S2 EMS Load Transition Breakup Problem

[Boostaddict]

Over a year ago I finished some new headers and took the vr4 to the local dyno for a complete ground-up re-tune on the s2 EMS starting with the s2 base calibration (all previous tuning was done on the old s1). No matter what we tried we could not tune out a major break-up below 2.2k rpm when transitioning to load (positive pressure). Anything above 2k rpm the car drove smooth and clean (part throttle, WOT, etc). Below 2.2k if you put any real load on the engine it would break-up/buck HARD like fuel cut. At idle (with no load) the engine ran smooth at all rpms (in neutral for instance). Swapping the s1 back in the car it ran fine (although the tune was much rougher). This s2 "quirk" made the car completely undrivable on the street so it sat in storage for over a year now. If I can get this tuning issue figured out maybe that will help motivate me to put it back together this winter (I tore it apart to sell off some parts and fix a few things).

I'm hoping another set of eyes can help pinpoint the calibration problem. A year ago I thought the issue might be related to the injector calibration/battery offset (it is known the EMS battery offset for RC 1200cc injectors is bad so you have to use the RC1000 or RC1600 battery offset tables) but I could never 100% sort it out. Doing a calibration compare with an old "good" s1 calibration from my car revealed a lot of differences but making many minor changes didn't fix the issue. Nothing appeared so drastically different that it would result in the car not running under 2k rpm with load.

The s2 box has been back to AEM for hardware updates that were not related to the problem. I read on the AEM forums that they came out with a new/additional start-up calibration earlier this year with the newest firmware version. I guess the first place to start is upgrading firmware and transferring my fuel/timing/misc tables to the newest start-up calibration to see if that fixes the problem. Still curious if anyone else has feedback. I know many 3S shops installed these s2 boxes on the same firmware version I'm running apparently without this issue.

Basic mod-list from this tune:
Built 3.0l engine with mildly ported stock-valved heads and big cams
Single turbo setup with my headers/intake/etc
RC1200cc injectors running e85 (was more like e75 at the time)

The problem calibration file:
http://northbendtech.com/wayne_k/vr4...2010.01v17.cal

S1 calibration file from ~ 6 months earlier at NG 2010 using the same fuel system with a different turbo/cam combo which did not have this problem:
http://northbendtech.com/wayne_k/vr4...2010.V1.19.cal

[Ray Pampena]

hey bro.. can you call me? 631 676 2448. im so pressed for time i havnt had much time to post

[Ninja Performance]

Was Ray able to help you?

-Chris

[Boostaddict]

I won't know until tomorrow when I have everything put back together and have a chance to fire it back up. Ray thought it might be too much accel fuel at low rpms. Looking at and comparing my calibration files it doesn't look that bad but I'll take out 20-30% fuel from the main accel enrichment vs. rpm table and see if it makes any difference.

[niterydr]

PM sent with a few notes.

[ruben2566]

Did you get this resolved?

[Boostaddict]

I did some troubleshooting. Upgraded s2 firmware, messed with the calibration some. Its running really rough with some other hardware changes I did and isn't straightforward. The vr4 is on the back burner for now. Other priorities for the time being. I'll probably mess with it some more this Spring.

[ruben2566]

Are the injectors low impedence? If they are, do you have the injector resistor pack bypassed, only with the S2 box, not the S1 box?

[Boostaddict]

Same low impedence injectors used with both s1 and s2 boxes for the past few years. Never touched the resistor pack.

[ruben2566]

That may be the problem. You should bypass the resistor pack with the S2 box by making a patch to connect all the wires together, so you can go back if you have to reinstall the S1 box.
After bypassing the resistor go to the setup wizard and select a <P&H DRIVER> for your injectors. Without the resistor the injectors work much faster and you may need to remove some fuel at lower load, since they open faster.