Home brew intake mods

[almightybmw]

Originally Posted by Daox

Cars at higher elevations do get better mileage. Its only only due to wider throttle throttle openings, but also having to push the car through less dense air. Of course, you do loose power.

I've gotten my best mileage in my GP here in the mountains, 35mpg, with a fully loaded car. I support the claim that higher altitudes equate to higher FE.

BUT I've also gotten the same mileage with a half loaded car driving from Portland to Fresno. Averaged 3000ft less over the same tarmac.

I can only conclude that the mountain passes at 5-6000ft are the reason I don't get a % higher than I did on the lowland 800 mile drive.

[bryan11]

Considering a few things here...

At higher altitudes, i.e. 5000 to 10,000ft ASL, there's less oxygen. The max power of a vehicle decreases at higher altitudes because the engine can't supply enough oxygen and must supply less fuel to run efficiently. Effectively, an engine rated for 110HP is cut to a lower level such as 70HP at say 8000ft ASL.

At the same time, air is thinner at higher altitudes, so drag (friction) is lower. The power needed to overcome drag at 50mph is less at 8000ft ASL that at sea level because the air there is about 1/16 as thick.