5.0 Mustang & Super Fords
2011 Ford Mustang 302 - Inside The Boss
How a dedicated team brought forth the greatest Mustang ever built
The first thing to say about the Boss 302 exhaust is it carries over the Coyote's short, tubular headers. Long-tube headers definitely help but were never seriously considered for production. The Coyote's catalytic converters were already pushed to the limit on the '11 Mustang GT, and mounting them any farther from either the engine or each other (there are two catalytic bricks nearly touching each other in one housing) is just wishful thinking.
In fact, the entire exhaust system is a carryover from the Mustang GT. The changes are slightly quieter tips on the mufflers (you won't notice) and the addition of sound-enhancing sidepipes labeled Quad Exhaust. The sidepipes are mainly the work of Noise, Vibration, and Harshness engineers Aaron Bresky and Shawn Carney, with generous assistance from Keven Soenen, an outside supplier representative and hardcore Mustang enthusiast who was critical in seeing the sidepipes through to production.
And that was no easy task. On the Coyote the expensive headers were the highly visible target in the cost-cutters' sights. On the Boss 302, it was the sidepipes. They were an easy target. The fallback plan (the Mustang GT system) was already established, and it was far easier and cheaper to do, so Shawn, Aaron, and Keven had to protect their baby all the way through the program. As they observed, "We had to become ground clearance engineers, heat engineers, just to protect the sidepipes." Education and sticking with the pipes once they had moved on to the design and production people proved key. "You have to be a good communicator to talk to the other teammates so they understand what it is we're trying to do. You can't just throw it over the wall; you have let them know, 'I'll be with you all the way through."
Initially a dual-mode muffler exhaust out the rear of the car was considered. But this gives a quiet idle and then at some point on the tach a noticeable step-up in noise when the second sound path opens. It's a notchy, artificial solution. A sidepipe system with cutout switches (dump valves) was the next idea, but the valves were far too expensive, so they were ditched in favor of dead simple blocking plates with a small hole in it to let a little sound out all the time, but up by the occupants so they could hear it.
This proved a winner, but the team had to continuously simplify and isolate the system from the rest of the chassis to get an acceptable sound quality. A 1-inch louvered insert in the sidepipe is the main sound control element in the system, but you can make a big difference by playing with the easily modified or removable blocking plates. A quick listen to the system with and without the plate inside Ford's development garage proved the sound quality is excellent without the plate. It's aggressive, with a rumbling idle and purposeful bark, but not overly so.
For easy street/strip legality, the system was specifically designed to accept an aftermarket dump valve (from Ford Racing) that bolts right into the system. We consider it a "why not" item, one the enthusiasts inside Ford wanted you to have in the first place.
In a testament to the excellence of the refined S197 platform we call SN-10, chassis engineers on the Boss 302 program weren't so much about debuting exciting new hardware, but refining and re-tuning existing parts and systems. Still, significant improvements were realized, among them a long-standing wish for a staggered-tire fitment and a quality limited-slip differential. To a chassis engineer such as Kevin Groot, the tire is key. "... [since] long ago, we in [vehicle] dynamics have been asking for staggered-fitment tires. We realized we were lagging behind; almost everything has staggered fitment tires. And we knew that the Brake Pack and Track Pack were getting limited by the fact that the rear tire was not as wide as some of the competition."