KJ Jones Senior Technical Editor
July 1, 2009
Photos By: KJ Jones

It's pretty much impossible to argue against the notion that innovation and Mustangs have enjoyed a hand-in-glove relationship for almost 30 years. As 'Stangs continue to evolve--from the EFI Fox-bodies that started the late-model phenomenon in the middle '80s to the S197s of today--aftermarket manufacturers are still developing products that are taking 'Stangs deeper and deeper into the high-performance stratosphere.

Hellion Power Systems of Albuquerque, New Mexico, is one of those companies. Led by multi-time NMRA Super Street Outlaw champion John "Do Work, Son!" Urist, Hellion has been considered a major force in the development of bolt-on turbocharger systems for late-model 'Stangs since entering the aftermarket back in 2000.

As a street-'Stang-enthusiast-turned-racing-champion, John knows all about the importance of "boulevard cred," and thus has focused his business on conceptualizing turbo systems that make big steam in cars that see daily usage more so than building setups for NMRA participants or other full-on race Mustangs.

Travis Franklin of Gear Heads Automotive and Performance checks the fitment of the Turbonetics low-mount, 61mm turbochargers that will make boost magic happen when they start feeding the factory supercharger in his '08 Shelby GT500. Travis picked up his low-mile, still-under-warranty Shelby for a song, and was 100-percent ready to set it up with Hellion Power Systems' Shelby GT500 Twin Turbo setup--a performance mod that is about as radical as they get right now for GT500s. Give that man the "ain't skeerd" badge he deserves!

The "Hell Raiser" system was Hellion's initial foray into the world of compound boost (turbos that work in conjunction with superchargers) for factory-blown Ponies. Designed for '03-'04 Cobras, the tricked-out turbo system is highlighted by a pair of Turbonetics 66mm units that blow boost directly into a Snake's blower, creating a multiplied air force that makes far more horsepower and torque (at low rpm) than a Terminator's supercharger is capable of making on its own.

Not to be funny, but we were blown away by the Hell Raiser setup when we saw it for the first time (the system was a unanimous "favorite-product-at-SEMA" selection by 5.0&SF's editors in 2006). The system is clean, innovative, and as we've learned from seeing cars that are outfitted with Hell Raisers, capable of taking a Snake's stock engine to the 1,000-rwhp level in a blink of an eye.

We'd never think of Terminators as being old news, but for the last two years, Shelby GT500s have been the hot ticket when it comes to factory-blown Ponies. With John constantly thinking of ways to make more power--even for cars that already have more than 400 rwhp--we knew it was only a matter of time before we'd hear that a compound-boost setup for the '07-present super 'Stangs would be created and available for us to check out.

John gave us the call in late 2008 and confidently described his latest creation as an all-inclusive, totally bolt-in, upgradable, no-cut (save for the OEM catalytic converters, which are eliminated from the exhaust system), no-weld, no-fabricate deal. He guaranteed it would easily put 700 horses at the feet of a stock Shelby GT500 'Stang, using only a pair of Turbonetics 61mm turbos and a GT500's OEM supercharger to get it done.

"The Shelby's blower is a positive-displacement device that basically takes air and makes it `smaller' by compressing it. Boost from our turbos actually help the supercharger compress and move air into the engine. The stock Roots blower really isn't as much of a restriction as people seem to think, and our Shelby GT500 Twin Turbo system proves this. Power under the curve is the big advantage of this system. There's no turbo lag, and compound boost literally can make unusable amounts of power for street GT500s with little effort," says John.

Claims of big-time rear-wheel horsepower coming easily through the addition of a single or combination of power adders certainly can be true. However, they're still the type of boasts that will quickly bury the needle on our "oh, really?!" meter, almost every time we hear them. With that said, we needed to personally satisfy our interest in the compound-boost setup for Shelbys, and, of course, let you all know what's up, right away.

The landmark tech effort took place in February 2009 when your tech editor arrived at Gear Heads Automotive and Performance in Arlington, Texas. Company-owner and lead-tuner Travis Franklin was ready and waiting with a mostly new, bone-stock GT500 that we used for the installation and the all-important workout on the rollers of Gear Heads' Dynojet chassis dyno.

Don't just skim through this one. The following photos and captions will let you know the real deal on whether the saying "everything's big in Texas" is true, at least in regard to compound boost and the horsepower it makes on our stock Shelby test 'Stang.

Travis uses SCT's Advantage III tuning software and XCalibrator 3 flash device to create and load a power-churning tune into the PCM of his newly compound-boosted Shelby GT500. The addition of turbos does not affect the engine's ability to start and run, but there's no way the hammer can be dropped the way it should be until you've got a good, pump-gas tune and safe air/fuel ratio (11.7:1) at wide-open throttle, which can only be achieved by having an experienced tuner like Travis Franklin dial it in. As an authorized Hellion Power Systems dealer with an in-house test Shelby, Gear Heads is working on developing custom SCT dyno tunes that are specifically calibrated for the new GT500 twin-turbo systems it sells.

On The Dyno
OK, up-front, we're now officially honest-to-goodness fans of the blower/turbo matrix, and we really dig Hellion Power Systems' twin-turbo setup for factory-supercharged, Shelby GT500 Mustangs.

The system makes big steam, and stupid torque in a hurry, as you see in the comparison of our project's baseline and two samples of the final dyno numbers! Lengthy spooling time and high impeller speed for the turbos is virtually nonexistent, and the power adder achieves its preprogrammed (16 psi for our test) boost limit almost as soon as you roll into the throttle. "I wanted the turbo system to give Shelbys the low-rpm power they lack and sustain that power through--and especially at the top of--the rpm range," says Hellion's owner John Urist.

Travis' Hellion-dressed Shelby GT500 had the rollers rockin' on Gear Heads' Dynojet during the post-install dyno test, putting down effortless at-the-feet horsepower and torque that steadily increased with each tuning change (timing/fuel increases). The turbochargers spool almost instantly and are deceptively quiet, which is something we weren't expecting. It really adds to the overall cool of the whole boosted-boost concept.

Our goal going into the experiment was to achieve at least 700 rwhp with compound boost on 92-octane pump gas, without exotic or aftermarket super-duty parts in the engine. The bullet under the hood of the '08 Shelby at Gear Heads was as stock as they come, with no issues other than surprisingly lower baseline power going into our test (compared to other Shelby projects). It emerged completely intact and still running like a stocker (at idle, cruising speeds, and so on) after an intense session of dyno flogging and relatively little tuning.

Note that our after-baseline dyno figures are categorized as Turbo 1 and Turbo 2, and represent numbers produced with the twins and the blower doing their thing. The readings in Turbo 1 were achieved with 16 degrees of timing and an air/fuel mixture that is relatively fat throughout the dyno pull. With a degree more timing and slight trimming of fuel, Travis had our test 'Stang pumping out 700 hp at the rear tires with no sweat.

While the performance capability of this system for stocker Shelbys is crazy, the maximum amount of power we recommend for this system--on an engine with factory internals--is about 725 at the tires. Of course, engines with extensive mods can generate much more (even with pump fuel). We have no doubt that the magic thousand ponies will run absolutely wild with Hellion's optional 66mm hairdryers in place.

Obviously, we tested the setup as a compound-boost-style power adder with the OEM blower in place and functional. However, John has designed the system so it can be installed on a Shelby's 5.4-liter engine in a non-compound manner as well. This requires removal of the blower's internals or a custom-fabricated intake manifold to make it possible.

 BaselineTurbo 1Turbo 2Difference
RPMHPTQA/FHPTQA/FHPTQA/FHPTQ
5,000386.56406.0611.46643.87676.3210.64646.36678.9910.64 259.{{{80}}}272.93
5,{{{200}}}393.45397.3911.34657.23663.8110.58666.71673.3711.04 273.26275.98
5,400401.07390.0911.36671.53653.1710.51678.04659.4711.15 276.97269.38
5,{{{600}}}403.15378.1111.38681.70639.4110.84691.18648.2711.04 288.03270.16
5,800410.29371.5311.40699.83633.7611.05697.25631.4111.14 286.96259.88
6,000403.05352.8311.40699.35612.1810.95700.63618.4711.28 297.58265.64
6,200n/an/an/a688.07592.4311.41688.39583.1711.42688.39583.17
6,400n/an/an/a683.91584.27 0.00637.65523.5812.24637.65523.58