September 29, 2005

It's no secret that superchargers do wonders for late-model Mustangs. Boost equals horsepower, and in most cases it's just attach and go. We learned with the older 5-liter stuff that the sky's the limit in terms of supercharged performance, but when it comes to the modular engines, there are fewer hard-core aftermarket parts. So you're faced with adding bolt-ons, topping the package with nitrous, a blower, or any combination of the three.

Of those choices, supercharging ranks as one of the most economical on a horsepower-per-dollar basis. Of course, nitrous can produce serious power for a small initial outlay of cash, but eventually the bottle runs dry. This makes a shot of juice great for drag racing, but for an increase in power that you can tap into at all times, a blower is the way to go.

Recently, we had a chance to sample some supercharged Three-Valve performance in the form of an '05 Saleen S281 Supercharged ("Earning Its Chevrons," Sept. '05, p. 50). Acceleration was great, as the blown 4.6 made awesome midrange torque, and power carried right up to the 6,100-rpm rev limit. The increase over the standard 300-horse GT engine was due mostly to the Saleen Series VI Twin-Screw blower that features an integrated long-runner intake manifold along with a two-stage, water-to-air intercooling system.

Saleen now offers its Series VI Integrated Twin-Screw supercharger with a two-stage water-to-air intercooling system for '05 Mustang GTs. The kit retails for $4,999.99 and includes all the parts and pieces to kick up your GT a few notches (not all pieces are shown).

According to Saleen, "The blower assembly contains twin screws, which push 2,300 cc of air per rotation [compared to 1,600 cc for the '04 Saleen blower]. As a result, the supercharger turns slower for equivalent boost, producing lower stress and lower air-charged temperatures. In addition, the supercharger portion of the assembly is mounted inversely, orientating the super-charger upside-down, thereby locating the outlet of the compressor above the intake ports of the heads. This allows for nice, long, straight runners, transporting the air directly into the combustion chamber with no restriction."

This system also sports an air inlet bypass, which allows air to bypass the blower at part throttle, which helps reduce heat buildup during normal driving.

Thankfully, Steve Saleen and his crew didn't forget about the rest of the Mustang population, and with that the company is now offering its blower kit for all '05 GT owners.

"With this kit we're going after the person who wants power and reliability," says John Spruill, a powertrain engineer at Saleen. "It's not a kit that is tuned on the ragged edge, but one that makes a great daily driver. Calibration is based on 91-octane fuel, and it will survive anywhere in America. It's also 50-state legal and the development is designed around meeting [Ford's] three-year/36,000-mile warranty."

Equipped with underdrive pulleys, SCT computer tune, and JDM/Kooks headers, the 4.6 Three-Valve produced 315 hp and 327 lb-ft of torque. Because the supercharger is designed around the stock pulley system, we had to put the factory pulleys back in place, thus knocking a few horsepower from the 315 total.

When testing the first Saleen S281, we were surprised to see the system developed just 3.5 psi of boost, but according to Spruill, that's all Saleen needed to reach its goal of 400 hp. "We had an expectation of output, and the efficiency of the design allows for a lot less heat," he says, "so we are able to reach the performance goal with less boost. The kit is designed to make 4 psi. It would have taken a lot more boost with older designs to accomplish that level of power."

Realizing the performance potential, we decided to do our own install on a typical GT. And the timing was right as JDM Engineering was preparing to put Saleen boost to an '05 Mustang belonging to Downs Ford Motorsport's Joe Amato.

Prior to the install, Amato's GT was upgraded with JDM/Kooks headers, a Steeda cold-air package, and underdrive pulleys. The plan was to leave the exhaust and the cold-air, but we'd have to switch back to the stock pulleys to get full boost from the blower kit. In addition, JDM went with larger injectors and its own tune, rather than using the Saleen PowerFlash computer that comes in the kit.

The GT was chassis-dyno tested to get the obligatory baseline horsepower and torque figures. It performed nicely, making 315 hp at 6,000 rpm and 327 lb-ft of torque at 4,200 rpm.

The compressor moves 2,300 cc of air per revolution. Amazingly, it sits upside-down so the air exits from the top. This allows the flow of air to transition smoothly into the runners.

The Saleen supercharger kit retails for $4,999.99 and includes everything needed to do the job. The kit does come with an informative instruction manual with plenty of illustrations, but it's not for the inexperienced mechanic. "The Saleen instructions are great," says JDM tech Shaun Lacko, who performed the work. "All the parts fit well, as described, and the instructions tell you how to do everything. There's almost nothing to figure out on your own. It even tells you what tools you'll need."

Performing the swap entails discon-necting and/or removing a few underhood items such as the battery, the wiring, the hoses, the intake manifold, the alternator, and some of the front engine dress. It is also necessary to remove the front fascia in order to install the heat exchanger. Lastly, the kit includes a Saleen PowerFlash performance computer, which is tuned for 91-octane and meets the standards for warranty and emissions.

While we realize the Saleen computer is specifically tuned for the kit and it works beautifully, Amato planned to up the boost with an aftermarket blower pulley, so he and D'Amore of JDM agreed to tune the factory computer using Superchips Custom Tuning software. "We're going to try 6-, 8-, and 10-psi pulleys, though the 10 may be a bit much for the compression," Amato says. "I'd need a new tune each time, so I wanted to tune locally instead of sending the computer back and forth to California. That's also why we installed the Cobra 39-pound injectors."

Once the labor was completed, we hit the dyno and then the track. You may recall that in our test last month, the S281 Supercharged kicked out 390 rwhp and ran 12.50, so we had both the before numbers for this GT as well as another baseline for comparison. And the kit didn't disappoint, as Amato's Three-Valve now produced 430 hp and 398 lb-ft of torque. That's a gain of roughly 120 hp and 76 lb-ft of torque with only 3.5-4 psi of boost. Imagine how much the power will increase when the boost is doubled. But extra boost will have to wait for another day, as we wanted to get to the track and lay down some numbers.

The compressor sits neatly under this uniquely designed intake system. Saleen says much of the low-end power comes from the long-runners in the intake manifold. While the inlet looks thin, it flows like gangbusters. "The shape of the 'snorkel' opening for the air tube is designed for maximum flow," says Cody White of Saleen, "and to maintain a constant volume of air as the air flows toward the rear of the engine, the housing widens and flattens out over the engine."

Going into the drag test, we knew the performance would be in the 12s. What we didn't count on was temperatures in the 90s, high humidity, and a low barometer reading. The weather was much better when we tested the last Saleen, but that's how the ball bounces. At least we can't be accused of always having killer conditions. So, with soup for weather we marched on and took Amato's Stang to the line.

The first attempt produced a non-stellar and extremely traction-limited 13.003 at 111.88 mph. Mounds of low-rpm torque caused spin off the line and crazy spin after the First-to-Second gear exchange. In fact, the GT smoked the tires all the way through Second, even though yours truly tried to pedal it. Finally, I hit Third and hooked up, but by then the run was a bust. At the 1,100-foot mark it was time to shift into Fourth, and then I crossed the stripe.

The next run, made immediately following with the engine hot, brought similar results, and the clock posted a 13.002 at 110.58 mph. The 60-foot times on those runs were 2.15 and 2.07, respectively.

We allowed the engine to cool, but we didn't use any ice or artificial cooling. We dropped tire pressure from 30 psi to 26 psi and we went back for another hit. This time I was smooth off the line with another 2.07 short-time, but I granny-shifted into Second to limit the spin. I was rewarded with a 12.80 at 112.15 mph. Sadly, the weather was getting even hotter and that was preventing us from besting the Saleen's 12.50, despite the fact that we had 40 more rwhp and were toting about with nearly 240 less pounds of baggage.

We had one last trick up our sleeves and that was to install a set of drag radial tires. With the potential for better traction, I was more aggressive in my launch technique. I got after it off the line (3,800-rpm launch with slight clutch slip) and the 60-foot dropped to 1.93 seconds. I powershifted Second--it hooked--and I marched on to a 12.40 at 112.18 mph. While we thought the GT could have run in the 12.30s, the hot weather was pressing us into submission. Amato took a turn, but didn't go any quicker, so we decided to park it until more boost was added. Then we could go for the 11s, even if the weather remained hot.

But even at Saleen's preset boost level, Amato and I were impressed with the performance, especially in the lower rev range. "The throttle response is 10 times greater now," Amato says. "Just hit the throttle and it moves. What I like the most is that the power comes on instantly and it pulls through all the gears. It's nice, but I would say we could make another 40-50 hp at the wheels once we up the boost. We [Downs Ford Motorsport] plan to sell the kits stock and upgraded with a cold-air, chip, and pulley package."

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