70mm or 75mm Throttle Body

5.0DuDe · Jan 25, 2006

okay this weekend i will be doing a fox tb conversion to my car

vortech v1

255 intank

80mm pro m

42 injectors and fpr

L/T and full exhaust

stock heads and everything else

my friend gave me his explorer intake which i was going to port and clean up a lil my question is should i go with the 75mm because i do plan on going with a AFR/custom cam/trickflow H/C/I in the summer time or will the 70mm enough for both combos now and later

nmcgrawj · Jan 25, 2006

75mm all the way....ya know, i've got a accufab piece im thinking about selling PM me if interested.

moneypit94 · Jan 25, 2006

I have done a lot of research on tb's sizes for supercharger/turbo applications lately.

For you i would think a 70mm or even 65mm would be sufficiant for both applications. I ran a 70mm on my 331 h/c/i v-2 combo.

IF!!! there would be a difference in power between the two it would be very small like a 1-2hp but advantages of a smaller one in my opinion out ways the 1-2hp.

Me i just stepped up to a 75mm for my new 427 twin turbo combo. My piping is 3" so there was really no need to go any bigger then 75mm... This was George Klass's suggestion to me. (accufab tech)

NA is completely diffent then Forced induction... Things flow 2 and 3 times as much Forced as they would NA

just my $.02

nmcgrawj · Jan 25, 2006

moneypit94 said:
I have done a lot of research on tb's sizes for supercharger/turbo applications lately.

For you i would think a 70mm or even 65mm would be sufficiant for both applications. I ran a 70mm on my 331 h/c/i v-2 combo.

IF!!! there would be a difference in power between the two it would be very small like a 1-2hp but advantages of a smaller one in my opinion out ways the 1-2hp.

Me i just stepped up to a 75mm for my new 427 twin turbo combo. My piping is 3" so there was really no need to go any bigger then 75mm... This was George Klass's suggestion to me. (accufab tech)

NA is completely diffent then Forced induction... Things flow 2 and 3 times as much Forced as they would NA

just my $.02

With a combo like this, what advantages does the smaller one have?

I figured with a h/c/i and a blower, you would want a bigger TB. What has your studies shown?

wytstang · Jan 25, 2006

moneypit94 said:
I have done a lot of research on tb's sizes for supercharger/turbo applications lately.

For you i would think a 70mm or even 65mm would be sufficiant for both applications. I ran a 70mm on my 331 h/c/i v-2 combo.

IF!!! there would be a difference in power between the two it would be very small like a 1-2hp but advantages of a smaller one in my opinion out ways the 1-2hp.

Me i just stepped up to a 75mm for my new 427 twin turbo combo. My piping is 3" so there was really no need to go any bigger then 75mm... This was George Klass's suggestion to me. (accufab tech)

NA is completely diffent then Forced induction... Things flow 2 and 3 times as much Forced as they would NA

just my $.02

Finially a voice of reasonon on tb's, I've read some of Klass's comments on tb's on hardcore that backed up what I believed. I agree 100%.....

VibrantRedGT · Jan 25, 2006

Mixed bag I guess but I'd say 75MM. I only say this if your intake has the same size opening.

95CobraMike · Jan 25, 2006

i went with a bbk 75mm... when i took my old throttle body off of my upper intake, the opening was 72mm at the point where the throttle attached... so i had my upper ported at the opening and back to 75mm....

moneypit94 · Jan 25, 2006

nmcgrawj said:
With a combo like this, what advantages does the smaller one have?

I figured with a h/c/i and a blower, you would want a bigger TB. What has your studies shown?

My advice to 50DuDe is to call Accufab and see what they say...909-930-1751
I could be wrong... it won't be the first and it deffently won't be the last.

a smaller one will give you more control of the air at lower rpms, making it more streetable. George isn't the only person who has suggested 75mm for my application. Brian k. the tech at Anderson ford motorsport told me the same thing along with rick anderson.

I have a 90mm opening on my intake and they all knew that. So matching up the intake to the throttle body doesn't work... in my case anyway.

Oh and Brian from B&G said for my application there was no need to move up past 3" tubing. He said he has seen 3" tubing turbo kits make 1300+ hp without pushing them. 3" is roughly 76mm i believe... Im actually downsizing by a mm. But those guys have a lot more experence then me so i did what they said.

why would you need to go any bigger then your piping size? The piping from the s/c to the intake that comes with the vortech kits is small. I modded a new one out of 3" exhaust for my old setup.

nmcgrawj · Jan 25, 2006

That makes sense. Just like George told me...there is no HUGE gain to be had with header primaries that dwarf your exhaust valve. The system is only as strong as its weakest link.

I guess i would like to see an application where a 75mm proved to be more streetable than say a 90 or a 65 compared to a 75. Do you get bucking? What happends when u cant "control" the airflow as well on lower rpms? And this is something that can not be taken up for with a proper cam selection or proper tuning right?

5.0DuDe · Jan 25, 2006

would i be able to use this one on my fox conversion with using a 75mm egr delete http://cgi.ebay.com/ebaymotors/86-9...ewItemQQcategoryZ33558QQitemZ8031837524QQrdZ1

Black95GTS · Jan 25, 2006

5.0DuDe said:
okay this weekend i will be doing a fox tb conversion to my car

vortech v1

255 intank

80mm pro m

42 injectors and fpr

L/T and full exhaust

stock heads and everything else

my friend gave me his explorer intake which i was going to port and clean up a lil my question is should i go with the 75mm because i do plan on going with a AFR/custom cam/trickflow H/C/I in the summer time or will the 70mm enough for both combos now and later

I believe your explorer intake is ported for 70mm. Use a 70mm TB. With a blower, you don't need the larger size as MoneyPit correctly pointed out. Because you're stuffing air in there and not relying on vacuum, its a whole different ball game. Turbomustangs.com has guys in the 10s using 65mm TBs.

Adam

5spd GT · Jan 25, 2006

I suggest a 70mm TB.

George Klass knows his stuff I have read his post on hardcore as well. Nice readings...

75mm TB will get you more possible bucking at low rpms. Tip-in. The pros of a "tiny" throttle body outweight the extra bit of power you get with a 75mm TB. Guys are running quite quick with 65mm TB's...Paul is one...

Just because the intake has an opening for "X" mm doesn't mean the TB needs to be that size to match. They are that "big" for growth later on for the customer. They also most likely assume your not going to need anything bigger than the "X" amount of mm given at the intake opening on the upper plenum.

88GT460 · Jan 25, 2006

75mm all the way

Stangfreak95 · Jan 25, 2006

75mm man for sure. I was n/a and went with the fox conversion and a Accufab 75mm tb. Check the pic in my sig to see if that 75mm was taking away some torque from my stang...again naturally aspirated. You're blown. You cant go wrong with that 75mm imo.

nmcgrawj · Jan 25, 2006

5spd GT said:
75mm TB will get you more possible bucking at low rpms. Tip-in. The pros of a "tiny" throttle body outweight the extra bit of power you get with a 75mm TB. Guys are running quite quick with 65mm TB's...Paul is one...

I guess what i dont get is what causes this "bucking" ? And is it not fixable?

70mm or 75mm Throttle Body

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