Michael Galimi
December 7, 2011

Throwing boost at a Coyote 5.0L engine has proven to be easy and effective. At press time, we counted approximately nine supercharger manufacturers offering several models, as well as a variety of turbocharger systems. Not to be forgotten are the nitrous oxide kits that give the Coyote a chemically charged kick in the pants, as well as a slew of bolt-on goodies.

Extra power is fun, but there comes a time when issues need to be addressed. At some point, many will replace a broken engine or rebuild in anticipation of more output. In either case, it's likely you will need an increased fuel supply.

The '11-'12 Mustang GT and Boss 302 utilize a returnless-style setup, meaning the fuel pump supplies fuel to the fuel rails and maintains a constant pressure without returning the unused fuel back to the tank. Some earlier systems use a regulator and a return line so the fuel circulates.

The fuel pressure regulator on the newest models is located in the OEM fuel pump hat. The previous generations of Mustangs (both return and returnless systems) use a standard fuel pressure setting of 39.15 psi--enthusiasts tend to round this number to 40 psi. That changes in the current platform, in which Ford engineers spiked fuel pressure to a base pressure of 58 psi. The high pressure changes a lot of things in the new Mustang, namely the fuel pump and fuel injector flow ratings--more on that later.

"We can do some stuff with the Copperhead PCM that we couldn't do with the Spanish Oak PCM," comments Kevin MacDonald, lead calibrator at JPC Racing. Tuners now have the ability to increase the alternator voltage to the fuel pump through the aftermarket tuning software. He continues, "We can increase the voltage output from 13.3 volts to a max of 14.5-15 volts at WOT. The extra voltage will drive the fuel pumps harder for increased output. It's much like a Kenne Bell Boost-a-Pump or MSD Programmable Fuel Pump Voltage Booster. Those two parts add a lot more voltage than we can with the ECU programming, though."

According to MacDonald, the limits of the factory fuel pump with the additional voltage tuning is somewhere in the 525 to 575-rwhp range. "We've seen a few cars make it to 560 rwhp before the system couldn't supply any additional fuel flow," comments MacDonald. He said a few factors come into play. Turbos tend to get away with slightly more power, while the range varies on superchargers, which depend on the level of horsepower used to drive the blower. Some superchargers require more power to turn, thus the rwhp limit of the fuel pump is less.

Adding a voltage controller like the aforementioned MSD or Kenne Bell unit helps increase the power potential, but those have limits too. The fuel pump's capacity, according to MacDonald, can be seen in the datalog during a dyno pull. As it nears its limit, the fuel trims in the tune will start to add fuel, the PCM will peg the fuel injector duty cycle, and the O2 sensors show the engine is starting to lean out.

There are few quick fixes that can help, such as resorting to larger fuel injectors, but MacDonald cautions that this is a band-aid. The larger injectors will cause a drop in fuel pressure but still supply a little more fuel. He cautions that running your Mustang on the edge has its consequences. "If the car was tuned in the hot weather and the fuel system is on the edge, then there will be some problems when the weather cools off and more fuel is needed," he noted.

MacDonald also noted another serious issue. There will be problems as time goes by and fuel filters clog and/or fuel pumps start to wear out. The slightly less fuel volume caused by either of those scenarios could lead to catastrophic failure, seemingly out of the blue--one day the car is screaming with ample fuel, but the next track outing results in a lean condition.

Last year we saw some shops compensate by switching to an '05-'10 Mustang fuel tank in order to run an aftermarket return-style fuel pump "drop-in" hat for the Three-Valve engines. Swapping tanks was a temporary fix until fuel hats for the new fuel tanks could be designed, tested, and manufactured.

JPC collaborated with CP-E to bring billet-style triple fuel pump hats to the marketplace. The two companies took it one step further by making it a return-style fuel system. Moving to a return-style system is the traditional way to provide fuel to an engine. It differs from the factory setup based on its name--it returns unused fuel back to the tank via an adjustable fuel pressure regulator. JPC's Justin Burcham tells us this is the system he recommends for anything over 600 rwhp, a number that is easily attainable with a modified Coyote 5.0L.

According to MacDonald, one of the biggest reasons to move away from the factory returnless fuel system setup is due to the two-speed mechanical duty cycle. The '11-'12 Mustang fuel pump operates in two speeds, one for idle and another when the engine is under load. The Copperhead PCM won't run three pumps with the two-speed mechanical returnless system. The JPC kit comes with three relays that activate the pumps at key-on and run the same speed 100 percent of the time rather than varying speeds like the factory fuel pump. It also requires the tuner to go in and turn off some codes since the PCM will be looking for the factory fuel pump, which has been completely removed.

The billet hat, dubbed TopHat, utilizes three Walbro GSS342 fuel pumps, and when rated at 40 psi, each pump flows 255 lph. Most fuel injector and fuel pump ratings are done at 40 psi, so be careful when trying to size the injectors and fuel pump in this application. Also, take into consideration that most fuel pumps are also rated at 13.5 volts.

MacDonald contacted Kelly Christians, a Walbro representative at TI Automotive and he informed us that the fuel pumps are only rated in 10 psi increments at both 13.5 volts and 12 volts. After a few discussions with Walbro engineers, Christians said the company estimates the GSS342 to flow 257.38 lph at 60 psi and 14.5 volts. Each pump could flow a bit more since the system is run at 58 psi, remember as the pressure goes up the volume goes down. Utilizing three pumps and taking into account the fuel lines and bends, the JPC kit will support more than 1,000 rwhp--with 1?2-inch fuel rails. JPC includes all lines and fittings, relays, MagnaFuel fuel pressure regulator, and MagnaFuel 25-micron fuel filter to go along with the TopHat and Walbro pumps.

Our test car was one that was in desperate need of more fuel. It's an '11 GT with a JPC Racing single-turbo system. JPC and RGR Engines added Manley steel rods and custom Ross pistons, but kept the top-half of the engine stock. A set of stiffer valvesprings was added to help control the valves when the boost goes north of 10 psi. The turbo car is the epitome of a sleeper as it made 615 rwhp and has been known to take down street bikes and some of the area's quicker cars. It's quiet--you don't even hear the engine at idle thanks to the factory mufflers and turbo kit.

The fuel system was holding the JPC gang back, and Clinton Smith was the first customer to order the return-style setup. The plan was to add the JPC kit and Injector Dynamics 725 fuel injectors. The injectors aren't nicknamed in pound-per-hour flow rates because of the varying fuel pressures in different applications. MacDonald and Burcham spec'd out the 725s based on several factors leading up to the 900-1,000ûrwhp potential of the vehicle in extremely high boost applications.

As a side note, the JPC system can be run with a 1:1 fuel pressure spike under boost thanks to the MagnaFuel fuel pressure regulator having the vacuum line provisions. MacDonald says this will make the car run lean at idle when the engine is pulling vacuum, bringing the 58 psi setting down below that level since it is set at 58 at zero vacuum. The engine will run rich under boost because at 10 psi the fuel pressure will be 68 and at 15 psi it goes to 73, and so on. The PCM will need to get retuned if the 1:1 fuel pressure spike is utilized. The other method is not to run the 1:1 pressure and rely on the PCM fuel tables to handle the extra fuel volume. In fact, with this method the only modification needed to the PCM is turning off some sensors that will be looking for the fuel pump.

To test the system, we asked the JPC crew to pick a decent boost setting for the Precision 76mm HPS turbocharger that comes standard in the kit. We already know that with just 10.5 psi of boost, the engine cranked out 615 rwhp through the MT-82 Getrag manual box and McLeod dual-disc clutch. One note, the car runs on VP MS109 fuel, which according to MacDonald, does require a little more volume than other fuels due to it being oxygenated.

The factory fuel pump with increased voltage could barely keep up with the 615 rwhp. JPC added the TopHat and made one click on the boost controller, essentially bringing the boost to 15 psi. As the chassis dyno stopped spinning, the computer displayed the results--832 rwhp and 790 ft-lb of torque. The air/fuel ratio remained rock-solid at 11.0:1, and the injector duty cycles were consistent without struggling to keep up with the boost.

For the supercharged crowd, the TopHat triple pump and JPC fuel system were installed in the shop's Paxton supercharged test car. It features a RGR-built 5.0L, CNC-ported heads from JPC, and custom JPC cams. The Novi 2200 was spun to 16.5 psi of boost, and the result was an impressive 847 rwhp through a Tremec six-speed and utilizing MS109 fuel.

Right now 832 rwhp is plenty of fun, but MacDonald says they will be upping the ante with the turbocharged 5.0L ride once the new billet fuel rails are in production. He estimates that 950 rwhp is possible once the Precision turbo is turned up to 20 psi.

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