FordMuscle: Granatelli Motor Sports' S197 Turbo Kit Makes 617 Dyno-Proven Horses

FordMuscle covered the Granatelli Motor Sports bolt-on turbo system for the three-valve S197 Mustang on January 4, 2013. The story, written by Jason Reiss, centered on a dyno video in which J.R. Granatelli's own 2005 Mustang GT put 617 horsepower to the rollers.

The Background Behind the Kit

According to the article, J.R. Granatelli brought years of experience boosting Mustangs to this project, including his time as the former owner of Paxton Superchargers. The kit was developed for the three-valve S197 Mustang.

Power Claims in the Article

• About 450 rear-wheel horsepower on an otherwise stock car using 91 octane fuel
• Close to 500 rear-wheel horsepower on 93 octane
• Both figures at 8 to 10 psi of boost
• Capacity for up to 800 horsepower at the wheels on a car modified to support it

The article noted that Granatelli Motor Sports asked customers planning to run more than 9 psi to call first, since the company recommends additional supporting modifications at higher power levels.

What Came in the Box

FordMuscle listed the main hardware as a 76mm Turbonetics turbocharger, a TiAL wastegate, a Granatelli bypass valve and a stainless steel hot side. A 2.5-inch downpipe was standard, with a 3-inch version optional. The cold side used aluminized tubing and twin Spearco intercooler cores, and the kit included the sleeves, clamps and hardware needed to install it. To learn how these boost-control parts work, see our Wastegate FAQ and Blow-Off Valve FAQ.

The 617 Horsepower Pull

On J.R.'s personal 2005 GT, the dyno recorded 617 horsepower and more than 646 lb-ft of torque, according to the article. The writer was most impressed by how flat and broad the power and torque curves were, which he said should make lag almost nonexistent.

These numbers came from one car on one dyno. Results on your car will depend on its condition, its supporting parts and the tune.

Watch and Read the Original Coverage

Read the full article at FordMuscle

Watch the dyno video on YouTube

Written by JoJo Granatelli — third generation at Granatelli Motor Sports in Oxnard, California, and the one who drives what the company builds. He set a quarter-mile record of 7.06 seconds at 157 mph at Famoso Dragstrip in August 2026. More about JoJo.