[Kev_205]

Now i've been pondering. How do you match individual tb size to the engine? Most 2 litres I see run 45's but some go for 48's and touring cars are yet bigger still at 50mm. I'm going to stick my neck out and say its cam profiles rather than cylinder capacity but if so is it just "try different combinations on the rr" or is there some complicated maths to chew on?
Then throw in optimum trumpet length to boot - but thats a lot easier to test on the rolling road