The supercharger was attached...
The supercharger was attached to the lower intake using a custom machined adapter plate. Note the pair of screws inside the triangular opening on the underside of the unit.
Naturally, the highlight of the Kenne Bell intercooled supercharger kit is the blower itself. In the case of the standard intercooled system, the kit featured a 1.7-liter twin-screw Autorotor supercharger. MM&FF readers should remember the testing performed on both the Lightning and Cobra motors originally equipped with the Eaton M112 Roots-style blowers. Simply replacing the Roots-style blowers with a more efficient twin-screw resulted in significant power gains (even at the same boost level). Compared to a traditional Roots-style blower, the twin-screw design offers improved flow capability (per blower displacement), decreased inlet temperatures, and even a reduction in the parasitic losses associated with driving the blower.
For those who want to take things to the next level, Kenne Bell will also offer the Three-Valve kit with the larger 2.4 blower, capable of exceeding 700 wheel horsepower with the proper engine combination. Check out the supplied graph for a rundown on the power gains offered by the blower upgrade. The only thing holding the motor back from exceeding 535 wheel horsepower was the stock clutch. Apparently the clamping force simply wasn't up to the task of withstanding the onslaught of over 500 lb-ft of torque.
The thing we enjoy about covering a supercharger kit from Kenne Bell is that those guys always seem to have answers, which is a good thing since we always have questions, like, "Did you run it at different timing levels? How about different air/fuel ratios? Did the variable cam timing have any effect on the power once you added the blower?"
Equipped with the new Kenne...
Equipped with the new Kenne Bell supercharger, the 4.6 Three-Valve GT produced 459 hp and 422 lb-ft of torque.
A perfect example of the kind of data generated by Kenne Bell's R&D was the sensitivity of the factory mass air meter. Believe it or not, you can no longer just pop on a cone filter in place of the factory airbox assembly, nor can you reorient, reposition, or even rotate the factory mass air meter without dramatically altering the air/fuel curve. This will come as a shock to those of us who cut our performance teeth on the 77mm Pro M meters in the 5.0 Mustangs, but the factory mass air meter is so sensitive that even rotating it from its original inclination will create havoc. Think about that when you order a cold-air intake system for your '05 GT. Unless the new air intake system comes with a revised program for the ECU, don't be surprised if the air/fuel ratio is way out of whack the first time you take it to a dyno.
The MAF sensitivity did not present a problem for Kenne Bell since it had to reprogram the factory computer anyway. This was necessary since the kit included a set of 42-psi injectors and a (larger) 90mm mass air meter to go along with the Boost-a-Pump.
The Boost-a-Pump and larger injectors ensured plenty of flow potential from the fuel system while the revised programming ensured that the fuel would be delivered in the correct amounts and at the correct time.
Ditto for the timing curve, as naturally the factory ignition timing curve was altered to ensure safe operation under boost. Use of the 90mm mass air meter allowed the power to be taken to 500 wheel horsepower without topping out the voltage reading (5 volts). The stock meter was only good for around 400 wheel horsepower before the voltage reached the maximum reading of 5 volts. The twin-screw blower combined with the efficient air-to-water intercooler allowed the Three-Valve motor to be run safely at 9 psi on pump gas without fear of detonation.
As with any good supercharger, additional power is just a pulley change away. This is especially true of the larger 2.4 blower, as running 14 psi through the 4.6 resulted in a peak power number of 535 hp and nearly 500 lb-ft of torque. It's likely the 600hp mark will fall once the factory clutch has been upgraded with the Centerforce dual-friction system. Kenne Bell was in the process of upgrading the stock clutch with the unit from Centerforce, as this story was being completed.
While impressed with the results...
While impressed with the results of the test run with the 1.7 blower at 9 psi, things got serious when Kenne Bell installed the larger 2.4 huffer and upped the boost pressure to 14 psi. The otherwise stock Three-Valve produced 535 hp and right at 500 lb-ft of torque.
Unlike the blower upgrades for the Two-Valve 5.4 Lightning and the '03-'04 Four-Valve Cobras, the kit for the '05 4.6 Three-Valve required a couple of dedicated castings, including a new lower intake manifold. Natur-ally, space constraints prohibited combining the blower system with the factory Three-Valve (long-runner) intake manifold. With space at a premium, the most natural position for the air-to-water intercooler was in the valley between the cylinder heads.
Unfortunately, this location was already being occupied by the lower intake manifold. The only way the two systems were going to fit was to have them cohabitate, thus the intercooler core was positioned inside the lower intake ( la the Four-Valve Cobra). This obviously eliminated the possibility of any appreciable intake runner length, but the immediate boost response offered by the positive-displacement blower more than made up for any loss caused by the new intake configuration.
Incidentally, for those '05 GT owners on a budget, the Kenne Bell blower kit will also be available without an intercooler. The boost supplied by the nonintercooled kit will be lowered to just 6 psi, but the loss of the intercooler core will drop the price of the kit substantially.
NA '05 4.6 three-valve vs....
NA '05 4.6 three-valve vs. Kenne Bell Blower Kit(9 psi)
The much-improved Three-Valve modulars have endowed the 4.6 GTs with NA Cobra performance thanks to a factory rating of 300 hp. Tested on the DynoJet, this '05 GT pumped out nearly 270 wheel horsepower, a sure bet that every one of the 300 flywheel horsepower was present and accounted for. One of the quickest ways to bring the GT up to supercharged Cobra specs (circa 2003-2004) is to add a supercharger. Given their repertoire of kits for the rest of the modular family, it was only natural that the guys at Kenne Bell decided to tool up for a system for the '05 Three-Valve GT. The infusion of 9 psi to the 4.6 Three-Valve upped the peak power from 268 hp to 459 hp. It would take a modified '03-'04 Four-Valve Cobra to pump out the kind of power this Three-Valve makes with the Kenne Bell blower. The intercooled system easily exceeded 400 lb-ft of torque from 2,700 rpm to 5,700 rpm, peaking at 422 lb-ft.
Kenne Bell 1.7 vs 2.4 Blower...
Kenne Bell 1.7 vs 2.4 Blower Upgrade (9 psi vs. 14 psi)
While we were excited about the 9-psi blower kit, the guys at Kenne Bell had something even more impressive up their sleeves. The standard 9-psi (intercooled) blower kit came with the 1.7L twin-screw blower, capable of supporting over 500 wheel horsepower. Apparently there was sufficient room in the engine compartment to install the larger 2.4 blower, upping the power output of the Three-Valve motor to an amazing 535 hp. Both the blower and (otherwise stock) Three-Valve motor had more to offer, but it was at this point that the stock clutch decided to check out. Rest assured the guys were hard at work swapping in a new clutch, pressure plate, and flywheel from Centerforce to allow them to further push the envelope. By the time you read this, they will have completed the installation of both the new clutch and an 8-rib pulley system in an effort to take the Three-Valve motor to 600 wheel horsepower.
Unfortunately, the stock clutch...
Unfortunately, the stock clutch was not up to holding 500 lb-ft of torque, so it quickly checked out......
......Centerforce came to...
......Centerforce came to the rescue with a new clutch, pressure plate, and flywheel to allow the gang at Kenne Bell to continue in their quest for 600 wheel horsepower.
Effect of Boost--2.4 Kenne...
Effect of Boost--2.4 Kenne Bell Blower(4.6 Three-Valve)
Forced induction engines are a joy to own thanks in no small part to the tremendous torque and horsepower potential. Perhaps the best part about ownership is the ease at which you can increase the power level. Case in point, this Kenne Bell supercharged 4.6 Three-Valve 4.6. Simply by changing the blower pulleys, the boost can be increased from about 7 psi to a high (on this testing) of 14 psi. The result was a jump in power from 432 hp to 535 hp. Of course, this power increase was only possible thanks to the tuning provided by the Kenne Bell programming. Keep the air/fuel mixture and timing curves reasonable and you can literally dial up the boost and power output of your Three-Valve engine.
Effect of Ignition Timing--Kenne...
Effect of Ignition Timing--Kenne Bell Supercharged 4.6 Three-Valve
This graph illustrates the effect of changes in the total ignition timing on the supercharged Three-Valve 4.6. The six power (and torque) curves represent the power achieved running 15, 17, 19, 21, 23, and 25 degrees of total timing. Naturally, this timing curve was run with race fuel, as the supercharged motor will not tolerate 25 degrees of total timing on 91-octane (California) pump gas. You can see that each successive 2 degrees of additional timing improved the power output by 6-8 hp. The final step from 23 to 25 degrees showed less of a gain, where the jump from 19 to 21 degrees showed the greatest. Tests like this can only be run if you have complete control of the engine-management system. Using SCT software, the gang at Kenne Bell was able to eliminate coolant and air temp variables and precisely dial in the air/fuel curve. This way, the only changes were the described 2-degree changes in total timing.