MG ZR: Cams & Maps

[Dum-Dum]

God, how small is it as standard? The GTi6 throttle body is 60mm.
Id be porting out the throttle body housing and knife edging the butterfly along with slimming down the throttle shaft and screws.

How big is the 1.8 throttle body? bigger isn't always better although I wouldn't expect the 2.2 hdi guy to understand

The 2.0 XSi one is 40mm ish and fitting the bigger GTi6 one increases power. In fact with petrol engine tuning fitting a bigger throttle body is often done to increase top end power. This is also why people fit individual throttle bodies for larger throttle area, thus less resistance and thus more power. Obviously only makes gains if the throttle body is the most restrictive part of the inlet tract but it often is. The only down side is low end drive ability as tiny openings give a massive amount of air.

As such bigger throttle body is better.