Fuel Trims are slightly negative, but AFR a lot leaner at wot than in Fuel Map
Aug 17, 2011, 12:06 AM
#1
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Fuel Trims are slightly negative, but AFR a lot leaner at wot than in Fuel Map
Hi,
I've got my injectors scaled, so that both idle and cruise fuel trims are around -2,5. And during cruise and idle the AFR is at 14,7. But when going WOT the AFR goes to 11,8 - 12,5, though in the fuel map I have 9 and less.
Did anyone have such problem? Would really appreciate if someone could point the direction where I could look for problem.
Thanks.
I've got my injectors scaled, so that both idle and cruise fuel trims are around -2,5. And during cruise and idle the AFR is at 14,7. But when going WOT the AFR goes to 11,8 - 12,5, though in the fuel map I have 9 and less.
Did anyone have such problem? Would really appreciate if someone could point the direction where I could look for problem.
Thanks.
Aug 17, 2011, 05:57 AM
#2
Injectors can be scaled so the trims look good, but they still aren't scaled properly. The only way to tell that the scaling figure is close to correct is by doing a wot pull.
Since you're around 3 afr points leaner than your fuel map, it could mean that your scaling is too high.
Other issues such as your fuel pump not being able to supply as much fuel as is required could also do the same thing.
Which injectors? What's your scaling and latecies?
Since you're around 3 afr points leaner than your fuel map, it could mean that your scaling is too high.
Other issues such as your fuel pump not being able to supply as much fuel as is required could also do the same thing.
Which injectors? What's your scaling and latecies?
Aug 17, 2011, 06:04 AM
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Injectors are PTE 780 and the scaling is 696. The latencies are the same as in merlins tuning guide.
I've actually tried lower scaling, like 622 and it gets better, but my trims are up to -12 with such scaling.
It also seems to me that my idle is much better with higher scaling, but I'm not sure about that (maybe it just seems so)
Is there any way to check if fuel pump is the problem besides replacing it?
I've actually tried lower scaling, like 622 and it gets better, but my trims are up to -12 with such scaling.
It also seems to me that my idle is much better with higher scaling, but I'm not sure about that (maybe it just seems so)
Is there any way to check if fuel pump is the problem besides replacing it?
Aug 19, 2011, 04:26 AM
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The most important mods are:
2.3 stroker
ported head
272 cams
FP Green
TBE
running 27psi.
Yesterday I've made it a bit better by disabling Lean Spool and lowering injector scaling one step to 680. So now my peak torque AFR's are about 1.5-2 points leaner than in the map, which is probably ok. But now my AFRs become very lean up top, though the map is maxed at 7.4, so basically the same as they were before. Also strange that they jump in such big steps (see the log attached).
2.3 stroker
ported head
272 cams
FP Green
TBE
running 27psi.
Yesterday I've made it a bit better by disabling Lean Spool and lowering injector scaling one step to 680. So now my peak torque AFR's are about 1.5-2 points leaner than in the map, which is probably ok. But now my AFRs become very lean up top, though the map is maxed at 7.4, so basically the same as they were before. Also strange that they jump in such big steps (see the log attached).
Last edited by EvolutionEst; Aug 19, 2011 at 05:01 AM.
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Aug 21, 2011, 07:06 PM
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maf tuning ...
maybe it is the maf is not matching your intake setup .
try this :
http://www.ecmtuning.com/wiki/maftca...nbyloggedboost
or this
http://www.ecmtuning.com/wiki/maftcalibrationbywbo2
using the first method , i manage to get mine low trim to -2 and mid to 0 . i'm still working on the boost area . but the above only works if your injector voltage latency is almost spot on . you gotta use the latency values that quite similiar in octane fuel used in your car e.g. 92 octane vs 98 octane from the evoM ... mine is 98 octane so i use 696 , i had to tweaked the latency at 14 volts to 0.888 . then redo the whole latency curve from that reference point to look like stock ... a new battery also helps to get a stable injector . mine old battery was logging from 12.5 to 14 volts . with new battery is now between 13-14 volts , make it easier to tune idle . after all this you should see you fuel map AFR = to actual AFR .
the stock maf calibration goes to 1600 hz , i have already hit that with 5000 rpm . it is still work in progress .. good luck , have fun ...
try this :
http://www.ecmtuning.com/wiki/maftca...nbyloggedboost
or this
http://www.ecmtuning.com/wiki/maftcalibrationbywbo2
using the first method , i manage to get mine low trim to -2 and mid to 0 . i'm still working on the boost area . but the above only works if your injector voltage latency is almost spot on . you gotta use the latency values that quite similiar in octane fuel used in your car e.g. 92 octane vs 98 octane from the evoM ... mine is 98 octane so i use 696 , i had to tweaked the latency at 14 volts to 0.888 . then redo the whole latency curve from that reference point to look like stock ... a new battery also helps to get a stable injector . mine old battery was logging from 12.5 to 14 volts . with new battery is now between 13-14 volts , make it easier to tune idle . after all this you should see you fuel map AFR = to actual AFR .
the stock maf calibration goes to 1600 hz , i have already hit that with 5000 rpm . it is still work in progress .. good luck , have fun ...
Hi,
I've got my injectors scaled, so that both idle and cruise fuel trims are around -2,5. And during cruise and idle the AFR is at 14,7. But when going WOT the AFR goes to 11,8 - 12,5, though in the fuel map I have 9 and less.
Did anyone have such problem? Would really appreciate if someone could point the direction where I could look for problem.
Thanks.
I've got my injectors scaled, so that both idle and cruise fuel trims are around -2,5. And during cruise and idle the AFR is at 14,7. But when going WOT the AFR goes to 11,8 - 12,5, though in the fuel map I have 9 and less.
Did anyone have such problem? Would really appreciate if someone could point the direction where I could look for problem.
Thanks.
Aug 22, 2011, 01:24 AM
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I will also try this MAF thing and see if it helps.
But I'm also starting to think that it is totally possible that I've got cheated by the workshop and did not get walbro pump installed, as I've just found a new gasket form the pump kit in my truck, which obviously should have been installed if the pump was changed, though the shop is telling me that the pump was installed. So what is the easiest and quickest way to check if I have wally installed? I've heard that it should be pretty noisy, which I think I don't actully hear in my car, so if someone maybe have any video with the walbro pump sound that I could compare to, I would be very grateful if you gave me a link.
Aug 22, 2011, 02:15 PM
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Injectors can be scaled so the trims look good, but they still aren't scaled properly. The only way to tell that the scaling figure is close to correct is by doing a wot pull.
Since you're around 3 afr points leaner than your fuel map, it could mean that your scaling is too high.
Other issues such as your fuel pump not being able to supply as much fuel as is required could also do the same thing.
Which injectors? What's your scaling and latecies?
Since you're around 3 afr points leaner than your fuel map, it could mean that your scaling is too high.
Other issues such as your fuel pump not being able to supply as much fuel as is required could also do the same thing.
Which injectors? What's your scaling and latecies?
the number in the fuel map is arbitrary and does not correlate to what the mixture is, it is simply a request more/request less function.
your afr measured will never match what you are requesting in the map.
Aug 22, 2011, 04:47 PM
#14
I'm not saying that the afr map and actual logged figures need to match, although it is possible to have them match up with some changes to the maf scaling and disabling lean spool. Having a difference of afr of 3 points is too much and suggests another issue.
Assuming everything else remains the same on the car and the injectors weren't maxed out before the new ones went in, when new injectors go in and the scaling and latencies are correct, the wot afr should be close to the previously logged figures.
The scaling looks ok, so it may be an issue with the fuel pump, or the injectors aren't big enough, although I thought 780cc should be just about enough for the green on pump fuel. It wouldn't hurt to pull the pump out, check that it's installed correctly and that it's actually a walbro.
Assuming everything else remains the same on the car and the injectors weren't maxed out before the new ones went in, when new injectors go in and the scaling and latencies are correct, the wot afr should be close to the previously logged figures.
The scaling looks ok, so it may be an issue with the fuel pump, or the injectors aren't big enough, although I thought 780cc should be just about enough for the green on pump fuel. It wouldn't hurt to pull the pump out, check that it's installed correctly and that it's actually a walbro.
