T/B Plenum Question
4th Gear Member
Joined: Sep 2006
Posts: 1,031
From:
RE: T/B Plenum Question
ORIGINAL: cliffyk
Here's a link to Accufab's flow data, about 1/2 way down the page you will find the 1996-2004 4.6L 2V data. The stock plenum only by itself (no TB) can only flow about 500 cfm, all the aftermarket units, except the C&L, can flow 600 cfm or better.[/align][/align]The aftermarket plenums have both larger passages, and are taller to provide a more gradual turn and higher stack velocity.A 4.6L at 6500 RPM has a theoretical intake flow of 14,950 liters/minute= 528 cfm--in the real world, 475 to 500 is all it needs. This is some 45 to 70 cfm more than the stock TB/plenum can flow without affecting performance...[/align][/align]I would alsoadd that without a custom or canned tune to take advantage of the higher airflow potential there won't be much gained except bragging rights--in fact I'd spend money on a handheld tuner (and load a premium fuel tune) before updating the TB/plenum.[/align]
Here's a link to Accufab's flow data, about 1/2 way down the page you will find the 1996-2004 4.6L 2V data. The stock plenum only by itself (no TB) can only flow about 500 cfm, all the aftermarket units, except the C&L, can flow 600 cfm or better.[/align][/align]The aftermarket plenums have both larger passages, and are taller to provide a more gradual turn and higher stack velocity.A 4.6L at 6500 RPM has a theoretical intake flow of 14,950 liters/minute= 528 cfm--in the real world, 475 to 500 is all it needs. This is some 45 to 70 cfm more than the stock TB/plenum can flow without affecting performance...[/align][/align]I would alsoadd that without a custom or canned tune to take advantage of the higher airflow potential there won't be much gained except bragging rights--in fact I'd spend money on a handheld tuner (and load a premium fuel tune) before updating the TB/plenum.[/align]
My Accufab 70mm combo on my 03 Auto vert made the car run lean, at least it felt that way, with noticeable loss in low end torque.
I also had the infamous idle hang which drove my auto tranny nuts when coming to a stop.
A tune would have fixed the problems but I prefer to stick with the stock tune for now.
If I were him, I would go for a tuner first.
P.S Everything was installed correctly, no leaks, TPS set, computer reset etc and the car is stock except for Magnaflow catback.
I actually swapped it out a couple of times just to see if I was imagining things.
I wasn't.
Putting the stock unit back resulted in the return of my low end torque. Via SOP dyno, but believe me you could easily feel the difference.
Thread Starter
Joined: Mar 2007
Posts: 26
From: North Carolina
RE: T/B Plenum Question
Yes it is an automatic.
I ran across this https://mustangforums.com/m_1322212/tm.htmand was wondering if it was really worth it as I want to keep the look of the stock plenum but install a 75mm trottle body.
I ran across this https://mustangforums.com/m_1322212/tm.htmand was wondering if it was really worth it as I want to keep the look of the stock plenum but install a 75mm trottle body.
1st Gear Member
Joined: May 2007
Posts: 55
From:
RE: T/B Plenum Question
C&L RPM plenum FTW. Not as expensive as the Accufab, and flows just as good. I read an article that said the best flowing combo was the C&L plenum matched with a BBK 75mm TB. You wouldn't feel the difference between the C&L and Accufab anyways, the Accufab is just shiny [8D].
2nd Gear Member
Joined: Jul 2005
Posts: 420
From: CT
RE: T/B Plenum Question
Be careful with the Accufab, especially with an automatic. I bought the 75mm TB and plenum and had to take it off after a week. My idle was all over the place and I can imagine that it would drive an automatic crazy. At least I have a 5 speed. I tried everything to get it to work. I am sure it gave me more HP but it wasn't worth the idle hangs. I even got a custom tune. Nothing worked. I'm stuck with it now because American Muscle will not take it back. Accufab agreed to look at it free of charge but I doubt they will find anything wrong. My car just did not respond well to this mod.
Joined: Oct 2007
Posts: 47
From:
RE: T/B Plenum Question
Shelbyville all you need to do is down grade to a 70 mm. 75 mm are for head and cam upgrades or superchargers. The 75 mm is to big, they are for a car that needs the extra air flow which is why the idle on the car jumps around.Some sites tell you this and some don't. Check Americanmuscle.com and read there specs on the 75mm TB it sayNOTE: A 75MM Throttle Body is suggested for pretty heavily modified GT as a stock and mildly modified GT does not flow enough to benefit from the larger Throttle Body.Sell the 75 mm and get a 70mm that should fix your idle.
Joined: Sep 2007
Posts: 17
From: West Coast
RE: T/B Plenum Question
kinda new here but I was just thinking about you guys saying there is a problem with the idle hang, could you possibly do the IAC mod to get rid of the hanging idle......correct me if Im on the wrong trail!!
Thread Starter
Joined: Mar 2007
Posts: 26
From: North Carolina
Joined: Oct 2007
Posts: 47
From:
RE: T/B Plenum Question
Look Check out americanmuscle and read the 75mm spec and the say NOTE: A 75MM Throttle Body is suggested for pretty heavily modified GT as a stock and mildly modified GT does not flow enough to benefit from the larger Throttle Body.
Get a 70 mm if you have stock car and you won't run into problems.
Get a 70 mm if you have stock car and you won't run into problems.