Throttle body size?

[LocoLobo]

ok, so what i've read so far it seems like everyone does the 65mm swap from a 96-04 gt mustang, i was wondering since i was looking at the different throttle bodies, why not go up to a 70mm or a 75mm? they seem to be about the same price and mount up just the same and would need the same work to fit a contour. I know too big can be an issue also, but the csvt is only a 60mm right? would a 70/75mm be too big?

I'm asking because i'm getting ready to do a tune and want to get it all done at the same time. I've got a 3L port matched, 24# injectors and msds headers...

 

[RAD Merc SVT]

Oh my god I have the same exact question for the same exact setup (just 65mm though) To add to his question how do you determine when you need a bigger throttle body?

 

[mmc757]

Depends on your LIM and UIM.
Assuming four intake valves open at any one time:
The area of your 35 mm valves is equivalent to a 70 mm hole
The area of the SVT spec LIM is equivalent to a 66.5 mm hole. Not sure on exact sizes of the non-svt LIM, but assume a little smaller.
The TB hole in the 2.5 UIM is only 57 mm. Not sure on the size of the hole in the SVT UIM, but I think its 60 mm.

So for your port matched engines, even if your using SVT UIM and LIM, anything larger than 66.5 mm is overkill and inneffective. If you went to some sort of 3.0 UIM and LIM, then there may be value in going as high as 70 mm, but thats about it.

 

[LocoLobo]

awesome, thanks for the info.

 

[Blackcoog]

I don't think you can even use a larger throttle body on a 3L UIM unless you find a way to get around the IAC routing issue (IAC routes through the stock 3L throttle body). Then you'd also have to port the plastic intake which might not work that well. Is there enough material and would it still seal to the gasket?

As far as the SVT UIM you have to port out the intake to match the larger throttle body. See this post over on NECO for how to get the SVT upper to work with the 70mm throttle body: http://www.newcougar.org/forums/for...ct-mavro-gato-99-turbod-3l-7.html#post1127646

For anyone who would run a 70mm MAF they would probably gut the secondaries and open the SVT lower up a bit anyway.