not reflashing a not-quite tuned car before a dyno run for highest hp... am i wrong?
05-20-2005, 02:35 PM
#1
not reflashing a not-quite tuned car before a dyno run for highest hp... am i wrong? ok, heres the deal:
a friend of mine put a 224cam in his 99z
we (me and some of my friends) have HPtuners and one of my friends flashed a 224cam tune onto my other friends car.
now we all agree, the tune wont be perfect... it'll need tweeking, but its still closer then stock was.
theres a dyno day tomarrow morning. 2 runs. hes probly going to get it with a wideband hooked up.
heres the question.
the LTFTs work out some driving around... i havent datalogged it since he reflashed the 224 tune on it, but its probly off somewhat.
in my opinion, i wouldnt reflash or tweek on it tonight.... since when you read or write to the PCM, it forgets the LTFT.... right now, i think the fuel trims are helping him.
one of my friends disagrees... he thinks that tweeking on it is fine right now... the fuel trims will be reset, but the car will be a little closer... and the fuel trims wont make much diff.... afterall, thats how the pro dyno tuners do it.
now he only gets 2 pulls.... its not like i can tweek on it, pull, tweek, pull, tweek pull all morning....
whats everyones opinion on that? leave it, or mess with it tonight?
a friend of mine put a 224cam in his 99z
we (me and some of my friends) have HPtuners and one of my friends flashed a 224cam tune onto my other friends car.
now we all agree, the tune wont be perfect... it'll need tweeking, but its still closer then stock was.
theres a dyno day tomarrow morning. 2 runs. hes probly going to get it with a wideband hooked up.
heres the question.
the LTFTs work out some driving around... i havent datalogged it since he reflashed the 224 tune on it, but its probly off somewhat.
in my opinion, i wouldnt reflash or tweek on it tonight.... since when you read or write to the PCM, it forgets the LTFT.... right now, i think the fuel trims are helping him.
one of my friends disagrees... he thinks that tweeking on it is fine right now... the fuel trims will be reset, but the car will be a little closer... and the fuel trims wont make much diff.... afterall, thats how the pro dyno tuners do it.
now he only gets 2 pulls.... its not like i can tweek on it, pull, tweek, pull, tweek pull all morning....
whats everyones opinion on that? leave it, or mess with it tonight?
05-20-2005, 02:43 PM
#2
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Unless the tune is rediculously off, fuel trims have nothing to do with WOT. How can you figure out if the tune is rediculously off? Take a look at closed loop fueling.
05-20-2005, 02:48 PM
#3
Originally Posted by txhorns281
Unless the tune is rediculously off, fuel trims have nothing to do with WOT. How can you figure out if the tune is rediculously off? Take a look at closed loop fueling.
ok. so at what point do the fuel trims have nothing to do with WOT? is there a cutoff limit? or is the amount so small on smaller trims that it doesnt matter?
i recall reading that the last fuel trims do have a effect at WOT....
and last time i ran the car (with the stock tune and the cam) in alot of places, the tuning was really off.
05-20-2005, 02:48 PM
#4
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The VCM doesnt lose the fuel trim learns when you reflash just the calibration file to the VCM. The only way it will lose the fuel trim learns, is if you use the VCM tools and do a RESET FUEL TRIMS.
Remember LTFT trims have no affect on dyno because you are doing closed loop tuning. Dyno you will be running Wide Open Throttle which is open loop, and the fuel trims learns are not looked at. WOT throttle you are doing PE tuning and tweaking the VE table to get to the a/f ratio you want to get the desired hp/tq ratio.
So no it wont make a difference, Id say put the tune in as you are right its closer and better than stock.
Dixit
Remember LTFT trims have no affect on dyno because you are doing closed loop tuning. Dyno you will be running Wide Open Throttle which is open loop, and the fuel trims learns are not looked at. WOT throttle you are doing PE tuning and tweaking the VE table to get to the a/f ratio you want to get the desired hp/tq ratio.
So no it wont make a difference, Id say put the tune in as you are right its closer and better than stock.
Dixit
05-22-2005, 02:46 AM
#5
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correct me if I'm wrong but if your ltfts are positive when you go into pe mode they will add extra fuel to the pe table. Hence the reason you want a slightly negative ltft's. May not be optimal for absolute max #'s but will probably be close non the less.
05-22-2005, 09:23 AM
#6
Originally Posted by plumbr
correct me if I'm wrong but if your ltfts are positive when you go into pe mode they will add extra fuel to the pe table. Hence the reason you want a slightly negative ltft's. May not be optimal for absolute max #'s but will probably be close non the less.
thats right, my car was lean at first and i was getting some knock and i had +6 on the fuel trims at WOT, it was rediculously rich, the o2s were reading 970 mv on me and 925 is normal a/f for me (close to it at least) so the computer was putting too much wot fuel in. i say you go out and make runs and change some things, make sure wot looks normal, no kr and ltfts are not + and the o2s read in a given range depending on headers or not.
now i see that you asked this a few days ago so it prob wont help now lol
