Diesel's new demands

Michael Schena, president of Michigan Custom Machines. Click here to read the complete interview.

Given the high cost of diesel fuels, testing for even more efficient diesel combustion engines has assumed a heightened priority among engine manufacturers. During a recent phone interview, I discussed the state of diesel engine testing with Michael Schena, president of Michigan Custom Machines (www.mcm1.com).

Q: Would you please provide some background on the 2007 standards?

A: Back in 1978, early passenger car diesels were known for their poor performance and belching smoke all to the tune of a clattery noise under the hood. Since then, a lot of work has been done in Europe and in the US off-highway industry to further the evolution of diesel engine technology.

The last regulation change took place in 2002. The next change occurs in 2007 and holds much more stringent requirements, while the 2010 standard will actually merge the emission standards for gasoline and diesel engines alike.

The biggest key to meeting these goals is in the fuel system. By going to higher pressures at the fuel-injector nozzle, the fuel can be atomized into finer droplets in the cylinder, giving more surface area and a cleaner burn.

Q: What is common rail injection?

A: Common rail injection is a type of diesel fuel system. Common rail consists of a high-pressure fuel pump capable of 2000 bar (about 30,000 psi) that feeds a heavy cast-iron vessel called the "common rail." Some engines have one or two rails depending on configuration. Special heavy-duty fuel lines feed the injectors that are actuated by an individual solenoid or set of solenoids in the injector.

Pressure in the rail can be controlled by the pump itself or by a relief valve on the rail itself. The beauty of this system is that it is very responsive and can electronically deliver fuel as often as engine revolution requires.

Q: What are some special requirements mandated by your customers?

A: Split-injection measurement is a big one. This is a feature of fuel injection that requires not only precise actuation, but also precise measurement. It is possible for a fuel injector to not properly dispense the correct amount of fuel for one of the splits, which would lead to poor engine performance in final testing if not caught early on. On a smaller scale, the remanufacturing and after-market industries rely on similar testing to meet OEM requirements and satisfy that "out of warranty" customer.

Q: What primary challenges lie ahead for makers of engine test and measurement equipment?

A: The requirements for handling higher pressure with thin, low lubricity fluids is always a challenge. These pressures will continue to increase to further improve fuel atomization. The sophistication of the fuel-injector actuation is always a challenge. Some injectors are actually using two solenoids to turn on and turn off the injection event, and in some cases, these solenoids are actually replaced by stacks of piezo crystal wafers that respond much faster than conventional magnetic devices. Of course, driving these types of actuators is totally different from conventional means. We constantly work to stay in pace with these challenges, so we can provide the best turnkey solutions for our customers.

Click here to read the complete interview.