Larger Throttle body on NA i6

ten[A]cio[U]s · 04-12-2008, 10:11 PM

G'Day,

In my bordem and curiosity I came accross an SS induction throttle body on ebay.

You see everyone trying to make their intake larger so they can get more air in.. So in theory increase TB and have 3" inatke you will get even more in.

My question is would this munt the A/F ratio's and would this make the car run too lean?

Say on a basically stock car. Larger cam, bigger fuel pump, Intake modified, and headwork.

Would this be a good idea in the chase of a decent time slip?

Ebay

ten[A]cio[U]s · 04-12-2008, 10:16 PM

Here is another example of a larger TB

Ebay

b2tf · 04-12-2008, 10:21 PM

Not worth the dollars in my opinion, I think the general consensus is that the stocker is a good enough size for a 6cyl. If a 70mm one will support 200+ rwkw on a V8, why would a 6 need bigger?

**SSD-85** · 04-12-2008, 10:24 PM

According to JMM, larger t/b's on a n/a i6 is pointless, unless your getting head work done. The reason being whilst you may increase airflow to your heads, your i6 inlets are still only a certain size, and the factory one (up to an au at least) is the "best" one. Correct me if i am wrong anyone.

ten[A]cio[U]s · 04-12-2008, 10:28 PM

It does make sence why it doesnt work. Just trying to get my head around it a little better.

Like everything is pointing to its not worth it, but has anyone tried using larger TB or tried anything in that area?

**SSD-85** · 04-12-2008, 10:34 PM

www.jimmockmotorsport.com , basically everything one could do to the N/A SOHC i6, he's done. and read the articles (found on the site) about the work he's done, quite amazing really.

b2tf · 04-12-2008, 10:48 PM

Quote:

Originally Posted by WeHaveIgnition

www.jimmockmotorsport.com , basically everything one could do to the N/A SOHC i6, he's done. and read the articles (found on the site) about the work he's done, quite amazing really.

And depending on who you believe, everything he's done has been either discredited, bettered or BS'd at one point or another.

**SSD-85** · 04-12-2008, 10:54 PM

Quote:

Originally Posted by b2tf

And depending on who you believe, everything he's done has been either discredited, bettered or BS'd at one point or another.

Okie dokey, sorry bout that. i spend too much time thinkin bout 8's anyway

b2tf · 04-12-2008, 11:11 PM

Quote:

Originally Posted by WeHaveIgnition

Okie dokey, sorry bout that. i spend too much time thinkin bout 8's anyway

Nothing to be sorry about, I dont venture much into TQE Territory either :hihi:

**Sorted** · 04-12-2008, 11:26 PM

Some one tested a larger throttle body on FordMods - be that it was a 68mm not a 70mm one but still has results CLICK HERE

Quote:

Originally Posted by FAST-XR

I finally got around to getting my car put back on the dyno after getting my TB bored out.

on the standard 64mm throttle body i made 143 rwkw @ 4900 rpm
on the 68mm throttle body i made 152 rwkw @ 5400 rpm

power curve from 4900 rpm and below was exactly the same
torque curve from 4900 rpm and below was exactly the same

it was only after 4900 rpm that things changed....
i hope that puts alot of the debating about throttle body size on an NA6 car to sleep!

superroo · 04-12-2008, 11:41 PM

Not worth it at all.

Our motors at full noise (6000rpm), with 100% volumetric efficiency (impossible without boost), will want to consume about 12,000 L/min (liters of air per minute)

A circle restrictor of 50mm, which is smaller than our throttle bodies, will flow a maximum of about 23,600 L/min.

So right there you can see that a larger throttle body is not needed.

Where it comes into play is the air velocity through that "restrictor". The lower the velocity, the more laminar (smooth) the flow is, which means the less "moving" air their is in the plenum. The less moving air, the less work the motor has to do to move it. Less work on the motor, more power.
But the higher the velocity, the more turbulent the air is, which means better mixture mixing. Better mixing, more torque.

I'm not a pro on this yet (currently studying mechanical engineering), so my knowledge is limited and possibly wrong.

Cheers

JoesAu · 05-12-2008, 08:50 PM

i opened the throttle body up on my car but left the butterfly standard and i picked up throttle response thats about it.

Sox · 06-12-2008, 08:55 AM

'superroo' is spot on.

The CFM requirement of our little 4L is less than 400cfm at 6000rpm. Even at 7000rpm we're talking less than 450cfm.
This is based on 90% VE, which is a pretty serious street engine.

Standard engines are around 70%, mild engines are around 80%, and heavily modified street engines are around 90%.
Race engines can be 100% and more.

Our standard TB's flow around 550cfm.

Even at 8000rpm and 100% VE, our engines only require just over 550cfm.

Clearly a bigger TB is not needed.

All a larger TB will provide is touchier throttle, because at small throttle positions the large TB will be flowing more than a smaller unit. So we think throttle response has improved.

**Stav** · 06-12-2008, 09:47 AM

Quote:

Originally Posted by Sox

'superroo' is spot on.

The CFM requirement of our little 4L is less than 400cfm at 6000rpm. Even at 7000rpm we're talking less than 450cfm.
This is based on 90% VE, which is a pretty serious street engine.

Standard engines are around 70%, mild engines are around 80%, and heavily modified street engines are around 90%.
Race engines can be 100% and more.

Our standard TB's flow around 550cfm.

Even at 8000rpm and 100% VE, our engines only require just over 550cfm.

Clearly a bigger TB is not needed.

All a larger TB will provide is touchier throttle, because at small throttle positions the large TB will be flowing more than a smaller unit. So we think throttle response has improved.

Now that is spot on!!! Best info I have seen in years !! Yes I have read on many occassions that a bigger throttle body will make throttle response more twitchy.

blackers10 · 06-12-2008, 01:54 PM

i have a ported and polished TB with the standard butterfly...
didnt feel much difference... maybe a bit more throttle response...
but id like to think it makes some what of a difference.. now just need an airbox for my pod filter

**Stav** · 11-12-2008, 06:20 PM

Quote:

Originally Posted by Sox

'superroo' is spot on.

The CFM requirement of our little 4L is less than 400cfm at 6000rpm. Even at 7000rpm we're talking less than 450cfm.
This is based on 90% VE, which is a pretty serious street engine.

Standard engines are around 70%, mild engines are around 80%, and heavily modified street engines are around 90%.
Race engines can be 100% and more.

Our standard TB's flow around 550cfm.

Even at 8000rpm and 100% VE, our engines only require just over 550cfm.

Clearly a bigger TB is not needed.

All a larger TB will provide is touchier throttle, because at small throttle positions the large TB will be flowing more than a smaller unit. So we think throttle response has improved.

A 60mm 5.0 windsor throttle body flows to 526cfm.
A 65mm acufab flows to 616 cfm
A 70mm tb flows to 726 cfm.

Our throttle bodies must flow around 680 cfm at 68 mm. Why did ford do this? They knew it wouldnt spin to 12000 rpm...

Our cars at 6000rpm need 390cfm!!

tex · 11-12-2008, 06:38 PM

What a total waste of money a bigger throttle body would be on a n/a I6.

Even the ooo's and rrrr's from the boys at the pub would turn to wtf

: if they new just a little bit about these engines.

Maybe it would be good cred at some schoolies leavers party? Or show and tell at kindy.