714HP, 281CI, Modular 2004 Ford Mustang Cobra
Kevin Dunn, Coppell, TX
What's a 700hp engine look like? Usually, we conjure up images of big-blocks with multiple carburetors, massive and convoluted headers, and an idle that sounds like a jackhammer. But hidden under the hood of Kevin's '04 Cobra is a different take on the 700hp engine. Unlike the wickedly nasty big-block we initially conjured up, Kevin Dunn's Whipple-supercharged four-valve 4.6L Ford still has its stock long-block, cast-iron manifolds and such docile manners, "your grandmother could drive the car." As if they were made to be supercharged, the displacement-limited (281-cid) modular V-8s take to boost like frat boys take to beer pong. How does this little engine ring up such huge power numbers? More boost and more octane. Let's investigate.
A. 2004 Ford Mustang Cobra - Dress-up
Kevin liked the wrinkle-black finish of his Whipple supercharger so much that he had the stock valve covers and True Forged intercooler expansion tank powdercoated to match it. The Powered By Ford coil covers are from a Ford GT.
B. 2004 Ford Mustang Cobra - More Air
After pulleys, the next biggest bang for your buck is a supercharger upgrade. Though the initial investment is steep, Terminators can handle much more boost than the factory Eaton blower can deliver. Twin-screw superchargers are popular upgrades, and Kevin opted for a 2.3L Whipple unit-pricey, perhaps, but the power rocketed to 561/544.
C. 2004 Ford Mustang Cobra - Exhaust
Adding headers is a big job in this tight engine compartment, so Kevin's car still has the stock exhaust manifolds. He runs high-flow Magnaflow catalytic converters and a Borla exhaust system.
Five hundred sixty-one horsepower on pump gas is impressive, but Kevin wanted more. However, he didn't want to have to rebuild the long-block with an exotic rotating assembly and aggressive cams. He ultimately decided to switch to E85. In addition to high octane ratings, E85 offers superior cooling effects for the intake charge and costs as much as regular unleaded in his part of the world. If there is a downside to E85, it's that it burns most efficiently at a 9.765:1 ratio, so you need more fuel for the same amount of air than you do with gasoline. Therefore, Kevin had to modify the fuel system, adding Ford Racing 80-lb/hr fuel injectors, a pair of Ford GT fuel pumps, a Kenne Bell Boost-a-Pump, and dual Ford FPDM fuel pump driver modules. He also replaced the stock fuel lines with bigger-diameter -8 line but kept the stock fuel rails. His fuel system operates at 50 psi.
E. Pulleys = Power
A simple pulley change adds a bunch more power, and that's one of the first things most Cobra owners do. Kevin was no exception, and engine output jumped to 469/430 at the wheels. Currently, he's got a set of Reichard Racing pulleys spinning the supercharger.
Kevin tunes his car using SCT's Pro Racer Package tuning software. It incorporates a Live Link datalogger, which he uses to monitor and record feedback from the engine sensors and wide-band oxygen sensors in the exhaust. He tells us his program is fairly conservative and he tuned more for driveability and street manners, rather than ultimate power. Running his current E85 setup, he pegs the boost gauge at 20 psi and cranks off 714/650 numbers at the wheels.
From the factory, the engines destined for the '03 and '04 Mustang SVT Cobras were some of the strongest modular engines built (except for the 5.4s used in the GT supercar). The cranks are forged, as are the Manley connecting rods. Forged pistons are set at a boost-friendly 8.5:1. Also, the blocks are cast iron, unlike all other DOHC engines Ford built. These engines were handbuilt at the Romeo Engine Plant's Niche engine line and were known internally as Terminators. Rated from the factory at 390 hp, Kevin's car made 402 hp/385 lb-ft at the wheels with nothing more than a K&N air filter when he bought it five years ago.
"When I decided to switch to E85, everyone thought I was crazy. Now half of Dallas is switching over."
Kevin Dunn, trendsetter