1hp=?
Thread Starter
Staging Lane
Joined: Nov 2001
Posts: 60
Likes: 0
From: Saginaw, TX
1hp=? People do extreme things to save a couple of pounds of weight. What I want to know is if I cloned a car and ran it against itself with the only difference being I added 10 lbs to the weight of one, how much extra horse power would that car need to make up for the extra weight? As near as I can figure 10lbs=1hp. Anyone else have inputs? I posted this over on ls1.com also, so sorry for the repeat.
Thanks!
Matt
Thanks!
Matt
On The Tree
Joined: Nov 2001
Posts: 191
Likes: 1
From: Dallas, TX
Re: 1hp=? You have to use a fixed reference point like:
3000 pound car with 300 HP = .1 HP per pound.
3010 pound car with 300 HP = .09966777 HP per pound.
Equals a difference of .00033223 HP per pound.
add .1 + .00033223
3010 * .10033223 = 302.0000123 HP
If i am doing this right you would need to add 2.0000123 HP to make up for the 10 pound increase in weight, for this particular car.
[ November 16, 2001: Message edited by: kewlbrz ]</p>
3000 pound car with 300 HP = .1 HP per pound.
3010 pound car with 300 HP = .09966777 HP per pound.
Equals a difference of .00033223 HP per pound.
add .1 + .00033223
3010 * .10033223 = 302.0000123 HP
If i am doing this right you would need to add 2.0000123 HP to make up for the 10 pound increase in weight, for this particular car.
[ November 16, 2001: Message edited by: kewlbrz ]</p>
TECH Fanatic
Joined: Nov 2001
Posts: 1,347
Likes: 1
From: Freeland, MD
Re: 1hp=? A lot of stuff is getting left out of this equation. First, trying to relate weight changes to peak horsepower ignores the fact that you have an entire powerband to contend with. I think the proper way to do this would be integral matching, i.e., you have to calculate the effects of the weight change on the integrated power curve, which can be approximated by the average horsepower over the area of the curve that you are most likely to use. Then you have to consider changes in weight distribution, traction, etc. As you can see, this quickly gets very complicated, and we haven't even brought torque convertors and/or gears into consideration.
Having said all this, maybe the simple peak power to weight ratio is the best rule of thumb, because figuring it all out gets very geeky and messy.
Having said all this, maybe the simple peak power to weight ratio is the best rule of thumb, because figuring it all out gets very geeky and messy.
Re: 1hp=? Also, don't forget that it depends which ten pounds you remove. Getting the ten pounds out of the motor or driveline (lighter pistons, rods, crank, flywheel, etc) will gain more than removing ten pounds of dead weight (like a spare tire for example). Any dynamic weight or unsprung weight reduction is worth a lot more.
John
John
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TECH Fanatic
Joined: Nov 2001
Posts: 1,260
Likes: 0
From: High Point North Carolina
Re: 1hp=? Unsprung weight has a 3X greater effect on acceleration then 'sprung' weight. Lets just talk simple stuff though....
average FBody
3400 lbs
340 rwhp
Thats 10lbs/hp
Take away 10 lbs, you have in effect added 1 horsepower. Of course its not exact, as the now the equation changes ever so slightly, but its damn close. In the case of skinnies (unsprung weight) my front wheels/tires weigh 52 pounds. By going to a skinnie/165 radial they will weigh 26 pounds per wheel/tire. Thus I am saving 26 pounds per side, x 2 sides = 52 pounds weight savings. Thats unsprung weight, so its like saving 156 pounds, or its like adding around 15 horsepower to the car. It should be good for a tenth easily, probably close to 2 tenths when you consider less rolling resistance and the 165s will cut throught the air a little easier....
average FBody
3400 lbs
340 rwhp
Thats 10lbs/hp
Take away 10 lbs, you have in effect added 1 horsepower. Of course its not exact, as the now the equation changes ever so slightly, but its damn close. In the case of skinnies (unsprung weight) my front wheels/tires weigh 52 pounds. By going to a skinnie/165 radial they will weigh 26 pounds per wheel/tire. Thus I am saving 26 pounds per side, x 2 sides = 52 pounds weight savings. Thats unsprung weight, so its like saving 156 pounds, or its like adding around 15 horsepower to the car. It should be good for a tenth easily, probably close to 2 tenths when you consider less rolling resistance and the 165s will cut throught the air a little easier....
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