High altitude driving issues

3% loss in power per 1,000' of altitude increase is correct.

I put my Allison in "D" and let it decide which gear to use...that procedure has worked so far.

skipnchar wrote:
With a normally aspirated engine (no turbo or super charger) you will be loosing something like 10% of your horse power for each thousand feet you go above sea level. If you have a turbo diesel or turbo charged gasser, this power loss is almost non existent. Also keep in mind that water (also coolant) will boil at a MUCH lower temperature at high altitude so you MAY have lost some water from your radiator. Check to be certain you have a GOOD radiator cap on your engine to keep the coolant under correct operating pressure.

More like 3% per1000 feet

Higher altitudes means thinner (less dense) air. Assuming similar air temps, there will be less cooling at higher altitudes. Also, part of being at higher altitudes usually means climbing long grades-----that means higher engine temps also.

I agree with most of the advice given here.
I've been driving in high altitudes for many years. It is normal to run a little hotter , however if you are running temps high enough to be harmful , I would certainly clean the charge air cooler and the radiator fins with a good degreaser. This is probably the culprit from what you describe.

For the last several years we have been in the CO mountains going over passes between 11,000 - 12,000 feet. As someone else mentioned , it is very important to keep your RPMs up by downshifting while going up these grades. The lower the RPMs the lower the fan speed. If the temps start increasing too much, back off your speed.

The best way to monitor all this is with a Silverleaf monitoring system. Using one of these systems can really help put you in control of these situations.
I use a Silverleaf VMSPC . I don't like to be without it.

Good Luck !

With mechanical injection pump at high altitude you will in effect have more fuel to air and with more fuel you will build heat.

Not for me Brett, as I am now unfortunately on LTOT or long term oxygen therapy so I just crank up the concentrator. Do not know if that is turbo or supercharging but it does serve the purpose. BTW the concentrator starts to de-rate at 10,000 ft. just like the turbo.

wolfe10 wrote:
It takes more breaths of air at 10,000' to supply your body than at sea level!

Superchargers are engine driven intake manifold air compressors and therefore have parasitic drag, but do not have the lag associated with turbo spool.

Turbo chargers are exhaust gas driven manifold air compressors and do not have parasitic drag, but by nature have a lag in the time it takes to increase the intake manifold pressure.

Pros and cons to each method of increasing intake manifold pressure.

Mal

Super chargers were originally developed for high altitude fighter planes and bombers to compensate for the lower atmospheric pressure at high altitudes. Turbo chargers are nothing more than superchargers that make use of exhaust gas expelled through a small turbine to spin the supercharger.
Steve

wallynm wrote:
I agree and you could change the equation by changing the carb jets based on altitude.

nohurry wrote:
Skip, I always enjoy and respect your posts, but that 10% per 1000 ft can't be right can it? That would mean if a N/A engine was running at 7000 feet elevation, it would only have 30% of its power. I know there is some loss, but I have heard figures in the 3% per 1000ft range.

And, to a degree, modern fuel injected engines compensate for altitude by adjusting mixture-- the Oxygen sensor(s) input to the computer does this. It can keep mixture at the stoichiometric ratio.

It will NOT put more oxygen molecules in the air-- so power WILL be down at higher elevations since there are fewer molecules per cubic foot of air.

Just the same for people. It takes more breaths of air at 10,000' to supply your body than at sea level!

Correct, my truck is tuned for 5000' feet, as that is the base altitude it operates at.