Installation of the Kenne...
Installation of the Kenne Bell blower upgrade on the '03 Cobra 4.6 boosted the power output by nearly 150 hp, from 537 to 682 hp. The torque was up from 530 lb-ft with the Eaton to 595 lb-ft with the twin-screw.
It should be mentioned that previous testing with a nitrous system (for another magazine) necessitated the installation of a Kenne Bell Boost-a-Spark. The ignition upgrade cured a high-speed misfire and allowed us to successfully combined nitrous and boost (from the Eaton) without misfiring. We are confident that the Boost-a-Spark-augmented ignition is what allowed us to run such elevated power levels with our coil-pack ignition (from a 2V 4.6L). The larger DUB crank pulley increased the peak boost pressure from 16.5 to 19.5 psi, upping the power output everywhere. The power gains were as high as 40 hp and 47 lb-ft of torque. The pulley swap allowed us to exceed 700 hp for the first time with our Ford Racing crate motor.
To this point, all of our testing had involved induction improvements. Now it was time to focus on the exhaust side of the equation. Though run in reverse order on the dyno, it is probably easier to understand if we describe the test procedure in ascending order. Originally we wanted to install a complete factory Cobra exhaust system to compare against a complete Bassani system (including headers). Unfortunately, the factory cat pipe supplied to us (on loan) was clogged. We discovered this only after hooking up the entire exhaust and attempting to run the motor. With the boost gauge showing in excess of 25 psi and the dyno indicating an output of less than 200 hp, we knew a problem existed. In the end, we replaced the clogged cat pipe with the supplied X-pipe from Bassani, giving us the stock exhaust manifolds feeding the Bassani X-pipe and the stock Cobra cat-back exhaust. The ordeal took several hours to straighten out, but we finally had a compete system ready to run. Credit the excellent Westech dyno facility for the ability to test complete exhaust systems on the engine dyno.
Since the Cobra motor took...
Since the Cobra motor took so well to the twin-screw, we decided to further increase the boost pressure. Changing the 7.75-inch crank pulley to a larger 8.5-inch version upped the boost from 16.5 to 19.5 psi. The power peak now checked in at 704 hp and 633 lb-ft. Power gains were as high as 40 hp and 47 lb-ft from the increase in boost.
The exhaust test was run with the Kenne Bell supercharger equipped with the 3.25-inch blower pulley and the smaller 7.75-inch crank pulley. Equipped with the stock exhaust manifolds, Bassani X-pipe and factory cat-back, the supercharged Cobra motor produced 666 hp and 578 lb-ft of torque at 17.9 psi. The boost reading is important as improvements to the exhaust system actually lowered the boost pressure. The first test involved replacing the factory Cobra cat-back exhaust with the Bassani 2.5-inch stainless-steel cat-back system. I would be remiss if I failed to point out the fact that the Bassani X-pipe sounded great. I've always liked the effect X-pipes have on the exhaust note and the Bassani system was no exception.
Installation of the Bassani cat-back upped the peak numbers to 677 hp and 587 lb-ft, while lowering the peak boost pressure to 17.2 psi. The Bassani cat-back exhaust improved the power output by as much as 12-13 hp elsewhere in the rev range. To illustrate what is possible with headers and open exhaust (for a drag race vehicle), we installed a set of 1 5/8-inch Flowtech (Hooker) headers, each running through an 18-inch section of 3-inch exhaust (no mufflers). The free-flowing exhaust system upped the peak power to 682 hp, while peak torque checked in at 595 lb-ft. Like the Bassani exhaust, the gains offered by the headers and open exhaust were more pronounced elsewhere in the curve.
This exhaust test completed our mods list in Part 2, look for a ported Eaton supercharger, CNC-ported heads and a whole gaggle of cams in a future episode of "Mods for 4V Mods."
Originally, we wanted to include...
Originally, we wanted to include testing of the Bassani mid-length header, but it would not fit on the dyno (interference with our bell housing).
We also wanted to compare...
We also wanted to compare the complete stock '03 Cobra exhaust against the Bassani system, but a clogged cat pipe limited that test. In the end, we decided to run the stock exhaust manifolds and feed the Bassani X-pipe.
The trick exhaust note was...
The trick exhaust note was reason enough to install the Bassani X-pipe. The stainless-steel construction and impressive build quality were two others.
Equipped with the factory...
Equipped with the factory cat-back, the Kenne Bell-supercharged Cobra motor produced 666 hp and 578 lb-ft of torque at 17.9 psi.
Swapping the stock exhaust...
Swapping the stock exhaust in favor of the 2.5-inch Bassani cat-back resulted in a power gain of as much as 12-13 hp. Interestingly enough, improving the exhaust flow with the Bassani cat-back actually decreased the boost pressure to 17.2 psi.
Equipping the motor with 1...
Equipping the motor with 1 5/8-inch Flowtech headers and a 3-inch exhaust system decreased the peak boost pressure further to just 16.5 psi. The racing exhaust upped the peak power to 682 hp and 595 lb- ft of torque.