that's a restrictor plate, it goes in between the carb and the intake manifold to reduce the amount of air in the engine. It's only used on two tracks on the circuit (Daytona and Talladega) because of the tracks sheer size and the fact that the whole race is run wide open. Without a restrictor plate a NASCAR car can run 235 mph at Talladega without a draft.

Oh and the aero changes per race. At larger speedways, larger rear spoilers are used to slow the cars down (and also help with drafting). While smaller tracks a smaller spoiler may be used. So NASCAR does have aero to help slow the cars down on larger tracks but it's more about the motor. Aero is used more to keep the field close. If one car begins dominating, NASCAR changes that cars aero to make the field more even. It's just a way to keep the racing exciting (Sorry F1 guys, but a race with 2 passes in the whole thing is kind of dull). The way I look at it: F1 is to ballet as NASCAR is to boxing. (and WRC is > both F1 and NASCAR)

 

Ok, I can see that, so what would the wild and crazy British Touring Car series be?

 

any body know about the handeling? do the cars have an independant rear suspension?

 

I don't think so. But that doesn't mean handling is bad. They are very highly tuned, purpose built race cars.

 

True on both points: some F1 races can be dull and WRC > *. :-)

 

I would say they must handle pretty good since they are capable of running in the 1.10's on the 2.45 mile Watkins Glen course. Thats pretty close to Daytona prototypes lap.

 

Keep in mind that the NASCAR cars that race at Watkins Glen and Sears Point are specially built road course cars. They also specially build short track cars, superspeedway cars, and intermediate track cars.

However, you are right that they must handle pretty good. Oval tracks are all about handling, and they have to do it in heavy traffic with messy aerodynamics. And as I note above, they actually optimize the handling for individual tracks and then adjust it all throughout the race.

 

My sense is you'd find a Cup car to be a very nice road-racing car in pretty much every respect except for braking... You might want an extra forward gear too.