idle tuning easy way??

[ozorowsky]

Hey everyone, I read a post a while back, but didn't save it where someone figured to log ltit's and figured that was measured in one type where as editor was something else? And then you just add/subtract? Anyone know what I'm referring to? Just trying to FINE TUNE idle. Thanks.

[405HP_Z06]

Hey everyone, I read a post a while back, but didn't save it where someone figured to log ltit's and figured that was measured in one type where as editor was something else? And then you just add/subtract? Anyone know what I'm referring to? Just trying to FINE TUNE idle. Thanks.

This should help:

Monitor your two LTIT's and STIT in the scanner. You will notice the LTIT should settle to a constant value after a few minutes (idle learn process) in PN and Gear for A4's and Gear for M6's. After the LTITs have settled take note of the following:

- the LTITs should be within the min/max limits shown in the editor (see the help file)
- the STIT should be close to 0

If the LTIT's are at either the min or max limit you have a problem with your base running airflow (if LTIT is max and the STIT is positive then your base running airflow is too low, if LTIT is min and the STIT is negative base running airflow is too high). Also it's good to watch your STIT when the fans come on so you can see if the correction is ok.

I tend to keep the limits at the factory settings and just change the base running airflow numbers and the various compensation factors.

The important thing to remember is the base running airflow is the starting point for the adpative idle routines. Most cruise control and rpm drop issues when coming to a stop are symptoms of the LTITs being at their limits due to base running airflow being out to much. This is most noticeable after a camshaft change.
The main one is the "Cooling Fan Airflow" this is the extra IAC airflow required to compensate for the alternator load when either one or both fans are on.

There is also the throttle cracker which opens the IAC based on RPM and mph, and the throttle follower which is a dampener/decay function for when you close the throttle suddenly.

The other is the AC. The AC is a little different as it is torque based, you'll need to head over to the Engine -> Torque Management -> Engine Torque section and look at the "AC Compressor Torque" tables. Again, watching your LTIT and STIT when the AC comes on will tell you which way you need to move things.

[ozorowsky]

There is an easier way to that. In my programming for dummies article, works WELL, but doesn't make it PERFECT. I'm trying to tweak to perfection. I saw ONE post a while back where someone scanned their LTIT's or something and then, figured that was in one measurement, VCM Editor was in a DIFFERENT measurement, then he converted it, then just added or subtracted what number should be from what it is and he got a perfect idle. I'm trying to figure out what they did again, because I want to add this to my tutorial.

[405HP_Z06]

There is an easier way to that. In my programming for dummies article, works WELL, but doesn't make it PERFECT. I'm trying to tweak to perfection. I saw ONE post a while back where someone scanned their LTIT's or something and then, figured that was in one measurement, VCM Editor was in a DIFFERENT measurement, then he converted it, then just added or subtracted what number should be from what it is and he got a perfect idle. I'm trying to figure out what they did again, because I want to add this to my tutorial.

Read the above post closely.

It translates to the following:

The LTIT and STIT are similar to fuel trims and are g/sec (grams air per second) error.

Log LTIT and STIT from a cold start to operating temperature and let the idle learn. Then whatever the +- LTIT (Long Term) error is adjust the corresponding value in the Base Running Airflow table by the error value. Remember to log the engine temp so you don’t start changing the wrong location on the table. When you get close you can use the STIT (short term).

If LTIT is at it's min/max limit than the Base Running Airflow table needs to be adjusted. If LTIT is max and STIT is positive than adjust RAF up by the LTIT value. If the LTIT is min and the STIT is negative than lower the RAF by the LTIT value.

[346na]

Where do I find these Idle trims?
I've looked everywhere in the scanner and can't find them - they're not in the "Insert Table PID" or anywhere else I've looked

Am I missing something here or are you guys just using the normal Fuel Trims ??? ??? ???

:huh2: :huh2: :huh2:

[405HP_Z06]

Where do I find these Idle trims?
I've looked everywhere in the scanner and can't find them - they're not in the "Insert Table PID" or anywhere else I've looked

Am I missing something here or are you guys just using the normal Fuel Trims ??? ??? ???

:huh2: :huh2: :huh2:

What version are you running? I think these are only available in 1.6 and above.

[346na]

I'm using version 1.7

I can't find them anywhere, I'll bet I'm just a dumbass and they are there somewhere.....

[ozorowsky]

what is raf?

[405HP_Z06]

what is raf?

Base running airflow

[ozorowsky]

what is conversion? When logging is lb/min, how do you convert that to g/sec? Any help?

[405HP_Z06]

what is conversion? When logging is lb/min, how do you convert that to g/sec? Any help?

Right click the idle PID's and change the output to metric and you will get g/sec display.

[ozorowsky]

COOL! TY

[ozorowsky]

I think I just about got it down. If your LTIT reads -1.23 do you ADD or SUBTRACT from Idle Air Flow vs ECT?

Also is this the ONLY thing you do for idle? Anything special for when AC is on? I'm trying to learn this as SIMPLY as poss. so I can add to my Programming for Dummies tutorial. Thanks.

[redhardsupra]

you add the negative number, effectively subtracting it. i have a spreadsheet that does it all for you, i'll post it soon.

[ozorowsky]

So if your LTIT is -1.8 ADD 1.8 at whatever temp necessary to the Idle Air Flow vs ECT table, rinse and repeat until you get to zero right?

[Dixit]

So if your LTIT is -1.8 ADD 1.8 at whatever temp necessary to the Idle Air Flow vs ECT table, rinse and repeat until you get to zero right?

No, if your LTIT is -1.80, then you subtrace your current value from that. IE, if your value at that temp is say 10.80, then you subtract 1.80 from it and you will be at 9.00.

Or just use the editor and PLUS -1.80 which will subtract the value automatically.

Dixit

[Dixit]

Also I think many forget to remember that when doing this you want to make sure both your fans are OFF and AC is off. If your FAN1 is on then it throws that STIT/LTIT value off. Use your VCM Controls and keep the FANS off just to make sure they dont kick in when your temp on kicks in.

Dixit

[chrisj6]

So make sure fans are off and your in closed loop, let the idle learn and log the 3 idle trims in the scanner (I only found 3). Then add or subtract the value logged from base airflow table as needed, correct?

Chris

[ozorowsky]

bump for chris, no one ever answered him.

[redhardsupra]

add them