MANual talk: Engine braking

Sruikyl

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Okay so I got my first car about 2 weeks ago, its a manual transmission and I love it to death. This thread is the product of an argument me and my dad got into regarding engine braking. Personally I don't think its a bad thing and I use it at every light or turn. He, on the other hand thinks it puts unnecessary wear on the clutch and engine. So far I know that engine braking can make your brakes last longer and helps cool the engine by sucking cold air in. He brought up the point that if theres no fuel being combusted the top end won't be getting lubed. He also insists that just putting it in neutral and coasting with the brakes will save clutch life. Thoughts and comments? Your personal preferences?
I tried finding a similar topic but didn't find anything, so sorry if I missed it.
 

MXM

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Riding on breaks is far FAR worse. They were never designed to do that, you need to fully release them to allow cooling down.
 

The_Finn

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anything that uses your clutch is going to wear your clutch it's just a fact. While i have nothing remotely close to empirical evidence i feel like clutch wear associated with engine braking is is going to be greater than normal up shift and rev matched down shift. All that said Brake pads which are designed to be used to stop you and are what $50 for the front end and maybe $30 for the rear? A clutch is closer to $500. I say use the things designed for stopping instead of the thing designed to be used at little as possible.
 
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Spectre

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Brake pads are consumable plus cheap and easy to replace. Clutches are not. Therefore, use the brakes and not the clutch to brake as a general rule.

You are also not cooling the engine when you are engine braking because the idle fuel cut circuit is engaged. This means your engine is running lean when you mechanically force it to suck in more air past the throttle and therefore it is actually running hotter.

This topic has also been covered before, though in multiple different threads.
 
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MXM

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Engine braking != clutch braking. I don't see how coasting in gear wears down clutch more than normal clutch use. Unless you release it veeery slowly due to rev mismatch.

It's not just the pad wear you're dealing with. Even with little force you're generating a ton of heat continuously. The heat is the main issue.
 

Sruikyl

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I'm not sure if theres different kinds of engine breaking but the way I've been taught is by downshifting then letting the clutch out slowly.When when the clutch is out and engine RPMs start to drop do the same with the next lowest gear. And spectre I forgot about idle cut, thats a good point, otherwise the engine would technically be off?
 

GRtak

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Using the engine to brake should only be done in an emergency situation. Normal cars and trucks are not like the heavy duty breathren with engine brakes. It can cause all sorts of lean run like issues and can tear the hell out of the thrust bearing in the engine.
 

The_Finn

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Engine braking != clutch braking. I don't see how coasting in gear wears down clutch more than normal clutch use. Unless you release it veeery slowly due to rev mismatch.

Any time you use the clutch it wears it. The downshift to engine brake is an additional clutch engagement so you are wearing the clutch more than if you either hold the clutch in or pop the car out of gear while using the brakes to slow/stop.


It's not just the pad wear you're dealing with. Even with little force you're generating a ton of heat continuously. The heat is the main issue.

I feel like the heat generated by slowing and stopping was probably built into the design of the system you are supposed to use to slow and stop the car. If it was really that much of an issue you would see cars with auto transmissions having beefier braking systems which is generally not the case AFAIK.
 
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JipJopJones

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What about going down a hill in a low gear to slow your decent? I do this all the time... and living in a very hilly area it's basically what I was taught to do. I've always thought engine braking was the thing to do. No?
 

Spectre

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I'm not sure if theres different kinds of engine breaking but the way I've been taught is by downshifting then letting the clutch out slowly.When when the clutch is out and engine RPMs start to drop do the same with the next lowest gear. And spectre I forgot about idle cut, thats a good point, otherwise the engine would technically be off?

No, but it would be at idle with almost no fuel being injected into the engine - very little air entering, too. And yes, that's the kind of engine braking we're talking about as being hard on the clutch. Just coasting down in the gear you're in isn't mechanically harmful, provided you disengage the clutch before the engine starts to lug.

What about going down a hill in a low gear to slow your decent? I do this all the time... and living in a very hilly area it's basically what I was taught to do. I've always thought engine braking was the thing to do. No?

This is done to keep your brakes from overheating on a downhill, or for traction reasons. It is a safety measure, mostly not needed on most cars made in the last 20 years (brake systems got a lot better). You are, however, trading off clutch life for necessary safety - and in that case, sure, that's acceptable. Doing it while running around the city on flat land, not so much. That's just kind of dumb in that case.
 
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Matt2000

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On the road, in a normal car it makes sense to use the clutch and idle when coming to a stop. With a van you should use engine braking to slow down more gradually and stop a load shifting.

Now, I know the question was related to normal use but the title says engine braking so I'll mention off road use. :p Engine braking should always be used off road, because as Spectre said it helps to maintain traction. It's also much more controlled than using the wheel brakes because you don't need to maintain pressure on the pedal. In some cases, light braking might be needed if you notice a situation where a wheel will lift off the ground, but if you need to do that then you probably shouldn't have driven down there.
 

bone

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Brake pads are consumable plus cheap and easy to replace. Clutches are not. Therefore, use the brakes and not the clutch to brake as a general rule.

You are also not cooling the engine when you are engine braking because the idle fuel cut circuit is engaged. This means your engine is running lean when you mechanically force it to suck in more air past the throttle and therefore it is actually running hotter.

This topic has also been covered before, though in multiple different threads.

no such thing as running lean if there is no combustion. the throttle is closed completely, creating a vaccuum in the cylinders, which slows you down, and creating a vaccuum = expanding the little air in there = cooling it down

i'm not saying you'll be able to cool down your engine by engine-brakeing, but it sure as hell won't overheat due to it

i engine-brake whenever i can, we are taught to do so from the very first lesson!

also: brakes fade when used constantly, no such problem with a clutch
 
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MadCat360

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also: brakes fade when used constantly, no such problem with a clutch

Not if you put in high temperature fluid. Honestly if any modern brake system faded on me for any reason except stamping on both pedals really hard for an hour, I'd be pretty surprised. Going down a hill (even a big one) shouldn't cook any modern (post-2000) system. Maybe on a really heavy car.
 

GRtak

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What about going down a hill in a low gear to slow your decent? I do this all the time... and living in a very hilly area it's basically what I was taught to do. I've always thought engine braking was the thing to do. No?

that is the one other exception I would agree with.
 

Spectre

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no such thing as running lean if there is no combustion. the throttle is closed completely, creating a vaccuum in the cylinders, which slows you down, and creating a vaccuum = expanding the little air in there = cooling it down

i'm not saying you'll be able to cool down your engine by engine-brakeing, but it sure as hell won't overheat due to it.

also: brakes fade when used constantly, no such problem with a clutch

Sorry, but you can cook a clutch just like you can brakes.

Also, if there is no combustion, how does the engine idle if you have your foot off the gas? It must get fuel, air, and in the case of a gas engine, spark.
 

bone

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true, but i've never heard of anybody cooking his clutch under brakeing, if they cook it, it's under acceleration, and frankly you have to be tool for that to happen

there is a huge difference between idling and engine braking. in a modern car with a board computer, look at the fuel usage.
when idling my astra says sth around 0.6l/h
when driving it says anything from 1 - 30l/100km
when engine braking, it says 0.0

as long as the engine stays above idle-revs and you give it no throttle at all, no fuel is injected (and no spark is generated - not entirely sure about this one)
 

thedguy

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Something that hasn't been brought up... the throw out bearings and crank thrust bearings. Won't somebody PLEASE THINK OF THE THROWOUT BEARINGS!

Every time you work the clutch you're putting a large amount of pressure on the crank, which is part of what causes DSM crank walk issues*, not to mention working the throw out bearing a lot more. Then you got the shifter bushings, syncros, drive-shaft u-joints, etc...


*MKIV supra's have been known to develop crank walk with really beefy single disc clutch. The solution is a twin disc clutch. It's issues like this why you don't just stand on the clutch when stopped.

Sorry, but you can cook a clutch just like you can brakes.

Also, if there is no combustion, how does the engine idle if you have your foot off the gas? It must get fuel, air, and in the case of a gas engine, spark.

I've done it, and plenty of people have failed miserably at burnouts doing it to clutches. I'm too lazy to show the Pontiac Trans Am screwing up as well as the Corvette guy.

Moral of the story, vautozone sells pads for most cars for $20 a pair and on disc brakes take 20 minutes to change.
Change a clutch once and you'll decide you'd rather destroy your brakes and have to work on drums.
Fight with broken clutch hydraulics in a cramped engine bay, you'll wish you were just changing the rubber hoses in the wheel wells.
Do I need to go on? Can you tell I can't sleep?
 
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narf

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He, on the other hand thinks it puts unnecessary wear on the clutch and engine. He brought up the point that if theres no fuel being combusted the top end won't be getting lubed. He also insists that just putting it in neutral and coasting with the brakes will save clutch life.

Engine wear? Not so much.
Clutch wear? Oh yes.
No lube due to no fuel? Fuel is not the main lubricant of your engine, the engine oil is.
Coasting in neutral will use more fuel than staying in gear.
Staying in gear will not wear the clutch.
Downshifting will either wear the clutch heavily or use extra fuel to match the revs or both.


My personal preference? Stay in the current gear, using no fuel and letting the engine brake. Use the real brakes when necessary, disengage the clutch when the fuel cutoff goes away at depending on your car 1000-1300rpm.
 

WillDAQ

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Coasting to a halt in neutral will potentially cause you to fail a driving test in the UK. It's considered poor car control.
 
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