One of our favorite customers owns two, count ‘em, two Ford GT’s. Both black. He open tracks one of them on a regular basis at many different road race facilities around the country. It’s got a smaller pulley, Ford headers, straight pipes (no cats or muffler) and a JBA custom dyno tune. In this configuration, it made 661 rwhp at 6,317 rpm and 619 torque on our Dyno Dynamics dynomometer. The air/fuel was mid to low 11’s, downstream ACT peaks at 142-deg, and the peak boost was 15.6 psi. This is all fine and well except that the car was louder than a ‘System of a Down‘ concert! Over 120-decibels measured around 50-feet from our dyno. He was asked to quiet the car down by some of the facilities that he races at. By the way, have you heard the “politically correct” term for racetracks in California? Noise parks. Gimme a break….
As a compromise, we installed a set of SuperTrapp mufflers on the ends of the straight pipes with 12-plates in each muffler. We put the Ford GT back on the dyno. We did one pull…and then another pull…cause we couldn’t believe the results of the first pull. Here are the average numbers from the two pulls with the SuperTrapps installed: 475 rwhp at 5,330 rpm and 565 torque; the air/fuel went to low 10’s; the downstream ACT went up to 180-degrees and the boost went up to 19 psi. The only good news for Earth Day is that the db level went down to approx 105.
So, we lost 186 rwhp in one fell swoop and of course picked up a ton of heat. Call us naive but we might have guessed we’d lose 40 to 50 rwhp so we were astounded. We wanted to confirm that something else wasn’t amiss, so we tore the SuperTrapps off and did another pull: 678 rwhp at 6,317 and 635 torque; air/fuel back to mid-11’s; downstream ACT peak at 152-degrees and peak boost at 16 psi. The thing screamed like a banshee. So, the exhaust baffles stole 203 rwhp. That’s like removing the output of a stock 5.0L. The only thing around our shop louder than that Ford GT are the Harriers that fly in and out of Marine Corps Air Station Miramar.
Back to the drawing board. So, next we installed only 8 of the 12 SuperTrapp plates on each side of the Ford GT exhaust and included a 1/16″ spacer between each plate. With this setup, the power level remained high (678 rwhp/643 torque), the boost was 16.2-psi, the ACT was 132-degrees, air/fuel hung in the mid-11′s and the sound level came in at 108db. Problem solved! – Bruce Tucker
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