Stinger 4424 on Turbo EJ25/STI Vanagon

[gtiplive]

Hey Everyone,

I'm new to the wonderful world of Westy's and I've recently swapped into my Vanagon a EJ25 w/ turbo and Stinger 4424 ECU. I live in Texas and I had the engine built in Alpine, CA. Unfortunately, on it's maiden voyage home the engine began running terrible the more I ascended into higher elevations and by the time I reached Utah, it couldn't even idle.

Luckily, I could still start it and it ran just as long as I kept my foot on the accelerator. So, I made it to Grand Junction where I found an awesome Subaru machine shop that had a dyno and, judging from the sexy gazllion-HP Subaru race machine in the their shop, exceptional experience tuning performance engines. They kept my van for a few days and re-tuned the Stinger on the dyno. When I got it back, it ran noticeably better (and with better MPG), but when I got further into the mountains it started acting up again...not as bad as it would idle, mostly, but not perfectly.

Long story short, it doesn't idle well at all at elevations above ~2500' max. and now back in Texas at nearly 700', it idles just great, but smells very lean and sputters before the boost kicks in. I can't find anyone in Austin that's willing to even look at it.

So, any suggestions? I can download the software and work on it myself (zero knowledge), but not clear where to start. Does anyone have experience with the Stinger ECU's and their "manifold pressure sensor" to see if it's malfunctioning? Any help is VERY VERY appreciated.

[gtiplive]

Here's some pics for some sex appeal.

[ps2375]

Have you asked around on a Suby sight? Is the Stinger ecu an aftermarket or a modded suby ecu? Have you discussed this with the builder?

OK, aftermarket. Looks like you'll need to either find a tuner who's willing to touch it or learn it yourself. Were is this thing made?

[Stripped66]

I'd spend more time tuning it before trying to troubleshoot an ECU problem that may/may not be there. Your ECU has an on-board MAP (pressure) sensor for measuring the engine's manifold pressure, and it is barometric pressure compensated to adjust for changes in weather/elevation. Obviously, the tune on the EFI when you received it was marginal at elevation, because the shop in Grand Junction was able to improve its performance at elevation.

Understand that the two issues you're dealing with, idle (at elevation) and the acceleration fuel enrichment (the stumble you're experiencing before boost comes in) are two areas of EFI tune/control that can differ substantially between brands of ECUs. If the shop doesn't have experience with your ECU, they can get it close on the dyno, but it takes time that they don't have to nail it down...compound that with reworking the fuel-map (as you're getting better MPG), and it's basically a root-finding algorithm, with each iteration of the tune getting closer to the ideal tune (again, time!). As far as idle goes, some ECUs have a complete shite control/tune capability over an idle air control (IAC) valve...to the extent that some are easier to tune idle with fuel and spark and not run an IAC at all. I can't comment whether this is the case with the Stinger 4424, but understand that this is another 'wildcard' for a shop not familiar with your ECU to try to tune around. BTW, from a cursory google search, many Subaru engines used a stepper-motor IAC, and the 4424 can only control pulse-width modulated (PWM) IACs. I would assume the builder knows the difference and used the proper IAC?

So, what to do?
1) Check the Vanagon forum here on the Samba and inquire about who else is running the Stinger ECU with Subaru swaps. You may find somebody familiar with the problem you're experiencing, or familiar with tuning these aspects of your ECU.
2) Learn to tune the EFI yourself. I'd suggest spending some time on the EFI forums at shoptalkforums.com . You'll find lots of general information that will help you understand how to go about addressing the idle and acceleration fuel enrichment issues, and perhaps even specific information on what parameters to change with your ECU.
3) Find somebody in Texas who's willing to take a crack at your ECU. I know there's some Texans on the Shoptalkforums who are competent tuners...but, Texas is also a pretty dang big state.
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[gtiplive]

[gtiplive]

[Paul.H]

I'm an expert with the Stinger-what ya need to know ?