well i did searching but its more like a he said he said thing im reading. i know that upgrading a 70mm would give me good throttle response for sure. also our cars (94 sn95) comes with a 70mm maf. im still deciding. ill be upgrading the intake soon until i get things intact. out of these 2, im looking for 1 thats good for both stock and aftermarket.
70mm or 65mm TB ?
- Thread starter tstang21
- Start date
millhouse
Founding Member
That throttle response you speak of comes at a cost….the loss of throttle modulation. The larger the throttle body, the less modulation you will have. When going too big, you’ll run into tip in issues where a very small amount of throttle amounts to a huge swing in the change of airflow into the engine. While this may be fine in a track only car, the loss of modulation can be a pita on a daily driver.
For your basic H/C/I car (stock displacement), a 65mm or 70mm TB is fine. If you were to add a cetri blower or turbo….once again, a 65mm or 70mm TB is fine. It’s not until you start getting into nitrous or KB blower setups where you start to realize the need for a larger throttle body.
legalize420
Active Member
just keep the stocker. its not a restriction and there will be little to no gain. i would lean more toward no gain.
S351Saleen77
Member
You guys look into this WAY too much. People have complained about touchy throttle with 90mm TBs....not 70-75mm TBs. 
The throttle modulation on my 70mm was the same as stock.
You guys act like if you go to a 75mm TB it wont be streetable. 
Again, I go by what people run at the track as to if I listen to them or not with advice.
The throttle modulation on my 70mm was the same as stock.
You guys act like if you go to a 75mm TB it wont be streetable. Again, I go by what people run at the track as to if I listen to them or not with advice.
Here is another good example I will throw out. If you are building a 408 and you decide to go with AFR 185 heads...Yes these heads "are fine" <-key words. However if you went with AFR 205 heads over the 185s that were fine you would pick up more power. Same thing applies here. If you are going to spend the money why not spend it on something that will give you the most for you money? Again a bigger throttle body CANNOT hurt power and if you think a 75mm TB is going to make your throttle so touchy that you hate to drive it then you clearly do not know what you are talking about. Carry on...
millhouse
Founding Member
You guys look into this WAY too much. People have complained about touchy throttle with 90mm TBs....not 70-75mm TBs.
The throttle modulation on my 70mm was the same as stock.
Again, I go by what people run at the track as to if I listen to them or not with advice.
Just because you are not able to discern the difference in modulation does not other cannot as well. There is absolutely NO way the modulation on your 70mm was the same as stock...it's purely a matter of physics.
The point many of us are trying to make is that if your power goals never go beyond the limits of a 65mm throttle body, why sacrifice the modulation? Not many argue the fact that they will make the same power.
That analogy has absolutely nothing to do with sizing a throttle body. Upgrading to a bigger/better head increases the volumetric effeciency of the engine...which in turn increases power. If you already had the properly sized throttly body, it would do absolutely nothing for power.
BTW, I'm sporting a stock throttle body....and it seems to be holding up just fine!
Ofcourse if you don't plan on more than 300rwhp then the stock would be fine. However everytime I suggest parts I have in my mind that the person I am talking to is like most people are which you can never have enough power. You get used to it and you get bored.
And my car ran faster than your car does with smaller heads, heavier car, and the same amount of boost out of one turbo not two.
I also know what I'm doing here chief.
Heres my version of your car http://www.youtube.com/watch?v=sHe3pvT4810
BTW, I'm sporting a stock throttle body....and it seems to be holding up just fine!
And my car ran faster than your car does with smaller heads, heavier car, and the same amount of boost out of one turbo not two.
I also know what I'm doing here chief.Heres my version of your car http://www.youtube.com/watch?v=sHe3pvT4810
millhouse
Founding Member
Ofcourse if you don't plan on more than 300rwhp then the stock would be fine. However everytime I suggest parts I have in my mind that the person I am talking to is like most people are which you can never have enough power. You get used to it and you get bored.
And my car ran faster than your car does with smaller heads, heavier car, and the same amount of boost out of one turbo not two.
Heres my version of your car YouTube - CAMMED Turbo 5.0
Honestly, a 65mm TB is going to be able to support almost all of the n/a horsepower out of a 302 at mild rpms. It's not until you start getting into more displacement and/or higher rpms that it would become a restriction. Don't get me wrong, there are some instances in which overbuilding is a great way to go....but for those that don't plan on running anything other than a mild h/c/i setup...a 65-70mm throttle body is more than adeqate.
As for your car....you need to be abe to differentiate the difference between having a quicker ET...and a Faster car. Your heavier car with smller heads and the same amount of boost is nearly 7mph slower in the 1/4 mile. Keep in mind, this is with me having a HORRIBLE 2.0 60' time. Once I get her to hook, I should be close to 130mph trap speeds. All of this on 2 undersized turbo's (yes, the turbine housings are far to small for my cam/heads). Regardless, most turbo savy people realize that having 2 turbo's rather than one in most appliactions does not equate to more power or faster track times...only slightly quicker spool up time.
millhouse
Founding Member
Getting to the end of the 1/4th mile faster = a faster car.
You may have gotten down the 1/4 mile quicker...but your car is definately not faster. With a set of slicks and a 5000rpm launch I'd be in the 10's EASY. The same cannot be said about yours.
Your previous comments were intentionally misleading...making one think that your heavier car with a much lesser setup was more capable than mine. T
The truth is, I've only been down the track once with my skinny 235 mt street radials and a malfunctioning 2-step. Combine that with a manual tranny and it's easy to see why I'm cutting horrible 2.0 60's.
Your car is MUCH lighter than my car could probably ever be. You have bigger heads, more mods, and you make 9rwhp more than me. Given my motor is more restrictive you are probably pushing more boost than I am too. So with a lighter car, more motor, and more positive pressure you are still slower than me in the 1/4th. My 3,500lb car still ran 11.82@122mph on 17" wheels with a 2.0 60' so your car does not impress me. Lets not turn this into a pissing match because it is pointless. 
I ran faster than you in the 1/4th with less to do it with. If you like roll racing then you would fit in well with my friend and his Supra. 
Back on topic yes a 65-70mm TB will work with someone that does not want to go more than 302 H/C/I. However as I have stated a bigger TB CANNOT hurt performance so why would you want to limit yourself to a 65-70mm TB now when in a few months to a year you might plan to stroke your motor and now you need more TB. Seems silly to me since you wont tell the difference in driveability between a 65-70mm and a 75mm. (Yes I have driven a HCI 5.0 with all of the above.)
My 3,500lb car still ran 11.82@122mph on 17" wheels with a 2.0 60' so your car does not impress me. Lets not turn this into a pissing match because it is pointless. I ran faster than you in the 1/4th with less to do it with. If you like roll racing then you would fit in well with my friend and his Supra. Back on topic yes a 65-70mm TB will work with someone that does not want to go more than 302 H/C/I. However as I have stated a bigger TB CANNOT hurt performance so why would you want to limit yourself to a 65-70mm TB now when in a few months to a year you might plan to stroke your motor and now you need more TB.
Seems silly to me since you wont tell the difference in driveability between a 65-70mm and a 75mm. (Yes I have driven a HCI 5.0 with all of the above.)
millhouse
Founding Member
Your car is MUCH lighter than my car could probably ever be. You have bigger heads, more mods, and you make 9rwhp more than me. Given my motor is more restrictive you are probably pushing more boost than I am too. So with a lighter car, more motor, and more positive pressure you are still slower than me in the 1/4th.
Back on topic yes a 65-70mm TB will work with someone that does not want to go more than 302 H/C/I. However as I have stated a bigger TB CANNOT hurt performance so why would you want to limit yourself to a 65-70mm TB now when in a few months to a year you might plan to stroke your motor and now you need more TB.
Dude, you crack me up. You are claiming that because you have itty bitty AFR 165 heds with your combo that you are at a disadvantage and have a more restrictive setup? Seriously, those heads are equally as good as the TFS heads usin forced induction! Once again, you are misleading in an attemp to prove a point. I also hate to break it to you, but 8psi of absolute pressure is 8psi of absolute pressure. My 8psi doesn't magically equate to more psi.
In all hoensty, I would expect your car to be faster than what it is....even at 3500lbs!
I'm not big on racing from a roll....and much more enjoy running from a tree. If push came to shove though...you wouldn't stand a chance from a roll (it sounds like you already know this though). You had a slightly quicker ET with a VERY similar engine combo & boost numbers...
Back the the TB discussion....I'm not arguing that a bigger thorttle body wont hurt performance. I'm all for planning for the future too....but simply buying a bigger throttle body just to have one is not sound reasoning....and will hurt modulation.
thanks guys for you input. so anyways, i talked to 1 of the guys at the shop. he builds motors acoarse and associates himself with ronnie wilson. i told him about the question i ask on here and said 70mm will be fine on the stock intake (sn95). it wont hurt performance. this is from a shop that works STRICTLY on mustangs. 70mm it is.
legalize420
Active Member
8psi on one motor isn't the same as 8psi on another motor. Boost is a show of restriction and nothing else. So if your car breathes better than my car then 8psi on your gauge is more positive pressure than 8psi on my gauge. Understand how that works?
Oh and about running me...bring it! We can do it at the track or on the street from a roll. Doesn't matter to me.
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