low fuel trim out of whack

I just swapped the 510's for 750's with a new chip. mid and hi trims stayed about the same (mid actually went from 11x to 100 even) and hi is at 103. But low trim is at 82.3 and won't move.

Is this normal with bigger injectors or do I have an issue some place ? trims were all within 10 of 100 on the 510's with the weather change, and right at 100 when i tuned in winter.

Mark

edit : 3xx miles on the setup, so I would asume it has had plenty of time for all trims to change to the right readings.

 

[atc250r]

Make sure your close throttle switch is working and pull a few PSI out of the base fuel pressure (assuming you have an AFPR). You have room to work with on the mid and high so leaning it out a little with less fuel pressure will work. Is the O2 sensor fairly new and cycling at idle? When the heating element went bad in my old O2 sensor it would be fine while driving but would stop working at idle due to it not getting hot enough.

John

 

Did the new chip also modify the injector dead time? Dead time is most important for low fuel trims and low injector duty cycle. I think the 720s are reported to be very "slow" compared to 450s and other ND injectors.

Edit:

I want to clarify this. low FT=80% (running rich) would mean that, if you had a problem with dead times, they are too big already. This would not be the case with stock dead times for 450s. Maybe those 720s are quicker than your ECU guy thought...

 

[powerplay]

When I installed my Denso 660s, I had to adjust the deadtime to get my trims right. My Keydiver chip was set for those injectors. The values Jeff uses are approximations, so a little change can be needed.

 

adjust your dead time ?? did jeff reflash or are you using some stand alone ? All I have is maft and safc. I don't think this matters much at the track but it's kinda sluggish when driving normal from stops.

I'm going to drop some base pressure for now and see what happens.

 

[powerplay]

If you don't have your own burner and software, Jeff would have to change it for you based on what information you provide him. I have been studying about the process for quite some time and I do my own changes. I am still a "babe in the woods" when it comes to what the people know about the ECU/chips like Jeff.

 

[CP]

Damn Scott; I learn something new about you every month /ubbthreads/images/graemlins/devil.gif

 

[powerplay]

Well, I did it because I really didn't like bothering Jeff. He has given so much of his knowledge and time I just felt bad. I read all of the information on the ECU forum and they are a big help to noobies, like myself. I have burned several of my last chips and I don't think I am anywhere close to being done yet.

 

You probably added too much deadtime. The most you want to add is 312uS for the FIC/PTE/Delphi 750cc injectors. If you added 432uS, like the Denso 720's, thats your problem.

 

[CP]

I just put in my new chip, along with 750cc injectors, Supra pump, and Aeromotive AFPR. After a few days, all my trims were at 139%.

I'm still trying to track down the source of my code 41 (see sig), which may or may not be related. I'm running a 3G MAS, stock exhaust, magnecore wires, new o2 sensor, changed the plugs with the oil, and changed the injector resistor pack.

I've got the battery unhooked this afternoon while I re-paint my 93 headlights, so the ECU will be starting from scratch again when I give it power. Base fuel pressure is set at 37psi. Do I need to raise it a bit to bring the trims down? I'm not so sure an SAFC (arriving this week) will be able to do anything about them.

 

[CP]

Well after hooking up the battery, I was back to 100% for all of the trims. I also turned my boost down to 15psi.

After my 20 minute highway drive to work, my low and mid trims were at 104%, and my high was 118%. As the car sat there during its one minute cool-down, I watched the low move up to 135% (until the car shut off). I expect them all to be at 139% again before week's end; probably sooner.

I'm thinking about completely re-wiring my injectors in the next two weeks. Any other ideas as to what could be causing this (code 41 still)?

Am I super rich or super lean? I notice a tiny bit of smoke (not sure what color as it's tough to tell in the rearview) out the tailpipe when I get on it the first time on every drive (after fully warmed up). It doesn't do this at any other time. Maybe it's just moisture that has accumulated in the exhaust while sitting.

I noticed that Jeff changed the A/F default setting in my chip, from 10.5:1 with the 450cc injectors, to 11.0:1 with the 750s.

It also doesn't like to idle when cold, at least not as well as it did with the other injectors and chip. Is this a base fuel pressure issue (currently set at 37.5psi)?

I'm almost positive this is all due to my CE code 41. I may convert back to the stock injectors and chip for my first track event in 2 weeks, where the car will be at or above 4000rpms for 25 minutes at a time.

 

[powerplay]

After you clear the code 41 code, how long does it take before it sets it again?

 

[CP]

Code 41 resets almost immediately with the car running.

I just went for a 15 minute spin, and my trims are now at 114%, 105%, 122% (LMH). The low moved down quickly as I watched it while idling.

 

Everything seems to indicate that your injectors aren't quite flowing what you expected, since all your TRIMs are high. If possible, increase your base fuel pressure to 40-41 psi. If that isn't possible, we'll have to burn a new chip, with the next lower step of injector compensation. To me, the most important TRIm is the HIGH TRIM, since that one usually is a good indicator of whether your open-loop A/F is on target. (The change from 10.5:1 to 11:1 on those open-loop maps will NOT affect the TRIMs.)
Did you recently have any work done to the ECU? I often find that code 41 (if the car runs fine) is caused by a bad trace to RM101, a resistor matrix that looks at all 4 injector outputs. Some of the traces are very easy to damage. Look for RM101 between the green injector caps, and trace each of the 4 lines to the center pin of each injector driver transistor. The common lead of RM101 is the bottom one, and you can trace it as it heads across the board to TR12. I've also seen acid damage around the caps cause a loss of the bias voltage and cause code 41.

 

[powerplay]

Good information Jeff! I think he has swapped ECUs with a known good one and still had the problem. I am sure Cy will fill us in.

 

[CP]

Quote:
If possible, increase your base fuel pressure to 40-41 psi.



Done. I also grounded the firewall plug and set the idle to roughly 900rpm, which was factored into the chip.

Quote:
Did you recently have any work done to the ECU?



No. I swapped in another ecu with my chip (450cc and stock fpr then) a few months ago and nothing changed. But it's running like garbage right now.

Quote:
I often find that code 41 (if the car runs fine) is caused by a bad trace to RM101, a resistor matrix that looks at all 4 injector outputs.



The car doesn't run fine. Does the resistor matrix consist four black boxes with three legs that stick out towards the green boxes?

Quote:
Some of the traces are very easy to damage. Look for RM101 between the green injector caps, and trace each of the 4 lines to the center pin of each injector driver transistor.



The workshop:


Quote:
The common lead of RM101 is the bottom one, and you can trace it as it heads across the board to TR12.



The one on the far right that heads off into the distance, looking at the five horizontal pins near the bottom of this picture...



What I think you're talking about is the bottom four pins (of that verticle row of 5) that follow the fat traces to the tops of those triangular fat blobs:



Quote:
I've also seen acid damage around the caps cause a loss of the bias voltage and cause code 41.



My caps are a few years old (7378E) "Paul"

 

[CP]

Well I upped the bfp to 41psi with the hose removed, and it seemed to do a bit of good last night while up to temp. The car had some trouble idling this morning when I started it up after the ECU reset...very low idle and stalling. This is WITH a working ISC and FIAV, but with the EGR blocked. This also happened while the engine was relatively cool when the revs drop to idle, such as when coming to a red light. After a partial stop and go drive to work, trims are 139,135,107 (LMH). The exhaust also stinks (I guess this is the one GOOD reason to have a leaky exhaust underneath the car in this case).

I'm thinking another chip is in order. The guy at FIC said these Delphi injectors typically flow less than advertized (780cc from Delphi, sold as 750s by FIC, since they typically flow 745-760cc when tested). Maybe I should get a chip for 720s? What base fuel pressure should I have the chip set for...37 or the current 41 I'm at?

 

Quote:
What I think you're talking about is the bottom four pins (of that verticle row of 5) that follow the fat traces to the tops of those triangular fat blobs:






Yes, exactly! Use an ohmmeter to check for continuity (

 

[CP]

The fourth one up (2nd from top) is dead. I tested all 5 from pin to pin, and that's the only one I don't get anything for. It doesn't read at that first pin it appears to go through either. But it does read from that pin to the driver. So my problem is from RM101 to R112. What's my next step given this new information? Is there anything else I can test that may be code 41 related? Please advise...

Oh, my trims were looking better when I got home after putting in 50 miles today: 139, 117, 107 (LMH). And I've upped the pressure to 43.5psi.

 

Well, that makes it easy! Just solder a small jumper wire from the transistor's pin directly to the RM101. No more code 41! /ubbthreads/images/graemlins/laugh.gif