Ok, I have to ask this question. Its been bugging me ever since I pulled the plug on the EGR. My first thought is Diesel don't ping per say. I mean, they compress air so there is nothing to ignite during the compression storke. Of course if the injector fires to early (way early) this could contribute to pinging/timing issues...so with that said, what about this pilot injection? Now there is fuel being compressed and so is it possible we could see pinging from the EGR mod? What do you guys/gals think?


By the way, great forum! I joined in July when I picked up my first Diesel/Duramax.


Thanks,Mike

Pinging on any engine whether it be gas or diesel is caused by combustion too many degrees before top dead center. Lower octane rated fuel has to be ignited closer to tdc because of the burn characteristics. That it is it ignites quickly and if it too advanced it tries to push the piston down before it is at tdc. Increasing the octane of fuel slows the burning process down and smoothes it out. The higher the octane the more advanced you can ignite the fuel. When you add propane injection to a diesel you are increasing the octane rating of the fuel and the diesel/propane burns slower and smoother getting the same results as high octane gas and advanced ignition.

Pilot injection is used to reduce diesel noise. They inject a tiny amount of fuel, which immediately is ignited by the compressed air. They follow that with the main shot of fuel to make the power. Since there is already fire in the chamber, this main shot burns as it goes in rather than exploding, reducing the noise. It all still happens near TDC. The only way to get ping in a diesel is by using propane or natural gas fumigation in too great a quantity. The mixture has to be kept considerably leaner than could normally burn in a spark ignition engine. Non-electronic diesels could ping if the pump timing is too advanced.