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Garrett Twin Turbochargers - A Bigger Playground - Garrett Mustangs
Bothwell Motorsports And Team Garrett Find A New Home With A Cool Pair Of Mustangs
While making big power with turbos isn't front-page news anymore, the fact that these guys ran as well as they did in this particular car has been something of a revelation. When compared side-by-side with other class competitors sitting in the staging lanes, Team Bothwell's '07 Mustang sits higher than its competitors, runs with a flat hood, and looks amazingly stock. The car was originally intended for a lower, true 10.5 ladder-bar class, but certain design considerations were built into it so that the car could be adapted to fit the various rules with different sanctioning bodies. Smith Racecraft of Dallas, Texas, built the chassis with single-framerail construction to allow a certain amount of flex and a long four-link. With the right shock and wheelie-bar combination, the team has found that the car responds well.
The other mild surprise is that unlike the 600-plus-cubic-inch, twin-turbo engines on alcohol in some other Outlaw 10.5 racers, this car runs with a relatively small 388-400ci small-block combination on gasoline. Ed Hansen Racing Engines assembled the mill with an iron block, featuring a 9.7:1 compression ratio and a set of aluminum Brodix/Neal BF201 heads. An ACCEL/DFI Gen 7 box manages the fuel distribution through RC Engineering 160-lb/hr injectors, which are fed through a -6 AN billet fuel rail. A Wilson 105mm throttle body and matching elbow direct the airflow into the engine through a cast intake manifold. Backing that up is a Keith Neal transmission with a Marty Chance converter that spins a set of 3.90:1 rear gears with 15-inch-diameter 33x10.5W Mickey Thompson rear tires.
On the turbo side of things, the team uses a pair of out-of-the-box 769112-7 Garrett GT4718 turbochargers with 60mm wastegates, which together develop anywhere from 2,800 to 3,000 hp. A Garrett liquid-to-air intercooler chills the inlet temps to lessen the possibility of detonation. Both turbos use a 56 trim compressor wheel with an 88mm inducer and a 117.6mm exducer with a 1.08 A/R exhaust housing. The ball-bearing center section provides a significant reduction in lag time, while eliminating the thrust bearing--the weak link in many journal bearing designs--altogether. With greatly improved rotordynamics and less susceptibility to oil starvation and contamination, these units offer the best of all worlds with quick spooling, large amounts of thermodynamically efficient airflow, and the best possible reliability. In fact, one of Garrett's primary goals with this car is to make it through the entire season with the same set of turbos.
"We're trying to show that these Garrett turbos can produce the power needed to run with anyone, regardless of engine size," Gil Bothwell says of the marketing message the race team brings. "We also want to demonstrate their unbelievable reliability by keeping the same turbos in the car all year long. It's a tremendous product that's basically maintenance free--and we've seen no failures."
"These things are only as complex as you want to make them," Steve Bothwell adds when asked what it takes to run a turbo car. "Is it harder than running a nitrous car? Initially, yes, but there's a million different ways to run a turbo car. Once you get the tune figured out, I think it becomes easier. There's a lot less parts carnage, and they're infinitely more tunable in a linear way."