altitude and speed density?

[BerniniCaCO3]

I was musing on how my car seems neutered in denver, colorado, the "mile high city."
The same power cruising, but when you floor it to 3500-4000rpms, it just... doesn't go.
Hoping that's just the altitude.

I have converted to massair.

But anyway, while massair should accomodate thinner air, does speed density have a means to calibrate itself to the higher altitude?
It has air temperature, it has throttle position, and vacuum readings [map]; with thinner air, the engine might pull less vacuum (on top of the lower outside pressure) than at sea level?

[sick88tbird]

Every naturally aspirated car will feel "neutered" at high altitude...just the nature of thinner air. All cars will adapt to higher altitude but that doesn't mean you'll make the same power that you would at sea level...otherwise you'd be asking the car to make some kind of magical bonus horsepower. Last time I ran my 351w powered T-bird(before parting it) was at about 800ft above sea level (jackson, SC)but the DA was around 3800ft and it refused to pull past 4500rpm...in fact it really nosed over past 4000rpm....on a bad day in Jersey I ran it at Atco(approx. 120ish ft. above sea level), and ran it out the back door to 5000rpm, no problem.

That night here in Jackson when I ran, I ran against 13-sec mustangs that could barely muster mid-14's and a bottom 12-sec goat that was running in the 12.90-13.10's. Forced induction cars are almost immune to higher altitude compared to N/A cars.

-Don

[gadget73]

did you leave the MAP installed as a BAP ?

S-D supposedly sort-of calibrates itself to higher altitude but it can only do that on a startup cycle. It reads ambient air pressure from the MAP before you start the engine and sorta uses that to tweak the fuel tables. Exactly how much and how accurate that is, I don't know. It would obviously do nothing if you rolled the key to start immediately before it had a chance to snatch that reading. Honestly I don't even know if it really can even do this, but if it is true, thats the best its going to get as far as altitude compensation.


The original main purpose to forced induction was for airplane engines. They are actually boosted to sea-level atmospheric pressure so they don't lose massive amounts of power as they climb. Thats why forced induction cars really don't give a damn about altitude.

[meandad]

My 86 GM was always a little buggy when you got it up into the mountains. It seemed to only be in a pretty narrow altitude band though, then it would be ok. coming back down it would do the same thing in the same altitude range.