Having to choose between two diesel engines, how can we compare the performance of two diesel engines that have the same RPM, and engine power output?
This isn't really a controls related issue, but since you've asked the same question twice here are a few things to consider:
-fuel consumption per kw
-length of time between maintenance outages
-duration of maintenance outages
-cost of spare parts
-cost of consumables (oil filters; air filters; etc)
-opinions of current users about reliability and availability
And, as the sourcing people and accountants Will remind you: the cost of the equipment. But initial cost is NOT the true cost; the true cost includes the cost of spares and maintenance outages and reliability and availability.
I would add local support quality, spare parts availability, and service availability. MTBF can give some indication of the engine reliability. Site capability of supporting the diesel engine must also be a consideration. How close the main factory and the language they speak give rise to a couple of rules of thumb. The further the main factory or where the technical support people reside is from you and/or if they do not speak the same language as you, the poorer potentially the support is likely to be (there are certainly exceptions to these rules but they need to be considered). Talk to people who have these machine to get their take on the quality and support for these machines. Be careful with references as the manufacturers will seldom give out a bad reference. Talk to the horse's mouth - maintenance techs in addition to engineers. See them run at a site if possible.
William (Bill) L. Mostia, Jr. PE
ISA Fellow, FS Eng. (TUV Rheinland)
WLM Engineering Co.