Jake Brakes and Slippery roads, just wondering....

The jake will lock up your wheels in an instant, if it's slippery enough. In the old days before electronic engines, you could actually stall the engine, because the jake would lock the wheels, you'd start to skid/slide, the rpms would come down like right now, and the jakes didn't cut out until the engine died. Then you had a real situation cause you were in a skid with a dead engine. There's many an old timer who had this experience before they had experience, lol. Anyway on to your question. It does apply torque to the driveline and thus to the wheels, but reverse torque compared to forward torque. The driving schools teach icy=no jake just to play it safe and cover their butt. It's the old black vs white without grey matter inbetween. (Pun intentional). If you are careful when you know it's slippery, you will be fine as long as you use the jake cautiously. Use the minimum setting first, if no beginnings of a lock up occur, gradually increase the jake setting but be always prepared to snap it off. It's one of those things that take time and experience to get used to. Let's say it is super icy, you are boogeying along at 60 mph and all of a sudden a situation happens in front of you requiring either you stop or slow way down. If you go on the jake, and it locks up, most likely you are travelling too fast for the conditions anyway. Your foot brakes might be less hazardous with ABS these days, but often it's a combination of GENTLY applying light jake, light trailer brakes, and perhaps some foot brakes, so as to reduce your speed whithout locking up, or having the truck or trailer start to go sideways. It's a thing that comes with time and experience, staying on top of changing situations, reading traffic ahead of you and being aware of potential situations before they occur. Oh, and a final note, bobtailing on ice is very dicey. You don't have the added help of a trailer to slow you down. The truck turns into a curling rock when you try to stop too fast, whether you use engine or wheel brakes (although, again, abs does help). Before abs came along, we had to fan the foot pedal to apply and release the brakes without locking up. It worked not too bad, but quickly used up air pressure which wasn't good. Anyway, there's some feedback for you from someone who first encountered icy roads in a big truck 41 years ago. Hope it helps, and good luck.

 

If your truck got ABS, check for its parameters, becouse all ABS units has jakes/retarder cut-off output and when rear wheels skid it disables jakes.

But not all trucks has this feature enabled. So if drive wheels skid - just step on clutch pedal and jakes will be off.

 

Stop thinking, you're way off base The Jake greatly affects the torque through the driveline, braking torque (opposite direction from drive torque). From a traction standpoint, the Jake is no different than a normal brake application of the same force. The tire does do not know the difference between the two.

The bottom line, in slippery conditions, the Jake can cause a loss of control. The ABS cannot help with a Jake skid like it can with a service brake skid.

 

First of all, while you are thinking about the mechanics of how they work, you'll need to understand the difference between a diesel engine and the gasoline engines you are probably more familiar with, as well as how the engine brake works.

The gas engines you may be familiar with have a butterfly valve which restricts air from entering the combustion chamber during the intake stroke. This partial vacuum provides some braking effect. The compression stroke doesn't have much to compress, and since there is little fuel/air mixture in the cylinder, the power stroke is equally weak. Exhaust valves open, and the cycle starts again when the piston approaches TDC.

The diesel engine lacks a butterfly valve. It breathes in as much air as it can flow through the intake valves on each and every intake stroke, whether you are off the throttle or have it mashed to the floor. The compression stroke pressurizes the cylinder, which heats it up, and then the fuel is directly injected into the combustion chamber. If you're off the throttle, even if zero fuel was injected, the compressed air in the cylinder acts like a spring and pushes the piston back with the same force it took to compress the air...but even at idle, SOME fuel (albeit very little) is injected, so there is actually a little combustion taking place as you are rolling down a hill off the throttle. In other words, there is very little resistance from a diesel engine to slow you down on its own.

Enter the compression brake. What it does is turn the diesel engine into an air compressor. The engine breathes in a full charge of air on the intake stroke and compresses that air during the compression stroke. Then, the compression brake will open the exhaust valves and prevent any fuel from being injected, thereby releasing the energy contained in the cylinder before it can push the piston back down during the power stroke.

As for what you've been told about the engine brake causing you to lose traction, that all depends upon how heavily you are loaded, what engine is in your truck, and how the engine brake is set up. If you are loaded heavy (especially on the drives), then you aren't likely to have any problems. Empty is another thing. If your engine brake is weak (older Macks are notorious for weak engine brakes) you probably won't have any problems using it. If you've got a 550 Cat with a 3-stage Jake, you might not want to use the high setting while deadheading in the snow. Most of the time, the engine compression brake will have slightly less power to slow you down than the engine has to push you forward. As a general rule, though, if the engine can't break traction while accelerating, the engine brake won't break traction while decelerating. HOWEVER, if you start applying the foot brake in addition to the engine brake, you might cause your drives to lock up. I've found that by using the engine brake and LIGHT pressure on the foot brake, I can stop reasonably well without locking any wheels, where turning off the engine brake and relying on slightly heavier use of the foot brake might lock up a trailer wheel. I'm also driving an older Mack, with a notoriously weak engine brake. If you're driving something different, your results may vary.

Confused yet?

 

This is the reason I don't run Canada any more

 

If it is slippery you need chains, if it is real slippery you need triples on all drivers and a couple of singles on the trailer.
You can use full jakes if you are set-up for it, you have the ability to use 2, 4, or all 6.
If you are unprepared for the conditions, then you want to park it, you prove nothing when you get into trouble and damage the truck or block the road.
The explanation of the Jake is very good. You can get the Mercidies and they have a constant velocity valve, and an Exhaust brake they give a steady braking force were the Jake is a pulsating brake.
Just a thought!

 

Here it is , point blank and period. Do NOT use engine brakes in slippery conditions . If you do you CAN loose control of the truck

 

Here I was thinking that the US was more likely to have ice . We have snow which is not half as bad as ice

 

It's not the snow or the ice it's the way they drive in CANADA.