What size throttle body

Jay C

New Member
Sep 30, 2010
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Omaha, NE
I will shortly be installing a FFIM on my car that is currently flanged for a Q45 throttle body. From what I have read online the Q45 TB is like an on/off switch due how much larger then stock it is 83mm vs 60mm. So I guess my question is what TB would be best for street use. Should I just buy the Q45 to stock TB flange and run stock, switch to the Q45 TB or find something in between such as a 65, 70, or 75? I have read up on the mustang TB and I know that they say to use 70 if staying N/A and 75 if boosting but that is on 4.6L engines. Also, I read Figgie's post about using an LS2 DBW set up but not sure if that is something I would even attempt. Lastly, what ports would I need on a new TB besides throttle cable and a TPS sensor? I like the look of this TB http://www.jegs.com/i/BBK+Performance+Products/129/1700/10002/-1 would there be any issues going this route? I know that the stock TB has vacuum ports and a provision for the PCV system. If I used a catch can and supplied vacuum to the hoses from those ports from a distribution block would that enable the system to operate as intended? Some info to help I am currently at BPU upgrade level and am trying to overbuild things now to handle 600 HP so I don't have to keep redoing the same stuff. Thanks for any and all help. Sorry if these are noobish questions. I just don't want to buy and install the Q45 if it will diminish the cars streetability.
 

BryanDyer

New Member
Jun 13, 2012
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Georgia
It wont make a difference as long as the Throttle body isn't smaller than your ic piping. It will only flow as much as the piping will let it. I mean stock is 2.75 inches which is big enough unless you're wanting to run 3 inch piing.
 

Jay C

New Member
Sep 30, 2010
283
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Omaha, NE
Well the turbo out is 3 inch and the inlet and outlet of the IC I want are 3 inch so I was going to go with 3 inch pipes. At least that was my plan but I haven't bought the pipes or IC yet.
 

mk3_7m

Member
Jul 21, 2007
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melbourne
I'd say make the effort on making the car convienent to drive. We have to make comprimises unfortnately.
 

BryanDyer

New Member
Jun 13, 2012
654
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Georgia
Jay C;1962478 said:
Well the turbo out is 3 inch and the inlet and outlet of the IC I want are 3 inch so I was going to go with 3 inch pipes. At least that was my plan but I haven't bought the pipes or IC yet.

What size turbo? Must be going damn big to need 3 inch..
 

figgie

Supramania Contributor
Mar 30, 2005
5,224
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Twin Cities, Minnesot-ah
NOOOOOOO!!

Just like everything else, size matters but not in the way you guys are thinking!

Too big a TB and it literally becomes an on/off switch in the lower TP%. Bucking and bronco-ing.
Too small and the top end suffers.

Personally I would not go above 90mm on a cable driven TB.

On DBW.. go as big as the new ones are (110mm on the LS-A engines).