Heres the rundown...

Im using the AEM FIC, car runs on E85, 700cc inj, walbro 255, return system at 70 psi base - it hits liek 85 under boost.

Ill start out with the ecu reset, my idle and under vacuum cells on the FIC will all be around -38 to -42 and my ltft and stft will be perfect. Monitored while driving stft will be between -8 and +8 and ltft will remain between -5 and +5 at the most, but most the time within -3 and +3.

Heres where the crazy ____ happens...

After awhile, no specified amount of time or anything, it will jsut happen eventually - the ltft will go to like -30 across the board - now the crazy thing is - it will stay at stoich! So basically there has to be something behind the scenes in the stock ecu that magically just decided to add +30 fuel and now the ecu is using a -30 ltft to cancel it out. What happens is this causes all kinds of problems throughout the tune. Its really hard to explain all the details here, however Ive looked through fic datalogs, and when this occurs, nothing changes at the fic, so it doesnt appear to be a FIC related issue, it appears for some reason something in the back end up the ecu is causing it to add a bunch of fuel which the closed loop adjustments than attempt to cancel out.

To make it even weirder... If i turn off the car and it sits overnight, or sometimes even just a few hours, itll go away. Also sometimes itll go away while driving than randomly come back?

Im about to start just replacing sensors until I find the culprit. MAF data looks proper, however my maf sensor is a bit banged up so maybe it intermittently is throwing a false reading and causing an issue?

Also if knock is detected by the stock knock sensor, will it only add fuel in real time, or is there some kind of fuel trim it adds permanently until the ecu is reset?

Also just FYI - im using an automatic ECU, and the car is a 5 spd swap The only codes Im getting are for the 2nd 02 sensor missing (which it is), and the tranny codes. Also I dont believe it has to do with either one of those as the problem just started out of the blue. The car ran fine for months after the swap without issue.

This seriousely makes me just want to go to a standalone... However Im flat out of money

 

It almost sounds like the FIC is losing +12v power. Are you logging with a laptop? If so the FIC will have enough +5V power from the USB port to log and appear to be working normally. This happened to me and it drove me crazy until I checked for 12V power in a log and saw it was at 0V.

Even after I fixed the 12V pwr problem the FIC would still act up occasionally with results similar to what you're seeing. It was like the injector driver circuitry just shut down. Maybe it overheats or something. I was far from impressed by the overal quality and reliability of the FIC. I strongly suspect that the FIC is causing the problem and not the ECU.

Good luck.

 

You seem to have a lot of variables that could be the problem. Get someone with a working car of the same generation ecu/maf as you and just start trading parts to see what is not working. Start off with the maf as I would want to make sure that is working first.

 

what happens at this point? does the car start bucking while driving?

 

The crazy part is, when it happens, the car continues to drive normal, its not noticeable until you try to go into boost (where its extremely lean) or hook up the scanner. Its like something in the ecu decides to add +30 fuel and the -30 ltft is an attempt to even it back out, or hell maybe the fic is for some reason adding a bunch of fuel due to a circuit malfunction or something.

 

Regarding battery voltage - it does seem to fluctuate quiet a bit, during normal cruise it continuously bounces between 13.4 and 13.9 - than under wot it drops to 13.0 - i know its a switched 12v circuit, im thinking maybe tieing it into the main ign wire at the key switch would help stablize voltage?

 

I dunno, maybe youre on to something, just looked at a log from when its running right (no -30 ltft), and the battery voltage is between 13.8-14.0 cruising and on wot doesnt drop below 13.3

 

If the FIC stopped pulling ~30% fuel, that could explain the -30 LTFT. If the FIC didn't add fuel as you transition into boost, that could explain why it's lean. Check all your FIC connections. If the connections are all good, you could try re-flashing the FIC (worked for me once). If possible, try another FIC.

The FIC's 12V pwr should come from one of the switched EFI circuits used by the ECU but the voltage fluctuations you're describing are normal. As long as the FIC always has at least 11V it shouldn't cause any problems. FWIW, the tuner at one of the most respected shops in the mid-atlantic region told me that they send a fair number of FICs back to AEM for "testing" due to various problems and that they always receive a new FIC back with the explanation from AEM that they couldn't find anything wrong. He also said that the new FICs they receive back never have the same problems.

 

Yea I just finished checking all the connections - all is good - also i checked a datalog from another car I tuned, and the voltage seems to be the same. Ive tuned 4 other cars with the FIC - none of which have any issue like this :/ Im ready to go to an AEM EMS lol Correct me if Im wrong, but with the EMS, the only thing the stock ECU is controlling is the DBW correct? The stock ecu no longer has any control over fueling or spark correct?

 

I still believe the problem is with the FIC. Mine did the same thing and after I removed it, re-flashed the firmware and tune and re-installed, it worked fine again. I can't say if it was a bad connection or the re-flash that fixed it but either way it worked for me. If at all possible try a different FIC.

I'm afraid I know nothing about the EMS.

 

i know this sounds retarded but i have seen this for myself...was a/c on when you exp this? or off?
when you turn the a/c on the ecu adds a percentage of fuel thats based off the stock injector size. It does this to compensate for the added load placed on the engine. now when you change to a larger injector the percentage doesnt change but the flow rate does;). This can cause issues in boost or out of boost. this is just a thought. I have noticed it using 850cc injectors. I could tune for 14.7 for idle and get it spot on, then turn the ac on and its out of wack (fuel trims). You will see a bigger difference if your running in open loop all the time (disconnecting primary o2).

 

Unfortunately car doesnt have AC But I *think* I may have found the problem I found an old MAF sensor that came from a motor I bought and built for another guy here in OKC - he had an 05 so i kept the maf sense it was an 07+ ;) I swapped it over, and low and behold - the maf reading (in lb/min based on ecu data) was WAY lower, so I tuned the vacuum and low boost accordingly, now it seems to be running perfect :/ Sounds like it coulve been a bad MAF - looks like it was reading nearly double the airflow of the replacement sensor :/ Obviousely this would cause the ecu to give a -30 ltft to compensate. Ill keep the thread updated but Im thinking I caught it Guess I shouldve tried this before posting, oh well, didnt remember I had the sensor until I started cleaning up the garage today and looking through my tubs of parts lol

 

Also, I appreciate everyone on here's willingness to help This site has helped me alot with the work Ive done to the tC. I have a vast mechanical background, but this is my first journey into the import world - and its sure been fun Im thinking im stuck on 4cyl now ;) lol - Nothing like the thrill you get out of making such a small motor make sooo much power

 

congrats..and i agree..nothing like building a 4cyl that performes like a kick ___ v8.

 

Glad to hear you found the problem.

 

Soooo... The same issue hasnt returned, however Im having another issue, which Ive battled for awhile. That being the bad throttle response and over all difficult-ness of this car to tune. None of the others Ive worked with have had this issue, and Im really thinking it comes down to my MAF setup. Its a blowthrough setup, however its in 2.25" pipe with a very badly designed maf holder which is prob causing my issues. Will be trying to redo this shortly.

 

Also, just curious, anyone in here using Deatchwerks 700cc inj wanna chime in and tell me what injector latency theyre using? Mines currently set at 1053 and Ive had fairly good luck in that range, just wonder if Im missing something. Ive read quite a few posts on the aem forums and other online articles about how to set this however it still seems theres no real exact science.

 

In my experience even seemingly small changes in MAF tube design and ID can have a very big negative effect. For example, my oem MAF tube was 71mm ID and with a 67mm ID tube I had a constant P0101 and tuneability issues. Switching to a 3" tube (72mm ID) made a huge improvement. No more P0101, much closer fuel trims and much smoother performance. I don't understand aerodynamics well enough to understand why but my data logs suggest that the 7% smaller MAF tube resulted in ~10% higher MAF readings in the medium rpm range. It seems as though the smaller maf ID created a different MAS signal curve rather than the +7% linear curve I expected.

In your case you're probably running your MAS in a 53mm ID AL tube (57mm - 4mm wall thickness; unless you're using 2.5" ID pipe) compared to the 63.5mm ID oem tube. That's almost 17% smaller, no wonder you're having problems. IMO you should switch to the gold-standard 2.5" OD tube (~60mm ID) that seems to work very well for boosted TCs. OTOH, if you are using 2.5" ID pipe, it must be the MAF flange or something else.

BTW, just email DW and they'll send you complete IRT specs for any of their injectors. How to properly use that info with the FIC is anyone's guess since AEM doesn't seem to know either. I must have asked AEM tech 6 times and never got a clear answer.

 

Yea Im fixing the maf setup next week. As for the injector latency, ive heard from many that youll want a number between the stock injector latency and your aftermarket injector. I found some data indicating at 13v our stock injectors have a latency around .65 ms. Ive also foudn some data indicating the injectors I have are around .5ms - so im thinking - I may be waaay off lol. According to this I should be around the 500-600us (.5-.6ms) range. Oh well Ill play with this later once the maf issue is also corrected. The car isnt my dd and umm i ran it damn near out of e85 tuning on it the other night, so i gotta take a couple 5 gal tanks and fill them up while im at work tomm (the stations about 2-3 mi from my work)

 

I think changing your MAF tube to ~2.5" ID and cleaning up the MAS flange will make a big improvement.

Setting the FIC IRT to a value *somewhere* in between oem and aftermarket is the best answer I could ever find too. FWIW, the Dezod supplied oem injector offset table in my X1 indicates a oem IRT of .82ms at 13V and according to DW, my DW 440cc have a IRT of 1.28ms at 13V. IIRC 1ms worked pretty well for me when I was running the FIC but so did .8ms.

Here is the complete oem inj offset data supplied by Dezod:

7V - 2.48ms
8 - 1.84
9 - 1.46
10 - 1.22
11 - 1.06
12 - 0.92
13 - 0.82
14 - 0.70
15 - 0.64
16 - 0.54
17 - 0.52




Wow! Epiphany time! I think I just realized why my idle fuel trims are so positive with these 440s. I have a UD crk pulley and when idling around 700rpm my voltage is down around 13.5V. The ECU is programmed for inj latency of .74ms but my 440s have a latency of 1.24ms at 13V. That seems like a very significant latency difference at idle.