PT Cruiser Supplemental Fuel System
The PT Fueler tm is a supplemental pump and precision fuel pressure regulator designed to solve the driveability problems of the Dodge PT Cruiser after the installation of a Whipple Charger. The PT Fueler tm eliminates the lean surge problem inherent on supercharged vehicles that utilize a speed/density fuel calculation.
Additionally, the PT Fueler tm, by making better use of the port injectors (and less dependent on the additional injector) greatly improves fuel economy and power!
If you are unhappy with your supercharged PT Cruiser, this product is for you!
OPERATIONAL DESCRIPTION OF STOCK PT CRUISER FUEL DELIVERY SYSTEM
The fuel system uses a nonadjustable pressure regulator that maintains fuel system pressure at approximately 400 +/- 34 kPa (58 +/-5 psi). The spring pushes down on the diaphragm and closes off the fuel return port. System fuel pressure reflects the amount of fuel pressure required to open the return port.
The pressure regulator is a mechanical device and is NOT controlled by the PCM or engine vacuum.
OPERATIONAL DESCRIPTION OF PT CRUISER FUEL DELIVERY SYSTEM AFTER INSTALLATION OF PT FUELER tm
As you can see from the above description the operation of the original PT Cruiser fuel system is designed to deliver a steady fuel pressure of 58 psi +/-5 psi. That means your PT Cruiser could run with a fuel pressure as low as 53 psi and as high and 63 psi. The PCM uses the oxygen sensor to correct the air fuel ratio for varying steady state fuel pressures. After installation of the precision SX fuel pressure regulator and booster pump the fuel pressure will track manifold pressure. With the precision SX regulator idle fuel pressure can be set precisely at 60 psi (or any other pressure above the factory setting for that matter). Also if the SX regulator is connected to a source of engine manifold pressure (which we recommend) fuel pressure will track manifold pressure. At low manifold pressures fuel pressure will be lower. At high manifold pressures fuel pressure will be higher.
The SX regulator has been set for 70 psi at the factory with no engine vacuum source connected to it. This would be your new steady state fuel pressure pressure if no source of engine manifold pressure were connected to the regulator. However when connected to engine manifold pressure the SX regulator will track manifold pressure in a linear fashion. Each inch of mercury equals 1/2 psi. At 20 in of Hg of engine vacuum the static fuel pressure will be reduced by 10 psi, hence the 60 psi at hot idle. If no supercharger were attached to the engine fuel pressure would track manifold pressure from 60 psi at idle to 70 psi at W.O.T. (wide open throttle). With a supercharger attached to the engine each pound of boost will result in a one pound increase of fuel pressure over the W.O.T. of 70 psi. At 5 pounds of boost pressure you should see 75 psi of fuel pressure provided the fuel pumps and fuel filter are OK.
It is desirable to use this system with the PT Cruiser and the Whipple Charger because the PT Cruiser uses a speed/density system to control the fuel delivery. Unlike a mass air flow system the speed/density system does not recognize the increase in air flow and hence tends to lean out. With the SX regulator and fuel pump indexed to engine manifold pressure the fuel injectors automatically deliver more fuel as needed. It is also more desirable to inject the extra fuel the engine needs with the Whipple Supercharger through the stock port injectors then it is through an auxiliary injector. Also because the port fuel injectors are now delivering more fuel while in a boosted mode less fuel needs to be injected through the auxiliary injector. Hence the auxiliary injector should be downsized or the Whipple computer recalibrated for the higher fuel pressures seen while in boost. You must change the Whipple auxiliary injector to a nominal 24 lb/hr. saturated type (Bosch #0280150947 typical). You can purchase a new auxiliary injector direct from BlowerWorks if you so desire.