When is a bigger throttle body necessary?

[JJR512]

A lot of people talk about manifolds and CAIs, but I see less talk about throttle bodies. CAIs have larger-diameter tubes from the air box to the TB. But what I don't understand is how can extra airflow through the intake is useful when it seems like the much smaller opening of the stock TB is a constriction point.

So let's say I'm working on my '15 GT and am replacing the manifold with a ported '18, and am also doing a CAI. Would it be any benefit to also replace the TB? I'm looking at the stock GT350 TB which physically is a direct swap (from what I've read elsewhere, correct me if I'm incorrect). It's 87mm, bigger than a stock GT (I forget what the stock GT is, 80 or 82 I think), and compared to other much larger 3rd-party TBs, is relatively inexpensive.

Thoughts and comments?

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[Idaho2018GTPremium]

The gains from a larger throttle body are somewhat small, esp. for a lightly modified engine. MotoIQ dyno'd all the Ford power backs, and just a K&N air filter swap. The K&N was worth 7 peak hp without a tune on the Gen 2 Coyote. Power pack 1 (K&N+Ford tune) saw a peak gain of 19 rwhp on the same car/same dyno. The Ford Performance power pack 2 includes the GT350 CAI and 87 mm throttle body, along with a tune. MotoIQ dyno'd the Ford power pack 2 and saw +26 rwhp gain (and +30 ft-lbs torque at the rear wheels) over stock (+7 rwhp over power pack 1). I don't know how much of that 7 hp gain over power pack 1 the larger TB is responsible for, though, I suspect not very much. So, the larger TB and GT350 CAI are only worth 7 rwhp combined (Power pack 1 = +19 rwhp, power pack 2 = +26 rwhp). Look at the dyno graphs comparing Power pack 1 and power pack 2 on page 5 of this article:

https://motoiq.com/tested-ford-mustang-gt-power-packs-1-3/5/

Edit: If I was doing what you are doing, I would probably replace the throttle body with the GT350 throttle body since they aren't that expensive, even though the gains are likely marginal at best.

 

[Chad1986]

Imho I wouldn't mess with it. Gt350 tb is known for poor drivability issues.just get a 18 manifold and e85 tune. Or better if you can afford it a ported cobra jet with a monoblade or twin 69tb. Will out perform the 18 all the way around

 

[GregO]

Imho I wouldn't mess with it. Gt350 tb is known for poor drivability issues

Good advice,
I champion Bret Barbers "Air Flow Solutions" 5 Axis CNC modded OEM TB. Use the search feature and you'll find a good amount of useful information on reasons to stick with the OEM 80mm TB.

 

[thelostotter]

The GT350 throttle body is great with the Ford Performance power packs, but it sucks with an aftermarket tune. Been down that road.

Stock throttle body unmodified or bored out by Maxbore is my recommendation.

 

[Idaho2018GTPremium]

Imho I wouldn't mess with it. Gt350 tb is known for poor drivability issues.just get a 18 manifold and e85 tune. Or better if you can afford it a ported cobra jet with a monoblade or twin 69tb. Will out perform the 18 all the way around

I believe the Cobra Jet manifold only outperforms the stock '18 manifold at very high rpms. It would be a good fit for a stage 3 cam that wants to rev close to 8k rpm for peak power. With a stock cam, a stock or ported '18 manifold will be a great bet, with better mid-range power and nearly as much moderately high rpm hp, but at a lower rpm.

 

[JJR512]

I’m only doing mild bolt-ons, no cams or anything like that. And it’s a street daily driver, so I’d like to keep as much low- and mid-range power as possible. I don’t believe the CJ is appropriate for my goals.

 

[Zinc03svt]

Looks up Gigs Performance on internet or Ebay. I have been successfully running one of his ported 88mm on my 18 for almost 3k miles. Throttle response is incredible. Plus he sells you a new TB so you don’t have to pull yours off and send it for porting. ;).

Is it necessary, no. Maybe 3-5 whp.

 

[Sammy123]

I have not noticed any loss of torque or performance down low/mid with my A10 CJ manifold, compared to ported 18 manifold/tb I had before. If anything it feels like I gained power everywhere in the power band, but especially up high. Stock 18 manifold, even ported, dies at 6800 and falls off significantly. CJ manifold holds its power much better all the way to 8000rpms.

I can't say about older Mustangs, don't know. But myself and other A10 owners who have gone CJ are really impressed how much better it is than 18+ OEM. I am using VMP 69mm twinjet throttle body, one of the bigger throttle bodies for the CJ manifold.

 

[JJR512]

Looks up Gigs Performance on internet or Ebay. I have been successfully running one of his ported 88mm on my 18 for almost 3k miles. Throttle response is incredible. Plus he sells you a new TB so you don’t have to pull yours off and send it for porting. ;).

Is it necessary, no. Maybe 3-5 whp.

Thanks, I’ll look into them! Meanwhile, can you tell me if that 3-5 whp is what they claim, and if so, mainly where in the powerband?

About how much does it cost?

 

[JJR512]

I have not noticed any loss of torque or performance down low/mid with my A10 CJ manifold, compared to ported 18 manifold/tb I had before. If anything it feels like I gained power everywhere in the power band, but especially up high. Stock 18 manifold, even ported, dies at 6800 and falls off significantly. CJ manifold holds its power much better all the way to 8000rpms.

I can't say about older Mustangs, don't know. But myself and other A10 owners who have gone CJ are really impressed how much better it is than 18+ OEM. I am using VMP 69mm twinjet throttle body, one of the bigger throttle bodies for the CJ manifold.

It’s interesting the way different people have different experiences. I’ve been told by others the CJ will be a bit of a loss at mid/lower. But I don’t know if they’re guessing, or looking at a graph, or what.

 

[Snake Plissken]

I’m only doing mild bolt-ons, no cams or anything like that. And it’s a street daily driver, so I’d like to keep as much low- and mid-range power as possible.

You might want to consider swapping your stock GT intake manifold to a '15-'17 F-150 intake manifold, if you can find one. You can pick up 25-45 more ft/lbs of torque with no loss in HP or change to your existing tune.

 

[CrashOverride]

From a tuning standpoint, a proper tune needs to know a lot about the throttle body. The gear ratio of the motor, the cross sectional area, max and min angles, and a lot of flow numbers. If you have access to HP Tuners, you will see just how much there is to mess with. This is why the GT350 has drivability issues because you can't just drop it in a Mustang and have it work, just like you can't drop in a larger diameter MAF housing and have it work. The computer can in some cases adapt, but just because it adapted (Possibly maxing out learned values) doesn't make it right.

You can somewhat reverse engineer throttle body data by doing lots of logs and playing with the values keeping an eye on trims, but it is time consuming and still not as good as having the exact numbers. The performance pack 2 and 3 work because Ford knows the values of the GT350 throttle body. If you buy a CrashSpeed (I'm purposefully using a ficticious name here) super-ultra-mega-sized throttle body, but don't have any of the engineering data, then you or your tuner will have an uphill battle to get it to respond good.

Ford obviously thought that the stock size was not enough for the GT350's NA power levels, so that might be an indication. That being said, (And I don't know if this is true) but I would think some supercharger kits re-use the factory throttle body, so if they do, then the kit manufacturers must have found for forced induction setups, it's not a big factor.

 

[bluebeastsrt]

A lot of people talk about manifolds and CAIs, but I see less talk about throttle bodies. CAIs have larger-diameter tubes from the air box to the TB. But what I don't understand is how can extra airflow through the intake is useful when it seems like the much smaller opening of the stock TB is a constriction point.

So let's say I'm working on my '15 GT and am replacing the manifold with a ported '18, and am also doing a CAI. Would it be any benefit to also replace the TB? I'm looking at the stock GT350 TB which physically is a direct swap (from what I've read elsewhere, correct me if I'm incorrect). It's 87mm, bigger than a stock GT (I forget what the stock GT is, 80 or 82 I think), and compared to other much larger 3rd-party TBs, is relatively inexpensive.

Thoughts and comments?

Who do you plan on using for your tuning?

 

[JJR512]

Who do you plan on using for your tuning?

VMP, they'll be sending it to me soon with a Rev X tuner and the '18 ported manifold.

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