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Old 09-06-2011, 10:26 AM   #36 (permalink)
Diesel_Dave
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Join Date: May 2011
Location: Indiana
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White Whale - '07 Dodge Ram 2500 ST Quad Cab 2wd, short bed
Team Cummins
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Quote:
Originally Posted by slowmover View Post
The correct type of chart to use is a BSFC map (BSFC vs speed AND torque). I'm not sure it Cummins publically releases it's BSFC maps, but most all modern turbodiesel BSFC maps have more or less the same general shape

Click to BSFC Thread posts #170-173 on Cummins.

A chart/graph might show 1,800-rpm as optimal, but it may also NOT account for winds. Speed, as the final variant, in other words.
Slowmover, that chart in post #170 was exactly what I was referring to (to not use). That's BSFC vs engine speed at full load. So 1800 rpm would be optimal if you're running up at 100% load--but that's almost never the case, so that particular graph is not really useful for our discussion here.

I did a little digging and I'm pretty sure now that Cummins doesn't publicly release the full BSFC maps. But having worked in diesel R&D, I can tell you that the basic characteristics are the same as that TDI map that I referred to earlier (post #37 in that other thread). Tho only exception to that is what Big Dave pointed out--many of the torque curves (including the Cummins ISB engine) have a flat top--just like you see in post #170. FYI, that's usually done not because the engine cannot produce more torque, but because the transmission can't take the higher torque level, so the engine limits the fueling such that that maximum torque is not exceeded.

Oil pan, I don't think you should have any trouble with the alternator. I've never sized alternators myself, but my understanding is that they are sized such that they can keep up with all the electrical loads with the engine at idle speed. If they weren't then your battery would get drained down if you were sitting idling.
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Diesel Dave

My version of energy storage is called "momentum".
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1 Year Avg (Every Mile Traveled) = 47.8 mpg

BEST TANK: 2,009.6 mi on 35 gal (57.42 mpg): http://ecomodder.com/forum/showthrea...5-a-26259.html


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