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The Augus issue of MMFF features an column by Richard Holdener that contains some simple math one can use to compute the effect of a given modification on a given car. The logic goes:

1. Compute the number of g's (gravities) you car produced in current form. The example he used was a 5 speed car with 400 lb feet of torque, a 3.27:1 final drive and a 2.95:1 first gear ratio. Drivetrain efficiency was set at 87% (average for a 5 speed - automatics would be lower) to compensate for lossed in the clutch, transmission and rear, and the tires had a rolling radius of 1.1 foot (racing slick, but close to that of many 315 drag radials as well). The car in the example weighed 3000 pounds. Here is the formula:

2.95 x 3.27 x 0.87 x 400 / (divided by) 1.1 = 3,356.98/1.1 = 3051.80 pounds of thrust. Next divide the thrust by the weight of the car:

3051.80 / 3000 = 1.017 g's of acceleration.

Changes to any of the variables will rais or lower the acceleration number, ie, add 100 lb/ft of torque with a nitrous kit, and you get 1.27 g's.

Change to 4.10 gears, and you get 1.278 g's.

Reduce the weight of the car by 600 lbs, and you get 1.271 g's.

Obviously you can also dollarize the equation, assigning the cost of the modification to the g's, ie:

Nitrous kit costs $1200, you gain .25 g's, the cost is $300 per .1 g gained.

Gears cost $600, you gain .25 g's, the cost is $150 per .1 g gained.

As you can see, the better investment purely from this standpoint are the Gears - more "bang for the buck". Lets say you could gain 33hp from a $400 throttle body and intake. This would be equal in value to the nitrous, at about $300/.1 g gained, though still inferior to the gears.

The article contains many caveats regarding things like aerodynamic drag not being factored into the equation - and this is true. But this forumula is at least invaluable in prioritizing the various modifications in at east a quasi-scientific manner.

If you can find it, seek out the article and read it (he has a similar write-up in the July issue regarding lateral acceleration, ie, handling and braking, that has similar potential in determining which handling modifications to do first.

I think aerodynamic loads get discussed next month. I for one am all ears.

tripleblack