Lose car weight, go how much faster?

[Dan Chambers]

Now if I can get it to rev above 4K rpm, that would be fantastic....I bet THATS worth more than a second!!

-JW

Hope so, James. I'd like a little more competition than last A-X .

Bill: After shedding a few pounds of bumpers and driver's seat, plus a few odds and ends, I noticed a touch of acceleration/braking difference, and a whole lot more handling change. With those big aluminum pendulums off the front and rear, the car feels like it has a different "pivot" point, and slightly crisper steering response. (As a study, take two socks and two tennis balls. Tie the empty socks together loosely and twirl them above your head. When you stop twirling, not the time it takes for the socks to stop spinning. Now do the same with one tennis ball at the end of each sock. Mark the time the socks finish spinning. Compare the times. The effect on a 944 with lightened bumpers is the same, albeit not so dramatic.)

As to weight to power ratios; I've heard anything from 5-Lbs/1HP up to 10-Lbs./1Hp. I'm not sure what the actual ratio is. My guess: it's car -specific. With a student my times are usually 1.0 to 1.5 seconds slower than when the right seat is empty. I think 944's feel weight loss a bit more since the HP is low to weight ratio.

As mentioned by others, it's not just weight removal: weight removal and location of weight removal are both important. I think any weight reduction is good .... I know I could use some!

Good luck.

[Bob Gagnon]

Current weight to HP ratio=the value of 1 HP in pounds at current weight and horsepower.

For example, if a 2000 pound car had 200 HP the ratio would be 10 pounds per horsepower.

Therefore, removing the first 10 pounds would equal one horsepower for the example above.

The next horsepower would then be worth 9.95 pounds since 2000-10=1990 pounds 1990/200=9.95. Another way to look at it, for a 10:1 HP/wt ratio we would only need 199 HP, 1 HP less in our 1990 pound car.

The lighter the car gets, the less you have to remove to equal 1 HP; less is more in action!!!

Also Dan's sock illustration is a nice one for polar moment of inertia and why it is more effective to remove weight from the ends of the car and the top so as to maximally lower the polar moment and center of gravity of the chassis, nice pieces of mass the engineers say. Low polar moment is why Boxsters are so nimble.

Also rotating unsprung weight-wheels and tires- is a nice piece of mass.

[TheStig]

To test your 100 pounds, just take a cute girl as a passenger and compare times with and without. This may be a bad example, as you will probably be happier with the cute passenger despite being slower

Thanks for the idea Jad! Time to call a date to the October 15 autocross

I've heard the 10 lbs - 1 HP thing too. I know that even a removal of 50 lbs (within the limited reduction in order to avoid getting more points) has helped a little bit regarding nimbleness. I don't think I would be the expert to say that my car's handling has improved dramatically after the weight reduction since I feel I'm not pushing the car hard enough around the Q. hmmm...

[JamesWilson]

Hope so, James. I'd like a little more competition than last A-X Shocked .

hehe, you'll get yours No seriously, I need to take care of this problem. We sorted out some fuel delivery issues over the weekend as well as clearing up some excess wiring, so that has helped, but now the car is running waaay rich and needs to go back on the dyno to be tuned. I feel that this cutout at 4K rpm is ignition-related, and we are testing EVERYTHING to see what the heck is going on.......

So until then, I'll just crank up the boost to keep up with you, even if I'm in 5th gear on the West Lot!

-JamesW