

https://www.evolutionm.net/forums/ev...ification.html

I know my crushed bpv causes crazy amoiunts of surge when letting off above 3500 after building any kind of boost aswell. From what I have seen no aftermarket BPV can do it right. Im gonna set out to solve this. at any thing but WOT this car is useless.

 

hey guys, I am still having this issue, and I have narrowed it down to 90-120ish load ranges, and 2000-3000 area. It looks like in my logs, that timing will go from a few degrees positive, right down to -8 or -10 in one line hold then cycle from there, the only way to get out of this spot is to increase the throttle. Also, what should the TPS be reading at idle? Mine reads 8.6%. I re zeroed out the mivec table in an effort to isolate this issue.

 

Has this been resolved? Could it be the MIVEC advanced too far in those load/RPM areas?

 

The problem has subsided coincident with warmer weather, and perhaps some progress in my tuning ability. I'll let yall know if it comes back by next fall though !