DWeikert wrote:
pnichols wrote:
However, since the exhaust braking engine back pressure mechanism is different than the gear braking engine back pressure mechanism ... maybe exhaust braking can somehow feel different to the driver. :h
The big difference is a gas engine just doesn't have the compression to slow down the vehicle like a diesel does. The transmission on a gas engine will take you into the high RPM's trying to compensate and still not do as good a job slowing the vehicle as the diesel at much lower RPM's.
Both a gas and diesel engine can downshift and use the engine for braking purposes. However, the gas engine is limited to only zero (and varying amounts of) throttle to vary engine braking. Once zero throttle is insufficient for braking, it's then left with downshifting forcing the engine into a high RPM state to increase braking. A diesel (
with an exhaust brake) on the other hand, can also use zero (and varying amounts of) throttle to vary engine braking. But, rather than downshift when zero throttle is insufficient, it can then selectively apply reverse thrust or throttle (for lack of a better word) with the exhaust brake rather than downshift like a gas engine. This is a
huge difference in engine braking capability (vs. gas) that must be experienced to truly appreciate. You can also place a diesel exhaust brake in manual, non-auto mode and use it full-time while driving in normal traffic. In this mode it activates everytime you take your foot off the throttle. In some types of traffic it can save untold amounts of wear and tear on your brakes. FWIW, on my '16 Cummins there is a dash display that shows the amount of exhaust brake in HP. Depending on conditions it can vary from approx. 70 to almost 200 HP. I might also add the sound of all this stuff going on under the hood can be quite entertaining on a long, boring drive in the mountains--lol!
