While traditionalists may...
While traditionalists may be all agog over the stock Bullitt's five-spokes, Mark is clearly enamoured with a flashier, more contemporary, street-scene look. The American Racing Hopster 18x8-inch front and 18x10-inch rear wheels play that trick to the max. Currently, the brakes are stock, but coming next are Baer two-piece Eradispeed Plus rotors for a little extra stopping power and fade resistance.
Next, Mark elected to fit a free-flowing MagnaFlow exhaust system. This was done at MagnaFlow's proto-type shop, where a combination of off-the-shelf and prototype parts were installed. The after-cat is PN 15673 from MagnaFlow's MagnaPack ready-to-wear collection for '99-'02 Mustangs. It uses 2.5-inch stainless steel tubing; 4x14-inch round, straight-through mufflers; and a pair of Souza-horn-sized, 3.5-inch polished tips. As with all MagnaFlow systems, it's a showy, well-built item. The MagnaFlow system delivered six otherwise missing horsepower. Six horsepower seems a bit low for an exhaust system on a blown car, especially since we've had great experiences with the MagnaFlow gear in the past. But, please keep in mind this is our first dynoing experience on Westech's Superflow dual-eddy-current chassis dyno, which we expected to deliver numbers a bit lower than a Dynojet. So our gains of 6.1 hp and 10 lb-ft of torque were respectable. But, after installing the system, MagnaFlow tested the system on a Dynojet and recorded big gains. In the end, our final numbers with the exhaust weren't that far off, with the Dynojet reading 6.9 more horsepower and 2.3 more lb-ft of torque.
The final power addition was done during our last dyno session at Westech. We asked John Mihovetz of Accufab and 4.6 drag-racing fame if he would install one of his billet throttle bodies on Mark's car. Always ready to ham it up for the camera, John was happy to oblige, and after a bit of grinding to open the upper intake runner, the dyno showed a 10.5hp gain from the larger throttle body.
More MGW billet trickery is...
More MGW billet trickery is found on the oil-fill cap; Mark has been pouring Castrol 10W-30 Syntec synthetic oil through it. Also unexpected was a premium-quality Denso oil filter. It's a new product from a company best known for spark plugs and oxygen sensors. The Denso filter's unique feature is a "torque-stopper" device to prevent under- or over-torquing the filter.
For those not keeping score as we've gone along, the Denso spark plugs, MagnaFlow exhaust, and Accufab throttle body combined to deliver an extra 31.5 hp, for a total of 369 hp at the rear tires. Torque rose a commensurate 31 lb-ft from the supercharged baseline to the final throttle-body installation. In other words, numbers any wildcatter would be proud to load.
Dyno Tales
While the modifications to Mark's car were performed over several weeks time, we were able to test the modifications part-by-part on the same Westech chassis dyno. Weather changes were also minimal between the dyno sessions, which grouped the baseline and spark plug tests on one day, with the exhaust and throttle body test on another. As the dyno sheets show, the final gains of 32 hp and 31 lb-ft of torque were nicely spread across the powerband, which makes them desirable for a smooth-running street car such as a Bullitt.
 Look close enough and you'll...  Look close enough and you'll see Mark's Mustang is something of a billet Bullitt, with even the license-plate frame bene-fiting from the MGW touch. The fuel door is also MGW billet material, but as the stock Bullitt fuel door is already bright, it doesn't immediately stand out. |  All our dyno figures were...  All our dyno figures were taken on Wes-tech's Superflow chassis dyno. We have yet to test the same car back-to-back on Superflow and Dynojet dynos, but reports from those who have-and circumstantial evidence-indicate the Superflow gives a lower power reading. So, if you're comparing Mark's power figures with others taken from a Dynojet, you may want to add 10-15 hp to Mark's. |  Denso's IT20 Iridium Power...  Denso's IT20 Iridium Power Plugs for the Mustang are one of those mods that can seem too good to be true. Power increases in the 15-20hp range are not uncommon on highly stressed supercharged 4.6 applications thanks to the tiny 0.4mm center electrode. It is said to unmask the spark plug to the air/fuel mixture and resist being blown out by high boost pressures. This can result in dramatic power increases should light, even imperceptible, misfiring occur. |
 Changing spark plugs on the...  Changing spark plugs on the 4.6 Two-Valve engines is not as bad as on the ancient 428 Cobra Jets, but it will give you and your dad something in common to talk about. The passenger side is the worst, as the throttle body must be removed to access the center two plugs. |  Bullitts use coil-on-plug...  Bullitts use coil-on-plug ignition. The small bolt retains the coil assembly atop the spark plug, so you'll be dealing with these small fasteners. Quarter-inch-drive hardware is a major help with this job, as the slender extensions are best for sneaking past the obstacles. |  It must be tough to be an...  It must be tough to be an exhaust technician at a place such as MagnaFlow. The work is great looking, with mandrel bends and stainless hardware, but it's tucked up under the car where it's rarely seen. Don't let the small, straight-through mufflers on the MagnaPack after-cat fool you; the system is daily driver-acceptable for a sportster. The X-pipe is a prototype for MagnaFlow's upcoming high-flow cat X-pipe on late-model Mustangs. |