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Discussion Starter #1
Ok so im getting bored and looking for my next mod. I have heard that tb and plenum arent really worth it unless your going fi? is this true?

Any other recommendations for another mod? maybe a maf?

Thanks guys
 

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Youll pick up a few ponies with the tb/plenum. The plenum is the main choking point of the air flow going in. Without F/I, there is no point in a bigger MAF, and you will see nothing from it.
 

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i just this weekend did the bbk 78mm throttle body plenum, I think its a good mod. With a Bama tune the car feels like it picks up faster, i can spin till third now
 

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I'm looking to sell my 75mm Professional Products tb and plenum. Like others said, you do pick up some power, not sure how much, but its a cheap mod when you buy used.
 

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If you already have the mods in your sig (LTs, X-pipe, CAI, SCT), then definately do the TB/plenum. You will notice a difference. The plenum is the main concern, even the factory TB is restricted by the factory plenum. Things like intake & head flow are important, but less of a concern on F/I than on N/A. When you are N/A, you are forced to rely only on the system flow (and it's restrictions) to fill the cylinders. That's the whole reason the 4.6 is so limited on HP and why we have to go F/I to make power. Make sense?

X2 on buying a used TB/plenum. It's a good mod, and buying them cheap makes it even better.
 

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If you already have the mods in your sig (LTs, X-pipe, CAI, SCT), then definately do the TB/plenum. You will notice a difference. The plenum is the main concern, even the factory TB is restricted by the factory plenum. Things like intake & head flow are important, but less of a concern on F/I than on N/A. When you are N/A, you are forced to rely only on the system flow (and it's restrictions) to fill the cylinders. That's the whole reason the 4.6 is so limited on HP and why we have to go F/I to make power. Make sense?

X2 on buying a used TB/plenum. It's a good mod, and buying them cheap makes it even better.
so you're saying that the n/a setup would benefit better from the plenum vs the f/i setup since the air is being forced through? Askin bc i dont want to waste my cash buying an aftermarket plenum if I want benefit from it.
 

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I felt a lot better throttle response with my BBK 70 mm TB. I am now in the hunt for a 70mm plenum. I think they are definitely worth the money to be honest.
 

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Ive got a 70mm t.b/plenum for sale if your interested
 

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Discussion Starter #9
how much matt02 gt and gunter? is there a difference between 75mm and 70mm other than size obviously. i heard the 70 is better than 75 in some cases.
 

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so you're saying that the n/a setup would benefit better from the plenum vs the f/i setup since the air is being forced through? Askin bc i dont want to waste my cash buying an aftermarket plenum if I want benefit from it.
No, it will benefit, probably even result in a bigger HP increase on your F/I car than on a N/A car, but then you're starting with more airflow. But, that doesn't mean it wouldn't help the N/A car as well. You may notice a slight drop in boost, which is a direct indicator that a restriction was eliminated and flow was increased, but the over-all power will increase. Think of boost pressure as an indicator of resistance to flow. Take your thumb off the end of the garden hose and the water flow increases while the pressure in the hose decreases. The factory plenum is restrictive, so going to an aftermarket unit will help regardless of whether it's F/I or N/A. How much it helps depends on the entire system. Sorry, I didn't mean to complicate the subject. My advice, buy the plenum. Others may disagree.
 

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Discussion Starter #11
so your saying plenum over tb? what brand? i see american muscle has accufab plenum and tb combo but only bbk tb
 

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Discussion Starter #12
i heard accufab was the best tb? what about plenum?
 

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Well I went did order BBK throttle body and plenum combo I will have pics once I install it. I've seen people polish there stick plenums but upgrade there throttle body!
 

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Given the plenum and air intake system are not restricting it, the factory 65mm TB flows enough air for a stock to mild 4.6L at 5K to 6K rpm. The factory plenum restricts even the factory TB, so I would start there. As you increase the VE of the motor by adding mods like cams, heads, exhaust, etc., or increase the operating RPM range, you raise the required cfm. Basically, unless the TB is restricting, you don't need to go any bigger. The nice part about EFI is that it does not rely on air velocity through the TB to properly meter fuel like a carb does. Going larger has little to no effect on off-idle or low speed drivability. 70mm, 75mm or the BBK 78 will all work good. Given your mods, I think going up to at least 70mm would be a good idea. You will experience an improvement in perceived throttle response, but that is mostly a result of the change in throttle modulation rate. The larger bore opens up more area for flow for any given amount of throttle pull. Kinda the same principal as a short throw shifter; the movement in the tranny doesn't change but it takes less physical movement by you to achieve it.

Opinions vary when it comes to brands, but it seems well accepted that Accufab is among the best in terms of quality and finish. Whether they're worth the extra money is your call. Trick Flow, C&L, BBK, Professional Products.....they're all good quality and very close in performance...and far better than the factory parts. It really depends on what you like and are willing to spend. Personally, it's a hunk of aluminum casting with no moving parts, so unless looks are top priority, I would go with whatever plenum you can get the best deal on. When it comes to the TB, quality becomes a little more noticeable, but If you stick with the name brands you should be fine. I bought a used Trick Flow plenum off eBay ($50) and a new Ford Racing 70mm TB that was on clearance from UPR for dirt cheap. After you install the TB, check to make sure the blade opens the full 90 degrees to WOT with the gas pedal to the floor. No point in buying a larger TB just to have it flow less air at WOT!
 
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Discussion Starter #16
Well I went did order BBK throttle body and plenum combo I will have pics once I install it. I've seen people polish there stick plenums but upgrade there throttle body!
i only saw the accufab combo where did you get the bbk combo?
 

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No, it will benefit, probably even result in a bigger HP increase on your F/I car than on a N/A car, but then you're starting with more airflow. But, that doesn't mean it wouldn't help the N/A car as well. You may notice a slight drop in boost, which is a direct indicator that a restriction was eliminated and flow was increased, but the over-all power will increase. Think of boost pressure as an indicator of resistance to flow. Take your thumb off the end of the garden hose and the water flow increases while the pressure in the hose decreases. The factory plenum is restrictive, so going to an aftermarket unit will help regardless of whether it's F/I or N/A. How much it helps depends on the entire system. Sorry, I didn't mean to complicate the subject. My advice, buy the plenum. Others may disagree.
I gotcha that all adds up not complicated at all. Appreciate that.
 

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Discussion Starter #20
so is it better to use same brand tb and plenum or doesnt matter?
 
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