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Old 08-01-2007, 11:31 PM   #26
Rene2.5RS
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Glad to see you got the car running right now.

MRF you do have a point that it should know exactly how much air is entering and do its job but I am still a firm believer that if you modd or change anything in the intake track that you should log your STFT & LTFT and if they are over 4% +/- that you should look to tune this out.

-Rene
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Old 08-02-2007, 12:06 AM   #27
cellobro
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^^^this makes sense to me, but there seems to be a general hysteria about tuning for after-market intakes/inlet pipes or hoses.

any explanation for this?

what rules of thumb are there for say, an APS cai and/or APS turbo inlet?
THANKS...!
Justin
Quote:
Originally Posted by akira02rex View Post
I went back to a 783cc inj. scale with mrf's maf table down low for good fuel trims at idle and cruising. I left the latency values stock as well.

I then took a couple a/f logs and modified the table up top to match target and actual a/f. I also have the 400g/sec rom fix which I mapped out to 400g/sec for security .

Car runs perfect now and I decided to hook up my trusty MBC and I'm keeping 20.6psi all the way to redline...maybe I'll turn it up some more .

People may say this is the incorrect approach of tuning the engine, but it sure does work well for me.
this is when I walked like a man: the #'s can mean NOTHING, it's what the AFR tells you. the # that works/yields acceptable afr/target boost et cetera is correct.
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Originally Posted by Master2192 View Post
Personally, I would say anyway that gives you good timing/afr values is the correct way regardless of what anyone says. If the car starts and drives like stock, then I accomplished my goal.
:amen:
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Old 08-02-2007, 08:22 AM   #28
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I recently tuned a friends 05 STI with the APS 65mm CAI (stock injectors) and I did have to rescale his MAF table as it was lean on the bottom end and slightly rich on the top with the stock MAF table. Yes, I tuned with an LC-1 WBO2.

I guess APS claims that you do not have to recalibrate the MAF for this intake but I would disagree.

Also, he added the TGV deletes and those caused a nasty rich spot right during spool where the TGVs would normally affect the injector spray. With the deletes, I guess we got a different, better, more consistent spray pattern and made the car rich.
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Old 08-02-2007, 10:07 AM   #29
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Quote:
Originally Posted by cellobro View Post
^^^this makes sense to me, but there seems to be a general hysteria about tuning for after-market intakes/inlet pipes or hoses.

any explanation for this?

what rules of thumb are there for say, an APS cai and/or APS turbo inlet?
THANKS...!
Justin
The way I see it is there are lot of people that attempt to correct non-air flow related items with the MAF table. It is also a tricky table to tune.

With what I said before about the STFT & LTFT ideally you would want to get a base log of these before the change. You would log Air Fuel Correction #1 and Air Fuel Learning #1 along with MAF voltage. From there you can see for certain MAF voltages if things are out of whack or not. If I see anything +/- 4% or higher I try to tune this out to about 3% or lower. Right now most of my LTFT are -1.56% or -0.78%. Also when your fuel trims are in the negative the car prefers this rather than when they are positive and adding fuel.

-Rene
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Old 08-02-2007, 10:51 AM   #30
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Quote:
Originally Posted by Rene2.5RS View Post
Also when your fuel trims are in the negative the car prefers this rather than when they are positive and adding fuel.

-Rene
if the LTFT is slightly negative, it's easier to start the car because of a slightly richer than 14.7 mixture. during cranking, the LTFT isn't referenced.

that being said, i prefer it the other way around so the car is slightly harder to start. that gives me a couple more revolutions at low engine speeds to get the oil moving before everything starts spinning at 1000+ rpms.
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Old 08-02-2007, 12:25 PM   #31
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good reading, responses appreciated, the learning curve moves.

question: LTFT? STFT? I'll google them, certainly, but an explanation here would be useful to more than just me, I think

thanks

Justin
EDIT: got it, more reading
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Old 08-02-2007, 03:22 PM   #32
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Quote:
Originally Posted by cellobro View Post

good reading, responses appreciated, the learning curve moves.

question: LTFT? STFT? I'll google them, certainly, but an explanation here would be useful to more than just me, I think

thanks

Justin
EDIT: got it, more reading
LTFT - Long term fuel trim, is a learned value over time which changes gradually in response to conditions such as fuel oxygen content, engine wear, air leaks, variation in fuel pressure, altitude and so on.

STFT - Short term fuel trim, is instantaneous correction value determined from the oxygen sensor readings. Under normal conditions it cycles rapidly around the 0 percent correction value and is only functional during closed loop operation.

Hope that clears it up for you.

-Rene
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Old 08-03-2007, 12:47 AM   #33
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yu-up.
looked that up, makes more & more sense.

will keep reading... thanks, man
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