Injector scaling and latecy for different injectors.
#739
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Ok, this is probably a basic part of this concept... but I'm trying to get it now that I dropped in some RC 1200's this weekend.
When you increase the injector latency the result will be more negative fuel trims (more fuel and negative AFR change), because the ECU assumes it takes longer to open the injector and thereby sends the fuel pulse longer.
Is the above statement correct?
If so, I think the method of adjusting latencies for getting the Mid/Low long term trims closer to eachother (mentioned here and here) does not work in practice beyond DSMLink. In trying to get my values closer I've mostly just made my fuel trims drop, and the STFT that used to by a nice straight up and down slope has turned very jagged and sawtoothed, as well as the car *seems* to run worse.
I get the % change at different pulse widths explanation that means that should provide more of a change at idle than cruise by adjusting that latency, but it doesn't seem to work well in practice by my experience. Can anyone else comment?
EDIT: Sorry, I meant to mention I think MAF scaling/tuning should probably replace step 5 & 6 for getting the trims close to the same.
When you increase the injector latency the result will be more negative fuel trims (more fuel and negative AFR change), because the ECU assumes it takes longer to open the injector and thereby sends the fuel pulse longer.
Is the above statement correct?
If so, I think the method of adjusting latencies for getting the Mid/Low long term trims closer to eachother (mentioned here and here) does not work in practice beyond DSMLink. In trying to get my values closer I've mostly just made my fuel trims drop, and the STFT that used to by a nice straight up and down slope has turned very jagged and sawtoothed, as well as the car *seems* to run worse.
I get the % change at different pulse widths explanation that means that should provide more of a change at idle than cruise by adjusting that latency, but it doesn't seem to work well in practice by my experience. Can anyone else comment?
EDIT: Sorry, I meant to mention I think MAF scaling/tuning should probably replace step 5 & 6 for getting the trims close to the same.
Last edited by fostytou; Mar 25, 2009 at 01:11 PM.
#743
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When you increase the injector latency the result will be more negative fuel trims (more fuel and negative AFR change), because the ECU assumes it takes longer to open the injector and thereby sends the fuel pulse longer.
Is the above statement correct?
Is the above statement correct?
If so, I think the method of adjusting latencies for getting the Mid/Low long term trims closer to eachother (mentioned here and here) does not work in practice beyond DSMLink. In trying to get my values closer I've mostly just made my fuel trims drop, and the STFT that used to by a nice straight up and down slope has turned very jagged and sawtoothed, as well as the car *seems* to run worse.
I get the % change at different pulse widths explanation that means that should provide more of a change at idle than cruise by adjusting that latency, but it doesn't seem to work well in practice by my experience. Can anyone else comment?
EDIT: Sorry, I meant to mention I think MAF scaling/tuning should probably replace step 5 & 6 for getting the trims close to the same.
I get the % change at different pulse widths explanation that means that should provide more of a change at idle than cruise by adjusting that latency, but it doesn't seem to work well in practice by my experience. Can anyone else comment?
EDIT: Sorry, I meant to mention I think MAF scaling/tuning should probably replace step 5 & 6 for getting the trims close to the same.
I have no idea about the rest and the MAF scaling...I'm still learning too.
Last edited by evodood; Mar 26, 2009 at 04:42 PM.
#744
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Fost,
The stuff mentioned in the early posts is correct. It took me a week to keep it straight in my head but it does infact do as claimed.
1. the 14V latency value is really the only one that counts, the rest are for extremes in battery voltage which you rarely see. So the 14 V value is the critical one. I figured out the slope of the latency line from the spec sheet and then offset the rest of the values after figuring out the 14V one.
2. Changes in latency do effect idle more than cruise, so if your trims are unbalanced adjust latency. If idle trim is higher more latency. If cruise trim is higher less latency. You should be able to make adjustments and see when the trims converge and then diverge.
3. I noticed that you really need to go the whole 16 mins and maybe more to get the trims to settle. Don't cheat at 15 mins and stop, you'll miss that 4th cycle which can really change things.
The stuff mentioned in the early posts is correct. It took me a week to keep it straight in my head but it does infact do as claimed.
1. the 14V latency value is really the only one that counts, the rest are for extremes in battery voltage which you rarely see. So the 14 V value is the critical one. I figured out the slope of the latency line from the spec sheet and then offset the rest of the values after figuring out the 14V one.
2. Changes in latency do effect idle more than cruise, so if your trims are unbalanced adjust latency. If idle trim is higher more latency. If cruise trim is higher less latency. You should be able to make adjustments and see when the trims converge and then diverge.
3. I noticed that you really need to go the whole 16 mins and maybe more to get the trims to settle. Don't cheat at 15 mins and stop, you'll miss that 4th cycle which can really change things.
Last edited by jid2; Mar 26, 2009 at 07:33 PM.
#745
#747
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I logged voltage for a few days and never saw anything but 14V 99.99% of the time. At Idle there is a voltage dip (10V) about every 4 mins, but it is literally a blip of .25s. I think you are good to use the same slope as what the stated latency should be offset for your 14V findings.
#748
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I logged voltage for a few days and never saw anything but 14V 99.99% of the time. At Idle there is a voltage dip (10V) about every 4 mins, but it is literally a blip of .25s. I think you are good to use the same slope as what the stated latency should be offset for your 14V findings.
..... but I'm not an EVO either