Weight Loss Program and Feeling Great

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"?

[Bavarian Motorist]

It depends what car we're talking about.



So no one knows if any of their batteries will fit my car? I am looking at the 11.5lb one and the 15lb one.

I'm sure it will fit, but I don't wanna just buy it and have it not fit.

[Adam]

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"?

Yes, I've heard that too, losing 100lbs or adding 10hp should lower the car's 1/4 mile time approx a tenth of a second but it depends on a lot of variables. Cutting a 100lbs off a 1,900lb Elise is going to make a more profound difference compared to say a 4,000lb M5.

[RacebyDesign]

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"?

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.

[Bavarian Motorist]

Gearing is probably the best mod you can do aside from FI, but people don't do it.


I hate my 5 speed because of this. I want closer gears...






Will order the battery in a couple days!

[RacebyDesign]

At least you dont have Toyota Corolla gears, lol.

Sounds good to me.

[John V]

Don't forget about the impact of wheels. Porsche wheels are very heavy by design.

The CCWs I just picked up are strong, and they weigh 12-14lbs less per corner than the stock ones. You get double bang for your buck because you're removing unsprung weight which is also inertial. Big improvement!

My '00 S is 2960 with the CCWs on and about 5 gallons of fuel in the tank. With no exhaust and minimal fuel for competition it's closing in on 2900. Not light, but better than a lot of cars.

[Bavarian Motorist]

Also lightweight wheels will free up horsepower

[RacebyDesign]

Besides the reduction in unsprung weight making the vehicle more throttle responsive/quick in a straight line, it also helps braking and suspension agility.

A great practice is to also check the specs of tires when it comes time for replacement. Find current tire diameter and weights from a website like Tirerack.com or from the manufacturer site. Sometimes squeezing a really wide tire on a rim that would better use a narrower tire isnt a great practice:

*Increases weight
*Ineffective contact patch
*Pinched sidewall leads to less responsive handling
*Many times increased rolling diameter

Setting our 2006 Altima SER up for G-Stock we have realized that using a 225/40/18 Hoosier A6 rather than a 245/45/18 is a better match for our 8" wheel. The tire is also 3 pounds less and 3 inches shorter than the 245 effectively decreasing our long second gear. The 245's will look MUCH better but thats not always the fastest way around the cones especially with soft rubber.

Boxster's dont always have the same luxury as tire brands/sizes are harder to come by and more expensive. However, if you can still work a staggered combination and effectively utilize your wheel widths the car will simply be faster than the "steam roller" crowd unless they are running 12" wheels, etc.

Light wheels and rotors help a ton; tires and wheel width can increase/decrease the most rotational mass from your equation since they are on the furthest point from the axles. Narrow and soft is better than wide and hard especially if you can drop some weight.

Then again, on a daily driven vehicle we cant always be replacing tires every 6k miles. There is definitely a fine-line to walk.