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Originally Posted by boggtown
Hmm, maybe. I always heard it as 100 LBs will give you a tenth in the quarter mile. To some extent at least. What was this "blow out price"?
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The 100 pounds per 10th or per 10 hp is a VERY rough rule of thumb but has been used in the past mostly with the musclecar guys. Its very similar to the 5 psi of boost is safe for any engine; or 11.5:1 A/R ratio will give the most horsepower at the safest tune.
The only problem with the 100 pound rule is it works *pretty* well when determining V-8 rwd 1.5-2.0 ton vehicles. Torque moves weight easily and most of those vehicles have a ton to start with (torque and weight).
A Boxster losing 100 pounds with its smaller engine and less initial weight is losing a higher percentage of mass as compared to a Mustang or Chevelle. Better yet, my 2100 Corolla-powered MR2 Spyder losing 100 pounds which is close to 5% of its entire weight.
The better solution is to calculate a vehicle with a very similar powertrain and play the power vs weight game. If you have a Boxster 2.5L compare whp with a Boxster S and try to get accurate weights of both vehicles. Then take off 100 pounds and recalculate the new power/weight ratio of both vehicles and contrast them with stock quarter mile times (take these with a grain of salt too as they vary depending on the day, car, and magazine).
Ready for more frustration? Two vehicles with equal power-to-weight ratios and drivetrain configurations can be vastly different. Depending on cam changes, aerodynamics, gearing, etc one car can be significantly faster from 60 mph upwards than another. This is why vehicles like the Boxster, S2000, and RX-8 can destroy some of the bigger dogs on the track. Of course there are other factors with that as well.
As for the Braille battery or the Odyssey PC680...both have custom battery trays available for those who dont want to weld and hack like I did to my box. I am adding those to the site as I write this.