diesel combustion questions
diesel combustion questions
(OP)
Gentlemen, my questions are about a method that I use to "tune a older style IDI diesel with mechanical injection"
Basically, I utilizes the Seebeck Effect of the glow plug and monitor the millivolts produced............I monitor this under real driving conditions............I only use the millivolts to provide a "relationship of temperature in the cylinder" and the different tune of the engine.............
My objective is to have the lowest rate of change in the millivolt readings from idle to operating RPM at high way speeds........
Example only...........say at idle I have a 5 millivolt reading and then at high speeds I have a 15 millivolt reading .......this would then be a 10 millivolt rate of change.............the objective here is to reduce the rate of change for idle to highway speeds say to 2 millivolts.............
Where I have achieved a very low rate of change (say under 3 millivolts) by "tuning" temperatures and injector timing, I have noticed a increase in fuel mileage, decrease in water jacket temperature and decrease in exhaust temperatures...........
First Question: Can I assume peak cylinder temperatures has decreased or has peak cylinder temperature stayed the same and perhaps efficiency has increased?
Usually, to get these very low rates of change, I have to advance injector timing from OEM speck................everything I have read says advancing the injector timing increases NOx levels (time factor before autoignition and cylinder temperatures)
Second Question: with the above limited information, what might I assume about NOx levels with increasing injector timing and the decreases in millivolt readings....................
Third Question: Is there a mathematical relationship between peak cylinder temperatures and engine efficiency.........
thanks in advance for your time and knowledge,
James
Basically, I utilizes the Seebeck Effect of the glow plug and monitor the millivolts produced............I monitor this under real driving conditions............I only use the millivolts to provide a "relationship of temperature in the cylinder" and the different tune of the engine.............
My objective is to have the lowest rate of change in the millivolt readings from idle to operating RPM at high way speeds........
Example only...........say at idle I have a 5 millivolt reading and then at high speeds I have a 15 millivolt reading .......this would then be a 10 millivolt rate of change.............the objective here is to reduce the rate of change for idle to highway speeds say to 2 millivolts.............
Where I have achieved a very low rate of change (say under 3 millivolts) by "tuning" temperatures and injector timing, I have noticed a increase in fuel mileage, decrease in water jacket temperature and decrease in exhaust temperatures...........
First Question: Can I assume peak cylinder temperatures has decreased or has peak cylinder temperature stayed the same and perhaps efficiency has increased?
Usually, to get these very low rates of change, I have to advance injector timing from OEM speck................everything I have read says advancing the injector timing increases NOx levels (time factor before autoignition and cylinder temperatures)
Second Question: with the above limited information, what might I assume about NOx levels with increasing injector timing and the decreases in millivolt readings....................
Third Question: Is there a mathematical relationship between peak cylinder temperatures and engine efficiency.........
thanks in advance for your time and knowledge,
James





RE: diesel combustion questions
RE: diesel combustion questions
Amazing that none of the Diesel engine manufacturers over the years noticed this phenomenon.
RE: diesel combustion questions
I agree there is a point when advancing the timing increases cylinder temperatures as indicated with the millivolt readings.......I stop advancing the timing at the very first reversal of the decreasing millivolt readings.............when I reach this point, and I check the injector timing, mathematically I am fairly close to the timing for the "estimate" of the cetane value of the fuel I am using and the different temperatures involved...............
Am I wrong in thinking that if ignition is retarded and you advance the timing that peak cylinder pressure per degree of rotation goes down?
James
RE: diesel combustion questions
RE: diesel combustion questions
It is my understanding that the measurement of "Rate of pressure rise per degree of rotation" begins with any increase in pressure from the combustion process up to peak pressure divided by the timing advance in degrees................
Example only: 1000 PSI peak pressure with a injector timing of 10° would equate to a 100 PSI rate of rise per degree of rotation......and with the same peak pressure and a 15° injector timing would be 66.66 PSI rate of rise per degree of rotation.....
James