So, how much horsepower does a stock S4 *really* have?
12-01-2001, 03:34 PM
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So, how much horsepower does a stock S4 *really* have?
The answer: it calculates out to 277.
The equation I used, given in the Sep. 2001 issue of Road and Track, is:
weight*(speed/234)^3 , where speed = trap speed at the end of the 1/4 mile and weight = weight of car, *but* you have to use weight of car + driver to get the accurate number. They give two equations for calculating HP given trap speed, but I found this one to be much more accurate; in fact, it's remarkably accurate, *if* you add the driver weight to the curb weight of the car, (i.e., the "as-tested" weight).
Here's a pretty good example: in the same issue, they tested the MB C32, which is rated at 349 HP, at a 13.6@105.4 1/4 mile. The car's curb weight was listed at 3605 pounds, with an as-tested weight of 3780 pounds.
Plugging it in, we get 3780*(105.4/234)*(105.4/234)*(105.4/234) = 3780*.0914 = 345 hp, only 4 hp off. Pretty cool, eh? I ran this on a bunch of car tests, and the numbers were always very close to the rated HP for the cars, normally well within the 5% they said the formula gives.
I also ran the results for S4, and found an interesting result: Road and Track's Oct. 1999 issue got a 14.1@98.5, with an as-tested weight of 3710 pounds. This gives about 277 horsepower, stock, which closely matches dyno tests of stock S4's we've seen. So, as everyone suspected, and as the car mags said, they *are* under-rated stock. :-)
I also ran this on the other road tests, in Car & Driver, Motor Trend, etc, and the results were typically the same. And I ran it on a bunch of other cars, at least twenty, always getting results that were very close to the cars' rated hp. Fun with physics!
I originally posted the above under a separate thread, but I thought it deserves its own thread. ;-)
The equation I used, given in the Sep. 2001 issue of Road and Track, is:
weight*(speed/234)^3 , where speed = trap speed at the end of the 1/4 mile and weight = weight of car, *but* you have to use weight of car + driver to get the accurate number. They give two equations for calculating HP given trap speed, but I found this one to be much more accurate; in fact, it's remarkably accurate, *if* you add the driver weight to the curb weight of the car, (i.e., the "as-tested" weight).
Here's a pretty good example: in the same issue, they tested the MB C32, which is rated at 349 HP, at a 13.6@105.4 1/4 mile. The car's curb weight was listed at 3605 pounds, with an as-tested weight of 3780 pounds.
Plugging it in, we get 3780*(105.4/234)*(105.4/234)*(105.4/234) = 3780*.0914 = 345 hp, only 4 hp off. Pretty cool, eh? I ran this on a bunch of car tests, and the numbers were always very close to the rated HP for the cars, normally well within the 5% they said the formula gives.
I also ran the results for S4, and found an interesting result: Road and Track's Oct. 1999 issue got a 14.1@98.5, with an as-tested weight of 3710 pounds. This gives about 277 horsepower, stock, which closely matches dyno tests of stock S4's we've seen. So, as everyone suspected, and as the car mags said, they *are* under-rated stock. :-)
I also ran this on the other road tests, in Car & Driver, Motor Trend, etc, and the results were typically the same. And I ran it on a bunch of other cars, at least twenty, always getting results that were very close to the cars' rated hp. Fun with physics!
I originally posted the above under a separate thread, but I thought it deserves its own thread. ;-)
12-01-2001, 03:37 PM
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what do you think of the 258 numbers that were thrown out after a recalculation from a dyno...do..
you remember that number? 277 is probably as good as it will probably get, huh? 14.1 stock is an excellent run
12-01-2001, 03:38 PM
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Audi/VW tend to be VERY conservative with their HP ratings. Euro Spec S4s....
Have a rating of 265, but they are the exact same car that we have. I would imagine Audi rated the S4 with lower HP numbers for insurance reasons.
12-01-2001, 03:46 PM
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Re: what do you think of the 258 numbers that were thrown out after a recalculation from a dyno...do
I'm not sure which one you're referring to; do you have a link?
But I always thought the HP of the S4 was underrated, given the times they were turning in the mags stock...they didn't gel with the cars' weight/hp ratio, when compared to other cars running the same time; nor did it make any sense that cars with the *same* weight/hp ratio were running slower times....but if you line them up with about a 13 lb/hp rating, it makes much more sense.
I suspect that stock ones are making anywhere from 260-275 hp...
But I always thought the HP of the S4 was underrated, given the times they were turning in the mags stock...they didn't gel with the cars' weight/hp ratio, when compared to other cars running the same time; nor did it make any sense that cars with the *same* weight/hp ratio were running slower times....but if you line them up with about a 13 lb/hp rating, it makes much more sense.
I suspect that stock ones are making anywhere from 260-275 hp...
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12-01-2001, 03:51 PM
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Re: Yeah...that'd be about 240 at the crank with a 25% driveline loss...too low for a 14.1 stock 1/4
I just had my car dynoed at adrenaline motorsports in Auburn MA, an apr distributor. Unless they ****ed up my cars pull, or my car is leaking boost, a stock s4 has 180- 189 hp to the wheels.
