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Have you done injector scaling like i said 45 posts ago?
I don't want to make software changes until I'm positive the hardware is 100% free of mechanical problems. I haven't had time to work on the car lately.
The PCM is trimming the fuel, so the result is stoich. This is closed loop.
yes i realize you are talking about closed loop, but your LTFT are pinned at the max value, so its not trivial that you would be seeing 1 lambda under closed loop conditions. It sounds like you are assuming that the ecu can achieve 1 lambda under any condition because of fuel trimming but that is certainly not the case, so my question remains, have you actually measured 1 lambda under closed loop idle and cruise?
yes i realize you are talking about closed loop, but your LTFT are pinned at the max value, so its not trivial that you would be seeing 1 lambda under closed loop conditions. It sounds like you are assuming that the ecu can achieve 1 lambda under any condition because of fuel trimming but that is certainly not the case, so my question remains, have you actually measured 1 lambda under closed loop idle and cruise?
This is correct. The ECU can provide only a +/- 12.5% LTFT correction to closed loop fuelling. However, the STFT can add on top of this to get closer to stoich, however, STFT is also limited, IIRC to +/- 25%.
Anyhow, after everything I've seen in this thread, it seems pretty clear to me that the tune is not good.
This is correct. The ECU can provide only a +/- 12.5% LTFT correction to closed loop fuelling. However, the STFT can add on top of this to get closer to stoich, however, STFT is also limited, IIRC to +/- 25%.
Anyhow, after everything I've seen in this thread, it seems pretty clear to me that the tune is not good.
totally, my point was simply is your ecu achieving stoich under closed loop or not. If it is your sensor is doing its job, if it isn't then that could be pointing to a potential problem. I completely agree all indicators point to a tuning problem.
This is correct. The ECU can provide only a +/- 12.5% LTFT correction to closed loop fuelling. However, the STFT can add on top of this to get closer to stoich, however, STFT is also limited, IIRC to +/- 25%.
Anyhow, after everything I've seen in this thread, it seems pretty clear to me that the tune is not good.
I understand exactly what you both mean. The short term was also being used to compensate at idle, but at cruise the long term was less than +12.5 (I think it was +9.3?) so it was closer.
The thing that baffles me is the tune was done by Buschur.
I'd bet good money on it being bad scaling/latency. On a evo without true flex fuel capabilities, any good variance in Ethanol content will swing trims.
You also fixed two vac leaks, that if the car was tuned with those, the current scaling/latency settings are now incorrect.
Multiple knowledgeable people have stated this now in the thread.
I drained my tank that had the E27 in it, and filled it half full with fresh 93 octane. My Ethanol sensor is reading E11, so I think that's good for straight gas.
I removed the injectors (you saw previously) and had FIC clean them. To my suprise, one injector was a little low (which was fixed).
I reinstalled them, removed the battery (to wipe computer fuel trim memory) and restarted the car.
After about 25 miles of driving. LTFT was about +5.4 (idle) and +2.3 (easy cruise).
Yesterday, I was thinking that I simply must be missing some sort of vacuum leak, and retested the car again. This time I shoved my smoke tester into the brake-booster hose that connects directly on the intake manifold. I let the system fill until I had smoke coming back out at my from the air-filter itself. The only place I have a leak is in my MBC. I get smoke from there.
I started the car and let it idle- I pinched off the hose going to the MBC with a pair of hose clamps. When I do that it looks like my LTFT goes lower (gets better!) it went down to +2.3 (previously about +5.4). When I removed the hose clamp you can DEFINITELY hear the vacuum leak in the MBC.
I'm wondering if I should install a small check-valve going to the MBC so that the MBC will only see boost- and not leak vacuum.
Granted, the fuel trims that I have now will not throw a CEL, but I want to understand this more and get it as close to zero as possible. I know I can scale the injectors with my laptop, but I want to understand everything mechanical that's going on first. (I'm kind of "ocd" about this kind of thing).
Sep 20, 2017, 10:40 AM
