I’m on a bus tour near Athens (Greece), and the driver has a small stalk on the right side of the steering column that he uses to slow the vehicle. He pulls it down, which apparently engages engine braking of some kind. It has several detents he can use to vary the braking power, pulling it down four or five notches for max, or one or two for less.
Here’s a picture.
It’s the “steering column switch for retarder and cruise control”
If you open up this 500+ page pdf and flip through pages 139-142 (or 125-128 as shown in the manual itself), it’ll show you how to use it.
It’s quite normal to have a “retarder” on trucks and buses in Europe. They operate by restricting the exhaust to make engine braking more effective.
This has two benefits: It saves wear on the brakes and on long inclines, it prevents overheating.
In general, heavy vehicles in Europe are more sophisticated than their North American counterparts. Fully automatic gearboxes are universal, as are cruise control and retarders. Many modern trucks and buses have rear-view cameras instead of mirrors these days as well.
Is that the same as Jake Brakes on a big rig?
So do they make that same sound we are all familiar with when tractor trailer drivers turn on engine braking?
Jake Brakes are, IIRC, a brand of engine brake.
That sounds like an “exhaust brake”, if that is indeed what that system activates.
@Joey_P, thanks for going to the trouble of looking that up for us.
@bob_2, I’ve been on motor coach busses pretty much every day for more than a week, and I’m pretty sure most of them (and most that I’ve been on in the US) had auto transmission. This one was a stick shift, which stood out (although I think it may have had an auto clutch, since it didn’t seem that the driver was using his left foot). I hadn’t noticed other drivers using the retarder before, although I wasn’t always in a position to notice, or just didn’t look.
I didn’t know the term retarder, or exactly how it functioned, but it was obvious it was some form of engine braking, as I noted in the OP.
@minor7flat5, it was nowhere near as loud as a Jake Brake, but it did sound somewhat similar.
Thanks, all.
One of the downsides of diesel engines in their most basic form is that since they don’t have a throttle plate on the intake, they don’t provide as much engine braking as a gasoline engine of comparable size. To get around this, you can add a throttle valve to restrict flow through the engine. But instead of putting it on the intake side - where the best you can do is develop a 14.7-psi drop across the valve - you put it on the exhaust, where the engine can build much higher upstream pressures and develop even more engine braking than a gasoline engine. Exhaust brakes don’t make a lot of noise.
Jake Brakes, a brand of compression release engine brake, are different. Once a cylinder goes through its normal compression stroke and reaches top dead center, the mechanism briefly opens that cylinder’s exhaust valve to release the built-up pressure, wasting the energy that was stored in that high-pressure gas during the compression stroke instead of delivering it back to the crankshaft during the expansion stroke. It’s that sudden release of high pressure every time a piston finishes its compression stroke that makes a “pop”. String those pops together on a big diesel spinning at 1200 RPM - and maybe even take your muffler off - and you get the growl that compression brakes are famous for.
I’ve seen eddy current brakes on municipal busses in the mountains but those have been a large lever on the dash, sort of like a parking brake.
It’s funny that this is the opposite of light vehicles, where you are very unlikely to find a standard transmission car in North America anymore.
Many truck drivers complain that they are taking all the “skill” out of the job and say that they would prefer manual boxes. Trucks are mostly purchased by hard-headed businessmen who care little about the preferences of their drivers.
When it comes to company cars, drivers’ preferences are often taken into consideration as well as the fact that automatics generally cost more on contract, mainly due to poor residuals.