jcmseven
Veteran Member
Oh, Builder!! Here we go again....I know we speak of the Cummins, but someone needs to keep the 6.4L bash in check before it gets away again. It is true the torque curve of the Ford is later, but if one believes this graph, its curve meets the Duramax torque curve, for example, at around 1900-2000 rpm, and then passes it. This is not by mistake, but happens to be where the Ford with 3.73 gears happens to settle when running on the highway at 65-70 MPH in OD, about towing speed for most today on the major interstates. If one shifts into "tow-haul" it will rev at about 2500, which is in the meat of its curve. It also correlates well with the shift points in the transmission. My truck idles at 900 prm, which would generate "off-idle" torque similar to the Dodge. This graph also seems to show the Blue Oval's graph showing more peak torque than either of the others. It also shows something (though the graduations could be slimmed a bit for a better comparison that has been shown before: the Duramax rating might be a bit generous, and the Cummins/PSD a bit pessimistic). I recall an article in "Truck Trends" back when the 7.3L Ford and the 5.9L Cummins were both out, and the Duramax was rated at less HP than now. They performed chassis dyno testing on all three and the Ford and Dodge were underrated and the Duramax was "generously" rated, based on actual numbers. As for the Cummins, it is a pulling motor. I agree the torque curve of the Cummins is perfect for towing. It will not win any races v. the other two, but with the low onset of torque and the very flat "curve" it would feel very strong and would be a very efficient puller. Only at the limit of performance and RPM would it lose ground to the other two. Yes, this is but one graph of many I have seen, but the theme has been the same with each. Who knows how accurate this curve really is, but it shares similarity with others I have seen. Again, though, I think one must keep in mind truly how similar the performance curves of these three powerplants really are. As for the economy, looking at towing numbers on the post-DFP trucks they are VERY close. The Dodge/Cummins is usually best, but not by very much.
John M
John M