I'm from Australia, and have imported a new Evo 7 GSR (ACD and AYC etc) from Ralliart New Zealand. I've had the car a few weeks now, and while its a lovely car to drive, but it has this horrible driveline shunt that I'm prepared to do just about anything to get rid of.

Its hard to describe, but basically while driving around town, if I'm driving in 1st or 2nd (sometimes even 3rd) with part throttle and I go over a series of bumps (eg over an intersection), or I back off the throttle too quickly, the car gets into a series of severe forward/backwards oscillations. The problem is compounded by my right foot (accelerator) being affected by the shunt, ie as the car oscillates, it makes my foot unintentionally apply and release throttle, thus setting up another shunt, etc etc.

The only way I can stop is to totally take my foot off the throttle until it goes away. To me it seems to be a combination of extremely sharp throttle response of the car, combined with the very jiggly/twitchy suspension settings.

Is this normal for Evos and I just have to live with it, or is there a problem with my car?
Is it a tuning issue that an aftermarket ECU or piggy back ECU could tune out?
Is it due to the east-west engine orientation, and could an engine damper rod could possibly help?
Could revised bushings or damper settings eliminate the problem?

Thanks

 

I have that issue with my car too. What I do is upshift to higher gear where i know it gets bumpy. It keeps the throttle response in check. Either that or lay off the throttle like you mentioned.

 

Ha...If this is the same thing as im thinking of... I do it accidently also If your in boost (over 3k) and hit a bump i accidently crack the gas causing a repeat effect... Just put your clutch in...or learn to control your right foot better... I dont do it anymore... But theres a huge *** bump in the road i leave for every day where you have to speed up to get too...then slow down for the bump...then go uphill...At 35mph is feels like your airborn

 

I have also experienced this problem, with my permenantly installed wide band I have been able to see exactly what is happening. Specific combinations of engine load and throttle input, create an overly lean condition causing the engine to hesitate/buck violently.
Aftermarket intakes and DV's seem to increase the likely hood of this event. From what I understand they can make the MAF sensor reading unstable under certain conditions. Adding fuel around these RPM/load points (especially throttle pump correction) should aleviate this intermittent problem.
For me it seems to happen around 3-4K at light/part throttle just as your transitioning from vacum to boost. Adding fuel through a remapped ECU, piggy back, or stand alone ECU, should get rid of this problem.
I believe it is a small hole in the factory fuel/correction maps, ultimately Mitsu should fix it by slightly adjusting the stock maps. It doesn't happen often and I plan to go with an aftermarket fuel control soon anyway so.....

 

Silver Surfer, thanks a lot, that is very useful. For what its worth, I emailed a company in the UK who do rally preparation on Evo 7's, this is what he thought.