Hi,
Well a throttle as rudra mentioned is used to control the flow of gas, in a car this controls the amount of air entering the engine on the intake stroke, more air = more power and more revs, Its simply a butterfly valve. Now in Fuel Injected cars we have something called a throttle body.
The throttle body is a housing where the valve (butterfly) is housed. It also has added sensors like the TPS (throttle position sensor) and a IAC valve ( Idle Air Control).
Now, Most cars out from the company have preset butterfly sizes, like an MPFI Zen has a 47mm or so body and a Esteem 51mm. By increasing this butterfly size you can increase engine response and inturn get a bit of power too as it reduces restriction. The Lancer responds very well to this mod, you can increase a lancers upto 66mm (requires a bit of modification). You can expect upto 14hp by this mod. And by doing this other mods like NOS, Filter and TC etc will work better.
Hope this answers your q.
CHeers
Dom |