Way cool at the track, today's...
Way cool at the track, today's huge horsepower is too much on the street. It will turn your tires into smoking balls of rubber. Adam scooped up these handfuls after our burnout photo shoot.
Although it took weeks of frustrating tuning, fabrication, and experimen-tation, we can sum up the Kenne Bell S197 Mustang GT 2.6H blower's high boost capabilities with the three dyno runs
The runs are labeled 16, 18, and 20 pounds of boost, which are the peak boost numbers. Most of the duration of each run, however, was made at half a pound of boost less than the peak figure. These "official" runs were made on the same day in rapid succession after all electronic tuning was finalized. Careful attention to maintaining constant temperatures and no adjustments other than changing blower pulleys allows comparing these runs to each other in detail. All data is from the ST Dynojet inertia dyno, using the "standard" correction factor. We prefer to use the SAE correction, but many shops use standard, as it reads a higher number. KB used the standard correction during the '03 Mustang Cobra test as well
Don't forget to eyeball the torque figures; they're fantastic
Click here for the Kenne Bell three-valve dyno chart
Kenne Bell recently introduced its own line of Twin-Screw superchargers, which we detailed in our Nov. '06 issue ("Home Screwed," p.48) and are seeing again in this article. Additionally, KB has just released an "H" version of the new 2.6 liter, which is the blower featured in this article and the first time it's been seen anywhere. Testing on the H-blower costs $100 more than the standard.
The H stands for "High Pressure Ratio," which is the internal pressure ratio (the compression ratio) of the Twin-Screw compressor. The only physical difference between Kenne Bell's standard 2.6 and 2.6H blowers is the 2.6H employs a smaller, shorter outlet. This effectively makes the rotors longer, allowing the supercharger to compress air for a longer distance. The blower's displacement, and most confusingly, the boost, does not change with the H blower, but the supercharger's efficiency increases. In other words, the H blower takes less horsepower to turn at high boost. This makes the 2.6H and 2.8H blowers desirable for boost pressures exceeding 15 pounds. Below 15 pounds of boost, the standard 2.6 and 2.8 KBs are preferred
To put some carefully obtained numbers to it, at 19.5 pounds (20-pound peak) of boost, the standard 2.6 blower made 622 rwhp and the 2.6H made 652 rwhp, a gain of 30 rwhp for the H blower. At 15.5 pounds of boost, the H was ahead by only 10 rwhp-569 versus 559. Below 15 pounds, the standard blower makes more horsepower, the more so as boost lowers into the more common 6 to 12 pound range.