Best sized throttle body and plenum

MDB919 · Jul 6, 2014

Alright guys, I've done a little searching around with not a lot of luck. I'm getting ready to put the top end of my car together and need some advice. This is where I am right now.... I'm not sure what throttle body and plenum I should use. I've got a 1998 mustang GT 5 speed. It has a full PI head/intake swap, Cms stage 2 cams, shorty headers, off road x pipe, CAI, and it will be dyno tuned. What would be the best choice for me? BBK has that 78mm throttle body/plenum combo, but I'm afraid 78mm may be too big. But this is my first 2v, so I really have no idea. Any advice would really be appreciated.

thanks,
matt

chris91 · Jul 6, 2014

I went with the Dragon Plenum and Pro Products 75mm TB. Not sure of numbers but they seem to do the trick.

D3VST8R96GT · Jul 7, 2014

Plans for the car?

Go big or go home

MDB919 · Jul 7, 2014

I'm trying to get 300 to the tires NA. I'm not sure if that possible with stock PI heads, but I'm going to give it a try. I might eventually do a plate nitrous system just for fun. But who knows.

Ferocious · Jul 7, 2014

75mm will suffice.

96blak54 · Jul 7, 2014

You need to deck the block .030 and get a set of flat top pistons with valve reliefs...then youll be touching 340rwhp...

nightfire · Jul 7, 2014

BBK 78mm plenum AND throttle. I'd advise against on an N/A 4.6 but you're cams are going to love the extra air.

MDB919 · Jul 8, 2014

That was my concern. That BBK 78mm combo is very affordable, but I don't want it to be too much and actually hurt the performance. I don't know if my cams are going to make it flow ENOUGH with unported heads. Ill probably just end up going with a set of 75mm's.

nightfire · Jul 9, 2014

A 3mm difference is negligible....and you get a TB/plenum combo. It is NOT going to hurt performance.

D3VST8R96GT · Jul 9, 2014

opcorn:

Caboose302 · Jul 9, 2014

MDB919 said:
I'm trying to get 300 to the tires NA. I'm not sure if that possible with stock PI heads, but I'm going to give it a try. I might eventually do a plate nitrous system just for fun. But who knows.

You'll get close but I have ported heads and just barely cleared 300 rwhp. But then again I also only have stage 1 cams. I've always been told that 70mm is best for NA with a max of 75 for ported heads and bigger cams but I agree, I don't think 3mm will make a difference. Your biggest restriction is coming to be your upper plenum if you get a bigger TB.

03DSGGT · Jul 9, 2014

I had full bolt ons and longtubes with stock heads, stock PI intake with the BBK 78mm piece, and CMS stage 2 cams and made 292 at the wheels. I'm thinking that with the bump in compression from the PI swap you will be knocking on the 300rwhp door...

D3VST8R96GT · Jul 9, 2014

Caboose302 said:
You'll get close but I have ported heads and just barely cleared 300 rwhp. But then again I also only have stage 1 cams. I've always been told that 70mm is best for NA with a max of 75 for ported heads and bigger cams but I agree, I don't think 3mm will make a difference. Your biggest restriction is coming to be your upper plenum if you get a bigger TB.

Well the 78mm is tb plenum combo.

Caboose302 · Jul 9, 2014

I meant if he decided to go with a 70 or 75

D3VST8R96GT · Jul 9, 2014

Ah I c.

330CubeGt · Jul 12, 2014

75mmishes is fine from a stock motor to a 600+hp motor no real need to go to a 78mm. Thats why you don't see many out there.
The price diff to hp increase is not there.

Sent from my SGH-T999 using Tapatalk 2

mustanggt01 · Dec 14, 2014

have you ever tried other plenums/throttle bodys?

nightfire said:
A 3mm difference is negligible....and you get a TB/plenum combo. It is NOT going to hurt performance.

I have tried many setups between the stock, trickflow/75mm, stock plenum/70mm, and the BBK 78mm combo (1780). I must say you are wrong and honestly you lose a load of torque and gain a load of horsepower.
From my experience the stock plenum with 70mm or trickflow/75mm combo is the perfect setup and you gain a bit of torque from both. When I went from the trickflow/75mm to that piece of junk BBK 1780 I was very disappointed and took it off in just 3 days and sold it on ebay. (01 gt) I have pulleys,K&N CAI, bama 93 tune,80mm maf, xpipe with high flow cats, welded in super 44's, 3.73 gears and back with the trickflow setup but I was using the 78mm BBK with these mods.

DropTopPony · Dec 15, 2014

nice bump

From the combo you posted I doubt you felt a difference when you switched between any of those combo's because the hp/tq increase/decrease is negligible from a plenum and tb on an n/a 2V. You are talking about differences of like 3-4 hp/tq between the best combo to the worst.

Many dyno tests were done back when these cars were new and huge gains were not to be had from any combo.

JerZeyStangz · Dec 19, 2014

I have a 75mm Mac T/B and C&L plenum, lost a tiny bit of torque in low end range, but gained a bit in the mid-top end range on npi heads. Its a trade off until you go forced induction or put a set of powerful heads on or a combo of both.

DropTopPony · Dec 19, 2014

JerZeyStangz said:
I have a 75mm Mac T/B and C&L plenum, lost a tiny bit of torque in low end range, but gained a bit in the mid-top end range on npi heads. Its a trade off until you go forced induction or put a set of powerful heads on or a combo of both.

Where you been hiding?