Big throttle body

[Clint32]

Hi what are you people using for a bigger throttle body on new plenums, have a xf that has a 63mm butterfly that i was going to use but it it big and ugly and the throttle linkage is messy to hook up, the stock rb25 one is 60mm, i think this will be a little small for 600hp which is what i wont it to be able to support easily, the only other i can find is a holley 80mm one for $500, is there any std car or aftermaket avaliable around the 70mm mark , cheers clint

[DoughBoy]

Q45 any chop? 100mm ext. diameter, around 90mm inside.

[Clint32]

deffinately big enough, you got one for sale? i would wont to see pics i have seen one on a trust plenum but cant remember exactly what it loooked like, wont something preety clean with minimal attachment on it

[DoughBoy]

I don't have any here atm, hang on will find a pic or something.

Edit: found a pic. It has a progressive throttle so it's pretty smooth despite it being such a large f**ker.

[Clint32]

looks good, depends if i can find one soon, and the cost, the holley billet allow one is $500 delivered so it would wont to be 300 or so to be worth it otherwise ill just spend the extra

[WazR32GTSt]

what about getting the stoker ported and a new butterfly made up?

Waz.

[Sydneykid]

i think this will be a little small for 600hp which is what i wont it to be able to support easily

Are you planning on using the standard inlet manifold and plenum?

[N I B]

We have new throttle bodys in many sizes, costs from 330 to 600 pending size and fittment.

[Clint32]

Are you planning on using the standard inlet manifold and plenum?

im using a subzero plenum, has a plate for the xf throttle body but would ratehr use something else

[Freebaggin]

im using a subzero plenum, has a plate for the xf throttle body but would ratehr use something else

Clint, do you have a pic of your new plenum? Maybe showing runners from the bottom side?

I'm thinking of new TB as well, every bit helps to keep pressure drops low once flows increase.

Bit I found somewhere:

Why use a bigger throttle body/Intake plenum?

There is a great deal of discussion on the need for an improved intake manifold or larger throttle body on a Forced induction vehicle. In order to better explain the need for this I have pieced together this step by step look at why it is necessary. My personal knowledge of this subject is in its early stages so special thanks to those that assisted for explaining it to me and performing the calculations so I can pass the info on.

Corky bell is world renowned for his knowledge on turbo charged vehicles and states that “A maximum air velocity of approximately 300 ft/sec thru a throttle body will keep flow losses acceptable” This is because at speeds above this aerodynamic drag will create unacceptable flow loss (ie Pressure Drop)

In order to work out the air velocity for any engines intake there are a set group of formula’s and information required. To illustrate this point I am using the details on a highly modified 3TGTE engine as owned by a Toymods forum member.

Please keep in mind this is a small area of things we are looking at and needs to be considered as part of the big picture.

Airflow Rate

Airflow rate = (cid x rpm x 0.5 x Ev) / 1728

cid = Cubic Inch Displacement

rpm = Revs Per minute

0.5 = This is due to the fact that a 4 stroke cycle engine only fills its cylinders only on one half the revolutions.

Ev = the volumetric efficiency of the engine ( I am using 85% as a average figure of a well designed system)

1728 converts cubic inches to cubic feet.

That being the case the 3TGTE in question yields the following equation:

Airflow = (110 x 7200 x 0.5 x .85) / 1728

Base airflow or cfm = 195

Pressure Ratio

The Pressure Ratio is the total absolute pressure produced by the turbo divided by atmospheric pressure. Therefore atmospheric is 14.7 absolute pressure.

Pressure Ratio = (Boost + 14.7) / 14.7

In this example we are using and extreme boost level of 38 PSI

Pressure Ratio = (38 + 14.7) / 14.7

Pressure Ratio = 3.6

Please keep in mind this is an ideal ratio assuming the ideal filter element and pipework etc is used. Any other areas of increased aerodynamic drag will add pressure to the atmospheric division value used. For example with an Oil filled pod type filter is not uncommon to have a pressure drop of up to 2 PSI thus producing a value of 12.7 on the base of the equation and an actual pressure ratio of 4.14

Now that we know the Pressure ratio and base cfm we can calculate the engines flow rate under boost. This is quite simply: Boost Airflow rate = Basic cfm x pressure ratio Boost airflow rate in this case = 195 x 3.6 = 702 cfm !!!!

Air Velocity

OK now we can get to the juicy bit. The stock 3TGTE throttle body is 2 inch in diameter. (So is the 2TGEU)

Air velocity = airflow rate / Area of section

The airflow rate is simple the airflow rate expressed in second (The cfm/60)

The area of section is the area of the throttle body divided by the area in inches of a foot to convert it to ft per second ( the Throttle body area in inches / 144)

To calculate the area of a circle use the equation pr2

(Note: a 2 inch diameter (50mm) throttle body yields an area of 3.14 inches 2)

Therefore air flow rate in this case = 702 / 60 = 11.7

Area of Section in this case = 3.14 / 144

Area of section = 0.021805555

Air Velocity = 11.7 / 0.021805555

Air Velocity = 536.56 ft/sec !

By comparison this exact same set up as fitted with a 70mm Throttle body (2.8 inches) would yield an Air Velocity of 273.50 ft/sec

Conclusion

No-one ever hesitates at the suggestion of fitting a sports exhaust or air filter. Hopefully this will help to show the benefits achieved by installing a custom intake plenum or more importantly a larger throttle body.

[Clint32]

no pics sorry mate, its welded to the std runners with a half circle top and bellmouths inside, im worried that the std one may cause some restriction and dont wont to have to redo anything on that side of the engine, cooler piping would have a 73mm ID so 70mm mine would be ideal, im thinking ill just get the 80mm holley one to make it easy and it looks the part

[Freebaggin]

no pics sorry mate, its welded to the std runners with a half circle top and bellmouths inside, im worried that the std one may cause some restriction and dont wont to have to redo anything on that side of the engine, cooler piping would have a 73mm ID so 70mm mine would be ideal, im thinking ill just get the 80mm holley one to make it easy and it looks the part

Sounds good.

Where is the best place to source one of those Holley TBs?

[Clint32]

horsepower in a box has them, still looking at some v8 stuff before i decide

[Evo_Lee]

Q45 any chop? 100mm ext. diameter, around 90mm inside.

the Q45 ones are quite popular...there are a few Evos here running with them...but really unless you going for over 600ps.

[Evo_Lee]

clint, the Q45 ones are quite popular and cheap...even a few Evos here are running with them, but unless your looking for over 600ps.

edit: just read you are looking for 600ps, so it would be the way to go.