Industry Testing

Why was the test developed?

Diesel fuel injectors have always been prone to injector coking. However, the potential for negative impact on engine performance, emissions and fuel consumption is increasing, as injector designs become progressively more sophisticated. For example, the Euro 5 type injectors fitted to the Peugeot DW10 engine have 6 injector holes of size 110 microns, which is around the width of two human hairs. Injector holes for Euro 6 designs are predicted to go down to as little as 80 microns, with as many as 24 holes being used. Also contributing to this trend are other engineering factors such as increasing fuel injection pressures and temperatures. 

Finally, growing levels of biodiesel blending are also likely to increase coking severity. OEMs will need to know how their equipment behaves with respect to fouling and are keen to understand how different fuels and deposit control additives can control any coking that may occur.

Euro 5 emissions standards will come into force for type approvals in September 2009 and this latest tightening of emissions legislation will be likely to result to further ramp up severity towards injector fouling and its consequences. The response by the Fuel and Additive industry through the CEC (The Co-ordinating European Council for the development of performance tests for transportation fuels, lubricants and other fluids) was an extensive program of work to develop a new diesel injector fouling test based on an engine representing latest technology. The culmination of all of this effort came in March 2008 with the final approval of a new method, F-98-08, based on the Peugeot DW10 engine. Lubrizol has played a very significant role in the development of the test, with early installation of the engine at its Hazelwood UK technical centre and leadership through chairmanship of the development group.

The Test 

The engine used in the new CEC injector coking test is a  Peugeot DW10 2.0 litre common rail unit with a maximum injection pressure of 1600 bar, fitted with Euro 5 standard fuel injection equipment supplied by Siemens. The test procedure represents a step change in severity compared
to the well understood CEC F-23-01 XUD-9 method, which is based on a much older indirect injection engine. The new method directly measures engine power, which is a function of the level of injector fouling. A high speed, high load one hour cycle forms the basis of the test. At the beginning of the test, the cycle is run sixteen times to break in the fuel injectors. Following this break-in period, the cycle is then repeated over an eight hour block with an engine power measurement being logged at the end of each one hour cycle. This is followed by a four hour `soak’ period. The eight hour cyclic running and four hour  soak is then repeated twice more, followed by a final eight hour cyclic running period. This results in thirty-two hours running time, with thirty-two corresponding engine power results being logged and twelve hours total soak time. Total
test cell time for the method is therefore sixty hours.