rear axle gear ratio
Getting ready to move up to a 3500. I've shopped the available trucks, and have a good idea of what I want. The two I have narrowed down to are a '14 and a '15 Ram 3500. Identical with the exception o...
Forum Discussion
brulaz wrote:4x4ord wrote:
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Therefore if the engine is capable of making the required 100 hp at 1300 rpm it will normally get significantly better fuel economy by gearing up and slowing the engine down.
But some folks claim that "lugging" the engine at low rpms below the 1700-1800 rpm peak is detrimental in some way. They prefer to generate their needed HP at higher rpms at or above the rpm peak (and with lower needed boost).
When towing on level ground, my CTD seems perfectly happy idling away at lower rpms (~1300-1500 rpm) and with higher boost as needed. It even seems to get better fuel efficiency like you say. And I suspect the higher exhaust temperatures from the extra boost might help with passive regen. But are there other potential engine issues I should be aware of?
I believe these new computerized engines can look after themselves. There is no way you're going to hurt a Cummins engine by letting it shift into a higher gear. If you have a standard transmission and the truck seems perfectly happy in the higher gear, you are not lugging the engine. I don't know much about the passive regen but what you say sounds reasonable. The higher exhaust gas temperature is due to a lower volume of air flowing through the engine for the amount of fuel being injected....another reason why better fuel economy results from lower rpm.....the engine pumps less air at a lower rpm even though the boost pressure may be running a little higher. The more air you push through the engine, for a similar amount of fuel, the cooler the exhaust will be.
