Engine Braking vs Brakes





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  1. #1
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    Default Engine Braking vs Brakes

    Ok, so reading on another thread about towing and sport mode and so forth, I read again about using engine to keep speed on a downhill.

    This made me thought about engine braking again.

    Why do people do it? Why not use your brakes? Isn't it cheaper to replace brake pads? Also, what about auto cars? Now, I don't really tow much, so don't have much of a need I suppose. Also, not talking about when 4x4ing where it is needed at certain times.

    So, please educate me a bit.
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    Default Re: Engine Braking vs Brakes

    Engine braking uses your engine at RPM to slow the vehicle down. No damage if done properly.

    Brakes uses the, well, brakes which then need to be replaced, more often, if towing a lot.

    Engine braking therefore better... but i'm sure someone will come along and give the technical aspect shortly.
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    Default Re: Engine Braking vs Brakes

    My reasoning:

    Especially wrt diesel engines, these big trucks uses their engines (with the help of retarders) to brake. And they easily do 1M km. So it most certainly isn't harmful?

    I know that comparing those huge engines with a little 4 cylinder is probably not the best.

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    Default Re: Engine Braking vs Brakes

    Quote Originally Posted by Andre Vorster View Post
    My reasoning:

    Especially wrt diesel engines, these big trucks uses their engines (with the help of retarders) to brake. And they easily do 1M km. So it most certainly isn't harmful?

    I know that comparing those huge engines with a little 4 cylinder is probably not the best.
    Well, I believe trucks are designed that way, especially when going down passes, where their brakes will either overheat or they will lose traction and skid to a crash. I suppose when towing something heavy down a pass you need to use engine braking, but that's the only reason or time except for when offroading that I can think of using it.

    Let's be more specific. When driving normally, and approaching a stop street or robot that is red, do you gear down and use both the engine and brakes to come to slow down, or do you use mostly brakes?

    I have always mostly used brakes, and I also have never had a gearbox failure on any of my cars before.
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    Default Re: Engine Braking vs Brakes

    I most definitely do not gear down for every stop.
    I use the engine to keep speed under control on steep down hills. Brakes can overheat very quickly, which reduces their effectiveness and will eventually lead to complete failure.
    Revving an engine high againts compression is really not good, so I don't allow my diesel engines to run against compression at over 2000rpm. I'd rather brake hard for a short burst to get the speed down and then ask the engine to control the decent as best possible, while allowing the brakes time to cool a little before the next brake pedal push.

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    Default Re: Engine Braking vs Brakes

    Quote Originally Posted by lizardalpha View Post
    Ok, so reading on another thread about towing and sport mode and so forth, I read again about using engine to keep speed on a downhill.

    This made me thought about engine braking again.

    Why do people do it? Why not use your brakes? Isn't it cheaper to replace brake pads? Also, what about auto cars? Now, I don't really tow much, so don't have much of a need I suppose. Also, not talking about when 4x4ing where it is needed at certain times.

    So, please educate me a bit.
    Engine braking used correctly causes NO harm to an engine at all. How it physically works is that the wheels through the gearbox is actually turning the engine faster than it would other wise be turning due to the closed throttle position. In fact in most modern engines the fuel supply will be cut in this scenario so the engine uses NO fuel at all. It takes energy to compress the mixture in the cylinder and that is what slows you down.

    In normal driving is not worthwhile doing, but in situations where you have long stretches of braking it will save wear on the brakes. Think about descending a mountain pass, yes you can brake all the way down causing extra wear on the brakes and even induce brake fade in extreme cases. By gearing down the engine is doing most of the braking for you saving wear on the brakes and avoiding brake fade. This especially relevant if you are towing.
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    Default Re: Engine Braking vs Brakes

    Engine braking if done right will cause no damage to any components. The main issue with brakes is that they convert momentum into heat very rapidly through friction in order to slow you down or bring you to a stop.

    Once brakes overheat, they don’t work anymore till they cool down. Regular overheating also causes the pads to glaze over and degrades the braking performance even more.

    Engine breaking relies on the resistance within the motor to slow the vehicle. That resistance is constant and it is designed to work under that resistance. You will not “overheat” anything by engine breaking. Diesel engines especially (I AM NOT FAMILIAR WITH MODERN DIRECT INJCTION PTROLS IN THIS ReGARD) ALSO CUT OFF THE INJCTRORS COMPLETELTY WHEN UNDER COMPRESION WHICH FURTHER INCREASES ENGINE BREAKING. If you rely purely on your breaks down a steep windy mountain pass, even with just a light weight trailer behind you, you will run out of breaks very fast. You need to use engine breaking to maintain speed at a safe level and only use the brakes when really needed, or to bring the vehicle to a complete stop.

    In my experience, manual gearboxes are far superior in this regard to autos (talking about LDVs and cars, not large trucks), but the new gen autos with multi clutch lock up torque converters are pretty much on par, and a lot easier to drive.

    I think MULLERZA explained it better....
    Last edited by RPiet; 2019/12/09 at 10:54 AM.

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    Default Re: Engine Braking vs Brakes

    When towing I almost always use engine braking on long declines, to be honest if I don't do it manually my sport changes down automatically to assist with braking.
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    Default Re: Engine Braking vs Brakes

    I always gear down.

    Firstly it helps with the deceleration.

    Secondly. I want to be in the correct gear for the speed (or is it velocity ? ) of the vehicle. When approaching a red traffic light, decelerating... gearing down and the light turns green, I'm already in the correct lower gear to accelerate again. Same with going around corners. You should be in the correct gear before entering the corner. That way you can just accelerate without changing down.

    Thirdly, it is just fun to blip the throttle to match the revs for the lower gear. The bigger engine the better.
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    Default Re: Engine Braking vs Brakes

    Ok cool.

    So it would seem it's mostly for avoiding brakes overheating on passes, and especially whilst towing.

    I have not had any issues driving normally, or even towing a little venter trailer in an auto, I just use the brakes when speed starts exceeding what the speed limit is, but I doubt you need to worry about in those circumstances. I mean I have seen trucks overheating brakes, and I suppose caravaners needs to worry about it as well, but normal car drivers don't.
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    Default Re: Engine Braking vs Brakes

    Quote Originally Posted by KobusDJ View Post
    I always gear down.

    Firstly it helps with the deceleration.

    Secondly. I want to be in the correct gear for the speed (or is it velocity ? ) of the vehicle. When approaching a red traffic light, decelerating... gearing down and the light turns green, I'm already in the correct lower gear to accelerate again. Same with going around corners. You should be in the correct gear before entering the corner. That way you can just accelerate without changing down.

    Thirdly, it is just fun to blip the throttle to match the revs for the lower gear. The bigger engine the better.
    When driving a manual I prefer to use the brakes to slow down to the appropriate speed and then gear down when at that speed, I hate it when the car revs high due to gearing down.

    In auto its not a problem, car will change gears accordingly.
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    Default Re: Engine Braking vs Brakes

    Quote Originally Posted by lizardalpha View Post
    When driving a manual I prefer to use the brakes to slow down to the appropriate speed and then gear down when at that speed, I hate it when the car revs high due to gearing down.

    In auto its not a problem, car will change gears accordingly.
    Manual means the gears are changing too low too soon if the engine is screamin'. That or it's a 4-speed small petrol engine vehicle.
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    Default Re: Engine Braking vs Brakes

    Quote Originally Posted by lizardalpha View Post
    ... I hate it when the car revs high due to gearing down....
    You are gearing down too soon.

    Everything should go smooth.
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    Default Re: Engine Braking vs Brakes

    Quote Originally Posted by KobusDJ View Post
    You are gearing down too soon.

    Everything should go smooth.

    No no, I don't do it, I have seen people do it, or experienced people do it.
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    Default Re: Engine Braking vs Brakes

    Quote Originally Posted by lizardalpha View Post
    Ok cool.

    So it would seem it's mostly for avoiding brakes overheating on passes, and especially whilst towing.

    I have not had any issues driving normally, or even towing a little venter trailer in an auto, I just use the brakes when speed starts exceeding what the speed limit is, but I doubt you need to worry about in those circumstances. I mean I have seen trucks overheating brakes, and I suppose caravaners needs to worry about it as well, but normal car drivers don't.
    True, you don't NEED to use it, but it's a good habit to gear down during long braking. For absolutely no effort you are saving wear on the car.

    Just about all modern auto's will have locking clutches in most gears, so you get exactly the same braking effect with an auto that you do with a manual.
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    Default Re: Engine Braking vs Brakes

    Quote Originally Posted by lizardalpha View Post
    ... experienced people do it.
    Clearly not that experienced then...
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  17. #17
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    Default Re: Engine Braking vs Brakes

    Quote Originally Posted by douglash View Post
    Clearly not that experienced then...
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    Default Re: Engine Braking vs Brakes

    Quote Originally Posted by lizardalpha View Post
    Well, I believe trucks are designed that way, especially when going down passes, where their brakes will either overheat
    This. If the brakes overheat they can fade, become ineffective or catch fire.
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    Default Re: Engine Braking vs Brakes

    Gearing down save the brakes. Even auto cars lately also gear down when decelerate. Worst I have seen is pressing the clutch together with the brakes when decelerate.
    Last edited by JLK; 2019/12/09 at 11:33 AM.
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  20. #20
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    Default Re: Engine Braking vs Brakes

    Quote Originally Posted by lizardalpha View Post
    Ok cool.

    So it would seem it's mostly for avoiding brakes overheating on passes, and especially whilst towing.

    I have not had any issues driving normally, or even towing a little venter trailer in an auto, I just use the brakes when speed starts exceeding what the speed limit is, but I doubt you need to worry about in those circumstances. I mean I have seen trucks overheating brakes, and I suppose caravaners needs to worry about it as well, but normal car drivers don't.
    When a truck's brakes overheat, it means the driver slipped up in selecting the right gears. You have to be wake-up because things happens quickly.

    Going down a pass and only using your brakes can end badly for you. If your brakes are heated-up already, and you come around a bend and the traffic is at stand-still, chances are your brakes could fail and you will round up a few cars.

    Letting the engine run against compression won't harm it.

    Being sensible about this is difficult to explain, every situation is different.

    My driving style is such that I have done close to 100K km on a set of brake pads on a Nissan Hardbody(diesel). Problem free.

    Best is to push your rig to the limits( when it's safe to do so) and to figure out the parameters yourself.

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