Lets talk about Uncorrected Power Numbers and real-time power numbers.

[lawdogg]

I've had the same car make 50 awhp difference between 2 consecutive days on the dyno with the numbers uncorrected and no changes to the tune. So, not only elevation, but weather conditions (barometric pressure, humidity, and temp) involved. There is no way to even tell.

+1

The calculator shows you how much the air conditions on any given day will alter the horsepower of a normally aspirated internal combustion engine. This calculator uses relative humidity which requires some caution because the relative humidity changes radically during the day as the air temperature changes. To use this calculator, just enter the temperature, barometric pressure, dew point and altitude and click on the calculate button. Air density is affected by the temperature and humidity of the air.

On a hot day, or at high altitude, or on a moist day, the air is less dense. A reduction in air density reduces the amount of oxygen available for combustion and therefore reduces the engine horsepower and torque.

This calculator shows you how much the air conditions on any given day will alter the horsepower of a normally aspirated internal combustion engine. For example, at 85 degrees F, 30.14 Inches Hg (mercury) barometer reading, 40% relative humidity and 5000 feet altitude, the engine only produces about 81.1% of the rated horsepower. The dynamometer correction factor shown above is the reciprocal of the relative horsepower number.

The dynamometer correction factor, the actual air pressure and the vapor pressure are included for comparisons to DynoJet chassis dynamometer test data. The air temperature should ideally be the temperature of the air that is going into your engine. The barometric pressure is the corrected to sea level atmospheric pressure that is typically reported on the local news or may be available from a local airport (this is not the same as absolute pressure, actual air pressure or station pressure). The dew point and barometric pressure can generally be gathered from a local weather report or the national weather service. The ambient dew point inside a closed building may be markedly different from the outdoor readings. The altitude can be found on topographical maps or by calling a local airport. For these calculations, the standard conditions are air temperature 77 degrees F, 29.235 Inches Hg Barometer, 0 feet altitude, 0% relative humidity.

Relative Horsepower Calculator

[familyMAN]

So are you going to tell us or just keeping filling a thread with guesses?

[CoopKill]

Is this Jeff's car?

[J. Fast]

Not to mention that altitude doesn't affect forced induction near as much as it does to a naturally aspirated car.

I heard that on the internet too, but that's not true. It affects it more than you'd think.

this. temperature has a LOT more to do with it than altitude. although to be certain, denser air will need to be compressed less, which does mean that it will heat less than air at altitude when compressed to a given PSI.

Well, if it was colder in Washington does that mean you lose less power?

I've had the same car make 50 awhp difference between 2 consecutive days on the dyno with the numbers uncorrected and no changes to the tune. So, not only elevation, but weather conditions (barometric pressure, humidity, and temp) involved. There is no way to even tell.

That seems a little unrealistic and I don't think it can swing that much with zero changes. On the other side of that I have dyno info from a temperature swing of 45 degrees and 10% humidity and the numbers were still within 5% of eachother.

What I'm after is discussing the reality of power loss based on a simple drive. Were talking a drive from the center of the United States to a Coastal City. You think you lose 5% 10% 20% 30% 40% you wouldn't even guess?




Blue is Washington at English Racing. Testing conditions: 64 degress and 64% humidity and 29.6 baro

Red is Colorado at MAC Autosport. Testing conditions: 72 degrees and 6% humidity and 24.5 baro

At seal level it goes from 200whp to 750 in 2 seconds

At elevation it goes from 200 to 600 in in 2 seconds

I'd like to thank H. Landry for the info.

[mehrshadvr4]

is it just me or the pic is not working?

[GTOJOE]

Yeah pic not working.

Rocky Mountain DSM Forums

requires a login to the site.

[Ray Pampena]

elevation (really baro) changes the power on a turbo car by a lot. although you can make the same boost, it requires much more backpressure to make the same boost.

[J. Fast]

Had to check with Hal since he's admin to copy and paste... Here you go!

Edit... Updated post #14 with sheet..

[mb3000]

I heard that on the internet too, but that's not true. It affects it more than you'd think.

Well, if it was colder in Washington does that mean you lose less power?



That seems a little unrealistic and I don't think it can swing that much with zero changes. On the other side of that I have dyno info from a temperature swing of 45 degrees and 10% humidity and the numbers were still within 5% of eachother.

What I'm after is discussing the reality of power loss based on a simple drive. Were talking a drive from the center of the United States to a Coastal City. You think you lose 5% 10% 20% 30% 40% you wouldn't even guess?




Blue is Washington at English Racing. Testing conditions: 64 degress and 64% humidity and 29.6 baro

Red is Colorado at MAC Autosport. Testing conditions: 72 degrees and 6% humidity and 24.5 baro

At seal level it goes from 200whp to 750 in 2 seconds

At elevation it goes from 200 to 600 in in 2 seconds

I'd like to thank H. Landry for the info.

My guess is + 140-180 uncorrected hp gain at sea level vs 5500ft.

[RealMcCoy]

The DA (density altitude) on the figures you provided are vastly different. DA on Colorado is 14176 ft, DA on Washington is 1094 ft. From that, I'm not the least bit surprised by the large difference in power.