what size TB 70mm or 75mm
07-24-2011, 10:03 AM
#1
Thread Starter
Join Date: Jul 2011
Location: new york
Posts: 9
what size TB 70mm or 75mm
I am planing to buy a new TB for my 2000 mustang GT its all stock except i have 3.73 gears and a drag clutch i have a set off bbk long tubes and a shot pypes off road h-pipe i am going to put on. i plan on doing the TB CAI and a upper plenum and a spacer soon but i want to get the rite TB for me and will getting cams make me need the 75MM. i am going to get a set of modularhead cams and steeda under drive pulleys . also what is a good tuner or should i just have the car dyno tuned when i do the cams.
07-24-2011, 11:38 AM
#4
TECH SAVANT
Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,938
Cams will not affect the needed TB size, because running n/a 70mm TB can flow much more air than a the 4.6L 2V could possibly pull in. The slightly smaller TB also maintains a higher charge velocity, though this only matters at WOT and very high engine speeds (5800+).
The most air a 4.6L n/a engine can possibly need is 528 cfm, and this would be at 6500 RPM and 100% volumetric efficiency (VE). An n/a engine cannot achieve 100% VE, and for the 2V 85-90% is more realistic. At 90% VE the most air that could be ingested is 475 cfm (also at 6500 RPM).
Here are Accufab's flow numbers, annotated by yours truly, which explain more of this--and which show that even the stock 65 mm TB when paired with any after market upper plenum can flow very nearly enough air to make any n/a setup happy.
BTW, as the flow data shows the upper plenum is the weakest link in the OEM intake not the TB.
For all of the above I chose a 70 mm TB, a 75 mm won't really hurt anything but it's not needed. The spacer falls into the same category. If you use it do before and after comparisons as you may find it negatively affects some rpm bands. The spacer adds height to the stock plenum, a good thing, however all after market plenums I have ever seen are already 3/4" to 1" taller than the stock plenum--and designed to not need a spacer...
The most air a 4.6L n/a engine can possibly need is 528 cfm, and this would be at 6500 RPM and 100% volumetric efficiency (VE). An n/a engine cannot achieve 100% VE, and for the 2V 85-90% is more realistic. At 90% VE the most air that could be ingested is 475 cfm (also at 6500 RPM).
Here are Accufab's flow numbers, annotated by yours truly, which explain more of this--and which show that even the stock 65 mm TB when paired with any after market upper plenum can flow very nearly enough air to make any n/a setup happy.
BTW, as the flow data shows the upper plenum is the weakest link in the OEM intake not the TB.
For all of the above I chose a 70 mm TB, a 75 mm won't really hurt anything but it's not needed. The spacer falls into the same category. If you use it do before and after comparisons as you may find it negatively affects some rpm bands. The spacer adds height to the stock plenum, a good thing, however all after market plenums I have ever seen are already 3/4" to 1" taller than the stock plenum--and designed to not need a spacer...
07-24-2011, 02:48 PM
#6
TECH SAVANT
Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,938
"Pairing" really isn't important and the basic dimensions are shared by all--Accufab is the prettiest, and most expensive--I have the Professional Products TB & Plenum which are the same as the Trick Flow parts and can be had for $250 or so if you shop around:
Last edited by cliffyk; 07-24-2011 at 03:14 PM.
07-24-2011, 03:18 PM
#8
TECH SAVANT
Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,938
Yup, the stock intake is a CAI and a pretty good one--being rubber it insulates well, and it is designed as a tuned reservoir/preliminary plenum to assist in minimizing standing waves in the intake tube.
Despite what the various vendor's marketing departments say, very few if any aftermarket intakes are any better and some are worse/much worse...
07-24-2011, 09:49 PM
#10
Thread Starter
Join Date: Jul 2011
Location: new york
Posts: 9
so should i not do a CAI just keep stock but i need a new cone bc the one on the car was changed b4 i got it and its beat what would you recommend for a new filter and would you recommended the 70mm Professional product Tb and plenum and no spacer