Will Altitude Effect My Tune?

[ws6ick]

I just moved from Colorado Springs to Kentucky where the altitude is 6000 FT above sea level in Colorado. When I start the car, it hunts idle for about 8-10 seconds and then it idles correctly. Cold start is fine its just the warm starts. I thought the MAF should adjust for the altitude change. Maybe I need to put some miles on it so the PCM can relearn the new altitude. Any inputs from the tuning pros would be greatful. Its on the 2000 Trans Am.

[daythecountrydied21]

Yes it will change it, I'd retune personally. The differences are pretty significant from CO to KY. I know a guy with a supercharged 4cyl whom is able to run 42# injectors with a 2.8 pulley because of living in CO when others would be more than maxing their injectors.
I take it that you're N/A. Which means you have some more power to unlock now that you're lower. Might as well do it if you can.

[Cantalope Kid]

If you have a custom tune and running Hybrid (Maf/VE) as from the factory your VE table should have been adjusted by the previous tuner for that altitude. You will need to verify the VE table is correct. Realize also that your STFT's/LTFT's will make corrections if you don't to get things where they need to be efficient on their own to a point.

[SilverG]

...it hunts idle for about 8-10 seconds and then it idles correctly.

Since I know my tune runs Open Loop for the frist 10 seconds after start up I would suspect yours is similiar. If it is off while in open loop that could indicate that the MAF/VE are off. Like the others have said, take some time and dial it back in.

You should see a noticable difference in power at the lower attitude. I saw my truck running -20% fuel trims while in the 8,000' range compared to Michigan.

[blownbluez06]

Try increasing the base running airflow table by 5% in the warm ECT spots and increasing the startup and friction airflow tables by 5% as well and see if it helps your warm starts. You may try another 5% if it starts getting you where you want to be on warm starts.
From 6000ft to sea level is the equivalent of adding 2.9psi boost. It's .03388 bar or 1" mercury for each 1000ft elevation. Increasing pressure toward sea level and decreasing pressure when going up in elevation. (inversely proportional).

[ws6ick]

Try increasing the base running airflow table by 5% in the warm ECT spots and increasing the startup and friction airflow tables by 5% as well and see if it helps your warm starts. You may try another 5% if it starts getting you where you want to be on warm starts.
From 6000ft to sea level is the equivalent of adding 2.9psi boost. It's .03388 bar or 1" mercury for each 1000ft elevation. Increasing pressure toward sea level and decreasing pressure when going up in elevation. (inversely proportional).

Ok, I will try this. I'm brain farting now, how do I add 5% to these tables?

[blownbluez06]

highlight the areas you want to increase by 5% and go to the top, enter a value of 1.05 and hit the X

[ws6ick]

Thanks. I just did a scan from cold idle to operating temp. I then turned the car off and re-started. Here is the scan.

[RWTD]

Look, it's this simple (and Cantalope Kid already stated such):

If you have a PROPERLY built MAF table, and you have the PROPER injector values inputted (ALL of them, not just the IFR table), all you need to do is properly adjust your VE table, then all of your fueling falls into place 100%. Provided your spark tables were generated correctly and not raped with blocks of the same amount of spark at all the various airflow points, then spark will, too, fall into place properly.

If all the above was done correctly, you may only need to work on the Idle parameters, if even (provided they were properly tuned in previously). Naturally, a check on everything else is always recommended, as this isn't a "perfect" world.

So the question we have for you is:

1: Was the tune actually built with proper MAF tuning?
2: Was the VE table actually tuned in correctly previously?
3: Was the PE table raped?
4: Were the spark tables generated properly for the various airflows?

All in all, this is why I feel it is important to tune a vehicle at sea level, and then you'll pretty much bet set in the future.

[ws6ick]

Look, it's this simple (and Cantalope Kid already stated such):

If you have a PROPERLY built MAF table, and you have the PROPER injector values inputted (ALL of them, not just the IFR table), all you need to do is properly adjust your VE table, then all of your fueling falls into place 100%. Provided your spark tables were generated correctly and not raped with blocks of the same amount of spark at all the various airflow points, then spark will, too, fall into place properly.

If all the above was done correctly, you may only need to work on the Idle parameters, if even (provided they were properly tuned in previously). Naturally, a check on everything else is always recommended, as this isn't a "perfect" world.

So the question we have for you is:

1: Was the tune actually built with proper MAF tuning?
2: Was the VE table actually tuned in correctly previously?
3: Was the PE table raped?
4: Were the spark tables generated properly for the various airflows?

All in all, this is why I feel it is important to tune a vehicle at sea level, and then you'll pretty much bet set in the future.

Not sure on all your questions. It was professionally tuned by a tuning shop in Colorado. It ran fine there until I moved to Kentucky.

[RWTD]

FYI, I spend a LOT of time in Colo Sprgs for pleasure, so if you're ever back up this way shoot me a PM and we'll meet up, grab a beer, and shoot da sh!t about our cars. I can even help you, as needed.

[blownbluez06]

FYI, I spend a LOT of time in Colo Sprgs for pleasure, so if you're ever back up this way shoot me a PM and we'll meet up, grab a beer, and shoot da sh!t about our cars. I can even help you, as needed.

That offer is like a sore peeter. Ya can't beat it!

[AleroB888]

I've been down to KY a few times, changed nothing on the tune, runs about one second quicker. The car has much more vacuum at idle down there, so fuel pressure regulation is affected.

If you are tuned for max performance at high altitude, for example if it's boosted as much as the engine can stand, you may have to detune it at sea level.