Fox T-Bird/Cougar Forums

Technical => Engine Tech => Topic started by: jcassity on January 16, 2008, 02:19:56 AM

Title: 302 throttle body
Post by: jcassity on January 16, 2008, 02:19:56 AM
Why did for put a dual throttle body on the F series and bronco's while the passanger cars got one?  The 351 got dual as well but much larger.

I am pulling the white cougs motor again here soon and the setup will look like everyones typical cookie cutter layout, nothing fancy other than megasquirt which is in transit.

later on this year, I want to transiton my hogged out lower intake to a single chamber followed by my TB and additional duct to the fender wells to the CAI.

just curious about what ford was thinking.
Title: 302 throttle body
Post by: Innes on January 16, 2008, 04:16:19 AM
Are you sure the TB on 351 is bigger then the 302, I always wondered but i thought i heard somewhere they were the same.
Maybe it has 2 duels for the rectangular intake opening, like the pass intake is more of a square so 1 circle would fit instead-I don’t know that’s my guess there’s probably a better answer.
I know they sell aftermarket TB for the trucks and there duel as well.
If the 351 is bigger I guess that would be a good upgrade from the boneyard.
I like this site for my bronco maybe they could help http://www.fullsizebronco.com
Title: 302 throttle body
Post by: V8Demon on January 16, 2008, 07:52:38 AM
The truck manifolds flow more air than their passenger car counterparts.  My guess is that this is part of the reason for the different TB's.
Title: 302 throttle body
Post by: vinnietbird on January 16, 2008, 08:35:39 AM
Aren't the truck upper manifolds and throttle body higher up than ours?
Title: 302 throttle body
Post by: jcassity on January 16, 2008, 11:25:03 AM
Quote from: vinnietbird;198076
Aren't the truck upper manifolds and throttle body higher up than ours?


yes,
they are much higher.  Infact, i believe the 351 is even higher than the 302.  I am not planning on using any of the truck intakes on the coug btw.

I have a 351 bronco 4wd 5spd and the TB is larger than the 302 truck tb's ive came across.
Title: 302 throttle body
Post by: Innes on January 16, 2008, 01:44:24 PM
According to this the 351 and 302 use the same TB but the intakes are totally different the 302 being square ported and the 351 being oval.
http://www.fullsizebronco.com/forum/showthread.php?t=6111&highlight=351+Throttle+body
Title: 302 throttle body
Post by: V8Demon on January 16, 2008, 01:57:54 PM
You'd need a cowl hood to fit a full, uncut truck manifold on a 5.0 in a fox passenger car.

When the EFI manifolds first came out it was not uncommon to see modified truck manifolds on Mustangs.  The runners were shortened a bit in some cases, a lot in others.
Title: 302 throttle body
Post by: Innes on January 16, 2008, 02:42:44 PM
I’ma still learning you guys are ages ahead of me w/this stuff.
I did realize I wouldn’t be practical to run the TB like a truck, but I now some run the lowers is it the TFS or Holly upper that bolts to the truck302 lower or was it salene or professional products. And whose mounts to the 351 lower.
Title: 302 throttle body
Post by: vinnietbird on January 16, 2008, 05:14:13 PM
With all of the aftermarket throttlebodies on the market,wouldn't it be almost pointless to adapt a truck t-body?Heck,I have a 65mm sitting on my workbench collecting dust.I've seen 90mm throttlebodies for our cars.Way to much air for my engine.LOL.
Title: 302 throttle body
Post by: grutinator on January 16, 2008, 06:38:44 PM
Quote from: jcassity;198094
yes,
they are much higher.  Infact, i believe the 351 is even higher than the 302.  I am not planning on using any of the truck intakes on the coug btw.
I have a 351 bronco 4wd 5spd and the TB is larger than the 302 truck tb's ive came across.


hes not thinking of running a truck tb on a car. nor wonderign how it could be done.

if i understand him correctly, he wants to know why ford desided to run a dual butterfly throttle body instead of one big one.
Title: 302 throttle body
Post by: jcassity on January 17, 2008, 12:18:12 AM
Quote from: grutinator;198181
hes not thinking of running a truck tb on a car. nor wonderign how it could be done.

if i understand him correctly, he wants to know why ford desided to run a dual butterfly throttle body instead of one big one.


:bowdown: yep.
Title: 302 throttle body
Post by: vinnietbird on January 17, 2008, 01:16:50 AM
The clouds have parted,the sun shines,and now I see.
Title: 302 throttle body
Post by: jcassity on January 17, 2008, 01:19:54 AM
Quote from: vinnietbird;198261
The clouds have parted,the sun shines,and now I see.


the point you made earlier is my same point in fact.
Title: 302 throttle body
Post by: vinnietbird on January 17, 2008, 08:20:35 AM
I have been enlightened.
Title: 302 throttle body
Post by: V8Demon on January 17, 2008, 03:47:28 PM
As stated above the truck manifolds flow more air.  They also have huge runners for torque.  Part throttle driveability pops into my head, but I've found nothing yet to confirm or deny this theory.

Many of Ford's cars nowadays also came with the dual TB's.  Pretty much any Cobra from '96-up, the newer 4.6 3V, the GT500, the Ford GT.....

*Edit*

Found this:  http://f150online.com/forums/showthread.php?t=307813

As per post #4 is seems someone else either has the same theory as I do about this or just knows something I don't:

Quote from: StrangeRanger from the above thread
The dual T/B and split upper intake is designed to increase intake velocity and improve volumetric efficiency at lower to medium RPMs, generally considered a virtue in a truck engine.


I guess the idea would hold true for a relatively small V8 meant to make power in the higher RPM range as well.
Title: 302 throttle body
Post by: softtouch on January 17, 2008, 04:06:55 PM
Quote from: V8Demon;198373
As stated above the truck manifolds flow more air.


Wouldn't all 5.0L engines flow the same amount of air?
2.5 liters per revolution of the crank.
Title: 302 throttle body
Post by: V8Demon on January 17, 2008, 04:31:02 PM
Quote from: softtouch;198378
Wouldn't all 5.0L engines flow the same amount of air?
2.5 liters per revolution of the crank.


That's where volumetric effeciency comes into play.;) 

You can get more air in and out of a motor.  With enough fuel to support it, you can make that engine have more power.  You can also set it up to have good power at differing RPM ranges.  This is why there are so many different approaches as to getting the same results.
Title: 302 throttle body
Post by: TurboCoupe50 on January 17, 2008, 05:39:53 PM
Quote from: V8Demon;198382
That's where volumetric effeciency comes into play.;) 

Yup, race engines with well tuned induction and exhaust systems, actually have more than 100% VE...

As for the dual throttle body, IF it's so great why did they go with a single TB and GT-40 intake on the 351 Lightnings??? Well I'll tell you this much... Cause 351 Truck manifolds SUCK(and I don't mean air)...With the small runners and sharp curve in the lower a good 5.8 will be choking at 4000 rpms... I gave one to the s guy a couple years ago...
Title: 302 throttle body
Post by: V8Demon on January 17, 2008, 06:06:56 PM
Quote
IF it's so great why did they go with a single TB and GT-40 intake on the 351 Lightnings???


Less concern for towing capability?  More emphasis on E.T's?
Title: 302 throttle body
Post by: TurboCoupe50 on January 17, 2008, 07:45:49 PM
Quote from: V8Demon;198414
Less concern for towing capability?  More emphasis on E.T's?


Sounds good to me... LOL
Title: 302 throttle body
Post by: softtouch on January 22, 2008, 05:22:21 PM
Whew!! Tried reading-up on volumetric efficiency. I'm going to leave that to the experts.