Fuel Injector Flow Bench
Addition to Existing Dynamometer Cart
Michael Galli, Kalee Gurschick, Andrew Gwarjanski, Lucas Farrar, David Raymond, Jakob Low
2012
Contents
Concept 1
Fabrication 2
Wiring 3
Theory 4
Testing Procedure 5
Sample Data 6
Parts List and Drawings 8
Concept
As the Mech Lab portion of the senior design class, the CSC 2012 Team designed and fabricated a fuel injector flow bench. The flow bench will provide a rate of fuel sent to the engine by the injectors. This value is critical in properly setting the engine controls. The rate is dependent on the pressure set by the fuel pump and the injector pulse width. To convert the engine to run with higher contents of ethanol, the pressure must be increased due to higher fuel density and lower energy produced per unit volume. The injectors may not be able to perform correctly under pressures higher than stock. The injector pulses open and close to send small amounts of fuel at a time to the engine. The pulse width defines the time the injector is open and is a key input in the engine control unit.
The schematic of the experimental set up is depicted in Figure 1. The fuel tank, filter, pump, and regulator are all mounted on the existing dynamometer cart. The line is then connected to a pressure gage that can connect to the apparatus containing the fuel injectors. These injectors will sit directly above the graduated cylinders used for measuring.
Figure 1: Concept Sketch of Fuel Injector Flow Bench
Fabrication
The graduated cylinders will be housed on a stainless steel base, shown in Figure 2 below. This base will also hold the injectors during testing. Each piece is fabricated out of 16 gauge stainless steel. It was cut using the sheer in AMC building. Pieces needing to be bent were also done using equipment in the AMC building. A dimensional drawing for each piece can be found in Appendix C. There was an existing bracket holding a fuel pump, and regulator on the cart. A similar piece was fabricated out 1” square steel tubing, with our fuel pump and fuel regulator mounted to it. This piece is removable and is attached with the existing hardware on the cart. This piece is shown in Figure 3. A new tank for mineral spirits, the injector test fluid, was also attached to the cart. The tank is mounted with a bracket made of 1” square steel tubing shown in Figure 4.
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Wiring
There was already a switch providing power to the bench included on the control panel. We needed to distribute this power to Microsquirt, the fuel injectors, and the fuel pump. Since an existing fuel pump was removed and replaced, as described above, the existing wiring on the cart was used. The fourth switch on the control panel powers the fuel pump. The fifth switch sends power to the Microsquirt controller and to the injectors on the fuel rail. From Microsquirt, pins 9 and 10 each connect to an individual fuel injector. These wires send a pulse signal to the injectors based on the test mode in the Microsquirt program. To protect the circuit, fuses were added, as shown in the wiring diagram in Figure 5 below. Ground wires were connected from the Microsquirt unit and the fuel pump to the frame of the cart.
Figure 5: Wiring Diagram
Theory
The maximum volume of fuel sent to a properly working engine is based on the engine output, the specific fuel consumption, and the duty cycle. The relationship is shown in the equation below.
Flow Rate=maxengine output∙specific fuel consumption∙maxduty cycle Equation 1
The flow rate is in pounds per hour. The maximum engine output is 80 horsepower for the 2007 Yamaha Phazer. The specific fuel consumption for this type of engine is 0.55 lb/hp/hr. The duty cycle is a percentage of how long the injector is open. The injectors should not operate above 80%. Combining these values gives the maximum flow rate shown below in Equation 2.
Flow Rate=80 hp.55lbhphr0.80=35.2 lb/hr Equation 2
The optimal flow rate for gasoline at stock conditions for the Yamaha Phazer is 35.2 lb/hr. Equation 1 can be applied to any engine.
For high impedance injectors, the period is a constant 66ms. The open time is the set pulse width and the close time varies to achieve the specified period. There for the trial time only a function the number of squirts as shown below.
t=(P)N1000mss Equation 3
Where:
t is trial time in seconds
P is the period (open time + close time), here 66ms
N is the set number is squirts
Using the time of the trial and density of the test fluid, the volume can be converted to a flow rate.
Testing Procedure
The injectors are pressed into the adaptors and the connectors are attached to the injectors. A graduated cylinder is placed under each injector to catch the mineral spirits test fluid after it exits the injector. Mineral spirits is added to the 1 gallon fuel cell. The empty graduated cylinders are placed on the scale and a weight is recorded.
The main power disconnect is switched to the “on” position and the ignition key is turned on. The fuel pump is turned on by simply flipping the switch on the control panel labeled “fuel pump”. The red light above the switch is on indicating there is power at the switch. The lines leading from the fuel cell to the injectors are now pressurized. A computer with TunerStudio software is attached to the auxiliary hook-up on the Microsquirt wiring harness. The program is opened using the computer. The Microsquirt switch on the control panel is flipped to the on position. This sends power to the Microsquirt engine controller and also to the injectors themselves. The gauges on TunerStudio are now interactive. The Tools menu is clicked and Injector Test Mode is selected. A new window is opened. On the drop-down menu, “Test Mode” is selected and the desired values for pulse width, close time, and number of squirts are set. On the bottom of the window the button labeled “Burn” is selected to save these parameters. On the drop down menu, “Repeat Test” is selected in order to begin the test.
After the injectors have gone through the desired cycle and the Test Mode has stopped, the graduated cylinders are removed and set on a level surface in order to get a volume reading. The graduated cylinders containing the test fluid placed are placed on a scale to get a mass reading. This value is subtracted from the empty cylinder weight and multiplied by the density of the test fluid to calculate a volume. The second volume reading is compared to the initial reading directly from the cylinder. The cylinders are emptied into the fuel cell and placed back under the injectors. A new pulse width is entered into the Injector Test Mode window and “Repeat Test” is selected on the drop down menu to run a new test. The remaining trials are repeated in the same manner described above until all desired pulse widths have been tested.
Sample Data
A test was done for the 2007 Yamaha Phazer fuel injectors. The value for pulse width ranged from 5 ms to 50 ms in steps of 5 ms. The number squirts was set to 250. These are high impedance injectors so the close time was calculated to ensure a constant period of 66 ms. The data from this trial is shown below in Table 2. The values used for unit conversion are found in Table 1.
Table 1: Unit Conversion Values
Density of Mineral Spirits [10] / 6.531 / lb/galWeight Conversion / 2.2046 / lb/kg
Volume Conversion / 0.0002642 / gal/mL
Table 2: Trial Data
Pulse Width(ms) / Close Time (ms) / Trial Time (s) / Trial Time (hr) / A (mL) / B (mL) / Sum (mL) / Volume (gal) / Weight (lb) / Measured Mass (kg) / Measured Weight (kg) / Average Weight (lb) / Flow rate (lb/hr)
5 / 61 / 16.5 / 0.00458 / 6 / 6 / 12 / 0.0032 / 0.0207 / 0.009 / 0.0198 / 0.0203 / 4.423
10 / 56 / 16.5 / 0.00458 / 13 / 13 / 26 / 0.0069 / 0.0449 / 0.019 / 0.0419 / 0.0434 / 9.464
15 / 51 / 16.5 / 0.00458 / 19.5 / 20 / 39.5 / 0.0104 / 0.0682 / 0.029 / 0.0639 / 0.0660 / 14.410
20 / 46 / 16.5 / 0.00458 / 26 / 26 / 52 / 0.0137 / 0.0897 / 0.039 / 0.0860 / 0.0879 / 19.168
25 / 41 / 16.5 / 0.00458 / 32 / 32 / 64 / 0.0169 / 0.1104 / 0.048 / 0.1058 / 0.1081 / 23.591
30 / 36 / 16.5 / 0.00458 / 39 / 39.5 / 78.5 / 0.0207 / 0.1355 / 0.06 / 0.1323 / 0.1339 / 29.207
35 / 31 / 16.5 / 0.00458 / 46 / 46 / 92 / 0.0243 / 0.1587 / 0.071 / 0.1565 / 0.1576 / 34.393
40 / 26 / 16.5 / 0.00458 / 52 / 52 / 104 / 0.0275 / 0.1795 / 0.081 / 0.1786 / 0.1790 / 39.057
Figure 6: Fuel Injector Flow Rate as a function of Pulse Width
The data was plotted and fitted with a linear curve. The equation of this line is used to determine the maximum pulse width. This is shown below in Equation 5.
Flow Rate=0.9703∙Pulsewidth Equation 5
Pulsewidth=35.2 lb/hr0.9703lb/hrms→Pulse width=36.27ms
The resulting maximum pulse width for the 2007 Yamaha Phazer fuel injectors is 36.27 milliseconds.
Parts List and Drawings
Part Number / Description / Supplier / Quantity555-100911 / Braided Steel Hose 6 AN / Jegs / 12 ft
555-100021 / 90o Female 6 AN to Hose Fitting / Jegs/Summit Racing / 10
361-804606 / 45o Female 6 AN to Hose Fitting / Jegs / 1
180° Female 6 AN to Hose Fitting / Jegs / 1
361-925106 / T-Fitting 6 AN Female Swivel on Branch / Jegs / 1
555-100242 / Flare Bulkhead Fitting 6 AN Straight / Jegs / 2
555-100333 / 6 AN Female to 3/8” Male NPT / Jegs / 2
555-100222 / 8 AN Female to 6 AN Male Reducer / Jegs / 2
361-992908 / 8 AN Fitting Cap / Jegs / 1
361-300106 / Female 6 AN to Hose Fitting Straight / Jegs / 2
361-840106 / Male 6 AN to Hose Straight Adapter / Jegs / 3
023-FBM2978 / 90° Female 6 AN to Female Swivel Coupler / Jegs / 2
555-100322 / Female 6 AN to Female 6 AN Adapter / Jegs / 1
JIF-31506 / Jiffy Tite 3000 Series 6 AN Quick Connect Female / Summit Racing / 1
128-3039 / Male 6 AN to 10 mm Adapter / Auto Performance Engineering / 2
400-920 / Fuel Pump Mounting Hardware / Auto Performance Engineering / 1
GSL414 / Walbro Fuel Pump / Auto Performance Engineering / 1
555-15032 / Fuel Filter / Jegs / 1
1728 / Edelbrock Fuel Pressure Regulator / Performance Parts / 1
1069-6AN / Fuel Pressure Gauge 1/8” NPT / Pegasus / 1
821-2010A / RCI Aluminum Fuel Cell / Jegs / 1
N/A / 8 mm Rivet Nuts / Fastenal / 25
N/A / Mineral Spirits / Central Storage / 1 Gal
N/A / 6061 Aluminum 1 in. hex stock / Lane Supply / 1 ft
N/A / 1 in. square stock / Lane Supply / 2 ft
N/A / 16 gauge stainless steel (3ft x 4ft) / Lane Supply / 1
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