5.0 Mustang & Super FordsHow To Engine
Ford Racing Cobra Jet Manifold Installation and Test
Flying Higher: Putting Ford Racing's CJ manifold to the test on a Boss 302
Wildly successful is an understated way to describe Ford Racing's re-started Cobra Jet program. Reviving the concept of Ford's historic '60s drag 'Stangs with the latest Mustangs was such a natural fit. Once Ford Racing put a part number for its factory-built drag cars into the system, it started selling out. Once these cars hit the tracks, records fell, and other car companies scrambled to emulate the program.
A boon to Ford and its performance car image, these cars are still rare and specialized. Cobra Jets aren't in every garage. Fortunately, they often spawn parts that will fit the Mustangs in your driveway. The first interations were based on the GT500's 5.4-liter engine, but the latest naturally aspirated Cobra Jets and boosted Super Cobra Jets are based on the Coyote and RoadRunner 5.0-liter engines found in street-going, '11-and-newer GTs and Bosses. By and large, this means many of the parts that contribute to the performance of the record-setting Cobra Jet will bolt to your street Mustang.
One of the most intriguing parts produced for the latest CJ is the composite manifold developed for the naturally aspirated version. Since Ford has the lock on intake options for modern 5.0s, the intake on the Boss 302's RoadRunner engine had been the only option available to those looking for more top-end power from their Coyote engines. Essentially, Ford Racing ran with some ideas that were initially kicked around for the production Boss 302 engine and worked them up for the rigors of drag racing. The result is an intake with a larger plenum and runners that pull harder at the top while running neck and neck with the Boss manifold down low.
"The idea was tossed around, but never formally part of the program," said David Born, engine engineer at Ford Racing. "Adam Christian did not prefer it, so we didn't look too hard at it."
It turns out that a round-bore throttle body is a pretty efficient, cost-effective way to get air into the engine. However, packaging a significantly larger round-bore body could be a challenge, and Ford Racing already had a nice twin-65 oval bore on the shelf. As such, David, who previously worked on the Coyote and RoadRunner programs over at mainstream, modeled up a Boss manifold with an oval-bore throttle body. The models looked promising, so they pursued it for the Cobra Jet.
"It (the dual-bore) is not the most efficient way to get air into the engine, but it is a good brute-force way to get the job done."
Of course, there is more to the intake than just the throttle opening. A new supplier's manufacturing process allowed Dave to move the seam between the upper and lower halves of the manifold down, which freed up room to open the runners around the fuel-injector bosses. Along those lines, Ford Racing was also able to slim down the three inner support posts from 30mm to 16mm, which freed up a couple horsepower. Clearly, David and the Ford Racing team were fighting for every last bit of flow and horsepower to best the already optimized Boss manifold.
"On the back of the manifold, the Boss is basically straight across," David explained. "The CJ has two round bumps. The supplier suggested full bellmouths on the rear runners, and it helped." Apparently, these smoothed runner inlets were present in the original Boss design, but were removed to facillitate engine installation from underneath. The CJ is meant to be dropped in from above in your garage, so fitment constraints are more flexible, which allows for more performance.
To find out how it stacked up against the Boss manifold in the real world, we hooked up with Power by the Hour in Boynton Beach, Florida, to install it on deep-breathing '12 Boss 302 with cams and long-tube headers. The swap is pretty easy, and the results were impressive. Check it out.
On The Dyno
We know from prior testing that the Boss 302 intake gives up a bit of torque to the stock Coyote in exchange for superior top-end performance. Well, the CJ manifold takes that a set further. It doesn't really give up much down low, although there was a momentary dip around 3,000 rpm. After that it's clear sailing to the top of the tach. Peak-to-peak gains shown on the higher resolution graph were 27.58 horsepower and 13.43 lb-ft of torque, with even larger gains along the curve.
"The most challenging part of tuning this setup is the new throttle body, which is really the case on any newer Ford. Proper throttle-body calibration is the key to a car that drives well," said Ken Bjonnes of Lund Racing (www.lundracing.com) of the calibration for this combo. "We did also play some with the typical cam timing we run with these cams as well as ignition timing. But the majority of the gains were from the intake itself and not any additional tuning..."
|Baseline||FRPP CJ Intake||Difference|
Pump Up The Volume
As you can see in the CAD illustration, the CJ differs significantly from the Boss intake
Our anecdotal research tells us that Ford actually considered moving the production Boss 302 to an oval throttle opening, but only for a moment. The team was able to achieve the desired results by sticking with the GT's round throttle body on the resulting Boss 302 intake. Starting with those initial thoughts, Ford Racing engineers worked with Team Mustang engineers like Adam Christian and Dave Born to develop an even higher-performing intake for naturally aspirated Coyotes and RoadRunners, a hybrid of which powers the naturally aspirated Cobra Jet drag Mustang sold via Ford Racing dealers.
As you can see in the CAD illustration, the CJ differs significantly from the Boss intake. However, if you examine the chart, it has far more in common with the Boss intake than it does the stock GT manifold. The CJ's runner volume is slightly larger than the Boss' but is measurably less than the GT's. Both the Boss and CJ have the same runner length, which is far shorter than the GT runner to improve high-rpm performance. It's the runner cross-section and intake volume where the CJ is much larger than the GT or Boss intakes. In this case, bigger is better when it comes to high-rpm naturally aspirated performance.
|GT Manifold||Boss Manifold||FRPP Cobra Jet Manifold|
|Runner Volume (x8)||33.722 ci||29.69 ci||30.417 ci|
|Runner Length||12.178 in.||9.327 in.||9.327 in.|
|Runner Smallest Cross-Section Near Injector||2.35 sq. in.||2.415 sq. in.||2.522 sq. in.|
|Runner Cross-Section at Bellmouth||2.81 sq. in.||3.378 sq. in.||3.378 sq. in.|
|Plenum Volume||299.258 ci||373.292 ci||414.061 ci|
|Total Intake Volume||569.034 ci||610.812 ci||657.397 ci|
Horse Sense: When it comes to Coyote intakes, Ford is still the only real game in town. When it debuted on the Boss 302, the Boss intake was the first upgrade available for '11-'14 Mustang GT owners. We tested it with good results on a bolt-on Mustang GT back in our June '11 issue ("High Times," p. 78).