emerica4601

iTrader: (5)

hey guys,
currently i have full exhaust and little hp mods thats about it. i know stock size throttle body's are twin 48mm. i was looking around and have seen that there at 52mm and also 58mm. i dont have a heavily modded car, but would the 58mm be the best for hp gains? or would the 52 be better because i dont have head work/cam done.

i was thinking slappin on a twin 58mm one and then gettin a fuel pressure regulator so then i can set my a/f ratio at optimum range.

let me know what you guys have done and what gains you have had off of ur tb.

METALBEAST

iTrader: (1)

The largestest TB size that is manufactured that will work with your stock intake will be the 52 mm TB (the stock intake will accomodate up to a 54 mm tb). That may be a little bit of overkill with just a bolton car and a 58 mm TB will be much too big to use.

C_Rules

iTrader: (7)

52 and 58mm throttle bodies are the same price. well at least thats what ive seen in the summit mags and was the case with the one i bought. i went with the 58 since it was the same price. i did have my intake ported and head matched so i guess i get to use the entire 58mm. if theyre the same price y not go bigger? unless someone says a 58mm tb on a bolt on car can hurt u performance wise.

emerica4601

iTrader: (5)

yeah thats my thinking behind it. ive heard that it may hurt ur performance if u dont have heads/cam and whatnot. i was gonna port my manifold so it can take a 58mm TB ....

emerica4601

iTrader: (5)

t t t

93BlackZ

with just a bolt on car i say stick with the stocker it handles plenty for just a bolt on car, if you plan on getting a H/C soon then yeah you might want but until then just keep the stocker it handles plenty for now. i vote suspension, or gears.

borninatransam

iTrader: (4)

a cheaper way out too if you just want a twin 52 lingenfelter offers ones that you send your core in and you get a stock port tb. i think its like 200 but its worth looking into. and with that you can do what you want as far as powder coating, painting, chroming, etc. but that kinda stuff is personal preferance.

TAEnvy

iTrader: (2)

Ideally at WOT you want the pressure inside the intake manifold to be = to atmospheric pressure. There's going to be some pressure drop through the throttle body, etc., but you want to minimize it.

That's why I'm an advocate of larger throttle bodies even on lightly modded cars. Some folks say because the math says the stocker flows enough to support 450hp that its all you need.

Well, yes, under ideal conditions it flows enough to feed 450hp, but its unquestionable IMO it will take less effort to suck 500cfm through a 58mm tb than through a 48mm tb and there will be less pressure drop in the process. The 58 is going to therefore allow a bit more air into intake plenum, and then when the intake valve opens there's going to be a little more pressure forcing air into the cylinder.

You can measure this yourself by doing data logging at WOT 48mm vs. 58mm and looking at the kPa differences in manifold vacuum. 100kPa is atmospheric. I was seeing 93-95kPA at WOT with a 52mm and when I went to the 58mm I get 98-100 consistently.

As Chris96WS6 so Eloquently put it on LS1LT1.com

besz28

good idea go for the 58mm, and port the intake to match, then when you are ready for heads and cam you have a 58 already.

blkchevyz

not sure about just bolt ons, but we put my 58 on my friends car that had most bolt ons and had the cc305 cam. it gained 8 rwhp. it showed a gain from 2000 rpms all the way up.

his intake was ported for the 58(did that when we put the cam in)

ks my ss

i ran a 58mm tb with just bolt ons.