Engineers at FAST™ give you comprehensive answers to the most popular questions about the EZ-EFI® Self-Tuning Fuel Injection System.
1. What type of ignition systems are compatible with the EZ-EFI®?
Since the EZ-EFI® is a fuel-only system, what ever you have already or would use on a carbureted setup will work. With that being said, the EZ-EFI® needs a very stable/clean TACH/RPM signal. For the best possible performance and elimination of noise issues, we suggest an aftermarket style ignition box. For example; MSD or Accel or any of the aftermarket CD ignition boxes that provide a good TACH output signal. The EZ-EFI® system does come with a Tach Adaptor to allow you get a TACH signal off of the negative terminal of the ignition coil or the TACH terminal of an HEI distributor. Due to that fact that this inductive signal is very noisy and varies with RPM, plug gap, cylinder pressure and so forth, sometimes the Tach Adaptor cannot maintain a clean enough signal for the EZ-EFI® to perform optimally.
2. Is there a special type of intake manifold I have to use for the EZ-EFI® system?
No. Any manifold you have used with a 4 barrel carburetor will work with this system. It has been tested with dual and single plane intakes. As with carburetors, using adaptor plates to adaptor a 4 barrel to 2 barrel is not recommended due to poor air and fuel distribution.
3. Will the EZ-EFI® work with E-85 fuel?
At present, the EZ-EFI® is configured to work with gasoline only. An upgrade to work with alternative fuels may be available in the future.
4. Can I use nitrous oxide with the EZ-EFI® system?
No. We do not recommend it. The reason being is that this system is self-learning and corrects the air fuel ratio in real-time. In your handheld you set a full throttle air/fuel ratio like 12.8 for example. The computer adds or subtracts fuel to keep it at that ratio. If you add nitrous to the engine and it is jetted to something like 11.5 air/fuel ratio, the computer will pull fuel out to keep the motor at the wide-open throttle air/fuel ratio (12.8) you set. Now, you could damage your motor from running too lean of an air/fuel ratio.
5. Can I use a turbo or supercharger with the EZ-EFI®?
No. The MAP sensor and tables in the firmware are only rated and scaled to 1 bar for normally aspirated applications.
6. What fuel pressure should I run with my motor? How do I set my fuel pressure?
The recommended setting is 43psi. This setting has been good for all applications with the exception of higher horsepower engines. You want to run the lowest fuel pressure you can and still have enough fuel at full throttle. This ensures the best idle quality. To ensure you have enough fuel at full throttle, you can watch the Injector Duty percentage on the Live Data screen and note if it goes over 90% at wide-open throttle throughout the run. You can also just do a full-throttle run and if the Injector Duty percentage ever reaches 100%, the EZ-EFI® will show an error code that you’ll see on the hand held. To remedy this, raise your fuel pressure 10psi, then go back through the Setup Wizard to change your fuel pressure settings in the ECU.
There are two ways to set your fuel pressure on a vacuum-referenced regulated system. The first method involves setting it with the motor running by unplugging the vacuum line from the regulator and plugging the line to the motor. Now, you adjust the regulator until the pressure reading on the gauge is at the pressure you want and then reconnect the vacuum line. The second method involves setting it with the motor off, but the power on. To manually keep the pump running while setting the fuel pressure, locate in the EZ-EFI® wiring harness, the green wire labeled “Fuel Pump Relay” or the green wire in the “Fuel Pump Controller” connector. These are both connected to the ECU’s fuel pump control. One of them should be going to a fuel pump relay (either your own or the one built into the relay harness in the optional EZ-EFI® Fuel Pump kit). Ground whichever of those two wires is not connected.
7. Are there any limitations to camshaft selection with the EZ EFI®?
It is recommended that a camshaft is selected that will provided at least 8" of vacuum at idle.
8. What is the average installation and set-up time for someone with moderate automotive experience?
Installation of the EZ-EFI® system, minus installing a return line and welding the O2 bung in, should average 3 - 4 hours.
9. How many cfm does the throttle body flow?
The throttle body flows 1000cfm. This is more than a carburetor with the same bore size due the fact that there are no restrictive components inside the bore.
10. What size are the injectors used in the EZ-EFI® throttle body?
The EZ-EFI® throttle body incorporates 4 x 88lb/hr at 60psi – high impedance injectors. These are a custom modified in-house fuel injector currently only available from FAST™.
Note: The drivers used in the EZ-EFI® ECU are only compatible with HIGH impedance injectors.
11. What type of distributor should I use?
Since EZ-EFI® doesn’t control spark, you can use whatever distributor you would normally use on a carbureted engine. We do suggest a good aftermarket CD ignition for best results.
12. Can the EZ-EFI® be used on a race car, or is it for street only?
Subject to the horsepower limitations described below, the EZ-EFI® is perfectly suitable for most street/strip applications.
13. Why does my TPS always read “2” on the handheld?
The “2” you are seeing is most likely the small page number displayed in the lower right hand corner of the screen. The TPS value is displayed in large digits above the “TPS%” text.
14. How much horsepower does the system really support?
The single throttle body system can support up to 600hp with the fuel pressure set to 60psi. The dual quad system can support 1200hp with the fuel pressure set to 60psi. An updated fuel system is required for this horsepower level.
15. Why doesn’t the handheld / ECU remember my fuel pressure setting?
The Setup Wizard uses fuel pressure to perform some calculations related to fuel flow rates. The results are what actually get written to the ECU. Not fuel pressure itself. So anytime you run through the setup wizard, it will display the same default fuel pressure to start. This is not an indication of a problem. The ECU does retain the fuel flow information.
16. Will it work on a 6-cylinder or 4-cylinder?
Yes. One of the main options in the handheld setup Wizard addresses number of cylinders in the engine.
17. Does the EZ-EFI® keep all the information it has learned even if I have to disconnect my battery?
Yes. Every time the ignition switch is turned off, the EZ-EFI® computer saves everything that has changed to non-volatile memory. It’s kind of like the hard drive in your computer. It’s saved there until the next time is gets saved over.
18. How tall is the throttle body compared to my carburetor?
The FAST™ 4150 Throttle Body is the exact same height as any standard 4150-style piece.
19. I am having trouble with the car idling very rich and unstable. What can I do?
This is almost always noise caused by improper installation. You can verify it by looking at the Live Data screen that shows TPS. Without touching the throttle it should show 0 %. Now, when the car is started and idling, it should still show 0% and not be moving around. If it is moving, that is noise and the EZ-EFI® computer thinks you are pressing the throttle and it in-turn is squirting fuel on every noise pulse. You can adjust the fuel adjustment fully negative and the problem usually improves (fully positive it will probably get much worse).
This is typical of noise related problems caused by an improperly installed wiring harness. The remedy is to make sure that the battery positive and negative wires of the harness are connected directly to the battery. Nothing can be spliced into them on the way to the battery. Ensure that your ignition box, if you are using one, is no closer that 18" of the EZ-EFI® ECU if possible. Ensure that the ignition (switched 12-volt PINK) wire is connected to a clean spot on the fuse block and not shared with anything on the way. If you connect your handheld to power via the cigarette lighter outlet, make sure the outlet is in good clean shape and not corroded or rusty.
20. What type of air cleaner do I use?
You can use any standard or aftermarket air cleaner you would use on a carbureted application to work with the EZ-EFI® throttle body. The dimensions and mounting hardware are the same as standard Holley 4150 style carburetor.
21. How do I hook up a Chevy, Dodge or Ford transmission kick-down linkage?
This requires a Demon-style cable bracket. As luck would have it, drivetrain experts at TCI® made a slight revision to their Holley-style bracket to work with the Demons as well. In order to connect a TV cable from a GM 700R4 or a 2004R to the EZ-EFI® Throttle Body, the following TCI® parts are required:
#376705 Cable Bracket
#376715 Geometry Corrector Bracket
#376800 Universal 700R4 TV Cable
As far as connecting a TV or kick-down cable to the Ford and Chrysler applications, Lokar is pretty much the only source.
22. When will the Dual Quad EZ-EFI® and Inglese™ EZ-EFI® systems be available?
Both are in stock and available now. Call our toll free EFI HELP™ line at 1-877-EFI-TEKK (1-877-334-8355) for more information, or simply go to the
FAST™ or
Inglese™ websites.
EZ-EFI® Frequently Asked Questions 
Linear Mode
