hello, can someone explain how exactly the engine brakes work? i have a 2017 superduty diesel. is it simply downshifting the transmission sooner, or is there actual exhaust braking going on.
it works great, just wondering how it works.

 

The engine brake feature will downshift the transmission and use the turbo to increase resistance with the engine.

The engine brake button has two "On" settings. I mainly use the second setting of Automatic.

 

I have been having the same question.

who is using these and for what?

Engine brake ON
Engine brake Auto
Tow/Haul mode - I love this when towing and believe does the same as Engine brake Auto, bot also changes shift points going up.

 

Engine Brake = Auto is sort of like having tow/haul on with the exception that it doesn't hold the RPM's in the first three gears when accelerating. Hit the brake pedal and it will hold that speed.

Tow/haul by itself will NOT use the turbo to increase the "braking" power.

My experience with Engine Brake = On is that you have to manually shift the transmission to get it to work. Hitting the brake pedal doesn't affect the turbo or the transmission (unless you have tow/haul on).

 

You've pretty much nailed it. Engine Brake ON means its always on, it just isnt that effective until you get into higher RPMs, so by down shifting manually you are increasing the RPMs and increasing the exhaust brakes effectiveness.

Engine Brake AUTO is sort of like a reverse version of cruise control, set it to auto, tap your brakes at 55mph going downhill and the engine brake will spin up to slow you down to 55mph and try to keep you there. Its very effective in my experience at this job. If you are towing extremely heavy it might not be able to keep you at 55mph all by itself, but its never not worked for me with my 12k lbs toy hauler.

Tow haul doesnt do anything with the engine brake as far as Im aware, they are two different systems that can work together if you have them both turned on, but I don't think tow haul turns on the engine brake automatically?

The engine brake is fantastic. Towing my trailer fully loaded through the mountains and grape vine in California was awesome, not a single white knuckle moment and just super smooth and care-free. One of the best reasons for going with the diesel imo.

 

Correct. Tow/haul by itself will NOT use the turbo to increase the "braking" power.

 

This is very clearly explained in the owner’s manual.

 

I know that it is a long manual, with a lot of info, but it's well worth the read.

 

I've always used Engine Brake ON and then the cruise control system together. set cruise control at 55 going downhill & the truck will basically do the same thing as Engine Brake AUTO. it downshifts & kicks in the brake to slow the truck to the desired speed.

Is there something that Engine Brake AUTO does differently? I've never actually used it because I prefer to use cruise control.

 

I could be wrong but I don't think you're getting actual engine braking with cruise control and Engine Brake = ON. To verify, switch your dash to the turbo boost screen and see what happens. That's what I did that led me to believe that the ON setting doesn't have much effect unless you're manually downshifting. Cruise control and Engine Brake = Auto should give you the effect you're looking for.

 

I'm going to have to try it. I know for a fact that with cruise control on, engine brake in the ON position & tow haul mode on, the brake (engine) kicks in & the truck will downshift as needed to maintain the speed set on cruise control. I don't have to downshift manually or hit the brakes (which would cancel cruise control).

I've never had an issue slowing the truck down in the "ON" position with the engine brake. These trucks are awesome. Hands down the best truck I've ever owned.

 

Yes, there is actual exhaust braking going on. The pitch of the vanes in the turbo are variable. The exhaust brake function changes the exhaust side vane pitch so they block (or better stated impede) the exhaust flow thereby using the engine as a brake on the power train.

As stated by others, any kind of exhaust brake works better at higher engine RPMs. If you turn the brake system to "on" and gear down so your engine speed is close to 3K or higher you will feel it.

The tow/haul mode only has to do with your transmission behavior. It changes the shift profiles to be more aggressive so you get more performance vs. fuel economy, and yes, gearing down sooner causes some drive train brake action as well. Just gearing down can cause the trans to heat up (not desired). And of course, using your mechanical brakes causes them to heat up and wear. Restricting the exhaust gas flow causing the pistons to apply stopping pressure on the crankshaft instead of in the usual "go" direction. Using the engine brake causes almost no wear while saving wear and tear on the brake pads and calipers.

For those of us that have used exhaust brakes for years we are used to turning on the brake and gearing down manually to get the benefits. I would assume the auto function is there to let others adapt to it more readily by using the brake pedal. To me this defeats the purpose of trying to reduce brake pad wear, but hey, hitting the brakes is natural to people so it would seem the engineers have tried to make the process intuitive.

 

Just a tap is all it takes.

 

Like HRTKD said, the Auto just does some of this for you. You are setting and releasing the the exhaust brake by tapping the brake or taping the gas. Go 55mph down hill, tap the brake and it will spool up the turbo and you'll feel it holding you back at 55mph. If you want to speed up to 60mph you tap the gas and cruise up to 60mph and tap the brake again and you'll feel it spool up again and hold you at 60mph. Its just like cruise control, but in reverse.

 

great explanation toymaster. that's exactly what i was looking for. i'm a minimal brake wear guy...or try to be.
thx