[Longboarder]

Altitude can positively affect performance in certain scenarios. The air is less dense and therefore less drag. The half mile event speed records set by Underground Racing happened at altitude at Colorado at the Shift Sector event in Colorado Springs.

When a turbocharger of a turbo motor is at its efficiency limit at sea level, it will lose power at elevation. However if a turbocharger is no where near peak efficiency at sea level and then goes to a high altitude, insofar as the turbocharger is within its efficiency levels and if the ECU is sophisticated enough to read density altitude, the ECU will compensate for the oxygen difference and request more boost to yield equal power as sea level. Therefore, as long as there is more "room" in the turbocharger, it can compensate by providing higher boost pressures (which means it is pushing more air molecules) to maintain the same power as sea level. Coupled with less aerodynamic drag, can produce better accel results at altitude.

[ghost34]

For comparison, In IL, my modded M235 AWD, best I got was 3.95s to 60, 12.1 1/4 but avg was 4.1/12.3. Now, at 6150 ft in colorado and same measuring equipment, my best is 4.3/12.8 but most are 13.0. I'm easily losing .7s at altitude, I'm shocked you hit those numbers at 6400', very impressive

[Remonster]

Originally Posted by tnd720

Lol… you have no idea what you are talking about. You realize that at altitude even with DME that can compensate to spin those turbos, where the f do you get more Air molecules to combust?

...what do you think the turbos are shoving into the engine if not additional air molecules?

You lose air *density* at altitude, increasing boost pressure will compensate and all modern BMW turbo engines have plenty of headroom to compensate for several thousand feet of elevation and hit their advertised power and performance figures.

The fact that the original poster in this thread got such quick acceleration figures is another point of proof.

If you're wondering why all modern BMWs seem to be "underrated" and make "so much" power on a chassis dyno, it's usually because the dyno operator is adding a weather correction factor on top of a car whose ECU has already compensated for the weather and has not lost much, or any, power compared to what it's rated for.

[02M3ForMe]

Regardless of the theory, we’ve already observed slightly better performance with the G80 at lower altitude/DA. Both 0-60 and 1/4 mile times are 0.2-0.3 seconds better than these results in optimal conditions.

It’s definitely very good news that performance doesn’t degrade significantly, even over a mile up.

[Long.sns]

Originally Posted by Longboarder

Altitude can positively affect performance in certain scenarios. The air is less dense and therefore less drag. The half mile event speed records set by Underground Racing happened at altitude at Colorado at the Shift Sector event in Colorado Springs.

When a turbocharger of a turbo motor is at its efficiency limit at sea level, it will lose power at elevation. However if a turbocharger is no where near peak efficiency at sea level and then goes to a high altitude, insofar as the turbocharger is within its efficiency levels and if the ECU is sophisticated enough to read density altitude, the ECU will compensate for the oxygen difference and request more boost to yield equal power as sea level. Therefore, as long as there is more "room" in the turbocharger, it can compensate by providing higher boost pressures (which means it is pushing more air molecules) to maintain the same power as sea level. Coupled with less aerodynamic drag, can produce better accel results at altitude.

Sounds great, but I was driving in the Austrian Alps last weekend and the experience taught me my turbocharged engine struggles at altitude. It was so bad at the higher altitudes that I thought I was going to have to get out and push. No joke, it felt like there were 15hp total.

[naywa01]

Originally Posted by Long.sns

Sounds great, but I was driving in the Austrian Alps last weekend and the experience taught me my turbocharged engine struggles at altitude. It was so bad at the higher altitudes that I thought I was going to have to get out and push. No joke, it felt like there were 15hp total.

Yep, even the F1 boys complain about the drop in power on their hybrid turbo V6 powertrains when they run in places like Mexico.

That's regardless of any benefit they derive from reduced drag (which in an F1 car aero can be significant, which is why they have the DRS in the rear wing to aid overtaking).

The loss of air density directly affects power, but in their case also has a knock on effect on the energy recovery systems for the hybrid system.

[naywa01]

Those are definitely good times, but the thing that really stood out to me are the 0 - 100 & 0 - 120, those are pretty much supercar levels of performance from not so long ago (sub-11 to 120, is slightly faster than a 997 Turbo)!

[W///]

It blows my mind that a 4 door sedan that can carry at least 4 people in comfort, as well as their luggage (while getting half decent fuel economy if you're careful) can be as quick as hyper cars I grew up with in a straight line.

[NISFAN]

Originally Posted by Longboarder

Altitude can positively affect performance in certain scenarios. The air is less dense and therefore less drag. The half mile event speed records set by Underground Racing happened at altitude at Colorado at the Shift Sector event in Colorado Springs.

When a turbocharger of a turbo motor is at its efficiency limit at sea level, it will lose power at elevation. However if a turbocharger is no where near peak efficiency at sea level and then goes to a high altitude, insofar as the turbocharger is within its efficiency levels and if the ECU is sophisticated enough to read density altitude, the ECU will compensate for the oxygen difference and request more boost to yield equal power as sea level. Therefore, as long as there is more "room" in the turbocharger, it can compensate by providing higher boost pressures (which means it is pushing more air molecules) to maintain the same power as sea level. Coupled with less aerodynamic drag, can produce better accel results at altitude.

My I add one correction, the mention of higher boost pressures. The turbo runs the same boost whatever the altitude. The pressure ratio will be different because the high altitude air is less dense, but the target boost pressure is the same. Not correcting it for you, you already know your stuff, others might have gotten confused.

[MilehighM3]

Originally Posted by Limegrntaln

Ive never seen a car that didnt perform worse at altitude. Altitide most definitely makes a difference, turbo or not. Electric is probably the only car thats not affected.

Diesels are also not effected

[MilehighM3]

Originally Posted by Longboarder

Altitude can positively affect performance in certain scenarios. The air is less dense and therefore less drag. The half mile event speed records set by Underground Racing happened at altitude at Colorado at the Shift Sector event in Colorado Springs.

When a turbocharger of a turbo motor is at its efficiency limit at sea level, it will lose power at elevation. However if a turbocharger is no where near peak efficiency at sea level and then goes to a high altitude, insofar as the turbocharger is within its efficiency levels and if the ECU is sophisticated enough to read density altitude, the ECU will compensate for the oxygen difference and request more boost to yield equal power as sea level. Therefore, as long as there is more "room" in the turbocharger, it can compensate by providing higher boost pressures (which means it is pushing more air molecules) to maintain the same power as sea level. Coupled with less aerodynamic drag, can produce better accel results at altitude.

Drag definitely has an effect at altitude, but not that dramatically at 5-6k. One of the main reasons shift sector cars can set records here in Colorado is also the runoff area available at the airport where the past events have taken place. The cars make crazy power indeed, more than they can really apply to the road at any given speed. Having watched and had a chance to chat with the guys running they have enough headroom in the turbos and can dial in the tunes given enough passes. When you're making ~3500whp any speed is possible with traction. The UGR records were set with a massive tailwind also, which is either a benefit or detriment to your run, depending on the time of day. Bottom line is gas powered vehicles loose power here and the OPs numbers are still very good.

[F85MTuNED]

Great job Op!

[vetteflier]

Garrett knows a bit about turbocharging. They state altitude has little to no affect on turbocharged cars unless they are at absolute max pressure already--as another poster noted. The M3/4 should be within a tenth at 7000' of what they would be at sea level. Air temperature has more impact than simple AGL elevation on performance, as well. Even in NA engines, 100 degree temps at SL run less power than 75 degrees at 5000'.