| As a continuation of the buildup process of my personal AshsZ2 ZTT and to satisfy the electrical component requirements of driving two fuel pumps in the most efficient manner, I have developed a new fuel pump control unit. It was discovered about two years ago during a tuning trip I made up to the PA/DE area while working on Dee Ridgeway's "DEVIL'S Z" that when running two fuel pumps on the OEM fuel pump control unit, the control unit's power MOSFET would burn up. After some research it was found that this component is only capable of handling a 30-amp continuous load. Two fuel pumps will easily pull more than this even at moderate loads. Many others have also come to find this problem - resulting in a strong odor of burnt electronics and a Z parked on the side of the road with hazards flashing. :-/ Another issue with a dual pump setup is a phenomena known as fuel pressure regulator overrun. This condition arises from the simple fact that the regulator is simply a variable valve which controls the fuel pressure by restricting the flow of fuel back to the fuel tank (via the return line). The regulator has a spring-loaded diaphragm that controls the valve pintle and this diaphragm is connected to the intake manifold. The purpose of the regulator's variable fuel pressure is to maintain a steady pressure difference between the fuel pressure and the manifold pressure such that for each millisecond of injector pulsewidth, regardless of manifold pressure/vacuum, will always deliver the same amount of fuel. Its target pressure is 3bar (44.1psi), so if the manifold is at 16psi of boost, the regulator will bump the fuel pressure up to 60psi (44.1 + 16) to maintain a 44psi pressure differential. If one opts to drive the pumps at full speed all the time (by way of the method of placing a relay to power the pumps at full voltage), or even using dual OEM fuel pump controllers, regulator overrun will occur which results in the inability of the system to maintain proper fuel pressure at low-load conditions - this causes the fuel pressure to be excessive in thiese conditions. This can be overcome by purchasing an aftermarket fuel pressure regulator that is designed with a larger valve body capable of higher bypass volumes, however, you will be running the pumps at duties exceeding what is required which will ultimately lead to a shorter lifespan of the pumps. You are also looking at the expense of the larger regulator and installation labor to top that. The OEM regulator is only capable of bypassing a limited amount of fuel - less than that of an aftermarket unit. Upon installation of two fuel pumps, even with them running at low speed (by OEM fuel controller), they deliver a quantity of fuel greater than the regulator can bypass, which results in higher than normal fuel pressure at manifold pressure conditions below ~0psi. Because of this, the new fuel pump controller has been equipped with user-configurable pump duty settings for each of the speed settings (with the exception of full speed, which is 100% duty in all cases). This adjustability will allow the user to lower the pump duty in low speed operation to prevent regulator overrun and lessen the load on the pumps themselves. The new Dual Fuel Pump Control Module has several useful features:
- Electrical current handling capability up to 120 amps (this is over-engineered, but the itent is to spread the load across multiple power transistors to increase robustness of the circuit).
- Electrical current overload protection.
- User-configurable pump duty speeds. This will allow the user to dial in the optimal pump duty at the various speeds which the ECU runs the pump at.
- The unit has an auto-sensing configuration circuit which will automatically detect if your vehicle is equipped with a 2-speed(NA) setup or a 3-speed(TT) setup.
- One of the best features is that this unit is a direct bolt-in replacement for the OEM unit, constructed using the OEM harness connector and designed for OEM mounting fasteners.
- For those who have performed an NA to TT conversion, whose vehicles lack the second control line from the ECU to the FPC for 3-speed operation, we have incorporated a short pigtail connection in the design which will allow you to run the additional control line up to your ECU to take advantage of the 3-speed control in the twinturbo ECU (this will require you to obtain a twinturbo ECU for your conversion to take advantage of this).
- The unit has both a board-level LED to indicate the pump duty as it switches through its various speeds and will be supplied with an external LED and harness which can be mounted in a convenient location up in the driver's line of sight.
- A 40mm cooling fan has also been incorporated to improve heat dissipation and the top cover of the board is replaced with a plexiglass cover with ports to access the on-board adjustments for speed control.
- To minimize pump noise, we have also included a base frequency adjustment to allow the user to minimize/eliminate pump harmonics. This was done to allow the controller to cater to various pump selections.
- Units will come pre-configured for optimal pump performance to eliminate initial setup times.
We will begin manufacturing of these units next week and will begin offering them as a product available through our website with on-line purchasing. Customers will have the option of an advance-core upgrade (where we send you one in advance with return of your original unit for a core refund) or as an upgrade service performed on the unit you send in to us. These units will be available for a price of $275.00.
In short time we will also be offering a complete bolt-on kit for dual Walbro 255L/Hr High-Pressure pumps into the OEM fuel pump bulkhead to simplify this aspect of the upgrade - custom machined from 6061 billet aluminum and provided with the necessary fittings.
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