Keith Browning Posted January 17, 2010 Share Posted January 17, 2010 In the 6.7L web course air management section the glow plug operation is described as Contrary to popular belief, the glow plugs do not heat the air in the combustion chambers, instead they provide an ignition point to light the fuel when it is sprayed into the combustion chamber. While this is accurate the widely regarded belief that the glow plugs heat the air in the combustion chamber is what we have always been told. Quote Link to comment Share on other sites More sharing options...
Aaron Posted January 17, 2010 Share Posted January 17, 2010 I saw this also. Do you think they are trying to say that the glow plug is a direct ignition point for the fuel? What I mean is the fuel is sprayed directly on the glow plug, is that what they're trying to say? Things is confusin. Good course though, I like how the test wsa broken down into 5 sections Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted January 17, 2010 Author Share Posted January 17, 2010 I guess that is what they are trying to say but you would think that the glow plug is super heating the air around it and the fuel hits that first so.... Are we splitting hairs here? Quote Link to comment Share on other sites More sharing options...
jimmy57 Posted January 17, 2010 Share Posted January 17, 2010 I ran across an explanation in a factory manual of brushes in a starter being armature brakes so that aramture would stop more quickly and not cause a flywheel ring gear mis-engagement if a subsequent start attempt was made. Maybe that same author was the one telling us glow plugs heated the air. I always had my doubts since the glow plugs are usually put in the line of fire of injector spray. (I've tested this a few times with spilled grease on red hot stove element when I have ventured into cooking exploits). Quote Link to comment Share on other sites More sharing options...
Cetane Posted January 17, 2010 Share Posted January 17, 2010 I think they serve both purposes. Otherwise why would we "wait-to-start" when its cold outside. These new plugs heat up super fast. Once the engine is running, I doubt the GP's have much effect on combustion air temp. There isn't enough time to propagate much heat. I am surprised to see how much the glow plugs run during normal operation, it isn't like it used to be. They run for a good portion of engine warmup(minutes not seconds) and shortly after overrun starts. It wouldn't surprise me to see more frequent GP changes. Quote Link to comment Share on other sites More sharing options...
jimmy57 Posted January 18, 2010 Share Posted January 18, 2010 I would think glow plugs assure more complete combustion on cold engines and with VERY tight standards using them longer and in a few more situations seems to fit. Heating still air does make sense and from years of cranking tractors not equipped with heater assist of any type, I can tell you rough initial running with loads of unburned fuel are the norm. Most owners would never tolerate all that white raw diesel smell in their garages and into their homes. I would think quieter combustion is a result also and owners do not get less forgiving with the passing years on noise. I have not seen any bars lowered, ever, only raised. Quote Link to comment Share on other sites More sharing options...
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