Throttle Body Opinions

[9lb302]

Didn't the 94-95 Cobra's come stock w/ the 65mm?? Also, I thought there were some dyno tests that showed you lost a little tq down low w/ the larger tb on a mostly stock motor.

 

[Piston]

Hmm.. this has me thinking now.. but what if you have 3 straws? one for the heads, one for the intake, one for the throttle-body..

if you make the t-body straw larger in diameter than the other two, does it really matter??? doesn't it more come down to how smooth the transition is??

Velocity is created by a smooth flow through all the straws. I would think Velocity is killed when you have a straw to small or too big down the chain. I would have to say small would be worse then big.

Honestly the TB question is a tough one. I think both people are right. However, when it really comes down to it the most important thing is to find the balance.

On the other hand you may be right, as I said earlier its a matter of need for air vs. need for velocity and finding a good balance between the two.

With your stock application I would say go 70mm if you plan on doing upgrades down the road. Go 65mm if you plan to keep everything the same (personally I think you might suffer a little bit, but then you might mod up your car quicker ). I think the 70mm you will have more to gain on the top end and lose more on the bottom end. The 65 will work good through out your range however may become to small in the future depending on what you end up doing. However, I made the mistake of going with a 70mm and now I think I have to spend some money on a 75mm on my new N/A High Revvin 331. Although, I'm thinking of running the 70 and putting on the 75 and see the difference maybe then there will be some proof I can shed on the situation.

COMBO I HAVE that warranted the 70mm TB
Edelbrock Performer Ported Upper/Lower Intake Flows 275cfm
TFS Stage II Ported Heads Heads ~280cfm @ .600
B2 Anderson Cam 1.6Rockers
75MAF & 24lb
MSD Coil, Ignition
Hooker 1 5/8 Full Tube Headers
3.73 Gears, 3550 Trememc
Bone Stock Bottom End.
Dyno Tuned by Anderson using Their PMS computer to a 325 RWHP.

 

[Black95GTS]

On my uncle's 2001 NA mustang, he switched from a 75 to a 70 after a few months. He felt that the larger TB hurt his power down low. He's got a bunch of goodies in his stang too, including a larger MAF and 24# injectors. I personally run a FMS 65mm with CAI, and it seems to be the perfect combination on my very lightly modded grocery getter. Also, I heard that if you use anything anthing 70mm or larger, you really should redo the MAF, I dont know how true that is though.

 

[stang_gt_1994]

I think people shouldent even speak unless they have dyno proof. I have a 70mm TB and it seems to work good, but I can't say totally because I have no dyno proof. All and all what kinda gains are we talking about from going up or down 5mm in size, 5 HP maybe.

 

[TMC]

I think people shouldent even speak unless they have dyno proof. I have a 70mm TB and it seems to work good, but I can't say totally because I have no dyno proof. All and all what kinda gains are we talking about from going up or down 5mm in size, 5 HP maybe.

Actually your 5hp estimate is pretty accurate from what I've seen. But don't forget, 5HP here and 5 there adds up with enough of them. But, yes in reality we are only speaking about a few HP total from one size to the next.

 

[stang_gt_1994]

Yes 5HP here and there adds up, but we are just talking about a increase or decrease from a TB. Its really a pointless subject about talkng about a 65mm tb and a 70mm tb on a NA setup.

 

[TMC]

Yes, I have haerd that on the internet among other places, but mostly my knowledge of physics and limited knowledge of thermodynamics tells me that. On the other hand you may be right, as I said earlier its a matter of need for air vs. need for velocity and finding a good balance between the two. I'm only trying to make a point about that concept, but you also have a good point, as I'm no expert on the practical application of it. the only things I have to go off of are my own personal combo and what everyone else runs. I have never runs 2 different TB's and dyno each. I'm sure 70 workds great for some NA combo's, I'll withhold judgement on the 75 until I see some dyno numbers.

I was just trying to explain the concept and use that along with what I know about 94-95 cars to help this guy pick a TB.

BTW - What kind of a combo are you running? Got any dyno #'s and/or times, I''d love to see em'.

here's a dyno from mid summer when the car was running 11.9's on DR's. The AF was very lean on those pulls ~13.5. after I addressed that issue the car definately made some more power.

Poor quality but it's what I have.