i was thinking of getting my holley 62mm throttle body enlargened. what would be the ideal size I should enlargen it to, retaining a decent idle and drivability? i'm using it in conjunction with a skunk2 intake manifold. Brief rundown of my car: ~8.5:1 compression ratio, fully prepped B18C head with B20B shortblock.. standalone engine management with turbonetics T3/T4 and lots of boost thanks

 

62mm is fine, save your money. There is this huge craze over having a large throttle body but with forced induction it doesn't really matter. You are forcing the air in anyway, so the gains you see for the dollar are minimal. If you have everything else done and for some reason keep running 10.00 but really want a 9.99 then maybe do it.

FI vs. throttle body is like a garden hose flowing water vs. the nozzle. Think of the nozzle as your engine, it can only breathe so much and you are forcing the water (air) through the hose (throttle body). You never really exceed the flow rating of your hose (throttle body), its just question of how wide open you can get your nozzle to be. The solution there is headwork, larger valves, etc, which again is something that I would do only after everything else is done.

Of course, I had both done, 64mm, but I'm a nut.

 

http://www.proflowdesign.com
Awesome business. They will send you a ported TB if they have one in stock and you send yours to them as a core once you receive theirs.
If they don't have it in stock, send them yours and they port it with a new SS butterfly valve. Once they get it, they finish it in a day and send it back......It was about $150 I think.

 

after careful consideration, i've decided to enlargen it to 68mm to be safe. I could go bigger, but the passageways to the map sensor would be affected. there is a leak with the throttle plate, so i've been using my stock B18C throttlebody. The car felt much more responsive with the 62mm holley installed.. btw, my intercooler piping is 3", and i do want 9.99, so maybe this will be worthwhile..

 

asides the topic, your intercooler piping is too big. 68mm will be fine though.

 

 

What are you talking about? The largeer the TB the less actual boost you run into. There for the less stress on your manifold and valvetrain. You'll also spool quite a bit faster with the larger TB because it isn't doing nearly as much work to get into positive pressures. You'll also free up some torque up top if you already have a 3in. DP to exhaust. To increase the flow rate even more increase the total intake charge pipes diameter around the bends by about 12%.

 

I disagree 100% with everything you said up until the "free up SOME torque up top." Like I said before, you may gain power, but for the money spent it is not the first thing I would do if he is already at 62mm.

"The largeer the TB the less actual boost you run into. "
what does that even mean?

"You'll also spool quite a bit faster with the larger TB because it isn't doing nearly as much work to get into positive pressures."

Not true. Your turbo spools off the exhaust side, not the intake. Your throttle body will, as I said before, probably never limit the amount your head can breathe, and therefore will not limit the amount it is putting out to spool the turbo. If there was a gain in spool time, you're talking maybe 25rpms if that. Big whoop.

"To increase the flow rate even more increase the total intake charge pipes diameter around the bends by about 12%."

Again, what does this even mean? Increase flow rate more increase intake charge pipes diameter around the bends by 12%. Are you saying make piping bigger around bends on the intake side? Where did you get this 12% number, is that the interest rate on your credit card that you bought piping with or something?

There are dozens of cars running sub 10 second times on 2.5" or less intake piping...

 

I would just leave the 62mm throttle body were it is and spend the money other places, you will need it if you want to run 9.99. The 3in intercooler piping is a little on the big side. Using 2.5" is plenty big for a B series motor.

 

Boost is created by the back-pressure in the charge pipe to manifold area. That's where it should be measured to get an accurate reading on how much air your actually forcing into the engine.

Less actual boost would mean the intake can actually ingests more of the air and sees less pressure there for creating more available torque and making the engine a little more rev. happy.

I can't help you if you do not understand how a less restrictive intake would help with your spool up after all the individual throttle bodies I'm sure you've seen on the market.

It's actually around 12.34731*% around the bends to keep the flow rate up with-out a drastic pressure drop. That's to create an even flow with-out any kind of drastic turbulance slowing down the air flow and ruining efficiency. I never said to increase the total diameter of the piping I just said the bends to improve the flow.

Personally I don't care if anyone listens to me it's your loss I was just providing info on how to improve the set-up with-out ruining the flow of an expensive TB by boring it out.If you can't understand any of this it's not my problem. I don't think a sub-10sec. car is very impressive if you ask me I wanna see it pass smog and be street legal too. Mine will pass smog be street legal, & run 9 seconds. Do what you want just don't flame me because you don't know about anything that I'm talking about.