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Ported Factory Supercharger Install - Huffin' `N' Puffin' ...
...And Blowing Down The House Thanks To A Ported Eaton On Our '03 Cobra.
Now, it may appear that Joe was speaking a foreign language, but what he means by a four pound crank pulley is often what Mustang tuners refer to as a larger diameter supercharger drive pulley that is mounted to the crankshaft to provide greater blower overdrive and four more pounds of boost without changing the supercharger's driven pulley, which is on top. This results in increased supercharger speeds in relation to the crankshaft, and more boost earlier in the engine's operating range. However, it should be noted that it seriously overdrives the supercharger beyond the factory-recommended shaft speed, but, what the heck, if all the cool kids are doing it, why can't we?
So with Joe's recommendation made, we turned to Metco Motorsports, which specializes in crankshaft pulleys for the '03-'04 Cobra. Metco's supercharger crankshaft pulley kit is modular in design and allows you to change the pulley size based on the boost increase you want. For instance, if you wanted two more pounds of boost, you'd simply use a two pound pulley ring, four more pounds of boost, you'd add the four pound ring, and for six more pounds of boost ... well, you get the picture. The best part about the Metco kit is how the design of the pulley does away with the factory 'cage setup that is bulkier and takes more horsepower to operate. By switching over to the easy-to-install Metco setup we saved about five pounds right off the nose and added some nice bling to the underhood area as the crank pulley's hub is fabricated from billet aluminum and the interchangeable pulley rings from black-anodized billet steel. Because the supercharger drive system also drives the alternator, you will have to replace the alternator pulley with a larger one to slow it down whenever you use a four pound-or-larger crank pulley.
With our new ported Eaton installed and pulleyed up with the blingus maximus Metco components, we headed to the dyno bay at Mustang Magic and rolled our Cobra onto the Dynojet 248c, as Joe plugged in his SCT Tuner to reprogram the PCM. By pulling some timing out down low and trimming the fuel curve to match, he was able to prevent any potential detonation from the big gains in boost that we were about to see.
On our first pull, we were able to notice a louder shrill from the blower. With nothing else, we were quickly rewarded with an incredible 471 rwhp and 506 lb-ft of torque. This was with a boost increase of four pounds (as advertised by Metco) from 12 psi to 16 psi. Horsepower-wise, we were looking at a modest 18 rwhp gain, but as Lauzardo mentioned, the peak horsepower gain wasn't going to be strong because at around 5,000 rpm, the stock Eaton started to lose in boost, going back down to about 12 psi all the way to redline. The primary issue here is the combination of the restrictive factory throttle body and inlet, as well as excessive supercharger speed, caused by internal turbulence that capitates the air. Much of the gains were throughout the bottom part of the power curve starting at a mere 2,500 rpm as we were seeing the gains from idle to the 4,000 rpm boost peak with a peak torque gain of 53 lb-ft over our previous best. With a relatively safe 11.8:1 air-fuel ratio at peak horsepower, we left it alone as the use of pump gas was important to us.
The only way to find out how extra horsepower translates in the real world was to head down to Old Bridge Township Raceway Park and line our car up on the dragstrip. With an aggressive slip-clutch launch at 2,250 rpm on the 17-inch Nitto Drag Radials, we were able to better our previous best of 11.925 at 118.92 with a new best of 11.59/122.5 mph. Granted, the track temperature was about 25 degrees Fahrenheit cooler, but there was no arguing how the car responded with its newfound power.