Spetter whipped out a base program that needed only three dyno pulls to complete the tune-a testament to his experience and knowledge with tuning. We were amazed that only three dyno pulls were all that was needed to extract great horsepower with a safe and reliable tune-up. Spetter kept it tame so the owner had no worries about detonation and could drive the car hard without fear of spitting out the internals or popping the head gaskets. For the average person, that means longevity and also cheaper tuning costs.
Utilizing 13 psi of boost, the red S197 spun the Crazy Horse dyno to 476 rwhp and 417 lb-ft of rwtq. A few back-up pulls and a timing change was all Spetter needed to lock down the super-charged Pony's destiny as a tire-fryer. Evaluating the boost graph showed a smooth, linear boost line that increased with engine rpm. We did notice a few bumps in the graph and we attributed it to belt slippage. It wasn't a severe drop in boost pressure, but there were a few dips as the boost graph shot upward. It might be a good idea to swap to an eight-rib belt setup for those who install a smaller blower pulley, an upgrade that is available directly from Paxton.
On the street, the car displayed docile manners in normal driving conditions-that was, until the throttle was jammed wide open. As the engine rpm increased, so did the rush of boost. Centrifugal blowers aren't known for low-end prowess, but having the boost turn on in a linear method certainly helps when applying the power to the stock Pirelli tires. We were bummed because Englishtown Raceway Park was closed for the season and the weather turned really cold up here in New Jersey, which meant we couldn't evaluate the performance on the dragstrip.
An oil return line is attached...
An oil return line is attached to the bottom of the blower.
After some time on the road with the Paxton blower in place, we decided a blower pulley swap would be a fun upgrade. Unfortunately, we were unable to swap it before this issue went to press. The idea with the smaller pulley is to drive the blower harder. With the impeller spinning faster, the boost will pick up in the upper rpm, but it will also ramp in quicker-which means more lower-end power. The stock pulleys are nice, but once you start spinning the blower harder, the blower gets deeper into the efficiency range. Reports from other people with the Paxton H.O. on S197 Mustangs say the car "seriously rips" once the pulley is swapped. Not that it is a slouch in stock form-remember the calculated output is well over 500 hp with the out-of-the-box system.
An upgrade in the exhaust system would also increase the power in the blower combination-what goes in must come out-and Franco's GT had stock exhaust manifolds and a Bassani x pipe system. The stock exhaust manifolds are choking the Three-Valve engine, and a pair of long-tube headers would work wonders with this setup.
The out-of-the-box Paxton helped a stock Mustang produce more power than the sought-after Shelby GT500.
 The head unit is bolted into...  The head unit is bolted into place. |  The radiator hose is routed...  The radiator hose is routed around the supercharger thanks to the relocated water exit from the water neck. |  The front bumper is removed...  The front bumper is removed for the installation of the air-to-air intercooler. |