What size throttle bodys are the stage guys running?

[BetMinesFaster]

Hey guys, got a dumb question, what size throttle bodies are you bigger inch stage guys running? Im looking at a new project and im trying to collect some info, Thanks:biggrin: Ryan

 

[Quick Turbo V6]

I'm running a 90mm Acufab T.B.

Scott

 

[BetMinesFaster]

Im building a healthy 4.3 with a 76GTQ turbo, tryin to decide what size tb to go with.....im thinking 80 and be done with it.....

 

[bison]

Hey guys, got a dumb question, what size throttle bodies are you bigger inch stage guys running? Im looking at a new project and im trying to collect some info, Thanks:biggrin: Ryan

You can easily calculate what you need based on the ci and speed of the engine. The flow of a TB is determined by its cross sectional area. Thats all that really matters. Not if its and aftermarket block or not. No need to go bigger than needed especially for street cars (especially on the small ci we run) since the added flow will cause a loss of velocity in the intake and cause lean outs without added pump shot.

 

[bison]

A 274ci engine only uses about 630cfm at 8000 rpm with no pressure drop. Looks like a 70mm is more than enough for almost all but the most serious race applications. It certainly isnt a problem on an 800hp or less blow through set up.

 

[gnxtc2]

Here's some data:

Flow Data

Billy T.
gnxtc2@aol.com

 

[BetMinesFaster]

Thanks for the info guys, Thats the suff I was looking for!

 

[Alky V6]

300 feet per second flow through the throttle body should be the max rate. If you use that to calculate your TB size, you may find that you need bigger than you think. I went 100mm. One of the main reasons for that decision was the way air enters our manifolds. Too bad we couldn't have the air enter straight down. With the way air enters the plenum I wanted to slow the speed down to control turbulence that may occur feeding the two front cylinders.

 

[bison]

300 feet per second flow through the throttle body should be the max rate. If you use that to calculate your TB size, you may find that you need bigger than you think. I went 100mm. One of the main reasons for that decision was the way air enters our manifolds. Too bad we couldn't have the air enter straight down. With the way air enters the plenum I wanted to slow the speed down to control turbulence that may occur feeding the two front cylinders.

Increasing plenum volume helps with this.

 

[S2V6RACER]

80mm. Just went over 164.6 MPH last weekend in TSO trim with conservative boost. Wonder when the off the shelf ATR 4 bolts will start holding me back. :biggrin:

3" intercooler piping from the turbo to the TB. :biggrin:

 

[strongman]

Throttlebody Size

70mm, 162.5mph, 26#, pt88, 3" pipes, ATR 4 bolts.

 

[strongman]

Throttlebody Size

70mm, 162.5mph, 26#, pt88, 3" pipes, ATR 4 bolts.

 

[bison]

70mm, 162.5mph, 26#, pt88, 3" pipes, ATR 4 bolts.

How many cubes? What is the shift point? Looks like the 70mm isnt much of a problem even with 1100hp

 

[JayC]

We have dual 75s on the car we're building.

 

[Otto J]

. Too bad we couldn't have the air enter straight down. With the way air enters the plenum I wanted to slow the speed down to control turbulence that may occur feeding the two front cylinders.

Don,Why cant you just make a manifold with an upward facing t-body?
It would require an elbow in the intercooler piping.
I wonder if there are some old open plenum stock style head intakes around that can be modified

 

[strongman]

Bison asked about cubes and shift points - 274 cubes, 7500 1st, 7800 2nd, Stage II heads, 258-258 cam.

 

[Alky V6]

We have dual 75s on the car we're building.

Are you going to have some type of progessive system for when you break open the throttle? I highly recommend it.

 

[Alky V6]

If I remember right, I calculated it out once that if the ultimate target is 1250 hp and above, you'd be better off with larger feed piping than 3". Does that mean you couldn't do good with just 3"? Of course not. But, it's hurting you.

 

[Alky V6]

Don,Why cant you just make a manifold with an upward facing t-body?
It would require an elbow in the intercooler piping.
I wonder if there are some old open plenum stock style head intakes around that can be modified

You have the right idea, Otto. I would prefer something more equal length and straight shot down the port than an 'X' manifold.

 

[Dusty Bradford]

A 90mm will feed 2000hp. For driveability I'd run as small as you can get away with. The off idle throttle input will be much less sensative with a smaller TB. Race car....80 or 90mm.