Throttle Body Size, any equations?
Thread Starter
Le Mans Master
Joined: Jan 1999
Posts: 5,135
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From: Long Island NY
Throttle Body Size, any equations?
Is there an equation to calculate the size throttle body you need? I've heard that going to big is not good, but a lot of guys (especially on camaroz28.com) have gone bigger with very good results.
I was thinking of Arizona Speed and Marines 54mm.
Jim
I was thinking of Arizona Speed and Marines 54mm.
Jim
Burning Brakes
Joined: Aug 2001
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From: San Diego CA
Cruise-In III Veteran
Re: Throttle Body Size, any equations? (Hammer)
Hammer-
I just realized your looking to do a heads/cam package rather than a stroker. I'm almost sure that the 54mm will be too much for your setup. I believe the AS&M flows in the neighborhood of ~900 cfm. The average 58mm flows around 1000cfm! I vote for their 52mm. It's MUCH cheaper, and its guaranteed to give you the HP without any problems.
BUT, here is what you asked for- http://www.newcovenant.com/speedcraf.../intakecfm.htm
For the record, MORE performance wanted to answer this question for good, and last year they tested both TB's on one of their 396's. They found an 8hp increase with a 58mm over a 52mm (I dont remember the tq number). That is certainly not enough to justify another $250! Besides, that was on a stroker motor...your bottom end is stock- shouldnt make as much difference.
Glad your going with the AS&M though! Good luck... :cheers:
I just realized your looking to do a heads/cam package rather than a stroker. I'm almost sure that the 54mm will be too much for your setup. I believe the AS&M flows in the neighborhood of ~900 cfm. The average 58mm flows around 1000cfm! I vote for their 52mm. It's MUCH cheaper, and its guaranteed to give you the HP without any problems.
BUT, here is what you asked for- http://www.newcovenant.com/speedcraf.../intakecfm.htm
For the record, MORE performance wanted to answer this question for good, and last year they tested both TB's on one of their 396's. They found an 8hp increase with a 58mm over a 52mm (I dont remember the tq number). That is certainly not enough to justify another $250! Besides, that was on a stroker motor...your bottom end is stock- shouldnt make as much difference.
Glad your going with the AS&M though! Good luck... :cheers:
Race Director
Joined: Aug 2000
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Re: Throttle Body Size, any equations? (Hammer)
Hi Jim,
Hows the little one doing? Good I hope!
About the TB size,your stocker is fine.
Its actually good for 383 cubes and more.
I'll explain why...
VE or Volumetric efficiency for a 350 engine is rated at about 532 cfm.
That assumes 100% of air being drawn in,which isnt possible on NA(naturally aspirated) motors.
SO the best number down is to assume around 80% VE which is about 426cfm.
(some engines may see close to 90% depending on mods)
The larger aftermarket TB's can flow like 750-1000 cfm of air.Thats way more then the engine will use...see where its going?
Unless you turbocharge,Supercharge or really work that motor,a larger TB isnt going to do anything more then the stock one can do for your driving.
And if you even somehow gain anywhere from 4-8HP from a larger TB, youll never know it unless you dyno it and then compare the price to HP gai you spent.Not that great eh?
Changing air intake pieces can help change the pressure in the manifold to increase power but NA isnt going to do much for an increase.
Just wanted to share that.
:)
Hows the little one doing? Good I hope!
About the TB size,your stocker is fine.
Its actually good for 383 cubes and more.
I'll explain why...
VE or Volumetric efficiency for a 350 engine is rated at about 532 cfm.
That assumes 100% of air being drawn in,which isnt possible on NA(naturally aspirated) motors.
SO the best number down is to assume around 80% VE which is about 426cfm.
(some engines may see close to 90% depending on mods)
The larger aftermarket TB's can flow like 750-1000 cfm of air.Thats way more then the engine will use...see where its going?
Unless you turbocharge,Supercharge or really work that motor,a larger TB isnt going to do anything more then the stock one can do for your driving.
And if you even somehow gain anywhere from 4-8HP from a larger TB, youll never know it unless you dyno it and then compare the price to HP gai you spent.Not that great eh?
Changing air intake pieces can help change the pressure in the manifold to increase power but NA isnt going to do much for an increase.
Just wanted to share that.
:)
Burning Brakes
Joined: Aug 2001
Posts: 969
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From: San Diego CA
Cruise-In III Veteran
Re: Throttle Body Size, any equations? (Bill's86Coupe)
He's looking at going with a very aggressive stage III head setup, mated with a performance cam. I would guess that his volumetric effeciency is somewhere around 83% or more. The stock 48mm TB maxes out at ~670 cfm. According to the calculator, he needs between 645 to 806 cfm to maximize the intake flow. IMO, the 52mm TB AS&M sells would work nicely- 790cfm. :yesnod:
Plus, you can use it with your future bottom end!
[Modified by 365ZUM, 12:52 AM 10/26/2002]
Plus, you can use it with your future bottom end!
[Modified by 365ZUM, 12:52 AM 10/26/2002]
Race Director
Joined: May 2001
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Re: Throttle Body Size, any equations? (365ZUM)
That's kinda the theory I'm going with. I bought a 52 when I had cam / headers but no heads. As such I knew the heads were the restriction but the price was very much right and that Holley is so pretty. Now I've added the heads, and it's possible that it's actually helping me out now, wouldn't swear to it, but it's possible. Besides, I never know what the future might hold for the bottom end.
The one overwhelming fact that I know and will repeat again, it sure is pretty. I believe the AS&M is also a very nice billet piece. Now if it was the stocker or a cast BBK unit, I'd stick with the stocker until I actually needed it. Beauty however is in the eye of the beholder, so I'll let you judge for yourself. Would this look right with the stocker?
Edit : stupid internet exploder, no copy image location command :smash: :smash:
[Modified by Nathan Plemons, 12:07 AM 10/26/2002]
The one overwhelming fact that I know and will repeat again, it sure is pretty. I believe the AS&M is also a very nice billet piece. Now if it was the stocker or a cast BBK unit, I'd stick with the stocker until I actually needed it. Beauty however is in the eye of the beholder, so I'll let you judge for yourself. Would this look right with the stocker?
Edit : stupid internet exploder, no copy image location command :smash: :smash:
[Modified by Nathan Plemons, 12:07 AM 10/26/2002]
Instructor
Joined: Jan 2002
Posts: 175
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Well... my opinion...
I'm not sure I agree with the ones that say it won't help... or you won't feel 8 HP.... well, sort of.
I just went from a 48mm to a 58mm TB and Good Grief ! ! !
I could tell a BIG difference.... course my motor is bigger. I would never of imagined that a little swap like that would make that much difference. It is certainly more throttle responsive... and pulls ALOT harder and even Higher RPM's.
Now... When I get my headers bolted on (1 7/8" custom) and remove those tiny stock headers... I am really hoping for some even higher RPM's.
I just went from a 48mm to a 58mm TB and Good Grief ! ! !
I could tell a BIG difference.... course my motor is bigger. I would never of imagined that a little swap like that would make that much difference. It is certainly more throttle responsive... and pulls ALOT harder and even Higher RPM's.
Now... When I get my headers bolted on (1 7/8" custom) and remove those tiny stock headers... I am really hoping for some even higher RPM's.
Race Director
Joined: May 2001
Posts: 14,165
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Re: Well... my opinion... (85Procharged383)
Forced induction changes the entire picture. When a motor is N/A it is relying only on the amount of air that it can suck in by it's own vacuum. With a blower you are forcing air down it's throat and as such can easily feed it more air than the stock TB will flow and thus see a nice gain by simply changing the TB. The larger displacement doesn't hurt either.
If you were using a stock 350 you would see different results. :cheers:
If you were using a stock 350 you would see different results. :cheers:
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Race Director
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Re: Throttle Body Size, any equations? (Hammer)
Jim,
Glad to hear good news about the baby...hope all is always well.
Do Keep us posted about the 54MM later on and hope ya see at least a few gains from it to make it worthwhile.Seems every engine may react differently so it may or may not benefit every other motor out there.Your package sounds pretty good too.
:)
Glad to hear good news about the baby...hope all is always well.
Do Keep us posted about the 54MM later on and hope ya see at least a few gains from it to make it worthwhile.Seems every engine may react differently so it may or may not benefit every other motor out there.Your package sounds pretty good too.
:)
