It seems like a common question in 4.6l 2v world, is what throttle body or plenum will yield the most horse power. This thread is aimed more for naturaly aspirated bolt on cars, but I will include dyno sheets for forced induction applications as well.

The common question (especialy by individuals just begining to mod their cars) is how big of a throttle body do i need, and what company makes the best throttle bodies and plenums, and what are the best combos.

Forced Induction applications will react more to upgraded throttle body and plenums, but naturaly aspirated applications will react as high to simple mods such as this.

I am going to start right away by saying that C&L plenums combined with a 75mm throttle body, make the best results on a naturaly aspirated bolt on gt.

car 1

2002 gt

C&L plenum and 75mm BBK throttle body were added

the car already had the following........
C&L 85mm Mass Airflow System with C&L inlet pipe
Under-drive pullies
Timing adjuster set to 12 degrees
Off-road X-pipe with Mil Eliminators
Magnaflow 2 1/2" cat-back exhaust

before plenum and throttle body- 263.5 horse power and 301.38 torque

After plenum and throttle body- 277.5 horse power and 318 torque

That is a 14 horse power gain and a 17 ft lb of torque gain

link to dyno sheets

C&L Intake Plenum For 2V 4.6L Mustangs

Back up pulls were done and a pull was done with a 70mm throttle body which resulted in a 3 horse power loss.

car 2

2003 gt

K&N Cone Filter
Under-drive pullies
Timing adjuster at 12 Degrees
Mac Pro-Chamber H-pipe

Baseline- 257.2 HP and 298.2 ft/lb of torque

with C&L plenum and 7mm tb- 266 HP and 307 ft/lb of torque
gain of 8.8 HP and 8 ft/lbs of torque

again a 70mm tb was swapped on and a 3 horse power loss was seen

link

C&L Intake Plenum For 2V 4.6L Mustangs

supercharged application car 3
2000 gt

10# P1sc S/C kit with a 3 core intercooler
42# injectors
Euro Focus pump (returnless friendly and flows 260+ lph)
Lightning 90mm MAF
Bassani cat-back


Air/Fuel Ratio graph from the dyno testing of Dan Hourigan's Supercharged Mustang GT
MAC off road H-pipe
Custom tuned Autologic chip

C&L plenum+ 75mm bbk tb gained 15- 20 horse power

link

http://www.cnlperformance.com/plenum07.html

car 4

NON PI 1997 automatic gt

Gains ranged anywhere from 7-10 rear wheel horsepower, depending on engine RPM.
Torque was improved by as much as 10-15 Ft/Lbs in the low to mid RPM's, with an average improvement of around 5 ft/lbs throughout the upper RPM's.

link

http://www.cnlperformance.com/plenum09.html

MOdular DEpot did a show down between trickflow, accufab, dragon, and C&L

StockAccufabC&LDragonTrick Flow
RWHP265.97272.38 (+6.31)271.13 (+5.16)270.69 (+4.72)270.19 (+4.22)
RWTQ303.54310.42 (+6.88)306.05 (+2.51)307.27 (+3.73)306.61 (+3.07)

these were done with a accufab 75mm throttle body

modular stated that they would have crowned accufab winner but the results vary from car to car that it could change. I reality all plenums were fairly close.

link

The Plenum Showdown Part II






I hope this thread has helped provide some good info, and crush the theory that a 75mm is to much for a bolt on gt.

 

I am a little confused. Towards the begining you state that the C&L plenum combined with a 75mm TB will make the most power. However, later you provide data that shows the Accufab plenum providing a better gain. Reading it again I can see that maybe the point was to show that a 75mm TB will always provide a better gain than a 70mm TB, but it may need some clarification. Also, we need to find some data on the 78mm BBK TB/Plenum combo. Bryan50Rogers on YouTube did a video where BBK installed it on his car and with before and after dyno runs, it was about 13 or 14 HP gain.

 

C&L with 75 was named winner because it was better all around instead of just peak. accufab was just peak. ill see what i can find on that bbk 78