fitting big bore throttle body.

[jaffaz32]

My Throttle Body is now 5mm oversized.

What is involved in fitting a big bore throttle body?

The thermal gasket do you have to make the hole bigger? i am assuming you do other wise it would be pointless having a bigger bore on the throttle body as the air would hit the lip of the gasket as the bore size it came from is bigger.

Then would you also have to increase the size of the inlet on the other side of the Thermal gasket also?

That's the first part to the fitement.

the second part is that my friend who is a mechanic looked over my throttle body and said it circulates warm water to keep it warm to stop the butterfly sticking in cold weather. He said in the UK it's not really needed as the tempreture doesnt get that cold here and it would be better to bypass is by putting a pipe to the two pipes as you want the air as cold as possible into the throttle body and not warm it up by this system.


And also my Throttle body is ever so slightly different. The one i have has a extra nipple on the top for a pipe as where mine doesnt have it, it looks blanked off from factory. What can i do with this?

Last question, how do you fit it? ie. if i remove the pipes will water piss out? or anything like that? if so what's a good method for removing and refitting?

Thanks.

 

[greenberet]

A stock NSX throttle body is tapered and I believe the plate inside has a diameter of 65.5 mm. The spindle on which the plate is mounted looks like it has a height of 6.2 mm when open, giving the throttle body a net cross section of 2963 mm2 at the plate when the throttle is fully open, which is equivalent to a 61 mm port. I believe the exit of the stock throttle body has a diameter of 64 mm and that the entrance to the intake manifold has a diameter of 66 mm.

Ideally, upstream of the intake ports, the cross section of the intake system should slowly increase, like a trumpet. Having the intake narrow down from 66 mm to 64 mm and then down to 61 mm can’t be good.

I called up Chris from Science of Speed a few months ago regarding their throttle body boring out service. He said their throttle bodies are bored out on a machine which was programmed so that the exit diameter of the throttle body matches the entrance diameter of a stock intake manifold. In addition, the plate inside the throttle body is enlarged by 5 mm, giving it a net cross section that is also equal to the entrance of the intake manifold.

So the SoS big bore throttle body sounds like it is a good match for a stock intake manifold but I don’t know whether the rubber gasket between the two also needs some work to keep the flow as smooth as possible.

Regarding how to fit it, MvM did a good write-up a few years ago with pictures: http://www.nsxprime.com/forums/showthread.php?t=75768.

 

[jaffaz32]

Thanks for the guide.

That should be allot of help.

so from the sounds of it, you jusst replace it and the other parts are already a bigger bore then the throttle body so should all just go together.

I have attached some pics. my orig one hasnt got a pipe the new one has got, was is this? can i blank it? and how would you suggest to?

circled with a red ring.


orig 2 shots.

new tb shots

 

[Big_D]

Why are you wanting to put on a bigger bore throttle body? From what I have read it doesn't do any good for a normally aspirated engine.

 

[greenberet]

my orig one hasnt got a pipe the new one has got, was is this? can i blank it? and how would you suggest to?

I don't know and since no one else has chimed in, I assume other people can't answer that off the top of their heads, either. Is your new throttle body from a different model year or type of NSX? If you look at the parts catalog, do your old and new throttle bodies have different parts numbers? In the catalog, can you see where the pipe is supposed to lead to? Can the fitting be unscrewed from the throttle body? Sorry I can't help!

Why are you wanting to put on a bigger bore throttle body? From what I have read it doesn't do any good for a normally aspirated engine.

From the hearsay I've heard, a big bore throttle body doesn’t do any good on a stock NA1, but a stock NA2 or modified NA1 should see slight gains.

 

[NSXCessive]

I remember looking this up during my S/C install its the Fuel Injection Air (FIA) Control system. It enables fresh air to be drawn through the throttle body and fuel injector port. Not sure what year you car is but mine is '00.