Newbie question: When does clutch burn?

[lapsio]

Sorry for potentially dumb question but what are conditions that cause clutch to burn? I'm kicking clutch quite often to put my BRZ off balance in order to slide on turns or whip an U turn. Sometimes on rare occasions I can smell the clutch. It's quite rare, so far maybe I smelled it like 3-4 times (out of 100 kicks or so).

I used to think that it happens when there are good conditions and tires are just too grippy so clutch can't stand that but recently I smelled clutch when launching on snow and I was like... wait... hold up. What the actual f*ck. It was like -4 outside 1 inch layer of snow, car was super cold, literally 0 traction whatsoever I launched it, did "burnout" at like 2kph because it was too slippery to even gain some speed and smelled clutch?... It seemed off... So when really does the clutch slip causing burn? Did I have too high rpm or something? Could it be that transmission was too cold and something funny happened? When clutch kick in BRZ can lead to burnt clutch? When kicking clutch am I supposed to rapidly let off clutch completely rapidly or give some super brief slip like 0.2s in order to not put too much stress on transmission? Car is fully stock. I'm on winter tires so I don't think they're all that much grippy...

inb4 it's my first rwd car and I only made 6k km so far so I don't have much experience driving such cars so there's extremely high chance I'm doing something terribly wrong.

[Grady]

Clutch dumps, burn outs, slipping clutch will wear it out quicker. Good news is the clutch on this car is easy to change. Have fun, burn out the clutch and change it. Then repeat until you are tired of doing it.

[PenGun]

"whip an U turn" That's what the armrest is for. I could do a 180 in an actual Mini Cooper quite happily, and under control. I have not tried my BRZ, I'm very old.


Alright silence. What I mean is the handbrake is what you use for a handbrake 180:

[Purist]

I burned out my clutch doing short warm up burnouts and aggressive gear changes on slicks. It was magical; the air was full of shiny little fragments of clutch reflecting the sunlight.




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[soundman98]

By the smell. It smells like burned, deep fried, cauliflower to me

[Purist]

Originally Posted by soundman98

By the smell. It smells like burned, deep fried, cauliflower to me

Nailed it.

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[Ultramaroon]

Actually, a well-executed clutch kick adds little to no extra wear to the clutch. My explanation may sound condescending but I don't mean it that way. I'm just pointing out stuff using physics-speak.

Clutches burn when they exceed a certain temperature.

Work = energy = heat

We need to dump energy into the clutch in order to heat it.

The engine does no work at all when the clutch is disengaged.

All the work from the engine goes into the transmission when the clutch is fully engaged.

When the clutch is slipping, some of the work from the engine goes to spinning the transmission. The rest of the work goes into heating the clutch.

Work is force applied through a distance, or torque applied through an angle of rotation. We can also think of it as torque through the number of revolutions in which it is applied.

Consider slipping the clutch for a whole second at idle speed. The crankshaft will have made about twelve revolutions in that time.

Now do it for a whole second at 3000 RPM. That's about fifty revolutions; over four times as many revolutions as those at idle.

So, if you slip the clutch for a quarter second at 3000 RPM, it's about as much thermal energy as slipping it at idle for a full second.

To control temperature, limit the time AND torque applied while slipping. If you ever feel it get spongy while slipping it, that's the feel of hot clutch. Avoid that and you're golden

[soundman98]

And long before that point does the smell of hot clutch waft into the cabin

[Ultramaroon]

Originally Posted by soundman98

And long before that point does the smell of hot clutch waft into the cabin

Mmmmmmmm.... not necessarily. Maybe I'm just extra sensitive but I've always felt it before smelling it. Worst was when I was teaching a friend how to drive stick. He got pretty good at level stuff so we tried a hill start. I knew it was bad just listening from the passenger side so I stopped him. Smelled it when we swapped places. Oh, man, it was like stepping on a loaf of Wonder bread. So many feels.

[Mars]

Originally Posted by Ultramaroon

...
Work is force applied through a distance, or torque applied through an angle of rotation. We can also think of it as torque through the number of revolutions in which it is applied.

Consider slipping the clutch for a whole second at idle speed. The crankshaft will have made about twelve revolutions in that time.

Now do it for a whole second at 3000 RPM. That's about fifty revolutions; over four times as many revolutions as those at idle.

So, if you slip the clutch for a quarter second at 3000 RPM, it's about as much thermal energy as slipping it at idle for a full second.
...

This makes sense to me (an accountant who wishes he spent more time studying physics). My only question is, if you're "dumping" the clutch rather than giving it a very quick slip, is the "shock" doing more damage to the clutch than the heat at that point? I would think it saves heat since there's less time slipping but wouldn't that instant jump in torque "shock" something in the system to cause extra wear than a light slip? Just genuinely interested in knowing since I too like to kick it out on the occasional U-turn (FRS drivers, am I right lol).

[blsfrs]

You can drive purdy much any way you want, as long as you acknowledge the consequences. It's a sliding scale: More abuse, the faster things wear out and break. The more you baby her the longer she'll last and be less likely to leave you stranded.

[Ultramaroon]

Originally Posted by Mars

(FRS drivers, am I right lol).

Yes. Absolutely right, but it's not a dump. It's a well executed clutch kick. Potato-potahto?

Bottom line is the shock felt by applying high torque for a short time does not burn clutches. It might break something downstream, but it won't be the clutch.

Just don't get caught

[Mars]

Originally Posted by Ultramaroon

...Bottom line is the shock felt by applying high torque for a short time does not burn clutches. It might break something downstream, but it won't be the clutch.

Just don't get caught

Well I will continue my current method as I've been doing it for a while and haven't seemed to have had any clutch issues nor smells! Also helps that I got a stage 2 since I knew I wanted to kick it a lot.

[soundman98]

Originally Posted by Mars

This makes sense to me (an accountant who wishes he spent more time studying physics). My only question is, if you're "dumping" the clutch rather than giving it a very quick slip, is the "shock" doing more damage to the clutch than the heat at that point? I would think it saves heat since there's less time slipping but wouldn't that instant jump in torque "shock" something in the system to cause extra wear than a light slip? Just genuinely interested in knowing since I too like to kick it out on the occasional U-turn (FRS drivers, am I right lol).

it's the "is it better to brake long and slow, or short and fast?" question.

i think the true answer lies somewhere in between.