Diesel Engine Overload: Fuel Consumption


I've just read your article "Avoiding Diesel Engine Overload."  The article, which I found on the internet, was most interesting and informative.
I sell hydraulic equipment (pumps, hydraulic motors, valves, cylinders, etc.) and I design and build hydraulic systems.  Most of my business is in "mobile" hydraulics (logging equipment, earth moving equipment, ag equipment, trucks, dredges, etc.).  Recently I've been trying to put together some data for our customers to illustrate the influence on fuel consumption rates of hydraulic system losses (wasted power through incorrectly engineered hydraulic systems, components, or plumbing).  Much to my disappointment, few machine manufacturers publish even the most basic fuel consumption rate information for their engines.  I understand the reasons for their reluctance, of course.
After reading your article it occurred to me that you might know some formulae that can be used at least to estimate fuel consumption rates given certain engine rpm/power/boost/exhaust temp combinations.
With even off-road diesel fuel now pushing nearly $3.00/gallon, people are more willing than ever to listen to a presentation on energy efficient hydraulic systems, but I need more extensive and detailed numbers to present than the few I have already.  If you have any suggestions for me I will appreciate receiving them.




All major Diesel manufacturers publish substantial hp, RPM, torque, and fuel consumption data. In addition to the published data, more modern electronic engines with the optional electronic gauges show real-time load and fuel burn rate data. With these engines, you can know quite precisely the load and burn rate.


For mechanical engines, much less data is available directly.  However, Flowscan ( provides a range of quite accurate gauges. They read the fuel flow to engine and the flow back to the tank on the return and compute real time burn rate. 


A general rule of thumb that is very stable across all engine manufacturers of high speed diesels is that they produce 18 to 20 hp per gallon of fuel burned per hour. So, if you know burn rate, you know the HP being produced accurately.


The easiest way to do what you want is to partner with a customer that has a bad hydraulic system and is willing to pay parts costs to you.  Put Flowscan gauges on his engine and measure flow under a repeatable hydraulic load or set of loads and no-load conditions. Upgrade his system with your parts.  Re-run the experiment.  Get a testimonial from him and write it up for your web site and for a brochure.

-- James


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