51mm tb

[knight5651]

Hi, im looking into getting a 51mm tb made up, theres a guy at a local machine shop that says he has done simular things before and that he would give it a go, i just wanted to check that the bore actually gets opened up to 51mm as i read somewhere about the tb's where someone said 50.8mm, sorry if this sounds stupid but ive tryd searching and cant find anything. just wanted to be 100% sure.

Thanx Alex

[Puncharado]

It doesn't really matter as long as the new butterfly is sized to suit.

[knight5651]

Ok cheers, i presume 51mm is the largest you can go?

[The Duck]

Why would you want to go larger?
51mm is more than enough for 250BHP+ on a charged engine with the TB on the pressure side of the charger.

I assume this would be enough power for you?

Cheers

Duck.

[hardchargin40]

You can never have enough power

But yeah 51mm is pretty much the limit on the casting and as Duck has said a sizeable power envelope.

ITb's would be the next stage.

[knight5651]

Oh yeah more than enough lol, just wondering really, just thought if im going to get it done i may as well go as big as pos, just seemed to make sence.

Thanx for the replies

[hayesey]

bigger doesn't necessarily mean better though, bigger throttle plate means less low speed throttle control and off boost air speed, both not great if the car is a daily driver (esp if it's also de-wedged which it invariably will be if you've had a bigger plate made).  Anyway yeah ~51mm is the most you can go to without breaking through the wall of the throttle body.

[LeonL]

If all fails i have one for sale in parts section at £100 posted

[dub-disaster]

bigger doesn't necessarily mean better though, bigger throttle plate means less low speed throttle control and off boost air speed, both not great if the car is a daily driver (esp if it's also de-wedged which it invariably will be if you've had a bigger plate made).  Anyway yeah ~51mm is the most you can go to without breaking through the wall of the throttle body.

can't twin plates combat this as used in the golf mk2 gti with one small palte for partial throttle and the second larger one opening with the smaller one about half way through, not sure but does the gt throttle body have this setup aswell?

[hayesey]

yes they can but a G40 doesn't have a dual stage throttle body.  A GT one could be adapted if you put idle and wide-open throttle switches onto it somehow (GT has a throttle pot normally).  You'd also need a remap to suit as the transition from low throttle opening to wide throttle opening behaves very differently to the single plate throttle.