Power loss at high RPM

Matt D. · 05-03-2010

I started a thread on EvolutionM but wanted to keep you all in the loop as well: http://forums.evolutionm.net/evo-eng...-high-rpm.html

After doing some work on the car to resolve an issue with leaking exhaust valves (see http://forums.evolutionm.net/evo-eng...ggestions.html) and adding a few other parts along the way I took the car back in to get retuned, but left with less than spectacular results and a new issue with the car dramatically losing power at around 7300rpm.

A quick rundown of what all was recently done to the car: http://mitsustyle.com/forums/showpos...&postcount=195

List of important stuff:
Evo 9 turbo
Megan O2 housing
Buschur 3" turbo back exhaust
RMR intake w/ Perrin filter
Nisei intercooler piping
Evo 9 BOV
MAP Rev2 intake manifold
MAP ported exhaust manifold
MAP Stage 3 head w/ GSC beehive springs
GSC S2 cams
At the time of tuning it had an eBay intercooler, but now has an ETS 3.5"

Boost leak test is good, compression test is 170-175 across the board.
Timing marks all line up.
Timing belt was done at 66k, 101k on it at the time of tuning, stock cam gears.
Even after the new intercooler the power loss still exists and is noticeable on the road.

Dyno graphs before the head swap:

HP vs AFR: http://img242.imageshack.us/img242/7246/afr.jpg
HP vs boost: http://img196.imageshack.us/img196/1521/boostw.jpg

Dyno graphs after the head swap and other parts:

HP vs AFR: http://img532.imageshack.us/img532/6112/hpafr.jpg
HP vs boost: http://img153.imageshack.us/img153/8072/hpboost.jpg

I took the valve cover off and everything looks good, nothing loose or out of place, no odd noises like a collapsed lifter or anything. At this point I'm stumped and am looking for opinions on what to do. I was in contact with Greg at GSC but after sending him my dyno graphs I never heard back from him. DB Performance tunes a great number of Mitsubishis, and this isn't Shane's first rodeo. He said that any more timing or less fuel it would knock, so I'm inclined to believe that the tune is spot on. It has been beat on it a fair amount since then and the high RPM issue still exists, though it has kept up with two different cars that dyno'd at 330whp on the same dyno.

The only other piece of info I have to add is that when the power drops at high RPM there is a slight vibration associated with it, but the car feels like it pulls out of that power loss when it reaches 8000-8400 and the vibration subsides. It's nothing violent at all, but is plenty noticeable.

Scheides has helped a ton with this car, he knows it as well as I do. I'll let him chime in with anything that may be worth adding.

EDIT: Forgot to add that we swapped out my coil packs and wires for those off a car with something like 16k miles on it, same issue.

carltalon · 05-04-2010

Is there anyway you can post up a log that we can look at. I'm assuming theres no knock? Is airflow staying up or is it droping off like the power curve?

Matt D. · 05-04-2010

There was no knock and timing wasn't pulled, I saw the log myself. I can't recall what airflow was doing. I asked Shane to look for logs just in case he still had them saved.