Those of us with recent Cummins engines (since they started using air preheaters) will notice that the factory alternators are actually pretty respectable.  My 2000 270Bs come with 105A Delco alternators. You would think this means I can charge at over 200A with the two installed in Dirona.  Well, it turns out that the 105A specification is more of a marketing number than an engineering specification.  Yes, they can produce 105A of output.  However, they can’t do this for more than a few minutes at a time, which is close to useless.  Now that we know that they can’t really produce 105A continuously, what can they do? 

Sometime back I wrote up an article investigating what charging rates can be produced continuously and reliably and how to achieve that number at minimum cost and hassle.  It was published in the May 2007 PassageMaker and we just put it up online at: http://www.mvdirona.com/TechnicalArticles/ChargingSystem.htm.  I’ve found that you can reliably get 70 to 80A and the alternators will run trouble free for years configured that way.  The article documents the investigation, discusses the limiting factors and shows how to configure your charging systems to get good results.

                                    --jrh

Snow fell in the Puget Sound this weekend as part of a big winter storm that swept the country. We were anchored at Port Madison, on the north end of Bainbridge Island, when the white stuff started. Even though the temperature was several degrees above freezing, snow began building up quickly. It was a wonderful winter scene.

Port Madison was a fitting locale for a snowy day in the Puget Sound. Bainbridge Island and Walt Woodward, editor of the Bainbridge Island Review, were the inspiration for local author David Guterson’s novel, Snow Falling on Cedars.

In the previous posting, Cumins Power Curves Confidential I talked about why having Power Curves for your specific engines is a good idea and why and argue it was a mistake for Cummins to not make this data available to customers. This data is now reported to be available. Apparently the Cummins folks I spoke with at 1-800-diesels were incorrect in saying the power curves were Cummins Internal Use Only and should have released them.  They directed me to PowerMaster@cummins.com who sent this letter explaining why customers don't need the data and that they were unable to release it due to corporate policy.  Apparently they were incorrect as well. Tony Athens and Etienne Grobler both followed up with Cummins and both were told the folks at PowerMaster and 1-800-diesels made a mistake. 

Etienne has approved me posting the letter they sent to him explaining the error: WaveMasterAtCummins.htm which offers more detail.  The good news is we can get the data we need (thanks for following up with Cummins Tony and Etienne). The bad news is there appears to e a surprisingly large number of folks in Cummins customer support willing to take a firm position with insufficient data. Nonetheless, I'm glad to see the power curves available to all. 

The updated article is at: http://www.mvdirona.com/TechnicalArticles/CumminsPowerCurves.htm.

--jrh

Since new, I’ve had the Cummins Performance Curves for my CPL 2205 engines but it was for a different rating.  Apparently the CPL 2205 engine was sold in a 260 HP Recreational  rating and a 225 Medium Continuous rating.  Sometime back I asked Cummins for the exact Performance Curve for my 270B (260HP Recreational) and was amazed when they said “sorry, we can’t get them to you, they are Cummins Confidential.” This is doubly weird in that 1) customers absolutely need this data to protect their engines and 2) the current generation Performance Curves are actually posted on their web site.

Their letter refusing to supply this data at: http://www.mvdirona.com/TechnicalArticles/CumminsPowerCurves.htm.  That page also gives an email address for you to send feedback to Cummins if you agree that not providing the data is bad for customer nor good for their business. Thanks,

                                                --jrh

James Hamilton, Windows Live Platform Services
Bldg RedW-D/2072, One Microsoft Way, Redmond, Washington, 98052
W:+1(425)703-9972 | C:+1(206)910-4692 | H:+1(206)201-1859 | JamesRH@microsoft.com

H:mvdirona.com | W:research.microsoft.com/~jamesrh

This year we spent Thanksgiving aboard in the South Puget Sound (the area between Olympia and Tacoma Narrows). With extreme high tides above 15 feet, we were able to explore the drying heads of several inlets: Henderson, Hammersley, and Eld. The weather for the most part was excellent—bright blue skies and little wind. Temperatures were often near-freezing, but we’ll take that over rain.

Pictures and stories from the trip are posted at http://www.mvdirona.com/Trips/SouthSoundThanksgiving2007.