Tech: 2015 Mustang Boss Intake Test

2015 Mustang Boss Intake Swap Featured

Born to Run

Adding a Boss intake to a 2015 GT lets it rev to the moon

By Steve Turner
Photos courtesy of Ken Bjonnes/Lund Racing

We have seen a furious development cycle for 2015 Mustang products. From 949-horsepower turbos to simple hood-lifts, the new Mustang has inspired the aftermarket just like we expected it to. However, beyond the basics of cold-air induction, we have yet to see much effort in opening up the intake of the new GT.

The stock intake manifold on the 2015 Mustang features Charge Motion Control Valves, but they move completely out of the way when then are open. However, we have heard that the throttle body opening might be a bit more restrictive than the previous Coyote GT intake.
The stock intake manifold on the 2015 Mustang features Charge Motion Control Valves, but they move completely out of the way when then are open. However, we have heard that the throttle body opening might be a bit more restrictive than the previous Coyote GT intake.

Students of the sport know that the latest version of the Coyote 5.0-liter engine took advantage of many of the lessons learned from development of the high-revving RoadRunner engine that propelled the corner-carving 2012-2013 Boss 302s. However, unlike that engine, the current V-8 had to fit under the swoopy bodywork of the new Mustang, so a taller intake like the Boss manifold was out of the question.

Moreover, the latest intake manifold incorporates Charge Motion Control Valves just before the junction of the intake and cylinder heads. These valves—which were formerly called Intake Manifold Runner Controls when the last appeared on the Mustang Cobra—are closed at low rpm to promote torque production. As the tach climbs, they move out of the way to let the air flow for enhanced power.

Ken Bjonnes of Lund Racing get started by removing the stock engine cover. Its retain pins pull right out of the receptacles in the stock manifold.
Ken Bjonnes of Lund Racing gets started by removing the stock engine cover. Its retaining pins pull right out of the receptacles in the stock manifold.

While it might be too tall, the Boss 302 intake is still a bolt-on proposition for the engine. As such, when we learned that Lund Racing’s Ken Bjonnes was trying a Boss 302 intake on his personal Mustang GT at Power by the Hour, we were excited to see the results. Ken added the intake to his GT, which had thus far been upgraded with a JLT Performance cold-air intake, American Racing Headers long-tube headers, and an American Racing Headers X-pipe.

“It bolted right on as expected, but as you know, it doesn’t fit under the stock hood,” Ken explained. “Options may be to lower the engine or install a new hood, but the intake isn’t staying on my car for now.”

With the beauty cover out of the way, Ken starts removing the fasteners from the stock intake.
With the beauty cover out of the way, Ken starts removing the fasteners from the stock intake.

Getting the taller intake to fit under the hood is only one of the pitfalls. The Boss runners are nearly 2 inches shorter than the stock intake runners, so it can sacrifice some torque. It also lacks those Charge Motion Control Valves in the runners, which the factory PCM expects to be there. Fortunately tuning is Ken’s specialty so he was well equipped to make the car play well with the new intake.

“The biggest challenge is deleting the new IMRCs for the 2015. In years past when they were used, it was a much simpler implementation,” Ken said. “With TiVCT in play, things get much more complicated in general and that carries over to the IMRCs.”

Because he wanted to perform a back-to-back test, Ken only tweaked the existing calibration in his car, via HP Tuners hardware, to get the computer to accept the missing Charge Motion Control Valves. He did not work on maximizing the combo’s performance.

Obviously you can use a traditional ratchet to get the job done, but Ken uses a small, rechargeable impact gun to expedite the removal of the stock intake.
Obviously you can use a traditional ratchet to get the job done, but Ken uses a small, rechargeable impact gun to expedite the removal of the stock intake. He was only swapping the intake for this test, so he wanted to make quick work of it.

“The main reason I did the test was to discover the higher rpm results. I don’t like how the stock 2015 intake really noses over above 6,500. After doing the headers on my car, I knew it wasn’t the exhaust,” Ken said. “So since I had the Boss intake lying around, I decided to give it a shot. And, it pretty much did as I expected. It lost a little down low and picked up tons of power up top. What I didn’t expect was for it to pull all the way to 8,000. I definitely want to see what a set of cams will do in this setup.”

Watch Ken’s S550 rev to 8,000 rpm on the Dynojet at Power by the Hour in Boynton Beach, Florida, right here…

As you can see from the dyno results, the new-school Coyote definitely howls at high rpm with a Boss 302 intake manifold. It does give up some low-rpm performance, which you might notice on the street, but at the track that high-revving power is enticing. It will be interesting to see what this intake will do with other mods and more tuning, but the early returns are certainly promising.

You will need to disconnect the factory fuel feed line. Be sure to place a shop rag under the connection to soak up any fuel that leaks out.
You will need to disconnect the factory fuel feed line. Be sure to place a shop rag under the connection to soak up any fuel that leaks out.
With all the fasteners and connections free, Ken disconnects the JLT cold air intake and removes the intake, throttle body, and fuel rails as a single unit.
With all the fasteners and connections free, Ken disconnects the JLT cold air intake and removes the intake, throttle body, and fuel rails as a single unit.
The bare valley of the 2015 Coyote engine doesn’t look much different than its predecessor. However, the cylinder heads feature many of the improvements—save for the CNC porting—found in the Boss 302 cylinder heads.
The bare valley of the 2015 Coyote engine doesn’t look much different than its predecessor. However, the cylinder heads feature many of the improvements—save for the CNC porting—found in the Boss 302 cylinder heads.
As such, it would stand to reason that bolting on the Boss 302 intake would the latest Coyote engine breathe. You’ll want to swap the new intake on, torque the fasteners to 89 in-lb, and reconnect the fuel lines and other connections.
As such, it would stand to reason that bolting on the Boss 302 intake would let the latest Coyote make the most of those heads. You’ll want to swap the new intake on, torque the fasteners to 89 in-lb, and reconnect the fuel lines and other connections.
Ken reinstalled the stock 80mm throttle body on the Boss 302 intake to make it a pure A-to-B test, but we can’t help but wonder if  a larger throttle body might help even more at high rpm.
Ken reinstalled the stock 80mm throttle body on the Boss 302 intake to make it a pure A-to-B test, but we can’t help but wonder if a larger throttle body might help even more at high rpm.
With the intake bolted on and the JLT re-attached to the throttle body, the Boss 302 intake was ready to run. Keep in mind that this intake will not clear the stock hood, so you would need to use drop motor mounts or a taller hood if you wanted to run the intake on your 2015 GT.
With the intake bolted on and the JLT CAI coupled with the throttle body, the Boss 302 intake was ready to run. Keep in mind that this intake will not clear the stock hood, so you would need to use drop motor mounts or a taller hood if you wanted to run the intake on your 2015 GT.
Wow. Look at that new Coyote pull with a Boss 302 intake. Where the stock just nose-dives at 6,700, the engine just keeps pulling all the way to 8,000 with the Boss manifold. The peak-to-peak gain of only 4.73 horsepower is deceiving, as the engine gains another 1,300 rpm of usable power up top.
Wow. Look at that new Coyote pull with a Boss 302 intake. With the stock manifold it just nose-dives at 6,700, but the engine just keeps pulling all the way to 8,000 with the Boss manifold. The peak-to-peak gain of only 4.73 horsepower is deceiving, as the engine gains another 1,300 rpm of usable power up top.
Clearly the Boss intake costs some power and torque down low, but when you consider those whopping gains of 33.41 horsepower and 24.38 lb-ft of torque at 7,200 rpm, it might be a trade-off you’d consider making.
Clearly the Boss intake costs some power and torque down low, but when you consider those whopping gains of 33.41 horsepower and 24.38 lb-ft of torque at 7,200 rpm, it might be a trade-off you’d consider making.

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