CalBoy101

As much as I'd like to bust out the wallet and get them for my 2002 GT, I can't find any convincing dyno reports that show a bigger TB and plenum help on a mostly stock 4.6 2v motor.

The dyno curves in the videos below are interesting to look at:

Stock 4.6 with Airraid CAI and Bama Tune:
http://www.americanmuscle.com/airaid...er-9604gt.html

Stock 4.6 with SR Plenum, Stack 70mm TB PLUS the Airraid CAI and Bama tune
http://www.americanmuscle.com/sr-9604-plenum.html

Its pretty interesting to see that the Airraid CAI and Bama tune combo alone actually make more peak HP than adding on the TB and plenum. The curves look very similar, it pretty much looks like the TB and plenum (at least those ones) don't help at all on this engine.

The only dyno results I've seen of a TB and plenum giving some reasonable HP boost are these ones:

C & L plenum with 75mm TB
http://www.cnlperformance.com/produc...bid=17&catid=3

They show dyno curves from 2 cars with typical bolt ons, one gaining 14 HP and the other gaining 8HP. They claim that the 75mm TB is important and that both these cars lost 3HP with a 70mm TB.

The C&L HP curves look a little funny to me as the gain is so constant across the board, I would have expected it to be mostly at higher RPM's.

Does anyone else have any firm data on the benefits of TB's and plenums on bolt-on type 4.6's?

So far I've only busted for the Airraid/Bama tune combo. So far I'm pretty happy with it, the Airraid is nicely made and installs well.

The Bama tune seems pretty good so far but I won't know for sure until I hit the strip in a couple of weeks. After installing their software upgrades I was able to load up to 10 different tunes on it which is pretty nice.

Its a little frustrating not being able to immediately change things like shift points (I've got an auto) but its still a lot better than not being able to change them at all. So far the turnaround from Bama has been quick on the tunes.

cliffyk

Read this "sticky". They are where you should start anyway...

CalBoy101

Nice writeup Cliff-

The Accufab flow numbers look like their claimed 11HP gain for their TB/plenum combo might be legit, that combo had the best flow in their tests.

At $439. for the set it ain't cheap ($40. per horse) but I guess speed cost money.

cliffyk

Keep in mind that no n/a 4.6L engine, regardless of how many valves, what cams, intake manifold or whatever cannot consume more than 528 cfm of air (at 6500 rpm). Any rated flow beyond that (at 2.0 inHg which is about as low as engine vacuum will go and still have airflow) is unneeded.

Also, based on my direct experience, simply swapping out the Accufab's or anyone else's aftermarket plenum will not show an 11 rwHP gain--without a tune to lean out the stock tune's grossly rich mix at WOT 5 to 7 rwHP is more like it. What it will do is allow the engine to spin up better past 5200 rpm and all the way to the rev-limiter.

The Pro Products/Trick Flow plenum (they are the same) will perform just as well as Accufab's. They are not as pretty, that is the only real difference. A throttle body is just a chunk of aluminum with a round hole it. Mechanical and assembly quality are important but there's not much in the way of design to influence a TB's performance...

the5schlueters

I did the BBK 78mm and the BBK cold air intake with no gains on a stock 96 motor. At least no noticeable gains the only thing I could tell that changed was the sound lol.