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  #16  
Old 04-06-2001, 03:31 PM
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Still trying

Hi, Kuan. Thanks for hanging in there with me.

As I noted earlier, both of those functions use a "cubed" exponent, which intrigues me -- this consistency sort of says to me, it doesn't matter what you're measuring (quarter mile, 0-60, or even the first hundred feet!), but that the horsepower required to achieve any performance improvement must INCREASE by an EXPONENT of THREE.
So, if I get a time (seconds) to a goal (e.g., of 60 mph, or to reach a quarter mile -- it doesn't matter), this improvement takes a cubed increase in horsepower.

So how about 1/((17.4/13)^3) ? The reason for the inverse (i.e., 1/x ) in the formula is that lower elapsed times are indicative of more horsepower, so the horsepower is an inverse function of the time.
This gives me a value of 0.417, which, as a portion of the original horsepower (154) indicates a 64 horsepower increase; which in turn suggests a new output of 218 horsepower.

I'm not scoffing at this estimate, as there is some credibility. 13 seconds is within the ballpark estimate (~12 seconds) of 0-60's for mid-'90s GWagens equipped with the 215 (or so) horsepower M104 engines. So I think I'm in the ballpark.

Thanks.



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  #17  
Old 04-07-2001, 10:43 AM
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Ken,

Your method tries to tie in 0-60 with hp. I guess the ideal way to do it would be to have multiple points, and then fit it to a model. I'll hazard a guess that these 0-60 times will fall into the center part of the curve, which if like most models is quite linear anyway. So, I would say using straight ratio your horsepower would be 199hp.

Kuan (now I really feel stupid)
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  #18  
Old 04-07-2001, 08:19 PM
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Hi, Kuan.

re: "...I would say using straight ratio your horsepower would be 199hp...."

Ha, ha, I can live with that -- still's better than the original 154 :-).
Best regards

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  #19  
Old 04-09-2001, 10:53 AM
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Horsepower calculation

Guys
I got a formula some years ago, I can't remember where from, goes something like this:

(standing quarter mile terminal speed in mph / 234) cubed. multiplied by the weight of the vehicle in pounds.

The engine in my P****** was dynoed at 543 bhp and using a G tech I have terminal 1/4 mile speeds of 129 mph , the car weighs 3300 lbs, so the figures seem to work.

This seems to work ok with cars with Cd around 0.3 to 0.35 but I guess on the G wagen the excess drag would be a problem, I suppose a before and after power increase test could have been the answer.
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  #20  
Old 04-09-2001, 12:18 PM
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My last post on this

Okay Ken, here it is. There's no matheditor for mercedesshop so you will have to see the scanned in sheet of paper. Basically you have 185hp, a little less than estimated by my previous lousy method.





[Edited by kuan on 04-09-2001 at 02:52 PM]
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  #21  
Old 04-12-2001, 09:26 AM
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Ken,

sorry for the brief reply here, but I am a little short on time. I have input your data into the calculation methods that I use (I believe they are based on similar methods of what you have done & accordingly have the same limitations)

I calculate your original HP at 146 (fairly accurate)

I calculate your new HP at 189 HP (seems reasonable)

I will e-mail you an Excel File with the equation built in.

The file includes a lot of historical data from my cars. Read if curious, ingnore if your not. It was too much trouble to delete. Let me know if this helps.

Dwight
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  #22  
Old 04-12-2001, 09:50 AM
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One small note to further explain or complicate. The HP curve of the new motor may differ from the old & affect the amount of overall work being done (i.e. my tweaked 77-930 motor produces considerable power but only from say 3800 to 6000 rpm...a very steep & thin horsepower curve)in a lightweight 2500 chassis. In contrast, my 500E produces similar HP at peak, but, over a much broader RPM range which helps somewhat in compensating for its 4,000 weight.

While the turbo is clearly quicker, the 500E does better than pure numbers would lead one to expect. Our calculations are overall HP to the rear wheels. The G-tech does smaller increments and accordingly, is better at providing more accurate peak horsepower but seems to provide unusually unexplainable information with some turbo charged cars.

There once was a method of using a recorder, a tach, the weight of the car, tire OD, and gear ratios to actually MAP a horsepower curve. I have the old curves I created for each gear mapped on a single graph of HP vs. RPM, but I now cannot recreate how I got them. Figures!

Some day I will be old enough to have an excuse for these momentary blips of senility.





[Edited by dwight hinton on 04-12-2001 at 09:54 AM]
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  #23  
Old 04-12-2001, 03:58 PM
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Thanks -- looking forward to getting the spreadsheet

re: "...I will e-mail you an Excel File with the equation built in...."

Dwight -- I'm looking forward to getting theat spreadsheet. Thanks very much.


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