Hello,

I was wondering if anyone knew if a car weighed 50 pounds less what would be the effect increase in horsepower??

Thanks

 

Ive been umder the impression that 100lbs off of a 3000 pound car is the equivalent to around 10hp. Not sure if this is correct though.

 

lightening the load improves your power to weight ratio. a way to get *rough* estimate and express the improvement in HP would be to divide weight savings by pounds per horsepower. so, if your boxster has a weight to HP ratio of 10 lbs/hp a 100 lb weight reduction would be *roughly* equivalent to 10 HP.

note: this estimate is only good for non-rotating parts like batteries and seats and mufflers. wheels and brake rotors and flywheels count for more because you use their moment of inertia instead of the their weight. but there's no fixed way to express this because the formula for moment of inertia uses the square of the radius of the piece you're calculating for.

 

+ 1....

 

Yup.

 

Don't forget that reducing un-sprung weight has a greater effect than reducing sprung weight. I've been told by many old school racers that reducing 1lb. of unsprung weight is equivalent to reducing 10lbs. of sprung weight. True or not, unsprung weight reduction definitely has a more dramatic effect.

 

yeah, but sprung vs unsprung doesn't enter into the horsepower discussion. it's all force = mass * acceleration.

sprung vs unsprung weight is about weight transfer and handling. unsprung weight -- by definition -- cannot be damped by suspension. the forces generated by sprung weight during acceleration, braking and cornering are (partially) absorbed by shocks and springs and dissipated as heat with the remainder going to the wheels and tires. the forces generated by unsprung weight are sent right to the wheels and tires unabated. so, a car with less unsprung weight will handle better. if it has good suspension.

 

Very true vick, I was thinking about handling. But don't forget that lighter brakes and wheels will aid in faster accelleration and braking. In any case lighter is better!

 

and, everything interacts with everything else in a way that's so complicated you can't keep it all in your head. (or at least i can't.) but what amazes me is how old track guys just instinctively know what to do.

you're right tho. bottom line: lighter is better.

 

Hahaha

That's why they're 'old'.