FI Tuner Question
Thread Starter
Instructor
Joined: Mar 2003
Posts: 239
Likes: 0
From: Colorado Springs CO
FI Tuner Question
Is this hypothesis correct?
When a FI car is run at higher altitudes (5000ft+), wouldn't you tune the PCM to be on the leaner side as compared to a car tuned at 1000ft altitude.
Here is what I am getting at: If we tune the car at 1000ft but the car will spend its life (for the most part) at 5000ft+, wouldn't you want to tune the car a little leaner at 1000ft cause it will see less oxygen in the same boost pressure at 5000ft+ ?? I understand that 7psi at any altitude is 7psi, but the amount of oxygen contained in that 7psi decreases as altitude increases.
Am I way off base on this assumption?
Thanks for the EXPERT responses....
Lonnie
When a FI car is run at higher altitudes (5000ft+), wouldn't you tune the PCM to be on the leaner side as compared to a car tuned at 1000ft altitude.
Here is what I am getting at: If we tune the car at 1000ft but the car will spend its life (for the most part) at 5000ft+, wouldn't you want to tune the car a little leaner at 1000ft cause it will see less oxygen in the same boost pressure at 5000ft+ ?? I understand that 7psi at any altitude is 7psi, but the amount of oxygen contained in that 7psi decreases as altitude increases.
Am I way off base on this assumption?
Thanks for the EXPERT responses....
Lonnie
Melting Slicks
Joined: Mar 2003
Posts: 3,116
Likes: 10
From: Macomb MI
Re: FI Tuner Question (lplott)
Yes..and no...
How that for an aswer..hehe..
Current engine controls read baro,airflow,temp and 02 concentration in the exhaust stream. at your elevation,assuming the MAF is not pegged will compensate for almost everything you can throw at it assuming its tunes correcty to begin with. The target AirFuel doesnt change, just the amount of fuel to arrive at it..Spark advance on the other hand is a different issue
You will find that the lower octane fuels in your area also help compensate the slow burn phenomina.
I always got a kick out of Colorado Springs area highest octane fuel was 89/90..
Phil
How that for an aswer..hehe..
Current engine controls read baro,airflow,temp and 02 concentration in the exhaust stream. at your elevation,assuming the MAF is not pegged will compensate for almost everything you can throw at it assuming its tunes correcty to begin with. The target AirFuel doesnt change, just the amount of fuel to arrive at it..Spark advance on the other hand is a different issue
You will find that the lower octane fuels in your area also help compensate the slow burn phenomina.
I always got a kick out of Colorado Springs area highest octane fuel was 89/90..
Phil
Le Mans Master
Joined: Apr 2001
Posts: 5,473
Likes: 717
From: Black Forest CO
Re: FI Tuner Question (lplott)
Actually under boost the MAP sensor is out of the loop because it is maxes out at 105%. Boost pushes the MAP over that.
Having your car tuned at Xtreme in Tempe and then driving it here in Colorado is no problem. I had my car tuned there and I have run it at altitudes over 10k feet and it runs fine. I was concerned about that too but it is just not a problem.
Having your car tuned at Xtreme in Tempe and then driving it here in Colorado is no problem. I had my car tuned there and I have run it at altitudes over 10k feet and it runs fine. I was concerned about that too but it is just not a problem.
Thread Starter
Instructor
Joined: Mar 2003
Posts: 239
Likes: 0
From: Colorado Springs CO
Re: FI Tuner Question (VortechC5)
Thanks Mark. Thought you might chime in sooner or later. I do trust the Xtreme guys, just wanted to understand a little better. I will set up a "show and tell" here in the Springs when I get it back and post on the forum. There are some nice roads between Phoenix and the Springs I am looking forward to playing on (easing on the throttle little by little). Don't want a show and tell from the repair shop....
Le Mans Master
Joined: Apr 2001
Posts: 5,473
Likes: 717
From: Black Forest CO
Re: FI Tuner Question (lplott)
I am very interested in your TTi setup. I saw the original one at Xtreme when they had it first installed. It is a very nice setup. I wonder if Xtreme would take my Vortech in on trade... 
