5.0 Mustang & Super FordsHow To Engine
SVT Focus Supercharger Kit - Under Pressure
Powerworks Unleashes Its SVT Focus Blower Kit
Focus Fact: PowerWorks' former parent company, Cosworth Technology-previously owned by Audi-has been gobbled up by another German giant, Mahle. PowerWorks is now a division of Mahle Powertrain.
Last year (Spring '05, p. 30), we laid out the impressive credentials of PowerWorks' first Focus offering: an intercooled Roots-style supercharger kit engineered specifically for the five-speed 2.0 Zetec. Said kit quickly earned our Two-Fanatical-Thumbs-Up award for its Mr. Hyde performance and Dr. Jekyll driveability. Since then, we've anxiously awaited release of the promised SVT Focus version of the kit, and the wait is finally over.
Engineering the SVT-specific kit required a fair number of changes from the base Zetec package. Some of those modifications, such as the increase from the Zetec kit's 36-lb/hr fuel injectors to the SVT's 42-lb/hr units, will be specific to the SVT version. But others, such as a relocated vacuum tree assembly on the blower air inlet neck and a totally repositioned remote oil filter, will from now on be common with a second-generation version of the Zetec kit. The SVT's six-speed Getrag gearbox-more specifically, its shifter-cable routing-also caused some kit additions and revisions. Other challenges in the SVT project included the tuning calibration peculiarities of its variable cam timing-a calibration that, in order to achieve CARB exemption, was programmed with emissions legality as a primary consideration (see Tuning for Boost sidebar).
What hasn't changed for the SVT kit is the M62 (62 ci of air per blower revolution) Eaton/MagnaCharger positive-displacement supercharger, with 2.8-inch pulley. Installed on a Zetec, this setup can generate as much as 13 pounds of boost pressure, but this drops to around 10 psi on the SVT Focus, thanks to its less restrictive cylinder head and exhaust header. If that concept gives you pause, just think of trying to blow an identical volume of air through a drinking straw (the Zetec) and a radiator hose (the SVT). Clearly, the lower-restriction passage will generate less pressure-pressure being nothing more than a measurement of resistance to flow. In any event, this drop in boost works out nicely since there's no way the SVT's higher static compression ratio (10.2:1 versus 9.6:1 for the Zetec) could have endured 13 psi of boost without drastic retardation of spark timing to lower peak cylinder pressures-something that would have more than cancelled any benefit from higher boost.
Like its Zetec counterpart, the PowerWorks SVT kit is intercooled. To be more specific, the hot breath of the supercharger gives up much of its BTUs to coolant circulating through an effective air-to-liquid heat-exchanger element located within the intake-manifold casting. At the other end of this liquid circuit, the coolant-constantly circulated by electric pump-is in turn chilled by air cascading through a much larger under-bumper-mounted heat exchanger. For those just tuning in, the benefit of intercooling is that the lower the air temp in the cylinders, the more spark advance they can take without risk of detonation, and greater spark advance generally equates to more power and efficiency, all else being equal. For these reasons, it's hard to find factory forced-induction applications without intercooling. On the other side of the ledger board, intercooling dictates a higher kit cost and a somewhat more complicated installation process.
Speaking of installation, bolting on the SVT kit is similar to-though a bit more complex than-the Zetec install we showed you previously. Feel free to refer back to it for more detail. PowerWorks' installation manual is outstanding, so what we'll mostly concentrate on in our captions is how the SVT kit differs from the Zetec's.
Was PowerWorks' SVT blower kit worth the wait? Well, let's see: Does 233 hp feel better than 150? Our official thumbs are pointing skyward again.
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One of the biggest tuning challenges, according to PowerWorks' Chief Project Calibrator Mark Blaha, was the SVT's variable cam timing strategies that work well to help torque and horsepower in naturally aspirated form but cause major problems under the extra overlap of boost conditions. "With the kit using 42-pound injectors," Mark told us, "the cold start and idle control were a lot more difficult than on the [Zetec] kit. That, coupled with the big-tube header and a catalytic converter that's 3 feet from the engine, makes it real difficult from an emissions standpoint." But emissions compliance was key, given the kit's CARB exemption.
The calibration is also conservative. "We do our calibrations-spark and fuel-based on what we know the engine's capable of handling for a long, extended period of time," Mark said. This conservatism is more spark than fuel oriented. In other words, some power may be sacrificed in favor of durability-we don't know about you, but we wouldn't have it any other way. Those of you seeking power for power's sake can always have a competent tuner flash a more aggressive calibration, but you do so at your own risk and immediately void PowerWorks' one-year kit warranty.
The tune is based on 91-octane fuel-the best available in some parts of the country-and since the PowerWorks tuning scheme takes the engine's rather ineffective knock sensor out of the programming loop, there's really no benefit in paying extra for, say, Sunoco 94.
One last point. We like the fact that PowerWorks has placed an intake-air-temp sensor in the left-most intake runner path, where it can read the temperature of the actual air charge entering the engine (Ford's factory intake-air-temp reading is taken right at the mass air sensor, which would be upstream of the blower). The new sensor location allows the processor to know exactly what air-charge temp it's dealing with and retard spark timing accordingly as temps rise. Even so, Mark says the spark-versus-heat tables are decidedly conservative for engine safety.
Subjectively, we knew PowerWorks had done it again, but to put some hard numbers to the gains we headed off to see our good pal Joe DaSilva at DaSilva Racing. More specifically, we went to assault Joe's Dynojet. The results-run at an ambient temperature of 66 degrees and corrected to SAE standards-certainly confirmed our suspicions.
You can see that, down low on the tach, the Roots is a torque generator, with grunt that soon launches the tach skyward, where the big horsepower then kicks in. With peak-to-peak gains of nearly 79 hp and 56 lb-ft, you can see why we need those differential and clutch upgrades. Soon.