Unless someone has changed the rules, Pro Stock does not run alcohol, therefore they are more limited on CR. When cup cars could use qualifying motors, they ran as high as 18:1 on race gas. Why? While there is increased resistance due to higher compression ratio on the compression stroke, there is also a considerable increase in efficiency on the power stroke which you are missing. The following does a decent job of explaining: "Cylinder pressures and output will increase as the CR is raised, but what is less obvious is that the increase in compression also increases the engines thermal efficiency. Thermal efficiency is a measure of how effectively the engine converts heat into mechanical power. To appreciate this it is better to consider the engines expansion ratio (ER). This is the opposite side of the coin to the CR and describes what is occurring as the piston moves down on the power stroke rather than what happens as it moves up on the compression stroke." Read more:
http://www.popularhotrodding.com/tec...#ixzz1jxVXExeV
Alcohol and gasoline are two different animals with their own specific requirements. You can't just look at one particular race engine because its fast and apply that to every other engine. While some Pro Stock engines only have approx. 15:1 to 16:1 static compression ratios, you are forgetting that with their cam and head profiles, the dynamic compression is approaching 18 to 20:1. Any more static ratio, and bad things start to happen.