Clearances inside a fuel injector are measured in ten-thousandths of an inch, and the duration they open and close is measured in milliseconds. Injectors are the last component in the system before the fuel is burned and converted to energy, so it’s important they be clean and function well.
To find out how important that is, we got in touch with David Deatsch, president of Deatschwerks (http://www.deatschwerks.com), an Oklahoma City company that provides application-specific, high-performance fuel systems solutions. Deatschwerks sells a line of fuel injectors and pumps and fuel system accessories. The company also offers dynamic fuel injector servicing.
One of the first things Deatsch pointed out was that there really is no predetermined service interval for fuel injectors, whether they’re in your racecar or your tow vehicle.
“We don’t have a real hard and fast guideline on when to get your injectors serviced because there are just so many variables,” Deatsch said. “If you’ve got 100,000 miles on your car, it’s not a bad idea to pull them and send them in, and get them serviced. It’s not something you need to do every 30,000 or 50,000 miles. It depends on how you use the car, the kind of fuel you use, etc.”
For this discussion, we’ll stick to racecars. For older street cars that have been converted to racecars, servicing the fuel injectors can provide some benefit. If there are no obvious signs of fuel delivery issues, servicing the injectors likely will afford a better idle quality, better fuel economy and perhaps a little bit better performance. But in racing, especially spec-class racing, anything you can do helps.
“We have a lot of customers who send them in every race,” Deatsch said.
“They’re sponsored drivers, and when you have a drag car or a road race car that’s tuned to the edge and you’re really pushing it, there’s not a lot of room for error. They’ve got a lot invested in their motors, so if you have a clogged injector, you can blow a motor. They do it for preventive maintenance.”
For amateur racers, Deatsch recommend servicing the injectors once a year. He said because racecars tend to sit a lot, there’s ample opportunity for varnish to develop, especially in the older pintle-style fuel injectors. Because of the way fuel sits on the tip of the injector when a car is shut off, it tends to foster varnish and clogging. And if you’ve recently begun running E85 in your racer, Deatsch said you should definitely have the injectors serviced.
“E85 really cleans the fuel system,” he noted. “It dissolves gummed up particles, rust, other types of materials that gasoline does not dissolve. So when you convert to E85, it’s going to kind of clean your fuel system, but all that gunk goes somewhere, and it can end up in the fuel injectors. It can gum them up pretty bad.”
Deatsch’s dynamic injector service includes teardown of the injectors, and cleaning them in a hot detergent with ultrasonic sound waves. They flow-test them afterward. Typically it takes one round of cleaning to get the job done, but if not, they clean them again.
“We clean them till we get all the injectors to within OE specs, 1 to 2 percent variance in flow rates,” Deatsch said, adding that they test pulse widths at 2, 4 and 8 milliseconds and at static flow. “We don’t change the flow rates of the OE injectors on a service. We just clean them till they are all balanced and matched.”
Deatsch also offers advanced injector testing, a process that includes one or both the linearity test and the battery offset test. Linearity tests pulse widths at .2- and .5-millisecond intervals from 1.2 milliseconds to 10 milliseconds, giving them 30 data points as opposed three.
“When you start getting up higher in the duty cycle ranges, the injectors don’t have enough time to rest after pulsing, and they start to go static, which means they won’t close all the way before the next injection cycle starts,” Deatsch said.
Conversely, in the low range, the injector pulses for such a short amount of time, it doesn’t have a chance to open all the way to deliver the proper amount of fuel. Typically it’s tuners who want that information because they can compensate for it if they know where the anomalies are.
Battery offset testing measures the delay in milliseconds that the injector experiences at different voltages and different pressures. With the battery offset test, the amount of that opening time varies with different pressures and different voltages. It also takes into account closing time. Not everyone needs this kind of test, but it shows you how critical the small details are.
“When you send a 2 millisecond pulse width from the ECU to fire the injector, the first 1.2 milliseconds could be taken up by opening the injector,” Deatsch said. “So if you ask for 2 milliseconds, and you don’t have battery offset information, if that offset is 1.2 milliseconds, you’re only getting .8 milliseconds of fuel.”
One way racers get better performance is by sending Deatsch more than one engine’s worth of injectors. After cleaning the injectors, Deatsch will flow-test them and put them into ideally matched and balanced sets, which provides increased power, smoother delivery and better economy.
“They’re looking for every little advantage they can find,” he said. “The more you send in, the better chance you have of getting a perfectly balanced set.”
While you have your injectors out for service, Deatsch suggested changing the fuel filter. If you have a car with rubber hoses in the fuel system, change those, too. Years of using E10 and E20 fuels can degrade the inside of rubber hoses, which could nullify the benefits of having them cleaned in the first place.
“It’s definitely the bottleneck of the whole fuel system, so that’s where all the gunk will end up,” Deatsch said. “If your filter doesn’t catch it, all the gunk will end up in the injectors because it’s a precise metering device and it will just get clogged up really easily.”
Linearity and Offset Battery Test Data Sheets
