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Mods Gone Wild
Mods for 5.4 Mod Motors
The Plan was simple-take an ordinary '05 Mustang GT and add enough power to push it past 200 mph. It sounds simple enough on the surface, but there is more to the equation than meets the eye. While 200 mph is often discussed and even advertised, the number of Mustangs that have actually cracked 200 are few and far between. Producing the power to propel a Mustang past the magical barrier is not hard, but building one to withstand the load and remain intact is another story. Striving for the double-century mark means having a motor that will stay together long enough to allow the power to be utilized in Fifth or Sixth gear.
While a top speed of 200 mph is impressive, the goal of this par-ticular buildup was to see how close we could get to 200 in the standing mile. While a mile may sound like an eternity for drag racers, the acceleration rate slows dramatically as speeds increase. A typical mid-10-second Mustang might see 125 mph in the quarter-mile, but will only increase the trap speed by another 25-27 mph in the next quarter-mile, just 20 mph in the next quarter-mile, and finally drop off to less than 20 mph in the last quarter-mile. That is, of course, assuming gearing is ideally spaced for this type of event.
When gunning for top speed, aerodynamics come into play as the aero loads work against the available horsepower to slow down the rate of acceleration. We know from experience that the '05-'06 Mustang bodies were built more for aesthetics than aerodynamics. The retro-modern look is high on the cool scale, but it's also high on the drag scale. Given similar power, an '04 Mustang will walk away from the less-aerodynamic S197 model.
This 200-mph madness came about after participating with Vortech in another standing-mile acceleration test for Road & Track magazine. The '05 Mustang was modified by way of a Vortech supercharger, a set of JBA headers, and open exhaust. Tuning with race fuel allowed sufficient boost (15-16 psi) and ignition timing (with ice water in the air-to-water intercooler) to increase the power output of the otherwise stock '05 4.6 Three-Valve motor from roughly 275 rwhp to 540. The considerable jump was amazing considering the power was achieved on a bone-stock motor, which included the significantly more fragile piston design used in the new Three-Valve motors. Apparently, Ford moved the ring lands on the '05 pistons up by 0.100 inch, thus greatly reducing the crown strength. While detonation will snap a forged piston nearly as quickly as a cast one, the added strength at least provides some peace of mind. Running roughly 540 rwhp, the Vortech supercharged Three-Valve motor pushed the '05 Mustang to 179 mph in the standing mile and eventually to a top speed of 192 mph as we were able to reach the 6,600-rpm rev limiter before shutting down (verified by the VBOX data systems used by Road & Track).
Propelling the '05 Mustang to 179 mph in the standing mile (and eventually 192 mph) required a few aero tricks, not to mention changes to the gearing in the transmission. The guys at Vortech put together one heck of a program that required burning literally gallons of midnight oil to make that Mustang a reality. It was the success of that car that prompted them to accept the invitation to a similar event put on by Motor Trend. This time, they were looking to improve their measured mile mark of 179 mph. In fact, they were hoping to reach 200, which meant, among other things, a ton more horsepower.
Being a blower company, Vortech had plenty of configurations capable of producing the required power, but what was needed was a motor. A call to Sean Hyland put the wheels in motion, as we requested a 5.4 Four-Valve. Since the original effort netted 540 rwhp with just 4.6 liters, Three-Valve heads, and a bone-stock bottom, we decided the power requirements would benefit greatly by a hike in displacement. After all, improving the power output of a supercharged motor starts by improving the power output of the normally aspirated combination. All things being equal, a larger 5.4 motor will make more power than a smaller 4.6. Since we were looking for more than just peak power, the extra torque offered by the increased displacement would also help the rate of acceleration.
Compared to the original 4.6 Three-Valve motor used previously, the 5.4 Four-Valve motor offered greater displacement, better cylinder heads and cam profiles, and the forged rotating assembly could withstand higher boost and power levels. This paved the way for a high-output supercharger that exceeded the flow capacity of the already impressive T-Trim used on the Three-Valve combination. The 5.4 supplied by Sean Hyland featured a forged reciprocating assembly stuffed into an iron 5.4 block. The forged pistons allowed us to get serious about the power production without fear of cracking a ring land.
The 5.4 was equipped with ported heads and a set of Stage 2 intake and Stage 3 exhaust cams that were designed for use with a centrifugal supercharger. We chose to run a Sullivan intake and 90mm throttle body, though the larger ports on the Sullivan intake were actually designed to match up with the larger 4V Navigator heads. The minor port mismatch probably had little effect on the power production.
Vortech specified a new reverse-rotation YSI blower capable of supporting over 1,200 hp, though we had no intention of running the motor at that power level. We were looking at making 900 hp, which would translate into roughly 750 rwhp. We liked the sound of adding a solid 200 hp to the numbers produced by the previous Three-Valve motor. This gave us 100 hp for every 10 mph needed to reach the 200-mph mark.
As luck would have it, we never got to run the car, since we ran out of time for the ambitious project (involving an engine swap, a custom transmission, and a complete suspension and brake makeover, not to mention all manner of minor modifications). While it was disheartening to have to pull the plug on the standing-mile event, the exercise gave me the opportunity to add yet another engine combination to my "Mods for Mods" series. Given the popularity of the larger 5.4 motors as potential swaps, not to mention the Lightning truck, and lucky Cobra R owners, we decided the 5.4 contingent deserved some recognition and a "Mods for Mods" series of their very own.
While we generally start off with a bone-stock motor and seek ways to improve upon the stock power output, this "Mods for 5.4 Mods" started out with something altogether more radical. This 5.4 Four-Valve motor from Sean Hyland Motorsports was anything but stock, and would serve well as a workhorse to run a number of tests. The first test involved the installation of the Vortech YSI supercharger originally intended for the top-speed shootout. Before adding the blower, the newly built 5.4 Four-Valve motor was broken in and run in normally aspirated trim. It produced 434 hp at 6,500 rpm and 387 lb-ft of torque at 5,200 rpm before the Vortech was added. I have to apologize to Vortech here as I feel that I let them down by configuring the 5.4 with nothing more than a six-rib blower drive. I was not able to locate a suitable eight-rib belt in the size required by the drive assembly and, instead of reconfiguring the drive (which required a great deal of fabrication), I went ahead and ran the motor hoping the six-rib was up to the task, at least enough to finish a couple of high-boost runs. It wasn't.
The six-rib drive system ultimately prevented us from reaching those huge power numbers, but it allowed us to see some big power numbers and even learn the effects of large-tube headers and ice water in the air-to-water intercooler. Using a custom tensioner, the six-rib serpentine system (coated with sticky track bite) provided sufficient tension to produce a repeatable boost and power curve to roughly 6,200 rpm. Beyond that, the belt slipped and the power plummeted. Equipped with the new Vortech YSI reverse-rotation blower, the 5.4 produced 843 hp and 689 lb-ft of torque at just over 15 psi. For our needs, the motor produced 799 hp at 6,100 rpm using a set of 1 5/8-inch Hooker street headers.
Suspecting the small headers might be limiting the power output, we installed a set of 1 7/8- to 2 1/8-inch race headers supplied by Accufab's John Mihovetz. Used on his old supercharged race car, the headers were large for most street applications, but since the power output had already exceeded 800 hp, we suspected the motor might benefit from additional exhaust flow. The headers were worth additional power, raising the peak power at 6,100 rpm to 823 hp, though the headers were worth as much as 35 hp at 5,600 rpm. Obviously, an 800hp motor will require something larger than your typical 1 5/8-inch street header, but good luck making a set fit in a 4V Cobra, especially one with a 5.4 engine swap.
The final modification on the list involved replacing the dyno water running through the Spearco air-to-water intercooler with ice water. The dyno water was actually hotter than ambient air by 15 degrees, so we knew additional charge cooling was available with ice water. We had planned to run ice water during the top-speed event and wanted to know if the modification was worth additional power, or was it just being used as a hedge against detonation? The ice water was run through the Spearco core using an electric pump and dedicated reservoir. Running 32-degree water through the intercooler was worth additional power, raising our peak number at 6,100 rpm to 852 hp. The gains offered by the ice water were as high as 35 hp at 5,900 rpm, so obviously it is a good idea to run ice water at the dragstrip or for a top-speed event where the transfer medium can be kept cold for the length of the full-throttle run. Naturally, this cannot be employed effectively on the street, as the ice in the water will eventually melt and heat up, lessening its effectiveness. We have more "Mods for 5.4 Mods" in store, including a Two-Valve Lightning buildup, the transformation of our current SHM motor into a Cobra R clone, and the installation of a pair of turbos. Mods gone wild indeed.
After our adventures with the 920hp Kenne Bell 4.6 motor, we suspected that this 800-plus-horsepower motor might benefit from the larger set of race headers as well. Swapping the 1 5/8-inch Hooker street headers for the 1 7/8 to 2 1/8-inch step headers supplied by AccuFab resulted in a sizable jump in power on this supercharged 5.4. Despite our trouble with the six-rib pulley system, the headers offered 35 hp at 5,600 rpm and showed consistent gains of 20-25 hp through most of the rev range. Replacing the dyno water running through the air-to-water intercooler with ice water netted an additional 30-35 hp. The lower charge temperatures had little effect on the boost supplied by the blower, but the increased air density provided an impressive power gain. The combination of the headers and ice water improved the power output of the 5.4 by as much as 55-60 hp. It's too bad the six-rib belt stopped us from successfully running the motor past 6,200 rpm. This combination would surely have exceeded 900 hp with an eight-rib or cog-belt system without changing the blower pulley to increase the boost.
In preparation for a top-speed event, Sean Hyland supplied this 5.4 Four-Valve motor specifically built for forced induction. The idea was to run the 5.4 with a Vortech YSI reverse-rotation blower supercharged at the maximum allowable boost/timing level available on 100-octane fuel. Naturally set to deliver maximum boost and flow, the YSI is capable of exceeding 1,200 hp, but our combination was designed for a top-speed event in which it would have to run on 100 octane. Thus, the boost level was kept reasonable to allow the motor to live at wide-open throttle for extended periods. Equipped with a 3.00-inch blower pulley and a 7.5-inch crank pulley, the supercharged 5.4 pumped out 843 hp and 689 lb-ft of torque. This was a considerable jump in power from the 434 hp and 387 lb-ft produced in normally aspirated trim. Unfortunately, the use of a six-rib belt presented a serious belt slippage issue that ultimately limited the effective operating range and power production of the supercharged combination.