UNDERSTANDING THE OEM FUEL SYSTEMIn order to plan a proper fuel system, a basic understanding of the OEM system is required. Let's get one thing straight...the Coyote fuel system is NOT an electronic returnless fuel system like the GT500. Yes, there is a Fuel Pump Driver Module (FPDM)...and yes, there is not a return line. However, fuel pump speed is NOT modulated to maintain a target fuel pressure...instead the FPDM is only used to reduce pump voltage during low load conditions...the rest of the fuel is simply "blown off" inside the fuel tank by a fuel pressure regulator. We classify this type of fuel system as mechanical returnless, since it is mechanically regulated and there is not a return line.
In order to accommodate this functionality, the OEM (driver side) pump module is configured to stuff the following components in a relatively small package:
- fuel pump (Delphi T-23)
- coarse pre-filter (to protect the fuel pump)
- fine post-filter (to protect the injectors)
- venturi transfer pump
- level sender
- fuel pressure regulator (static)
- suction tube connector
- check valve
LIMITATIONS OF THE OEM FUEL SYSTEMThe in-tank components of the Coyote Mustang were engineered to work together. Incremental upgrades such as voltage boosting the pump are generally not substantial enough to exploit the weakness of the other components. However, a substantial upgrade such as multiple upgraded fuel pumps requires high capacity filtration, and upgraded regulation with the additional functionality of manifold pressure (boost) reference, upgraded electrical system, and larger fittings and feed/return lines.
Additionally, some E85 conversions require additional E85 enhancements, such as stainless filtration media, filter loss monitoring, ethanol content monitoring, etc. ...none of which are possible with the OEM fuel system.
UPGRADING THE COYOTE FUEL SYSTEMOur high end customers use our fuel pump modules that can deliver up to 4.5 times the pump capacity of the OEM module. As you can imagine, this needs appropriate support components so the entire system can function properly. Here is a quick rundown of how we spec out a built Coyote fuel system:
Our module retains the OEM level sender and has it's own venturi jet pumps so you don't lose any functionality of the original fuel tank. However, our module can hold two or three big pumps that can deliver more fuel than any single electric external pump. Needless to say, these pumps don't leave enough room to install the rest of the necessary [upgraded] components, so they have to go outside the tank.
Unlike the OEM filter, which is inside the tank, we provide a large, external, serviceable fuel filter that can be equipped with stainless steel filter element for E85 compatibility. Additionally, placing the filter outside the tank allows pressure monitoring before the filter, which we consider necessary with E85 builds. BTW, the OEM Coyote filter is not E85 compatible.
More flow requires a larger check valve. Our check valve is simply too large to fit inside the fuel tank, so we simple install it on the end of our external filter
Engines that sip fuel at idle, but guzzle massive amounts of fuel at WOT need a larger regulator that can accurately deliver fuel throughout the entire range of fuel consumption. Additionally, most tuners prefer a "boost referenced" fuel pressure regulator for forced induction motors.
The factory electrical system is simply not sized properly to handle high current aftermarket pumps, nor does it separate the individual pumps into isolated circuits so that pumps may be properly "staged" to maximize reliability. A proper electrical upgrade is the most overlooked aspect of a high capacity fuel system.
FUEL LINES AND FITTINGS
Properly sized fuel lines are necessary to delivery the planned supply flowrate. Undersized fuel line will create increased backpressure at the fuel pumps and reduced flowrate to the injectors, resulting in excess wear on fuel pumps and reduced fuel system capacity.
ETHANOL CONTENT MONITORING
If you have a high capacity fuel system and want to monitor the ethanol content of your alcohol blended fuel, the preferred way is to intercept the RETURN line with a GM flex fuel sensor. Our built Coyote fuel systems have return line access for easy installation of this sensor. (and it's an option in our kits)