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Discussion Starter #1
Ok doubt there is any real concrete mathematical answer to my question, but any input would be great. Say you have a set hp engine... stock 222hp or 325hp, whatever. Say the car weight is 3500 lbs. Then you bench a few tests like 0-60 and 1/4 mile... is there any way to tell how much weight you would need to reduce your car to lessen your 0-60 by 1/10 sec or 1/4 mile by 1/10 sec (I'm just making up numbers here). Of course all other factors would have to be equal. Like say you dropped your weight 200 lbs to 3300, how do you think that would that change your numbers?
 
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there is an old formula with car weight and horsepower. For every 100 pounds you can take off the car you add about 10hp at the wheels and .05 off your quarter time at the dragstrip
 

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Here are two formula's that might be useful in answering your question.

ET Method:
hp= weight/ (ET/5.825)3rd power

Trap Speed:
hp= weight (speed/234)3rd power

These are both for quarter mile times, one eigth mile just devide by 2. However you have to know what the weigh of your car is, or at least close to it, to come up with an accurate HP figure.

Sorry about that I don't have the conversion to metric for our friends overseas.

One question for those 3kers and Stealth folk oversea, does your speedometer have both km/H and MPH? Ours do.

Dave Best
3Si #62
 

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Dave,
Are those formulae at the crank or wheels?
 
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Actually, the old saying is that if you drop 100lbs, you gain .10 sec in 1/4 mile performance but you don't add ANY hp to the rear wheels, you are just accelerating less mass, which provides quicker acceleration because you have the same amount of power but less weight to accelerate. It is also said that for every .067 seconds you reduce your 60' time, (2/3 of a tenth of a second), you reduce your 1/4 mile E.T. by 1 full tenth. Example, if you are running 13.50 with a 1.967 60' time, and then run a 1.90 60' time, you will most likely run a 13.40 provided all other things are equal.
 
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Discussion Starter #6
Another simple way to visualize the effect is this:

Our cars weight to horsepower ratio is 3737lb/320hp = 11.7 (using '99 numbers).

Adding or subracting 11.7lb from the car has the same affect as adding or lossing 1HP.

Ken
'95 VR4
 
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