Muscle Mustangs & Fast FordsHow To Engine
The Test: Camshafts & Coyote Manifolds
The aftermarket exists to produce a wide segment of improvement parts for a vehicle. While some of these modifications can be for aesthetics, just as many are for performance. The OE’s aftermarket parts were always looked as nice upgrades but didn’t always provide the punch in power people were looking for. Well, Ford Performance has changed that perception with its line of Coyote intake manifolds.
Simulation software has come a long way, with prices to match. It can be hard to justify purchasing such software unless you’re moving millions of dollars of product. But if you are an OEM like Ford, it is a requirement to stay ahead of the pack on ICE (internal combustion engine) development. Performing highly accurate simulations in software minimizes the design iterations needed to build the perfect manifold. From that point, rapid prototypes can be built to dyno-test final variations and manifolds can then go into production. This has led Ford Performance to produce the two most common Coyote intake manifolds found on the market: the Boss 302 and Cobra Jet.
“The runner design for the GT, Boss, and Cobra Jet manifolds all started the same,” says David Born, Ford Performance Parts engineer. “The length was adjusted from the GT down to a shorter length for the higher revving Boss engine. Its length was determined by the package space and flow characteristics of the plenum. Ideally, we wanted the runners on the Boss to be a bit longer to lower the peak engine speed (the manifold is tuned for a 7,750 rpm power peak), but packaging the carryover GT fuel rails and the assembly of the rails meant we could not push the runner length and the plenum out any further than we did.”
Born continues: “The Cobra Jet used the same runner design as the Boss, with the exception being the reduced bump around the injector pocket. The Cobra Jet uses a different manufacturing process that allowed the bump to be reduced, which in turn reduces the flow losses around the bump and provides an increase in performance.”
But what about the GT350 manifold? Yes, this is another option if you can control the charge motion control plates, but our 2014 5.0 dyno mule did not. As a bonus, we tested the Boss and Cobra Jet manifolds with and without Comp Cams’ NSR (No Springs Required) Stage III naturally aspirated camshafts to see how the powerband would change versus the stock Mustang cams. To read more about that test you can click here. Other than the Ford Performance throttle-bodies, JLT cold air intake, Hooker Blackheart 1 7/8-inch primary long tube headers, and custom SCT X4 tuning by Eddie Rios of Addiction Motorsports, our engine was stock.
Comp Cams NSR Stage III Camshafts
Duration at 0.050: 236° intake, 239° exhaust
Valve Lift: 0.492 intake, 0.453 exhaust
Lobe Separation: 126°
GT Manifold Specs
Runner Volume (X8): 33.722 ci
Runner Length: 12.178 in.
Runner Smallest Cross-section: 2.35 sq. in. near injector
Runner Cross-section at Bell Mouth: 2.81 sq. in.
Plenum Volume: 299.258 ci
Total Intake Volume: 569.034 ci
The stock GT intake manifold is nothing to laugh at. With only 302 ci on tap, Ford engineers needed to develop a manifold that made stout peak power numbers while also maximizing low-end torque. The GT manifold will, in pretty much any circumstance, make better midrange torque than any intake manifold in Ford’s arsenal. The GT manifold served as our baseline specimen, tested with the aforementioned stock and Comp Cams camshafts.
In addition, we equipped the GT and Boss manifolds with Ford Performance’s M-9474-M50 90mm throttle-body. We tested the throttle body here. With the stock camshafts, horsepower came in at 457.0 at 6,400 rpm while torque numbers peaked at 419.0 lb-ft at 5,200 rpm. What shocked us was how far the Comp Cams camshafts pushed up the powerband once they were installed, to the tune of 505.8 hp at 6,700 rpm and 426.5 lb-ft of torque at 5,500 rpm. While the stock cams with the stock manifold is done making power at 6,800 rpm, a fairly flat power curve with the Comp cams extended out another 1,000 rpm.
Boss 302 Intake Manifold With Ford Performance Throttle-Body
Runner Volume (X8): 29.690 ci
Runner Length: 9.327 in.
Runner Smallest Cross-section: 2.415 sq. in. near injector
Runner Cross-section at Bell Mouth: 3.378 sq. in.
Plenum Volume: 373.292 ci
Total intake Volume: 610.812 ci
The Boss 302 intake manifold first debuted on the Roadrunner 5.0 engine in the 2012-2013 Boss 302. With forged pistons, stiffer valve springs, CNC-ported heads, and more aggressive factory camshafts, the Roadrunner 5.0 was designed to keep the revs up on the road course. The runners were shortened 2.851 inches from the GT variant to push the powerband up another 1,000 rpm. Additionally, plenum volume increased 74.034 ci.
“The Boss manifold was really an evolution of the GT manifold,” says Born. “We knew we wanted to tune the manifold for higher engine speed. This meant shorter runners that didn’t really package in a scroll-style manifold. So the ‘runners in a box’ design concept was the natural fit. Again, the plenum design is quite similar to the GT, but flipped over; if you were to straighten the GT runners so they fed straight in to the plenum, you’d see that the design is pretty similar to the Boss. There are some changes that were made based on CFD (Computational Fluid Dynamics) analysis, but the design is similar.”
Power came in at 492.1 hp at 7,400 rpm and 402.2 lb-ft at 5,400 rpm. A gain of 35.1 hp at 7,400 rpm and an expected torque loss of 16.8 lb-ft 5,400 rpm. Just like the GT manifold the Boss really came alive with the cams installed. 542.7 at 7,700 rpm and 404.2 lb-ft of torque at 6,600 rpm was the new number, a gain of 50.6 hp and 2 lb-ft of torque. While low-end torque is sacrificed, by 5,400 rpm, the graphs are nearly identical. The effective powerband with the camshafts increased another 500 rpm.
Cobra Jet Intake Manifold With Ford Performance Dual-Bore Throttle-Body
Runner Volume (X8): 30.417 ci
Runner Length: 9.327 in.
Runner Smallest Cross-section: 2.522 sq. in. near injector
Runner Cross-section at Bell Mouth: 3.378 sq. in.
Plenum Volume: 414.061 ci
Total intake Volume: 657.397 ci
The head honcho, the big cheese, the Cobra Jet intake manifold. Highly regarded as the best Ford Performance manifold on the market, it is nearly identical to the Boss 302 manifold except for three aspects: the throttle-body, upper plenum, and area around the injector.
“The Cobra Jet design is really just the Boss manifold with a dual bore inlet added,” explains Born. “The Cobra Jet design had the strut tower clearance as well during development, but it was dropped at the last minute. CFD had shown the recess to cost a bit less than 1 horsepower. It was decided to drop the clearance in the name of ultimate output.”
The Cobra Jet manifold will show the best peak gains out of any Ford Performance manifold on a naturally aspirated engine. Where it really shines is on a forced induction combination that can take advantage of the larger throttle-body opening and plenum volume. We opted for the Ford Performance twin 65mm Cobra Jet throttle-body (PN M-9926-CJ65). There is another option for a single bore Super Cobra Jet throttle-body (PN M-9926-SCJ). We don’t recommend the SCJ throttle-body for a naturally aspirated or low-boost Coyote engine since the tuning window becomes drastically smaller due to the loss of vacuum reference at part throttle. Both throttle-bodies come with an adapter pigtail that will swap pin-for-pin with the stock throttle-body connector.
But how does it perform? 504.7 hp at 7,500 rpm and 412.4 lb-ft at 5,400 rpm. A further gain of 12.6 hp and 8.2 lb-ft over the Boss 302 manifold. The Cobra Jet not only outperforms the Boss 302 at peak power but also in the low-end torque range.
How does the Cobra Jet react to upgraded camshafts? 546.9 hp at 7,800 rpm 410.5 lb-ft at 6,600 rpm. Simply remarkable power numbers on an engine running on California 91-octane pump gas. Since the Coyote is now becoming so volumetric efficient, the gains with camshafts wasn’t as prevalent (but still considerable) as the other manifolds. Horsepower increased 42.2 with only a 1.9 lb-ft of torque loss.
|A Look at the Numbers|
|GT Manifold||457.0 hp at 6,400 rpm||419.0 lb-ft at 5,200 rpm|
|Boss 302 Manifold||492.1 hp at 7,400 rpm||402.2 lb-ft at 5,400 rpm|
|Cobra Jet Manifold||504.7 hp at 7,500 rpm||412.4 lb-ft at 5,400 rpm|
|Comp Cams NSR Stage III|
|GT Manifold||505.8 hp at 6,700 rpm||426.5 lb-ft at 5,500 rpm|
|Boss 302 Manifold||542.7 hp at 7,700 rpm||404.2 lb-ft at 6,600 rpm|
|Cobra Jet Manifold||546.9 hp at 7,800 rpm||410.5 lb-ft at 6,600 rpm|