Throttle Body Opinions

la8111 · Feb 24, 2004

I own a 94 cobra and I'm looking to upgrade. Ive read and talked to too many people and get too many answers back in forth on whether to go w/ 65 or 70mm throttle bodie's. My previous car ran a 70, but w/ a blower. Really simple question, I know, but dont want to buy two in the end. This car will never see a blower anytime soon and my current mods are minimal. I've been told stock for this car is a 60 and feel like a upgrade to 65 instead of 70 would be a waste, while i've also read 70 to be to much. Also, can the tps sensor be adjusted on 94's. Thanks.

VibrantRedGT · Feb 25, 2004

Get the FRPP 65MM TB, comes with the sensors. The 65 is even good with a blower. TPS can be adjusted at idle. Hog out the copper inserts on the TPS with a drill bit. Bolt the TPS on the TB by hand. Now you will have wiggle room to adjust it to .94-.98v at idle. After you find the desired voltage tighten the bolts down.

TMC · Feb 25, 2004

IMO you need a larger TB for N/A cars than blower cars cause you don't have anything but atmosphere pushing the air into the motor. I vote for 70mm at a min and would even suggest a 75...especially if your every going to upgrade from the stock heads/intake on the Cobra.

1105 · Feb 25, 2004

TMC said:
IMO you need a larger TB for N/A cars than blower cars cause you don't have anything but atmosphere pushing the air into the motor. I vote for 70mm at a min and would even suggest a 75...especially if your every going to upgrade from the stock heads/intake on the Cobra.

I'm going to have to disagree with you and go with what Vib said. 65mm should be the largest you would want to go on a N/A 302. a 70mm and 75mm would be better for a blown car, stroker, or both. And yes, go with the FRPP TB.

Venom351R · Feb 25, 2004

I agree w/ 1105...65 MM Max on N/A cars....70MM on Blown cars.

TMC · Feb 25, 2004

I don't understand why the blown cars need a larger TB than na cars??? Blower cars have a BLOWER forcing air into the motor. NA cars don't have that advantage and you think that they need to be even more restrictive???

Here are some examples of what I use and what seems to work;

My NMRA Factory Stock car used a 70mm unit. That is the larges allowed by the rules and performed best. I tried the 65mm unit and it didn't make as much power or torque on my car. If your not familiar with the NMRA you can check some stuff out at www.stangcrazy.com but the basics of the combo are...N/A stock cam, Explorer intake, GT-40P heads shorty headers, 70mm tb. That's a very mild combo and very similiar to la8111's stock Cobra items.

My street 95GT has a larger Holley intake and TFS heads with a cam and LT's and uses a 75mm TB. Now I check and submitted my info to the 1/4mi list and I have the fastest car on the N/A list and I did it with a stock shortblock. The only other one I tried on that motor was a 70mm unit and it was about .1sec slower than the 75 on my car.

So, that's "proof" that bigger is better. Whatcha got?

red94fiveo · Feb 25, 2004

Two keys to power are both flow and velocity. While a big throttle body will flow more cfm than a smaller one, it will sometimes kill velocity on an N/A car.You're right, NA cars don't have air forcing into the motor, so as a result they really need that velocity. This is why I would say nothing bigger than 65mm on an N/A, unless its a crazy-a** combo. Just my opinion, I think you'll find that most other people around here will think the same way.

jetuomi · Feb 25, 2004

like everything it has to be matched to your application.

I'm using an rpm2 intake manifold and the 70mm t-body matches well to the flow of the intake and heads I'm using.. 65 wouldn't be enough on the top-end (peak hp coming around 6000 rpm with FTI cam).. Many guys who know what they're talkin' about (FTI even) mentioned I might want to go with 75 and use a minimum 4.10 gear !!

what you do change is the low-speed velocity, cause if your car can suck the air, it'll suck all it can get, and that's why some NA cars will use 75, they suffer down low (but have 4.56 gears) but haul up top..

its all in what you want to do with your combo.

1105 · Feb 25, 2004

red94fiveo said:
Two keys to power are both flow and velocity. While a big throttle body will flow more cfm than a smaller one, it will sometimes kill velocity on an N/A car.You're right, NA cars don't have air forcing into the motor, so as a result they really need that velocity. This is why I would say nothing bigger than 65mm on an N/A, unless its a crazy-a** combo. Just my opinion, I think you'll find that most other people around here will think the same way.

Nicely put

TMC · Feb 26, 2004

red94fiveo said:
Two keys to power are both flow and velocity. While a big throttle body will flow more cfm than a smaller one, it will sometimes kill velocity on an N/A car.You're right, NA cars don't have air forcing into the motor, so as a result they really need that velocity. This is why I would say nothing bigger than 65mm on an N/A, unless its a crazy-a** combo. Just my opinion, I think you'll find that most other people around here will think the same way.

...but prove to me that anything larger than a 65mm unit will lose power on the car in question here please. I've given you an example of my car with very similiar parts that used a 70 with good results, better than with a 65mm TB. I would have loved to use a 75 but it wasn't legal for the class. Where is your proof that a larger TB would be a mistake for this guy?

Did you hear that on the internet? Cause it's mostly just hype and theory until you go out and try it like I have.

randomjoker · Feb 26, 2004

THROTTLE BODY AIR FLOW DATA (In CFM):

just stole this outta the FAQ post.. i dont know if it will help you in your decision..

1.Ford Stock 5.0L 60MM, 526 CFM
2.Accufab 65MM, 616 CFM
3.BBK 70MM, 726 CFM
4.Accufab 75MM, 845 CFM
5.Accufab 90MM, 1225 CFM

jjd975 · Feb 26, 2004

What mods have you done to the car? Theres a good chance that the TB would be either a poor choice or a waste of money at this point.

red94fiveo · Feb 26, 2004

TMC said:
...but prove to me that anything larger than a 65mm unit will lose power on the car in question here please. I've given you an example of my car with very similiar parts that used a 70 with good results, better than with a 65mm TB. I would have loved to use a 75 but it wasn't legal for the class. Where is your proof that a larger TB would be a mistake for this guy?

Did you hear that on the internet? Cause it's mostly just hype and theory until you go out and try it like I have.

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'.

95snoozer · Feb 26, 2004

BBK 70

its what I have... and the elbow for an aftermarket intake is 70mm..... whats the stock opening on the 95 cobra intake though?

TMC · Feb 26, 2004

red94fiveo said:
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'.

OK, your theory holds some water and I'm sure that taken to the extremes it would prove to be true. That is if you had an extremely small (40mm or so on a 1000 HP capable motor) tb or an extremely large tb (say 90mm on a stock 5.0) you would have definite problems. Even with less drastic mismatches I'm sure there would be some negatives. However, I don't see any such problems with la8111's car using something larger than 65mm.

Please don't take offense from that Internet comment I made...It's just that the TB size thing is one of the biggest fallacies that I often see on the boards. Theory aside most times going to a 70 will not hurt performance in any way over the 65 is what I've found from real world testing.

BTW - Which combo are you interested in? The FS car or my 95GT?

dTas95GT · Feb 26, 2004

you could change the analogy to a straw sucking air. too small of a straw and you don't get enough air and you strain to bring it in... to big of a straw and you don't have enough sucking power to effectively move the air in and out with enough force. the right size straw will produce the maximum amount of air at the maximum velocity.

jetuomi · Feb 26, 2004

dTas95GT said:
you could change the analogy to a straw sucking air. too small of a straw and you don't get enough air and you strain to bring it in... to big of a straw and you don't have enough sucking power to effectively move the air in and out with enough force. the right size straw will produce the maximum amount of air at the maximum velocity.

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??

red94fiveo · Feb 26, 2004

TMC - I was curious about your 95 GT combo.

BTW - I don't think a 70 will hurt performance, I was merely saying that I think a 65 is usually adequate, but as discussed before I may be wrong. I agree that you would have to have a pretty huge throttle body to start hurting performance.

TMC · Feb 26, 2004

Basic Combo for my 1995 GT – 2003

· Stock shortblock
· TFS TW heads – upgraded valve springs – 59cc chambers – Ported In/Ex (~185cc runner) - 7/16 rocker studs
· Holley Systemax II intake – unported
· SVO adaptor elbow matched to 75mm
· Edelbrock 75mm TB
· Pro-M 77 meter w/30# injectors
· 1.6 rockers
· Erson 226/234 - .568/.568 – 110 lsa cam
· Mac 1 ¾” LT’s
· Dr. Gas 2 ½” X pipe
· Flowmaster 3-chamber mufflers w/dumps
· 4.30 gears
· Stock EEC
· Tremec 3550 trans
· Centerforce DF clutch

I have a dyno sheet at home that if I get time I could scan but it may be a while cause I've got a ton going on right now. Only made 336 rwhp and even less rwtq...I think around 315 or so. Very flat HP and TQ curves though which helped the car really motivate.

Best pass was a 11.63 @ 118.47 mph - average passes were 11.6's @ 117. There was more ET in it with the power it made but I never properly addressed the suspension so it was limited by that.

TMC · Feb 26, 2004

Throttle Body Opinions

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