[W126 Coupe] 0-60 times?

[Jim Ham]

The density ratio of air at 3000 feet vs. sea level is 0.91 assuming 
standard conditions. Standard temperature at 3000 feet is 48 deg F., not 
too far from your test temperature of 52 degrees. So at a first guess, your 
power will be down by about 9%. I doubt that the lower drag at elevation 
will make much difference in a 0-60 run as the average speed is only 30mph. 
Windage (loss from internal friction in the engine and transmission) won't 
change much with altitude. So my first guess is that your time should 
increase by 9% over sea level and that's less than a second. Have I missed 
something here?

Regards,

Jim Ham

At 05:09 PM 3/20/2006, you wrote:
>
>The altitude compensation is for the MIXTURE only; all air breathing 
>engines suffer from loss of pressure at altitude and the effects of 
>density altitude.     A forced induction engine may be able to normalize 
>the charge or it may not depending on many factors.
>
>At roughly 10000 feet MSL or 3000 meters the air is half as dense as it is 
>at sea level.    All air breathing engines start to show the effects of 
>altitude at as little as 1500 feet or 500 meters in standard conditions 
>sooner when it is warmer.     Standard conditions for sea level are 60 F 
>or 15 C and the temperature lapse rate is 3.5 F or 2 C drop for every 1000 
>feet of elevation.
>
>All air breathing engines only produce rated power at SEA LEVEL in 
>standard conditions.     Every other situation reduces power output to 
>some degree.     High humidity also adversely affects engine performance; 
>the water vapor in the air displaces oxygen that would be present in dry 
>air.
>
>Cold dry air is best for air density, while hot dry air produces the least 
>drag.    In a car the drag issue is minimal at low speeds so the cold air 
>is preferred.
>
>There are correction factors to normalize for the above and most dynos 
>factor these into the data they provide.    The G-tech is not able to 
>solve the problem only raw data.    The numbers could easily be .4- .5 
>seconds slower then sea level.
>
>Steve
>----- Original Message -----
>From: <mailto:vance.rowley at tiscali.co.uk>Vance Rowley
>To: <mailto:mbcoupes at mbcoupes.com>Mercedes Coupes Mailing Lists
>Sent: Monday, March 20, 2006 4:17 PM
>Subject: Re: [W126 Coupe] 0-60 times?
>
>Mike,
>
>  If I am not mistaken, all the SEC's have an altitude sensor that is fed 
> into the ECU. This in turn will adjust the mixture to compensate for the 
> altitude above sea level. So unfortunately, I don't think you are going 
> to get much of a different result at sea level. Unless of course you are 
> in thick fog which would improve your engine performance considerably 
> with such dense moist air. The only problem is you can't see where you 
> are going.
>I also have a G-Tech pro and found the accuracy extremely good. Have you 
>tested your braking from 60 as well?
>
>Good luck with your conversion.
>All the best,
>Vance.
>----- Original Message -----
>From: <mailto:mramay at att.biz>Mike R.
>To: <mailto:mbcoupes at mbcoupes.com>'Mercedes Coupes Mailing Lists'
>Sent: Monday, March 20, 2006 4:56 PM
>Subject: [W126 Coupe] 0-60 times?
>
>Went out last night and did the final runs on the SEC before the 
>conversion work starts. I wasn’t particularly pleased with the results but 
>it is what it is. The empty, dead – end road I found was not especially level.
>
>
>
>For the mathematicians amongst us, can these 0-60 times be corrected to 
>sea level? How much did I lose in time as the runs were made almost 3,000 
>feet above seal level?

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