Working with one of the leading twin-screw engineers, Kenne Bell designed its own superchargers. By combining the larger-bore rotors in a billet case (for superior strength compared to a cast case) with improved rotor design and specific inlet and discharge patterns, Kenne Bell was able to produce bigger and more-efficient blowers. The new Big Bore blowers not only provide more airflow and power potential, but the airflow comes at a lower charge temperature with a drop in parasitic loss (power required to drive the blower). According to Kenne Bell, the Big Bore blowers are better in every way.
While improved blower efficiency can increase the power potential offered by the twin screw, the really big news is the increased displacement. KB's Big Bores are now available in displacements ranging from 2.1 liters all the way up to a whopping 2.8 liters. That is over a full liter more than the original 1.7 used on our own Project RSC and nearly half a liter more than the 2.4L blower used to produce 960 hp on the modified '03 Cobra motor. That's easily 1,000-plus horse-power with a twin screw.
Every bit as impressive is that the new Big Bore blowers fit where the original blower once stood. We have physical proof that the 2.1L blower bolts right in place of the original 1.7L; we tested it on Project RSC (see graph). According to Kenne Bell, the Two-Valve motors will receive the 2.1L blower, while the '05-'06 Three-Valve and 5.4L Lightning motors come with the 2.6L blower. The 2.8L blower is reserved for the Four-Valve Cobra motors and the 5.4L 4V used in the Ford GT. The 2.8L will also be installed on the new 5.4L GT500. Just imagine what a GT500 would feel like with a 2.8L twin-screw blower under the hood. We don't think we'd even bother driving it with the factory blower-just drop it off at Kenne Bell for the massive upgrade. That would be one kick-ass Shelby Mustang.
Blower efficiency was further...
Blower efficiency was further improved on the Big Bore blower with a revised rotor design. Just like impellers on a turbo or centrifugal supercharger, the rotors on a twin screw help determine overall efficiency.
The great thing about the...
The great thing about the Big Bore blowers is that with careful design, the slightly larger blowers are a direct replacement for their smaller Autorotor counterparts. This 2.1L Big Bore blower dropped right in place of the original 1.7L used on Project RSC.
The modular design allows...
The modular design allows different snout lengths to fit specific applications. In some cases, the snout length is quite short to provide clearance in the rear of the blower for the throttle inlet.
While shooting the fancy new blower on a sheet of colored paper is all well and good, we could hardly expect to drive out to Kenne Bell's for just a photo shoot (no matter how cool the new product). No sir, it's dyno time or nothing for us. Recog-nizing our addiction, the guys at Kenne Bell agreed to provide us the necessary fix by allowing us to test one of its new Big Bore blowers on project RSC.
Though we didn't plan for this test as part of the project, it is nice to have a project car when opportunities like this arrive. We hope to run the new 2.8L blower in the near future on a Ford GT or GT500 motor, but for now we'll whet your appetite with the power gains offered by the 2.1L blower.
We installed the intercooled super-charger kit from Kenne Bell on the modified 4.6L Two-Valve motor. The kit included the standard 1.7L blower, the air-to-water intercooler, and everything needed to produce as much as 9 psi of boost. For this test, the 1.7L blower was equipped with a 3.00-inch blower pulley and run with the timing and air/fuel curves locked in place to make the motor as repeatable as possible. With the 1.7L blower making 7.5-8 psi of boost, the 4.6L Two-Valve motor produced just over 400 hp and 395 lb-ft of torque. After swapping on the new 2.1L Big Bore blower (with the same 3.00-inch blower pulley), the boost pressure jumped to nearly 12 psi, while the power numbers followed suit to the tune of 452 hp and 453 lb-ft of torque. With an effortless 50 hp from the 2.1L, we can't wait to get our hands on one of the Big Bore big boys and really put the spurs to it.
Kenne Bell twin screw Blower Test:1.7L vs.Big Bore 2.2L
In a direct comparison test between the twin-screw blower designs, the new 2.1L Big Bore Kenne Bell blower offered significantly more power than the older 1.7L Autorotor. Equipped with the same drive pulleys (3.00 blower/6.5-inch crank), the 2.1L Big Bore increased the boost pressure supplied to the modified '96 Two-Valve motor by nearly 4 psi, from 7.75 psi to 11.50 psi. The increased boost and efficiency offered by the 2.1L improved the power output from a tad over 400 hp to 450 hp. The peak torque rose a similar amount, from 395 lb-ft to 453 lb- ft, with significant gains offered throughout the rev range. With the proper motor combination, this 2.1L would have no trouble exceeding 600 rwhp. Now, just imagine what the 2.8L blower is like.
While we had excellent results...
While we had excellent results from the initial testing with the 2.1L blower on the modified Two-Valve motor in Project RSC, we can't wait to get our hands on the 2.8L. All four of the Big Bore blowers are the same height and width. The increased displacement comes from an increase in length (2.1L versus 2.8L shown).
We previously tested the snout...
We previously tested the snout upgrade for the supercharged 5.4L Ford GT motor, but Kenne Bell also has a 2.8L blower upgrade for the already impressive Four-Valve motor.
To test the Big Bore blowers,...
To test the Big Bore blowers, we decided to run one of the new 2.1L units on Project RSC. For this test, the 1.7L installed previously was run with a 3.0-inch blower pulley that produced just under 8 psi. The modified Two-Valve motor produced 405 hp and 395 lb-ft of torque.
The 1.7L blower was then replaced...
The 1.7L blower was then replaced with the larger 2.1L Big Bore blower, with impressive results. The increased displacement and improved efficiency of the Big Bore increased the boost pressure (using the same 3.0-inch blower pulley) to nearly 12 psi. The peak power numbers rose right along with the newfound boost, from 405 hp to 453 hp. The peak torque stood at 453 lb-ft of torque, with a sizable jump in average torque throughout the rev range.