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by LinuxBender 1602 days ago
Diesel engines themselves have no engine braking. Each personal vehicle implementation of diesel engines have worked around this using different techniques. The most common outside of big-rigs is a turbo that tightens a spline or closes a feedback baffle.

To the operator of the vehicle it will appear there is engine braking on modern diesel engines. Older pickups and cars have no engine braking.
1 comments
spookthesunset 1602 days ago
> Older pickups and cars have no engine braking.

So what did they do on long downhill mountain passes? Just ride the brakes? Were the brakes designed to accommodate being ridden for so long?

Asking 'cause I downshift all cars I drive when going down mountain passes...

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LinuxBender 1602 days ago
They would drive slowly and carefully and take alternate routes when possible.

Just ride the brakes?

No that will overheat and glaze the brakes. That is why long steep hills initially had run-away ramps created. The run-away ramps are still used but not nearly as much as they used to be. In many places alternate routes were created for people towing heavy things. A good example of this is the grapevine on I-5 in southern California. There is a truck route and the main route. That also has many run-away ramps.

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spookthesunset 1602 days ago
> In many places alternate routes were created for people towing heavy things.

That, uh, sounds pretty inconvenient!

So without engine brakes if you downshift in an older diesel does the engine just rev right up and the car doesn't even bother to act like it is slowing down? That has to be pretty weird....

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mcguire 1602 days ago
Eastbound on Interstate-40 on the eastern slope of the Appalachians the truck speed limit at the top of the pass is 35mph and there are very, very many warning signs including radar-activated lights. There are also three or four runaway-truck ramps (filled with loose gravel) that are somewhat frequently used, and often trucks pulled over to the side to let their brakes cool.

(The Rockies have even more of this sort of thing, but I haven't been out there in quite a while. :-( )

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BenjiWiebe 1602 days ago
It very much slows down. Just not quite as much as a gas engine. You still have friction losses (especially as you get higher rpm), losses from alternator, water pump, engine fans, oil pump, etc.

One of my vehicles is a VW Jetta TDI (diesel, ALH engine).

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frosted-flakes 1602 days ago
TDIs have turbos.
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