Haltech elite self learning fuel trims

Hi Andre,

First off I found this webinar very informative and has definitely helped me towards using this function most effectively, thank you for making this video. Ive been using this function on my corvette for about 6 months now since I put the elite in. So I find that at idle one bank seems to always max out the trims. For instance when set at 20% for a max trim it will always reach a -20% trim, while the other bank is not far behind. Even if I add it to the base table it seems to always max out regardless. My first question is for an already properly tuned engine what is an acceptable fuel trim? Does having trim maxed out constantly suggest there is something wrong with the ecu or the engine itself? Or does issue this have something to do with my gain table set up or possibly a result of another tables set up?

How far off are the AFR to the target?

Ideally for a properly tuned fuel map I'd like to see the short term trims no more than +/- 5% as a basic rule of thumb. Chris's question though is valid - What is the measured AFR vs your target? If it's pulling -20% and still rich then it may have simply been that the base numbers are just miles too rich.

The other issue to watch (which I'll assume isn't your issue) is that if you have the wideband sensors incorrectly assigned to the wrong bank, you'll get into a situation where one bank goes max rich and the other goes max lean as the trims are being applied to the wrong bank of cylinders.

Its interesting that you mentioned the possibility of having them reversed because this did happen to me in the beginning and I contacted the guys at haltech and they had me reverse the banks. I target 14.7 at idle and tuned it initially for this. Unfortunately I haven't kept good track of what the exact conditions are everytime i check it. Typically i have seen the car hover around the target when it is at idle. Overtime I have checked the fuel trims it has maxed out its negative trim on one bank and typically the other bank is around 5-10%. Overtime I check the trims I add them to the base table and eventually it brought my idle VE value as low as 28%. i do have a relatively large cam at 24x/25x, but from what I have learned through these courses and seen in other cars I have played with thus far that number seems super low. The car has been away for the winter for the last few months so I haven't checked it recently, but it was still doing this last time i checked the trims and added them to the base table. I will start it tomorrow and let it run for a while to see if everything is still the same.

If you have a significant split in your bank to bank fuelling discrepancies then these will still remain in the individual bank long term trim tables - The Haltech kind of splits the difference and then applies the average trim to the base table.

If you're seeing any more than a 10% trim bank to bank though I'd be looking deeper as to why - That in my experience isn't typical and may indicate an issue somewhere in your fuel delivery or equally it could be a faulty lambda sensor.

thankyou andre

Hi,

I have recently just installed a 2500, moving from a ps1000 and I have noticed that the long term fuel trim (LTFT) table doesn't seem to be populating, besides the short term fuel trim (STFT) doing it's thing - the map is fairly reasonable, but even with +/- 10% on the STFT, no values in the LTFT have populated.

I have changed the gain table to match that in the webinar, the PID settings are as per the base map, LTFT is enabled and the setting are pretty much exactly the same as the webinars (would have to watch it again to be 100% sure). The delay table is as per standard, and I even halved the delay time. Still unsure if this would need to be lower, 1.5s @ 2000RPM, 1s @ 3000RPM, 0.75s @4000RPM.

I have checked to make sure it is not operating during post start correction and coolant correction.

Any idea's as to was could be cause the table not to populate? I would learn towards the sensor/ control unit, but on account the STFT is working correctly. I use an innovate MXTL unit, the sensor is new as I only put it in with the new engine, feeding the 0-5V to the Elite - although it has already started playing up on me as of this evening, but that's another story.

Any ideas would be greatly appreciated.

I ended up emailing haltech about the issue.

Turns out, the issue was non-zero values in last column of the post-start fuel correction table - these values were outside the general operation of the car, so had never been used/review or adjusted. The LTFT was disabled in the setup page when post-start correction was active.

So, zeroing the last column in the post start fuel correction fixed the issue, and the LTFT is now working.

Alternatively, allowing LTFT to work during post-start correction would have also fixed it.

Sorry I didn't see your reply there pohl. Glad Haltech could help you out and thanks for sharing the solution.