http://www.exprobase.com/Default.aspx?page=117

Just googled and read this. Was thinking how to make the best of the stock 70mm throttle body. Yes, this will require a bigger maf and a new intake plenum neck but that is not as bad as replacing the dbw throttle body for everyday drivability.

 

That's a lot of reading. Are you planning on porting/polishing the OEM throttle body or what?

 

I've seen something like this posed on another forum and it was shoot down by an engine builder. I can't remember the forum or the exact reason but he suggested Bernoulli's principle actually caused a bottleneck and the theorized low pressure - velocity bump would not be realized. But it was only one guy's opinon.

Honestly, I think it would be easier to fab up a new neck and modify an existing 75-80mm housing to accept a Z33 DBW actuator/motor assembly. However you don't know what problems you'll find until you try and fail. But the biggest deterrent, what's the best case scenario 5-10 hp at peak rpms...for a ton of time, headache, and possible drivability issues.

Cool read though, thanks for sharing.

 

Probably not even that much of a power gain.

You could easily fit a larger TB to the stock plenum, but the gains must not be there. If there was a market for it, there would be aftermarket supply. Look at the LS engine market, bigger TB's are all over the place and available in any size you want.

On the flip side, it never hurts to try, and any gain is still a gain. It's easier to find 2-3 horsepower in 10 places than 20-30 hp in one shot.

 

One thing I like from reading that page is the 8 degree outlet cone. I doubt it matters much in a large application like a TB, but there is about a 2mm size difference between the TB and manifold inlet on the HR setup, a spacer of the right thickness could yeild a smooth transition and give that optimum angle as opposed to the flat step it has now.

 

the mouth of the throttle body is over 75mm, the bulk of gain would be behind it

 

i dont have time right this second to read the whole thing, but i did skip down to the preventive actions. i noticed it mentions to reduce the flow rate. so, is this suggesting that decreasing velocity on the intake side will help reduce pressure drop? it would seem like velocity would be a good thing. i guess reducing the flow rate goes hand in hand with increasing the flow/restriction area. hmmm....