Throttle-Body Upgrade

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Sep 9, 2010 | 12:02 PM

STH

Thread Starter

Racer

Joined: Mar 1999

Posts: 258

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From: New Mexico

Throttle-Body Upgrade

Is there a measurable difference between a 52mm and a 58mm throttle-body?

Presently; I have a 52mm BBK on my 1990vette. It’s a 383 with an Edelbrock TPI intake, AS&M big tube runners, 24# injectors, and a modified air box. The vehicle also has Edelbrock Performer (60879) heads.

This year I’m upgrading

; ordered is a USM Stealth Ram, AFR 195 Heads, and 35# injectors. Should I upgrade to a 58mm throttle-body? What improvements would I expect to see going from a 52mm to a 58mm throttle-body?

Thanks

Steve

Sep 9, 2010 | 12:15 PM

engle1147

Le Mans Master

Joined: Jul 2007

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From: Tampa Florida

Quicker thottle response with the larger TB off idle. I'm not sure you need it though - depends on your what your flow increase demands are. I'm sure others will chime in on this.

Sep 9, 2010 | 12:35 PM

Kubs

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From: Akron Ohio

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Quote:

Originally Posted by engle1147

Quicker thottle response with the larger TB off idle. I'm not sure you need it though - depends on your what your flow increase demands are. I'm sure others will chime in on this.

You need to match the inlet CFM with the amount of air used by the engine. Too much can actually cost you power. I know people running 330-380 RWHP and still using a stock 48mm TB.

Sep 9, 2010 | 08:49 PM

LT4BUD

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From: Hinckley Ohio

Quote:

Originally Posted by Kubs

You need to match the inlet CFM with the amount of air used by the engine. Too much can actually cost you power. I know people running 330-380 RWHP and still using a stock 48mm TB.

Wonder how much more power they would get if they upgraded to 58mm????

Sep 9, 2010 | 11:24 PM

jesredvette

Racer

Joined: Nov 2006

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From: Sierra Madre California

Actually, a larger TB would have a more sluggish response off idle, wouldn't it?

Sep 10, 2010 | 12:06 AM

GREGGPENN

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From: Overland Park Kansas

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Quote:

Originally Posted by jesredvette

Actually, a larger TB would have a more sluggish response off idle, wouldn't it?

Probably not. On EFI cars, the intake tract (intake runner + head runners) is where the port velocity characteristic is created. Injectors do a much better job of providing the correct fuel to go with the air flow. And, the injectors don't alter it.

By using a smaller-than-necessary TB, you can't really speed up the air per se. By using a larger-than necessary TB, you at least guarantee enough air is available. And, since each part of the intake "chain" creates some form of restriction, reducing the individual components usually results in, at least, some gain.

For the OP, the gain could be enough to make it worth while -- especially if looking for every last 100th.