The CJ manifold started as the BOSS with the oval throttle body and cleanup around the injectors. — Jesse Kershaw, Ford Racing

Our $9,999 budget Coyote has been going through the ringer at Westech Performance . Fresh off the final LS3 Vs Coyote shootout video and article series , we pushed on with further testing. One of the biggest questions on our testing was, “Why didn’t you run a Cobra Jet manifold?” Looking back after the fact, we should have probably made the budget for it work, but regardless, here’s how Ford Performance’s full slate of intake manifolds panned out on our street Coyote build.

Ford Performance is in a unique situation as an OE performance counterpart, they produce all the most commonly used intake manifolds on the market. This is not something we’ve ever seen on the Mustang since the full conversion to composite manifolds has taken place.

The Manifold Roster

Factory GT

The factory GT manifold has been the best manifold on the market for preserving the best low end torque. The long runner configuration made this manifold great by harnessing the maximum amount of low-end grunt.

BOSS 302

The BOSS 302 manifold was the first aftermarket piece available on the market and came standard on all BOSS 302 Mustangs. The shorter runners allowed Coyote lovers to adjust their powerband up another 400-500 rpm. The low end torque sacrifice was a given, but was hardly noticed once the vehicle is out of first gear.

“We knew that the BOSS was directionally where we wanted to go,” Jesse Kershaw of Ford Performance recalls. “The ‘runners in a box’ approach yielded solid results but we also knew the throttle body was the limiting factor. Using what we had available was fairly straight forward adapting the dual bore or oval throttle body to the same basic design. Slight changes were made to optimize flow around the injector because we didn’t have to worry about noise that would be a concern in the production program. We basically took the list of things the OEM program wanted to do but couldn’t to meet standards for idle quality and noise.”

Cobra Jet

Ford Performance’s Cobra Jet intake manifold can best be described as the next generation BOSS 302. “It’s slightly different but negligible amounts,” explains Kershaw. “The CJ manifold started as the BOSS with the oval throttle body and cleanup around the injectors.”

Eliminating the recess at the top of the manifold that was previously designed for strut tower clearance helped increase plenum volume. The other noticeable change was the throttle body opening that was converted to a GT500 style. “The big concern is idle and potentially emissions,” continued Kershaw. “We sell the Cobra Jet manifold and the throttle bodies for off-road use because of that.”

When we asked Kershaw how Ford Performance was able to maintain a strong torque curve with the Cobra Jet while increasing peak horsepower, he responded, “Ford has proprietary modeling software and simulation that allows us to ‘get it right’ often with few iterations of design. Of course testing always validates what we think we know so it’s still critical. By lifting off some restrictions we were able to maintain a preferable torque curve and pick up horsepower.”

GT350

The newest manifold to the OEM manifold market comes from the GT350. Ford revisited the Intake Manifold Runner Control (IMRC), also called Charge Motion Control Plates, feature that manipulates the intake’s runner velocity. If you could build a manifold that took the best of a short and long runner design, this is basically what Ford was trying to accomplish.

The key to the GT350 design is that the control plates are virtually recessed in the runner while in the resting position and doesn’t act like a mini throttle body when compared to Ford’s older IMRC design. A similar design comes standard on the 2015+ Mustang GT and helps produce an additional 2+ mpg, 20 lb-ft of low end torque, and better idling characteristics.

The biggest bummer of running a GT350 manifold on a 2011-14 engine? You lose the ability to control the charge motion plates and an adaptor is required to bolt on a 2011-14 throttle body.

In regards to the throttle body redesign, Kershaw mentions, “Maintaining idle and emissions is critical and far easier with the round throttle body. The GT350 was able to hit its performance targets with a slightly larger 87 mm over the GT’s 80 mm. The GT350 manifold has proven so good that we tried to make a slightly modified Cobra Jet manifold that would package under the S550 hoodline but it wasn’t any better than the stock GT350 with the stock, round throttle body. With a cowl hood or lowered engine, the Cobra Jet manifold is worth some power but few customers are interested in going down that path. We developed a 92 mm but the gain was so minimal that we have shelved it for now. Plus, it would be off-road only and currently we don’t see the level of aftermarket support to make it worthwhile.”

Our Test Mule

If you want to read the complete story on the Coyote engine build, you can go here. The quick hits: 11:1 short-block with a slight overbore, Comp Cams CR-Series Stage III camshafts, upgraded Comp valve springs, MSD coils, and Triangle Speed billet gears.

One of our biggest questions on this build was in regards to the short-block rebuild and the billet gears. We were working with an F150 that was in an unknown condition. You can give up as much power as any modification can make by having bad ring seal, plus the F150 Coyote uses a lower quality 10.5:1 piston. As far as the billet gears go, we knew we were going to be turning a lot of RPM with Cobra Jet manifold and this is another pace they fail. Yes, the most common failure is on supercharged applications, but there are many other situations, most commonly found by the rapid inertia and acceleration change that you’d commonly find when launching a car at the dragstrip.

Dyno Testing

Factory GT

We started our tests with the Factory GT manifold to develop our power baseline. We were actually very surprised how well the manifold works down low. Producing 364.7 lb-ft of torque at 3,900 rpm, it peaks at 5,400 rpm with 429.2 lb-ft. Peak horsepower is achieved at 6,700 rpm with 491.1. The stock manifold can be revved to 7,500 rpm with the CR-Series camshafts and doesn’t fall off too much.

491.1 hp at 6,900 rpm

429.2 lb-ft at 5,400 rpm

Average Power: 373 hp, 376 lb-ft – 2,800-7,500 rpm

BOSS 302

Simply put, the GT manifold absolutely murders the BOSS manifold all the way up to 6,600 rpm. By 6,700 rpm when the GT peaks at 491.1 horsepower, the BOSS is gaining by 2.7 hp and ends up peaking with 510.4 horsepower at 7,600 rpm, though pulls cleanly to 8,000 rpm.

Comparing torque at 4,200 rpm the BOSS is down a whopping 46.9 lb-ft compared to the GT. By torque peak at 5,400 rpm the BOSS 302 is making 398.4 lb-ft, 30.8 down from the GT. If you compare average power and torque across the dyno run, the BOSS 302 is the worst performing manifold out of the four.

510.4 hp at 7,600 rpm

398.4 lb-ft 5,400 rpm

Average Power: 376 hp, 361 lb-ft – 3,000-7,800 rpm



Cobra Jet

Until around 5,900 rpm the power differences between the BOSS 302 and Cobra Jet manifolds are negligible. The Cobra Jet averages about 10.8 horsepower and 11.6 lb-ft more than the BOSS 302 from 4,200-5,900 rpm, then the CJ beings to take off. By 6,500 rpm the CJ is 14.7 horsepower and 15.3 lb-ft up. The Cobra Jet manifold peaks at 7,600 rpm while making 531.2 hp, 20.8 horsepower ahead of the BOSS 302. We were all but certain that the Cobra Jet was going to come in at the top horsepower winner.

531.2 hp at 7,600 rpm

408.6 lb-ft at 5,400 rpm

Average Power: 386 hp, 370 lb-ft – 3,000-7,800 rpm

GT350

The GT350 was the wild card in this test. We’ve had plenty of experience with the other manifolds to know about where they were going to end up. But where would the GT350 fit into the equation?

The BOSS 302 versus GT350 graph is the most interesting to look at as it seems like these manifolds are going blow for blow to create more power. In the end, the GT350 edges out the BOSS by 5.4 horsepower and 3.2 lb-ft of torque, though the GT350 makes it 700 rpm higher than the rest of the intakes at 6,100 rpm. This manifold comes in second place in the horsepower but third in torque. With working motion control valves, it would probably be a lot closer to the GT manifold.

515.8 hp 7,500 rpm

402.6 hp 6,100 rpm

Average Power: 381 hp, 365 lb-ft – 3,000-7,800 rpm

The showdown between the GT manifold and the GT350 is similar to the BOSS 302 with maximum torque loss of 46.1 lb-ft at 5,400 rpm

We would consider these manifolds to be nearly identical with a slight edge to the GT350. We wish we could have seen what the operational Charge Motion Control Valves would have played into the mix.

Our Picks

All four of these manifolds serve their purpose in the performance community. The GT manifold is probably best suited for road race and autocross cars looking for the power coming off the corners. If all-out high horsepower for drag racing is your thing, then stick with the Cobra Jet manifold. The BOSS 302 is a cost effective upgrade as a mid-level upgrade for the 2011-14 GTs and the GT350 respectively for the 2015+ GTs.

Testing and Tuning Ryne Cunningham of Cunningham Motorsports handled the tuning through an SCT X4 device, which was loaded to a Ford Performance controls pack. All pulls were made on California’s horrible 91 octane pump gas. In regards to the tune, Cunningham noted, “The stock manifold required less overall camshaft advance and much less though the mid-range (due to knock) compared to the BOSS 302 intake. The GT350 manifold took similar cam timing to the BOSS 302. The Cobra Jet throttle body requires several changes to the ETC tables of the PCM in order for it to run right, plus the MAF frequency per given amount of airflow is reduced. Lb/min of airflow per given MAF hz must be increased to compensate.”

491.1 hp at 6,900 rpm

429.2 lb-ft at 5,400 rpm

Average Power: 373 hp, 376 lb-ft – 2,800-7,500 rpm

GT

BOSS 302

510.4 hp at 7,600 rpm

398.4 lb-ft 5,400 rpm

Average Power: 376 hp, 361 lb-ft – 3,000-7,800 rpm



+/- to GT manifold: +19.3 hp, -30.8 lb-ft

Cobra Jet

531.2 hp at 7,600 rpm

408.6 lb-ft at 5,400 rpm

Average Power: 386 hp, 370 lb-ft – 3,000-7,800 rpm

+/- to GT manifold: +40.1 hp, -20.6 lb-ft

GT350

515.8 hp 7,500 rpm

402.6 hp 6,100 rpm

Average Power: 381 hp, 365 lb-ft – 3,000-7,800 rpm

+/- to GT manifold: +24.7 hp, -26.6 lb-ft

More OEM Goodness from Ford Performance

When we asked what’s in store for 2015+ 5.0 enthusiasts, Kershaw remarked, “We are really close to releasing our Power Upgrade kits for the 2015-2016 Mustang GT and Power Upgrade 3 that includes the GT350 manifold. This is the first time we’ve offered one of our manifolds with a CARB EO. You can now rev over 7,000 rpm and it picks up huge of the stock manifold, nearly 70 hp at 7,500 rpm! However, it loses some mid-range and is pricy. The Power Upgrade 2 uses the GT350 throttle body and CAI picks up 21 hp peak, over 40 lb-ft at 1,500 rpm and will be a very reasonably priced.”