[Cardiak]

Picking up first modded car from out of state that has basic bolt ons. Intake, long tubes, free flow cats, 95mm throttle body. The car was tuned at a shop that's located at 1,348 above sea level on 93. 93 isn't very common in my state. Will the car need to get re-tuned if I ever plan on using 91?

[KingLT1]

Yeah it should have the timing maps recalibrated for the lower octane or it will rely on the knock sensors to keep it alive. 93 octane isn't even enough to keep the engine off the knock sensors with the stock tune.

[LT1_William]

flex fuel brother !!!

[Cardiak]

I forgot the mention that the car currently lives at 630ft. It will be relocated to between 830 and 971ft. Just want to clarify that even if I run 93, it will still need to be re-tuned?

Flex fuel is a future possibility.

[arpad_m]

Originally Posted by Cardiak

I forgot the mention that the car currently lives at 630ft. It will be relocated to between 830 and 971ft. Just want to clarify that even if I run 93, it will still need to be re-tuned?

Flex fuel is a future possibility.

No need. First, the difference in air density between 630ft and 970ft is only ~3%, which is very easy to compensate for, and second, you are going from denser to thinner air, so if anything, your current tune will be safer and you'll lose a bit of performance.

It's when you have the car tuned to the max at, say, 8-9000 ft (thin air -> tune sets fuel volume for max performance -> perfect AFR) and then go down to sea level with the same tune that you have to watch out, because your fuel system may run out of capacity: as the ECM is trying to adjust (increase) the fuel volume to match the higher air density, it reaches the limit and can't go further because your hardware simply can't push more fuel, and your mixture leans out, potentially leading to engine damage.

[Cardiak]

Originally Posted by arpad_m

No need. First, the difference in air density between 630ft and 970ft is only ~3%, which is very easy to compensate for, and second, you are going from denser to thinner air, so if anything, your current tune will be safer and you'll lose a bit of performance.

It's when you have the car tuned to the max at, say, 8-9000 ft (thin air -> tune sets fuel volume for max performance -> perfect AFR) and then go down to sea level with the same tune that you have to watch out, because your fuel system may run out of capacity: as the ECM is trying to adjust (increase) the fuel volume to match the higher air density, it reaches the limit and can't go further because your hardware simply can't push more fuel, and your mixture leans out, potentially leading to engine damage.

Excellent. Thank you.

[KingLT1]

The MAF sensor is in place to account for air density change. So changing elevations won't matter.

Also, you won't have to worry about fuel system running out ever with your setup even on Full E85 in any DA. So that is a non-issue.

Now us guys that have forced induction cars have to pay attention to air density change because we are running closer to the limits of our fuel system capacity. Also, when air gets cooler and denser, the superchargers make more boost which requires more fuel. But again, with naturally aspirated engines it's not a non-issue. The stock LT1 fuel system is good for 580-600whp on full E85 naturally aspirated.

[Cardiak]

Originally Posted by KingLT1

The MAF sensor is in place to account for air density change. So changing elevations won't matter.

Also, you won't have to worry about fuel system running out ever with your setup even on Full E85 in any DA. So that is a non-issue.

Now us guys that have forced induction cars have to pay attention to air density change because we are running closer to the limits of our fuel system capacity. Also, when air gets cooler and denser, the superchargers make more boost which requires more fuel. But again, with naturally aspirated engines it's not a non-issue. The stock LT1 fuel system is good for 580-600whp on full E85 naturally aspirated.

Thank you for this.

Unfortunately, the seller wasn't completely transparent on a couple of things with the car so I had to back out. I will keep this information in mind for the future.