rpm when towing
When towing with my ram diesel how do I tell when I should downshift. it seems to tow so easy, but slows when going uphill at 60 what should my rpm show.
Forum Discussion
ShinerBock wrote:
Some of those aren't facts.
Diesel torque stems from its more explosive combustion which pushes the piston down with more force the fact that diesels generally have longer strokes than gasoline engines which creates more low end torque, but also limits max engine speed. Turbos only make the output greater just like they do with gasoline engines.
Comparing the the torque output of a Honda 1.5L to Cummins pickup engine is just plain silly. They are built and rated for two different things. The Cummins is de-rated significantly to keep exhaust and other temps in check for towing while the Honda is not. If you put that Honda engine in a tow vehicle application then I can guarantee that the torque rating will go down. The Cummins also has more restrictive emissions equipment limiting that power a long with turbos and cams made for two different applications.
If you want to make both engines that you used an example for a more even playing field, then you would use the QSB 6.7L which is not de-rated for towing and has about the same emissions equipment as the Honda. The QSB 6.7L has a max output of 542 hp @ 2,900-3,300 rpm and 1,250 lb-ft @ 2,000 rpm. It is down to 890 lb-ft by the time it hits max hp at 2,900 rpm. That would put it at 187 lb-ft per liter at peak torque and 132 lb-ft per liter when it hits max hp at 2,900 rpm.
Torque comes from the amount of energy in the way of fuel that can be burned in an engine per revolution. Larger displacement yields more torque. Higher boost pressure ... more torque. Diesel needs more air to properly burn than does gasoline so more energy can be burned into a set volume of air if gasoline is used as the fuel as opposed to diesel.... therefore gasoline has a higher potential for making torque than does diesel. You are right that the use of an engine has a lot to do with its design. It won't surprise me if the newer gasoline DI/turbo engine technology and the fact that gasoline requires less restrictive measure to be used to meet emission requirements causes engine builders to turn toward designing gasoline engines to be favoured over the diesels for towing.
