How do power to weight ratios play a role in a race? For example, my camaro has 200 hp with a curb weight of 3306 lbs and a 2009 Scion TC has 164 hp with a curb weight of 2905 lbs. Which car has the advantage, how do you calculate that ratio, and how is the ratio read i.e. a lower number is better or a higher number is better? Just wondering thanks.

 

Divide the h.p. into the weight of the car. For your Camaro 3306/200=16.53. Meaning each horse is moving 16.53 lbs. of your car.
The Scion, 2905/164=17.71 lbs per h.p. It's close, and that's why drag cars strip off every unnecessary ounce of a car.
If those two numbers came out the same, the Camaro would still have an advantage because it has more bottom end torque and the h.p. comes in lower in the rpm band of the engine.
A lot of small 4 cyl. engines have the peak h.p. way high in the rpm's, above 5000. High rpm h.p. isn't what pulls you off the line unless you're flooring the gas and dumping the clutch. And an automatic trans model wouldn't stand a chance.
EDIT: One more thing...now add a 200 lb. passenger in your car and the ratio goes up to 17.53 lbs./h.p. A good rule is, when racing, dump your buddy out on the curb.

 

not a bad explanation. I usually do power/weight, in which case you typically want to maximize the number. it depends on how you think, and its just a convention.

another thing to remember (along the lines of the passenger) small hp, low weight cars are affected much more than a high hp high weight car with the addition of a passenger. which is why I prefer the v8