I am doing long term planning for a small fleet of tugboats. A lot of the engines (propulsion, generators, hydraulics) are Detroit Diesels of various sizes (e.g., 4-71, 6-71, 12V-71). Newer engines are more efficient, but it is not clear to me how this can be quantified. I am trying to make decisions about repowering vessels and would like to see some metrics that I can use to calculate fuel consumption for a given workload. Is there a place or places where I can get information on fuel consumption for work done for individual engine models?


1 Answer 1


Some engine manufacturers use BSFC which is the fuel consumption compared to the power produced.

As you know the engines you want to look at you should be able to get the figures.

  • $\begingroup$ This is very helpful. But I am having trouble finding BSFC numbers for some of my older engines. For example, googing "12V-71 BSFC" does not lead to a canonical reference. Any pointers would be appreciated. $\endgroup$ Commented Jan 20, 2021 at 17:55
  • $\begingroup$ @GeneMcCulley you have done the obvious and contacted Detroit... $\endgroup$
    – Solar Mike
    Commented Jan 20, 2021 at 20:39
  • $\begingroup$ I have not successfully engaged with Detroit. I have found many old brochures with vague charts. I have used the contact numbers and so far found nobody at the modern incarnation of Detroit who can talk to me about the engines they made from 1938-1995. $\endgroup$ Commented Jan 20, 2021 at 23:01
  • $\begingroup$ Then if you can’t find the info, run some dyno trsts to get it. $\endgroup$
    – Solar Mike
    Commented Jan 21, 2021 at 5:03
  • 1
    $\begingroup$ I spent hours and hours running several engines on dynos including a Rover Gas Turbine... perhaps the manufacturers do make data available but it may be in forms that you have to work at to extract the info you are interested in. Make sure you check the units for the data. $\endgroup$
    – Solar Mike
    Commented Jan 21, 2021 at 14:21

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