Throttle bodies

[Dum-Dum]

Got a few questions bugging me about converting to ITBs.

Does it really matter what size the bodies are as long as the combined area of their throttle plates is greater than the area of the single standard throttle plate.

Im guessing that the bigger you go the better the gains but if standard is 70mm then even 40mms should give a reasonable gain.

Would it be adviseable to have the same area of throttle plate as the area of the 2 inlet valves?

Also what size is the standard throttle plate?

[JackLewis_Dturbo]

one thing i do know is you want zero restriction! so each body needs to be bigger than the 2 ports it is feeding atleast.

40mm is the sort of size you would put on a 106 gti so go bigger if you can....there must be kits out there ready to bolt on?

[Dum-Dum]

Im aware there is bolt on kits out there but im trying to increase my understanding.

You say youd want bigger than the area of the valves but as standard the the throttle area cant even be half the area of the valves.

[cwspellowe]

You don't want oversized as they'll flow FAR too much air and it will run like crap. Bigger = more power, smaller generally = more midrange, so it's a compromise.

[Dum-Dum]

The area of 34.1mm inlet valves is 2.867cmsq so double that, square root it, divide by pi and times by 2 and youd want 48mm bodies.

Suppose that makes sense actually.

[cwspellowe]

and that makes it how many % faster?

/troll

[JackLewis_Dturbo]

Im aware there is bolt on kits out there but im trying to increase my understanding.

You say youd want bigger than the area of the valves but as standard the the throttle area cant even be half the area of the valves.

but a standard throttle body isnt designed to give the same response of ITBs regarding air flow and throttle response....

IMO it would be a little silly to throttle body a car without head work like port and polish and a gas flow for maximum gains..

[Rippthrough]

38mm will flow to about 180bhp before they get really restrictive, 40's should be good for about 200. Does depend on tract length and engine rpms too though, higher revs and shorter tract's generally require wider bodies - you might go to 44mm for 200+bhp on something with lots of revs to go at for example.

[Poodle]

and that makes it how many % faster?

/troll

Ripp's idea sounds good, go with that.

[chrisrallye]

i am running 48mm bodies but i know a lot of people run 45mm.

[ginge191]

and that makes it how many % faster?

/troll

Are ITB's lighter than the standard inlet.. errm

/retroll

[Dum-Dum]

Are ITB's lighter than the standard inlet

I dont think theyll be much lighter, maybe a little bit. Probably about the same TBH

[Matt]

Lightweight

http://www.jenvey.co.uk/home/twin-thrott...tyle-tb45i