2015 Ram 3500 review

ScottG wrote:

kohldad wrote:


Engine braking. Yes, it does exist because of the use of the vvt to let the engine build compression.

Can you explain this part? VVT usually refers to a turbo, which of course your 6.4 doesn't have. Or does that refer to something aobut the trans?

Thanks,
Scott

VVT - I am guessing that is Variable Valve Timing.

My Ford car has that too, and it can change the intake and exhaust valve timing to increase power in the higher RPM's.

Gas engines do have compression braking, though not nearly as much as the CTD. It is actually the transmission that normally is the limiting factor in slowing the vehicle on a steep hill. The automatic transmission is just not going to transmit nearly as much braking HP as the manual transmission that the driver was used to.

Anyway he is reporting that he is not needing to ride the brakes down the hills. Typically when I am driving around town, I downshift my cars out of overdrive when I am going down short 500' - 800' long 5% to 7% downgrades, and typically all the cars that I am following are riding the brakes all the way down the hill to keep speeds at 35 MPH (within the city limits).

With my motorhome, I will downshift, and when the speed reaches 3,000 - 3,200, I will lightly apply the brakes to control speed. At anything less than 2,500 RPM, the engine is barely doing anything to slow the vehicle. At 3,000 - 3,200 then you are getting about 50 braking HP. 4,000 might have 75 - 100 braking HP because it is a 460" gas V8 and automatic transmission. However I don't like pushing the engine RPM that high going down a hill, and that can tear up the transmission.

With the 2004 CTD and manual transmission, running at 2,500 RPM down a hill in 3rd gear, the engine can be producing well over 100 braking HP and everything is fine. The manual transmission can handle 150 - 200 braking HP. However the CTD can not be revved above about 3,000 RPM, I think that the governor is set around 2,800 RPM. Ford and GM V8 diesels can rev much higher. They have much smaller diameter pistons and 2" shorter stroke, so they can run higher RPM's and make more HP.

This is a good report on the Dodge. I am thinking about getting a gas pickup next. Not the diesel, they are just to expensive, and I don't plan on driving it more than about 8,000 miles a year to pull a fifth wheel. The $8,000 additional cost over the gas engine is huge in my budget!

Fred.