FAST™ Fuel Injector Flow Bench

The fuel injector flow bench is a critical piece of equipment for any fuel injector or EFI system manufacturer. However, commercial benches used by most companies today are little more than fuel injectors mounted above graduated cylinders. Once turned on, fuel passes through the injectors and into the cylinders for a set time. The injector is then turned off and the liquid in the container is measured. A manual calculation is made to determine how much fuel the particular injector would flow in an hour.

Even though this time and volume based technique is the industry standard, it leaves plenty of room for potential error. The engineers at FAST™ realized the drawbacks in this method and decided to create a new, more accurate flow bench with much needed expanded capabilities. Leading the project was FAST™ Electrical Engineering Group Leader, Ron Turnpaugh.

Turnpaugh and his team of engineers were responsible for designing, building and testing the bench. From writing the software to plumbing the system, everything was done in-house from scratch. It was more expensive and time consuming than simply buying a traditional fuel injector flow bench, but it resulted in a unique piece of equipment that far exceeds anything on the market in terms of accuracy and functionality.

The biggest difference that sets the FAST™ bench apart from everything else is its ability to read information dynamically. As soon as the injectors start flowing, the computer displays the flow rate data from up to eight separate real-time flow meters.

The FAST™ bench has two main sections: the electronics and the fuel system. The electronic components are comprised primarily of a FAST™ ECU and a PC. The ECU is used to drive the injectors because it contains the same onboard calibration files used by FAST™ EFI systems. The PC collects flow information through two purpose-built data acquisition boards. Sensors attached to the fuel injectors send data to these boards. The computer then logs the fuel pressure, battery voltage and everything else that’s critical to the injector working properly. That data is displayed in real-time on the computer screen or saved into an Excel file for later use.

The fuel system on the bench includes a fuel pump, plumbing and on-board fuel cell. If the operator changes settings in order to mimic an engine being revved, the computer will immediately show that more fuel is being used. Turn it down like you’re letting off the gas and the display will show less fuel being pushed through the injector. Since the constant return system drains fluid back into the tank instead of filling up chambers, there is no limit to how long it can run. For safety reasons the flow bench doesn’t use actual fuel. Instead it uses a special non-flammable calibration fluid that has the exact same specific gravity as gasoline.

The injectors are controlled by an actual FAST™ ECU. That means every injector modified and tested by FAST™ engineers has been proven to work perfectly with a FAST™ system. So when customers orders one, they can rest assured that it will work seamlessly with their XFI™ or EZ-EFI system.

“Every company has a little different way of doing things; every company sets their peak, hold and current a little different,” explains Turnpaugh. “Our flow bench uses calibration files from our own ECU for each injector for different voltages and opening times. Since our injectors are actually tested with our equipment, when you look at the flow sheet and see an injector is rated at a specific number of pounds per hour, you know that it’s been tested on our equipment so it’s exactly accurate when used with our systems.”

The flow bench has multiple uses in the FAST™ R&D center. Turnpaugh elaborates, “It has a test mode that’s just a “go or no go” type mode. You click on a part number and the ECU knows exactly how much it should flow. Then you just turn it on and it’ll turn red or green. It’s a real quick and easy way for manufacturing to check the injectors. We’ve been using it for that because every single injector we modify in house gets tested.

“As for engineering, the bench has a mode where you can actually vary the pulse width all you want. It logs the fuel pressure, battery voltage and everything that’s critical to the injector working. It can log all everything and export it out in an Excel spreadsheet so you can work with it and do any kind of calculations you want on it. We actually made a whole line of injectors using these features to calibrate them.”

Because it contains a complete fuel system, FAST™ engineers also use the bench to test new fuel pumps. Using it in a reverse application, the fuel injectors become the static part of the equation. The engineers simply swap out different fuel pumps and watch to see how the flow numbers change at different pressures. In this way they can characterize and select different pumps in order to make sure each one will support the horsepower needed for each different FAST™ EFI kit.