Compound Boost 2003 Mustang Cobra Twin-Turbo - The Manhattan Project

In the early '40s, the U.S. government-along with Canada and Great Britain-embarked on a mission to create a new type of weapon. The Manhattan Project was formed to research the splitting of an atom in order to create an explosion that the world had never seen. Atomic energy was neither a new concept nor one that hadn't been researched before the Manhattan Project was started. The Germans had been researching atomic power as an alternative source of energy since the late '30s. It was a race to see who could develop the technology quicker.

Moving forward to today's high-performance Mustang world, the race for speed and more power has brought about a project at Hellion Power Systems (Albuquerque, New Mexico)-developed under the same veil of secrecy as the Manhattan Project in nearby Los Alamos. The company has developed a new kind of turbo system to battle the GM and Mopar contingents as well as further pull away from the sport compacts and outrun the crotch rockets. They kept the project secret in order to develop and perfect the turbo system before the public got a glimpse of it. Once the bugs were worked out, they invited us to witness this new system firsthand.

Hellion's new modular-motor turbo system has a pair of turbochargers that blow into a super-charged '03 Cobra engine-utilizing a concept called compound boost. It's not a new term as, "diesel engines have used turbos on top of super-chargers since the '60s," according to Hellion's John Urist. Over the past six months, he has been collaborating with Dave Austin, head engineer at Turbonetics, on the possibility and effectiveness of this setup. The discussions centered on pres-sure ratios created by compounding stages of compressors and how it relates to performance. Austin has vast knowledge on the topic, and even cited a project in the '80s he worked on with Jim Feuling and Jerry Magnuson that had a turbo huffing into a Roots-type supercharger.

Compound boost is a term that is quite common outside the Mustang world. The typical compound boost setup is to have one turbocharger-usually a large one-blowing into a smaller turbo, much like the latest 6.4L Power Stroke. It helps generate serious low-end torque and still breathes easily upstairs. Another benefit is that it allows high boost pressures without high turbo speeds, keeping the compressors in a more efficient range. Compounding boost in diesel engines has also been accomplished with a turbo blowing into a supercharger. We've also seen it perform on a smaller scale in the sport-compact world. Volkswagen is coming to market with a 1.4-liter engine that will feature a turbo blowing into a supercharger induction system.

Urist took it one step further and has run Hellion's new twin-turbo kit into the blower. It created shocking results that will have even the most hard-core guys asking when is enough, enough? Hellion is set to hit the market with twin-turbo systems for all '96-'04 modular engines, including Two-Valve and Four-Valve combos.

The kit featured here is universal and can be used with a supercharger or without it-the difference will be in the turbocharger sizing to fit different applications. The piping and turbo mounting is universal in all systems and mod-motor applications. For those brave enough and in need of the excess, check out the turbo/ supercharger system. It will not disappoint your appetite for ridiculous power levels. We watched this setup throw out a certifiably insane 1,188 rwhp and an even more impressive 1,015 rwtq-through a stock engine including the factory cast-iron exhaust manifolds.

"We wanted to create a system that would spool quickly and make an enormous amount of low-end power," Urist says. "The turbos are 66 mm and would normally be too big for this engine, but when combined with the super-charger, they're perfect. As you can see in the graphs at the end of this story, the low rpm power is big, and it simply doesn't fall off on the top-end. You can run this engine higher and still make more power.

"The Roots-style supercharger is a constant-displacement device. It moves air against a restriction, which is the engine, and it creates pressure. The downside of the supercharger is that it's not as efficient and takes more power to drive than a turbocharger. So peak horsepower per pound of boost with our compounded setup will differ from turbocharger-only applications."

Simply removing the supercharger and adding a '99 Cobra intake will increase peak horsepower, but low-end power would be sacrificed. The reason behind the madness, though, was to create a combination that provides superior low-end and average horsepower.

The easy part was designing the system and getting it plumbed to the throttle body. The harder side of the project was ensuring the car would operate properly when on the dyno. Delivering the right amount of fuel was first on the list. Urist wasted no time and converted the Cobra to a return-style fuel system. The stock tank was removed and a sump was added to the bottom. Moving the fuel forward to the engine is the job of a -10 supply line, a Weldon 2345 fuel pump and filter, 1/2-inch fuel rails, and 160-pound fuel injectors. A Weldon Dial-A-Flow was also installed for street driving. A single -8 line has been tasked with returning the unused fuel to the tank.

"The fuel system is capable of feeding anything the engine can handle," Urist says. "It might seem like overkill, but we wanted to set it up for future projects that include running E85 fuel, which requires about 40-50 percent more fuel volume than gasoline."

Other areas of concern were with the drivetrain, ignition system, and engine management. The latter two were solved with one component. Urist ordered a PMS engine-management setup from Anderson Ford Motorsport. Stock electronics are kept in place, and the PMS plugs into the computer box. It's capable of driving the low-impedance fuel injectors, as well as firing spark in high-boost applications.

We were pleased to see how effective the PMS was in this application. Running such high boost (44 psi) was relentless on the ignition system, and the add-on proved to be quite durable. The PMS was programmed to go stand-alone at 3,000 rpm and reference a map sensor. Urist controlled the injectors easily using the handheld tuner. He adjusted the fuel volume based on the air/fuel ratio meter. Timing was a rather conservative (for race fuel) 19 degrees on the big power pulls.

The stock clutch certainly wasn't going to hold up to the abusive torque curve that this system was going to produce. Urist called his friends at ACT to build a clutch to withstand the abundance of torque. The company shipped a single-disc unit that was rated at 920 lb-ft. At the time, Urist thought the clutch rating was sufficient. In the end, our test subject cranked out 1,015 rwtq, and the clutch survived the onslaught on the chassis dyno. The IRS is a different story; the wheels bowed inward during the dyno pulls. It lived, but the question was, for how long? We think the axles will snap easily on the street, even with straight-up radial tires.

The engine was responsive to timing and rpm changes. Urist opened the wastegate by making one turn on the knob and started with 14 degrees of timing. Utilizing just 4 psi at the turbos and 16 psi at the manifold, the power registered 611 rwhp and 646 rwtq. That's a far cry from the 385-rwhp output that bone-stock '03-'04 Cobras normally put out on the Dyno Edge chassis dyno.

We wanted to see some big numbers, but the Hellion crew stepped things up, one chassis pull at a time. Another run was made at 14 degrees and at the 6,000-rpm limit, with the only change being an increase in boost. Output was 846 rwhp and 720 rwtq, as boost registered 23.70 at the turbos and 38.50 in the manifold-this combo needed more timing. Urist inserted his opinion: "These turbos needed to be hit harder down low, and the fuel curve had to be leaned out some more."

It was time to make big power, so the timing was upped to 16 degrees, and the Cobra was run up to 6,500 rpm. The results were 1,048 rwhp and 900 rwtq, with turbo boost coming in at 26.8 pounds and the manifold registering 41. One more pull was made, and Urist cleaned up the fuel map a bit and put the timing at 19 degrees. The turbo boost showed 27 psi, while the mani-fold saw a peak of 44 psi due to increased engine rpm. Spinning the blower harder will result in a greater manifold pressure. Final output was 1,188 rwhp and 1,015 rwtq.

The combinations are limitless when you factor in different pulley and turbo setups. Don't think for a moment that this setup is strictly for '03-'04 Cobras. Running a Roots-style blower on any engine with a single or twin turbocharger setup will produce great power-just be sure your engine is capable of handling it. Compounding boost can yield excellent results, even at low turbo levels like 13 psi (roughly 22 psi at the manifold), and make a nice, healthy street machine out of your Mustang or Cobra.