Just remember that power to weight isn't everything. Would you rather have a 4000 lb car with 800 hp or a 2000 lb car with 400 hp? The power to weight ratio is the same, but depending on the track you'll get completely different results. Say you are on an oval. You get a lot more top speed out of the 4000 lb car, as the raw power will help and drag areas aren't typically scaling directly with weight.