This talk about composite hoods and dry-cell batteries has me thinking about the performance gains of reducing my car's weight.

Aside from the obvious handling improvment, I'm trying to figure what the power gains will be. Before I get flamed: I relize reducing weight doesn't increase HP or torque numbers (ie. composite hood doesn't produce 15 hp)- but makes better use of the available power of the engine (improves hp:weight ratio).

My question is this: is there a formula to figure out what the 1/4mile times & speed improvement would be of removing 1 pound from the car?

I have a calculator that tells you HP based on weight, 1/4 speed & ET. -->http://www.corral.net/tech/brakehp.html

I need to go backwards and find out what a reduction in weight will gain in 1/4 ET and speed vs. how much HP would be required to achieve the same ET and speed if the weight stayed the same. I'm no math wiz, but I think the result would be a hp:weight conversion factor.

BTW: enter 3400lbs, 15.7 ET and 89 MPH in the calculator and you get pretty close to the 2002 C230K stock horsepower.

 

the formula that I have always used ( I got this from HotRod Magazine) was for every 100lbs you take away its like adding 10hp. Same thing for adding weight too. The other formula I used also from HotRod mag, was for every 10 hp you add you get a .15 quicker 1/4 mile and a 1/10 quicker 0-60 times. Thats why the Vette Z06 is so much faster than the regular Vette. its 450lbs lighter and has 40 more hp. So using the factor above the Z06 has 85 more hp than a regular vette.
I think if you get a pulley, chip, intercooler, drycell battery, and a CF hood, you could a drop your 1/4 mile time by 1/2 sec. around the same for the 0-60 times too.

 

So if I lose 20lbs of weight I gain 2HPs

off to the gym...

 

One formula is:

HP=(mph/234)^3 * weight in lbs.

mph is trap speed in 1/4 mile

I've never seen a formula that utilizes ET before. Maybe I'll back calculate that formula sometime to see how ET effects things. Most of these formulas just utilize the trap speed because, theoretically, this is when the motor is closest to producing peak horsepower.

Cheers, BT

Edit: I was inspired to look for another calculator, found this one, it'll give you estimated ETs and trap speeds from weight and HP.

on-line dyno

 

Thanks fellas.

At first glance, I'm getting the equiv. of about 5hp per 100lbs reduction. Not as good as I had hoped...

 

hahah...i like this one...

 

Now im definitely goin on a diet. I'll get 5 horses if i can get down to my high school weight