I just finished putting my Evo 8 back together with the following build. While attempting to tune it, my tuner came across an issue. When the engine gets to 2500RPM, it spikes lean as if it's cutting the injectors off. We can't figure out what the problem is. I have replaced the TPS and done a compression test. I'm running on the stock ECU. What else could be the problem?

Block:
Manley Rods
ARP Main and Rod Bearings
Mahle Pistons .02 over

Head:
Street/Race head by Curt Brown
GSC SS valves
Kiggly Beehive springs
Race port
Bronze valve guides
Competition multi angle valve job
New seals
Pressure checked
EGR port tapped and plugged
GSC S2 Cams
ARP Head Studs
Ported Intake Manifold

Exhaust:
No Name 3" Exhaust
MAPerformace O2 Housing w/ EWG Dump
Turbosmart 40mm External Wastegate
Ported Stock Exhaust Manifold

Forced Induction:
MAP EF4 Turbo
Turbosmart Wastegate
Omni 4 Bar MAP Sensor
Speed Density

Drivetrain:
Shep Stage 2 Transfer Case
Competition Twin Disc Clutch and Lightened Flywheel

Fuel:
FIC 2150cc Injectors
Walbro E85 450LPH Fuel Pump

 

speed density? might be better with MAF

 

Do you have the resistor pack delete installed for the FIC 2150's?

 

Sounds like a speed density tuning issue. My car had issues with the same thing until Aaron at English tuned it..

 

Yes, I do.

Speed density tuning issue. Such as?

 

It's an issue with the tune. Generally fixed by in the speed density tuning section, in the RPM/VE and MAP/Load tables, as well as when the car goes into open loop and making sure the fuel table has enough fuel in it in those areas.

 

yeah thats what i figured ^ but im not a pro so i was hoping a professional tuner would came in here and said that for him self but yeah... not many people can tune SD

 

I'm no pro. But when I was wrangling with the previous tuners tune on my car, Aaron gave me some pointers that made it 10x better, and then I ultimately just had him tune it and drives about like stock except for the cams which take away some off boost power.

 

My tuner can definitely tune speed density, and he's already played with everything that you said.

 

logs?
would need to see the data.

 

That's what my previous tuner said too. He has several other cars that ran perfect on SD, but he could never figure out mine. Tried blaming it on something electrical. So I went to Aaron and, voila, fixed...

 

You can check if it's a fuel cut or not. On the datalog, does the injector PW go to 0ms while the throttle is opened?

 

2d or 3d SD Rom?

 

What does your fuel rail and fuel pressure regulator setup look like?

I recall reading about some people having issues in the 2500RPM area due to fuel system resonances. They were partially fixed by adding a fuel pressure dampener. If you search around I'm sure you'll find the thread.

 

yep. certain combos of fpr, rail, and/or injectors cause a lean spot from 2200-2600 rpm due to some kind of resonance issue. i have verified that a damper pretty much eliminates the issue. it can be tuned out with sd too.