Power at altitude

Post Fri Apr 22, 2011 1:46 pm

A guy I know lives in Hawaii and has an E39 M5. He complains that it has less power than he'd like when he takes it on his favourite drive through the mountains.

So what can you do about thin air robbing you of power?

Post Fri Apr 22, 2011 3:04 pm

not a lot.
have more power in the first place!

Post Fri Apr 22, 2011 3:22 pm

I suppose it depends just how hight these mountains are (i.e. how low the barometric pressure drops) and does the M5 have a barometric sensor?

Post Fri Apr 22, 2011 4:06 pm

Where I have the most fun driving is up between 1500 and 3000 meter elevation on the high mountain roads, and this is where I'd especially like the extra power as there is significant power loss at those elevations due to the thinner air.

He's looking at a supercharger as an option. Would there be anything you could do with ECU etc to compensate for altitude - maybe adjust the fuel/air mix or something along those lines?

I just thought this was an interesting question...

Post Fri Apr 22, 2011 4:10 pm

Also, that high mountain driving is all the car gets used for really - it's a pure toy - so sacrificing low altitude performance wouldn't necessarily be a big problem..

Post Fri Apr 22, 2011 4:14 pm

CHR1S1990 wrote:I suppose it depends just how hight these mountains are (i.e. how low the barometric pressure drops) and does the M5 have a barometric sensor?

as above..!!

not sure if the ECU on an M5 has provisions for any barometric correction, but aftermarket ECUs do. Heres an extract from megasquirt:

"MapDaddy 4 Bar MAP Sensor with Barometric Correction

The 'MapDaddy' 4-bar Manifold Absolute Pressure (MAP) Sensor upgrade for the MegaSquirt, with one primary 4-bar MAP sensor for standard MAP Sensor duties, and a second for realtime barometric correction so that your fueling calculations will stay accurate in the event of an elevation change (mountain runs anyone?)"