Street Rod Fuel Injection - No Carb Diet Part 2

INJECTOR SIZE
GMPP supplies injectors with their kit, however, we swapped these out for FAST injectors. Should you anticipate a higher horsepower application, here is something to keep in mind when determining injector size. Typically you would take into consideration the cubic inches of your engine and horsepower. For small cubic-inch motors like a 305, you would probably use 19.9-lb/hr injectors; the popular 350-inch small-block with horsepower somewhere between 225 to 275 would take 21.9-lb/hr injectors; and for the next jump to 300 to 375 hp (ZZ4, LT1, and LS1) you might use 24.9-lb/hr injectors and the new LS6s, which are 405hp, use 28 lbs/hr injectors.

INSTALLATION OF ECU
The FAST XFI Electronic Fuel Injection proved to be an easy installation. The ECU was mounted inside the passenger kick panel behind the upholstery and the wiring run forward to the engine compartment with an offshoot going to the fuse panel located behind the dash on the driver side. The fuel pump is grounded in the trunk area and the positive wire comes forward to the fuse panel. However, that's the really easy part. The segment that would normally "trip" a rodder would be the laptop tune-up. The FAST system comes with C-Com XFI-version software and communication table. Installed are parameters and a guide to get you going.

While the computer is connected and online, press the F9 key to display the main dashboard. You should be able to read the following dashboard parameters with the engine not running and the ignition on:
The TPS reading at an idle should be relatively low, and should increase as you open the throttle. If it doesn't go all the way from 0 to 100 yet, that's OK.

The MAP sensor should read approximately 20 kpa once the proper calibration has been entered. For now, a reading of 88 to 105 kpa or higher is OK. The air and coolant temperature sensors should read the approximate outside temperature, assuming the engine hasn't been run for some time. Battery voltage should be at least 12 volts. Check the LEDs on the face of your new FAST XFI ECU. The power should be lit as soon as you turn on the keyed power while crank and cam will flash once until you start turning over the engine. The cam will only flash if you're using a cam input of some type. NOTE: Keep the fuel injector harness unplugged at this time.

If all the above conditions have been met, then it's time to move on to the next step. If not, you'll need to go back and check connections in your wiring harness for things such as loose connections, improper grounds, or possible faulty sensors.

Engine Displacement (CID)
This parameter is apart of the ECU's calculation to determine the amount of fuel to inject when running in Speed Density mode. Enter the engine's displacement in cubic inches. This must be entered correctly or the engine will run richer or leaner than intended.

Map Sensor (1-5 Bar)
This parameter is used to scale the readings from the MAP sensor. MAP sensors are rated by their maximum sensing range. A 1 Bar sensor can read up to one Bar of pressure (atmospheric pressure), a 2 Bar sensor can read up to two Bar of pressure and so on. Enter a number between 1 and 5 that corresponds to your MAP sensor's rating.

Number of Cylinders (2,4,6,8)
This parameter is a part of the ECU's calculation to determine the amount of fuel to inject. Enter the number of cylinders the engine has. This must be entered correctly or the engine will not run correctly, if at all in some cases.

Injector Flow Rate (lb/hr)
This parameter is apart of the ECU's calculation to determine the amount of fuel to inject when running in Speed Density mode. It is also used for fuel flow and mileage calculations. Enter the flow rate of the injectors in lb/hr. This must be entered correctly or the engine will run richer or leaner than intended. Keep in mind that fuel pressure affects flow rate. When manufacturers rate injectors, it is at a certain fuel pressure. Injectors from FAST are rated at 45 psi. Firing Order
Enter the firing order of the engine. This information is used to correctly label the individual cylinder corrections setup screen. Changing this setting will NOT change the order in which the injectors actually fire. That is a function of the wiring from the ECU to the injectors. The injector wiring harness can be swapped out or modified if the system is installed on a different motor with a different firing order.

Sensor Calibration
This section will take you through "calibrating" your throttle position sensor and manifold absolute pressure sensor to give you full resolution for better engine control and optimum tuning results.

TPS Calibration
The throttle position sensor sends a varying 0-5-volt signal to the ECU as the throttle is moved. The TPS Calibration table tells the ECU how to relate the voltage level with throttle opening. A TPS calibration is typically linear.

MAP Calibration
The MAP sensor sends a varying 0-5-volt signal to the ECU based on the vacuum/pressure the sensor is exposed to. The MAP Calibration table tells the ECU how to relate the voltage level with vacuum/pressure. MAP sensors typically have linear calibrations. Information on MAP sensor calibration should be available from the sensor's manufacturer, which in this case is GMPP.

Start Your Engine
The last step in this process is to plug in your fuel injector harness. Your engine is now ready to be started. If your vehicle is running and you would like to check your system, one of the best tools you could have is an infrared heat gun to check the exhaust temperature of each header tube. If all injectors are good, they should be within 35 degrees of each other at idle. They are normally between 225 and 300 degrees. For example, if you have one or more with a higher temp, you usually have a lean injector or one that is dripping. (Snap-On Infrared Temperature Measuring Instrument RTEMP6PB.)

Camshaft
Future plans call for one more modification and that is the changing out of the carbureted camshaft for a COMP Cams XFI 'shaft that should really bring the car to life, enhancing performance, economy, and driva-bility. A carbureted engine requires a strong signal or airflow at the carburetor booster to draw the correct fuel into the engine. Since that excess flow is not required in a fuel-injected engine, overlap and low lift flow requirements are not as critical. Therefore, COMP's engineers designed the new XFI series with wider lobe separations and higher lift.

In Conclusion
The data presented is an overview and is meant to get you going through the process but nothing--and that is to be repeated, nothing--is meant to replace reading the instructions from FAST and following along with their proven procedures.

It took 12 hours from start to finish converting the GMPP 383 crate motor from a carbureted engine to a Ram Jet 383. We spent about 40 miles driving time while Dave of FAST spent it observing the laptop computer and making final adjustments. Once this was done, we parked the roadster and the next morning made one last adjustment to the Cold Start (IAC) procedure and it was off on a 1,952-mile drive back to the West Coast from Memphis, Tennessee.

The car performed flawlessly and the high temps, humidity, and long days didn't affect the engines running (although I was a bit warn out) and it was noted that the car went from 14-15 mph to 16-17 mph. Well, there you have it. Going from carburetion to fuel injection.

(Editor's Note: To make sure I paid attention: A special "thank you" must be given to the following who made this project come together in the span of five days! A big "at-a-boy" goes to Bill Martens (special programs manager for GMPP) and Ken Casey Jr. (performance parts specialist for Burt Chevrolet) for helping us with the technical "wherefores" of the GMPP Ram Jet system. Additional accolades go to Dave Henninger and Tony Duncan (both project engineers for FAST), Mike Bond and David Page (both R&D for COMP Cams), and a special "at-a-girl" to Hailey Naylor (marketing coordinator for COMP Cams) for maintaining a steady stream of "answers," parts, donuts, and traffic coordination throughout the entire project! I would also be remiss if I didn't thank Mark Campbell of Street & Performance, Rick Craze of Lokar Performance Products, and Gary Clausen of Pure Choice for stopping during the midst of the NSRA Street Rod Nationals to make this story possible in the span of five days.)