Help me choose a throttle body

Justin

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Mar 31, 2005
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If I were going to go F.F.I.M then I would want a new throttle body. The Q45 is great but I think its a bit too big for my needs. Unless someone can convince me otherwise :)

My goal is a low 12 second quarter. About 400 HP or so? MAX
I'm going to be running 550's, probably a MAFT Pro (or VPC) and 57 Trim (For now, definatly getting upgraded to who knows what later)

Running 3" pipe with a 3" tb seems excessive to me, almost to the point where its TOO big...

Lets discuss two things, is 3" going to be too big for me? and if so, what throttle body should I use?
 

starscream5000

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Aug 23, 2006
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If you want another throttle body beside the stock one (2.75") iirc, then mustang TBs are the way to go. You've got tons of sizes to choose from, and they're cheaper than just about any other, and the TPS on them will work with one little mod (search on tookwik's threads). The restriction in the IC piping system is always going to be the smallest diameter pipe/hole. If you have full 2.5" piping and IC with 3" inlets and outlets, then the piping is the restriction because the next largest diameter is the TB (2.75")

If all you want is 400 HP, then the stock TB and 2.5" piping with a good IC is all you will need. Many people have used these and made well over 500!
 

sethron71

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Jul 19, 2005
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Hey justin,
I did 440RWHP with stock TB and 2.5" IC pipes. Just now doing up to a 3" TB and 3" IC Piping. I know I posted them before but check out this 3" TB (both):
p461808_1.jpg

sm_photo_missing.jpg

The FFIM is most likely gonna be 4" so you might as well go with a 3" TB and then you can go bigger on piping if you want but if you stay small with the TB you are stuck to buy another if you wanna go bigger. HTH
P.S. I have family in Spokane so maybe I will make a run over there this spring and we can meet up for a cruise.

Seth
 

suprarich

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Nov 9, 2005
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Justin said:
My goal is a low 12 second quarter. About 400 HP or so? MAX
I'm going to be running 550's, probably a MAFT Pro (or VPC) and 57 Trim (For now, definatly getting upgraded to who knows what later)

Upper 300 rwhp will net you lower 12 sec 1/4 miles. this all can be done with the stock throttle body.
 

QWIKSTRIKE

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Apr 3, 2005
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Justin said:
If I were going to go F.F.I.M then I would want a new throttle body. The Q45 is great but I think its a bit too big for my needs. Unless someone can convince me otherwise :)

My goal is a low 12 second quarter. About 400 HP or so? MAX
I'm going to be running 550's, probably a MAFT Pro (or VPC) and 57 Trim (For now, definatly getting upgraded to who knows what later)

Running 3" pipe with a 3" tb seems excessive to me, almost to the point where its TOO big...

Lets discuss two things, is 3" going to be too big for me? and if so, what throttle body should I use?


Not at all.....it's no where near too big. I get instant response with my set up. I got a 12x24x4 IC A GT4067r, and a 3 litre custom intake manifold. What Lagg is all I can say
 
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tookwik4u89

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starscream5000 said:
TPS on them will work with one little mod (search on tookwik's threads)
Mine was an easy mod, but I use the 90mm Q45 with the q45 TPS, I'm at 500 RW with an auto, and I didnt want to upgrade again later.

I may be crazy, and I cant back it up with proof, but when I changed to 3" pipe, 12x24x4 I/C, Q45, And Ron R shorty, I feel the response is much better off idle, from a stop, and spool wise. I used to have stock intake, tb, and 2.5 pipes with spearco I/C.
 

adampecush

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May 11, 2006
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starscream5000 said:
The restriction in the IC piping system is always going to be the smallest diameter pipe/hole. If you have full 2.5" piping and IC with 3" inlets and outlets, then the piping is the restriction because the next largest diameter is the TB (2.75")

as i have told countless people in the past, this is just plain incorrect. Grab a fluid mechanics book and have a read, you shall find out why.
 

QWIKSTRIKE

475rwhp459torq an climbin
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tookwik4u89 said:
Mine was an easy mod, but I use the 90mm Q45 with the q45 TPS, I'm at 500 RW with an auto, and I didnt want to upgrade again later.

I may be crazy, and I cant back it up with proof, but when I changed to 3" pipe, 12x24x4 I/C, Q45, And Ron R shorty, I feel the response is much better off idle, from a stop, and spool wise. I used to have stock intake, tb, and 2.5 pipes with spearco I/C.


I discovered this 4 years ago when I first did my 3" upper stock pipe. Everyone that says differently hasn't got a clue, and has never used a 3" pipe to even offer such information!

YOU ARE NOT CRAZY!
 
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Justin

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Mar 31, 2005
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adampecush said:
as i have told countless people in the past, this is just plain incorrect. Grab a fluid mechanics book and have a read, you shall find out why.

Will you tell me why please? I'd like to have all input possible, but I probally couldnt' understand fluid mechanics even if I did read the book ;)


The input from you guys is really making me thing I'll just do the Q45, specially since its not too difficult to wire up. I like instant responce and killer low end :) I'm excited!


WOOOOOOHOO!
 

jdub

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starscream5000 said:
The restriction in the IC piping system is always going to be the smallest diameter pipe/hole. If you have full 2.5" piping and IC with 3" inlets and outlets, then the piping is the restriction because the next largest diameter is the TB (2.75")

adampecush said:
as I have told countless people in the past, this is just plain incorrect. Grab a fluid mechanics book and have a read, you shall find out why.


I would like to hear this explanation ;)
Especially the effect pipe diameter has on air flow critical velocity and the effect on critical velocity through a smaller opening from a larger pipe. I believe Bernoulli had quite a bit to say on this subject ;)
 

QWIKSTRIKE

475rwhp459torq an climbin
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[QUOTE=jdub]I would like to hear this explanation ;)
Especially the effect pipe diameter has on air flow critical velocity and the effect on critical velocity through a smaller opening from a larger pipe. I believe Bernoulli had quite a bit to say on this subject ;)[/QUOTE]


Belive it or not there is a thread that shows this anomaly on S/F. We had this discussion years ago when I first went to 3" pipe from the stock setup! What a debate it was about restrictions and flow. Man it would take me some real effort to dig this up so I am not going to.;):naughty:

Imagine blowing through a straw, and a garden hose. Which will take more effort to fill a balloon. Now be wise with the answer that you make here ok.;)
 
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jdub

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The size piping depends on the capability of the turbo to provide flow at or just below the critical velocity. Critical velocity is determined by the piping/TB/IC inlet & outlet diameter. A diameter of 2.5" might not be a restriction for an upgraded CT26, different story for a GT4067r ;)

BTW - Justin said he was running a 57 trim...I assume he means a CT26. The turbo needs to be matched to the piping and IC for max efficiency.
 

QWIKSTRIKE

475rwhp459torq an climbin
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jdub said:
The size piping depends on the capability of the turbo to provide flow at or just below the critical velocity. Critical velocity is determined by the piping/TB/IC inlet & outlet diameter. A diameter of 2.5" might not be a restriction for an upgraded CT26, different story for a GT4067r ;)

BTW - Justin said he was running a 57 trim...nothing about the turbo itself. The turbo needs to be matched to the piping and IC for max efficiency.


Doesn't matter if the turbo can keep the flow constant without dieing.This has been discussed up the waszu. The ct26 making 14 psi should feel more responsive with a larger diameter pipe untill it runs out of steam! This all falls under volumetric air flow. Again simplisticly put it's like the garden hose, or straw syndhrome. When I did it years ago I didn't have a GT4067r. So from my own personal experience, and the proven air flow dynamics made in S/F on this very same topic, Get the larger tb, and don't worry. Not to mention having to do it all over to add the Q45 tb later is a waste of time, and money! As long as the pipe off the turbo is 2.5 " to a 12x24x3 IC, and then have a 3" intake all will be fine with that 57.trim upgraded ct26
 
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jdub

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QWIKSTRIKE said:
Now be wise with the answer that you make here ok.;)

Oh...trust me. "If" I decide to take the time to explain the science, it will be based on physics and not the usual "it feels better" stuff that's rampant on this forum ;)

The garden hose vs. soda straw is a good analogy, but it does depend on the turbo. The turbo's capability to move volume (not psi) has a huge impact on the diameter required for the piping/TB/IC. Using the "bigger is better" stance, why not use 4" piping with a CT26?
 

QWIKSTRIKE

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jdub said:
Oh...trust me. "If" I decide to explain the science, it will be based on physics and not the usual "it feels better" stuff that's rampant on this forum ;)
The garden hose vs. soda straw is a good analogy, but it does depend on the turbo. The turbo's capability to move volume (not psi) has a huge impact on the diameter required for the piping/TB/IC. Using the "bigger is better" stance, why not use 4" piping with a CT26?


The more you, and I discuss things the more I like you! How about a Sam Adams on me J.:biglaugh: :naughty:

Besides we are not talking 4" pipes, and only discussing 3" pipes so stay on the topic at hand; that theory is not worth wasting my breath on.
 

jdub

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It will have to be later...gotta fly a plane from Tucson to DC ;)

BTW - you are correct in telling Justin to go with the larger TB. It will not have a big effect unless it restricts flow (the larger one won't) and allows later upgrades. Personally I like the Mustang TB, but whatever works. The piping diameter...well a bit different story ;)
 

QWIKSTRIKE

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jdub said:
It will have to be later...gotta fly a plane from Tucson to DC ;)

BTW - you are correct in telling Justin to go with the larger TB. It will not have a big effect unless it restricts flow (the larger one won't) and allows later upgrades. Personally I like the Mustang TB, but whatever works. The piping diameter...well a bit different story ;)


I'd say as long as he stays away from that Accufab 100mmtb he will be fine lol.
 

NashMan

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i just usieng lexus v8 thottle body they do ahve one wiht out the trac plate

this whould be the best for plug and play and it's 75 mill 5 mill shy of the q45
 

jdub

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You have to look at the turbo, intercooler, piping, and throttle body as a system. One part affects the efficiency of the others…you have to look at the CFM flowed by the turbo, the capacity and pressure drop of the IC, and the diameter of the IC piping and TB.

Piping size has a huge impact on flow...the CFM flowed through the pipes is what gives you the power out of a turbo. It has two big components - velocity & volume (the CFM). You can look at boost psi as "rate"...it will increase flow, but only to the point where velocity becomes critical...that is 300 ft/sec. Flow also becomes more turbulent above this velocity and hinders flow…the measurement for this is the Reynolds Number...the higher the value, the more turbulent the flow. In a perfect world, you want air flow to overcome inertia and produce laminar flow...in our IC piping, that is very difficult (if not impossible) to do. The best we can do is keep the Reynolds Number to a minimum.

To get the max efficiency, velocity needs to be close to this “magic number”. Above it, you will get a compounding increase (it's not linear) in pressure drop and will reach a point pretty quickly where you're achieving no gain. The same effect occurs with the Reynolds Number…air flow will become much more turbulent. The combination of both creates a sort of “back pressure” in the system negating any further gains. Below critical velocity, the turbo will take more time to fill the volume of the piping and you will get lag. How much lag is going to depend on the volume produced by the turbo.

The volume flowed is determined by the most restrictive pipe diameter in the system. Below critical velocity, increases in the CFM produced through a set pipe diameter by the turbo will show as large gains (both felt and dyno). Above critical velocity the motor will “run out of breath”, especially at high rpm. The most restrictive diameter in the system will cause this…it’s a pressure drop combined with turbulent flow. Mike Mallory experienced this due to using a CarTech IC with 2” inlet/outlets with IC 2.5” piping and a stock TB:
http://www.supramania.com/forums/showthread.php?t=31165

To see what I’m talking about, here’s a neat little calculator for determining mean gas flow inside a pipe:
http://not2fast.com/gasflow/velocity.shtml

We need to make a couple of assumptions:
Turbo Flow – 930 CFM (Boss 67mm compressor @ 75 lbs/min)
OAT – 75 deg
IC flow is sized to turbo flow
Compare 2.5” dia to 3.0” dia pipe.

For the 2.5” pipe…Mean Velocity: 454.6 ft/sec…Pressure Drop: 1.71 psig…Reynolds Number: 588857

Clearly less than optimum for this turbo.

For the 3.0” pipe…Mean Velocity: 315.7 ft/sec…Pressure Drop: 0.82 psig…Reynolds Number: 490714

Much better…note the pressure drop is cut to less than half.

Also of interest is the effect a stock TB has using this turbo…its diameter is 2.36”:
Mean Velocity: 510.1 ft/sec…Pressure Drop: 2.15 psig…Reynolds Number: 623979

Note the pressure drop is 2 1/2 times that of the 3” pipe. I point this out to illustrate the restrictive effect a sub-sized TB can have…it’s significant. If you were to substitute a 3.5” TB the Mean Velocity drops to 231.9 ft/sec, the Pressure Drop is 0.44 psig, and the Reynolds Number is 420612. Since the TB is so short, using a larger diameter TB will have little or no effect on lag. This is what I meant when I said using the larger throttle body is a better choice above.

Now, I realize this appears like I’m making a case for using larger IC piping…for this 67mm turbo I am. Keep in mind this is one of the larger turbos available for the 7M…lets run the numbers for a turbo that flows 600 CFM:

For the 2.5” pipe…Mean Velocity: 293.3 ft/sec…Pressure Drop: 0.71 psig…Reynolds Number: 379908

Kinda looks the same as the above turbo flowing 930 CFM on 3.0” piping ;)

For the 3.0” pipe…Mean Velocity: 203.7 ft/sec…Pressure Drop: 0.34 psig…Reynolds Number: 316590

Hmmm…nearly a 1/3 drop in velocity. Think that might cause a little lag getting the boost to the motor?

One other thing about all this: The IC itself can cause a restriction. In Mike’s case above, it was the small inlet/outlet…the flow capacity of the IC is also a big factor. Too small an IC for the CFM produced by the turbo, same restrictive effect. Too large and you will get lag.

Also I want to point out theory can be quite different than reality. This little analysis does not take into account bends in the piping, the interior surface RA, or little leaks in the system. All these (and more) can impact performance. It does give you a very good place to start though and illustrates that bigger piping is not always better. However, in the case of the throttle body, it is better to err on a larger size.