[bigyikes]

This one is pretty cool and definitely surprised me.

> Motor Humming or Whirring when Navigating to a Supercharger

…

> In some circumstances (such as cold weather), it is normal for the motor(s) and components to make noise, such as humming or whirring as it generates heat to warm the Battery.

Super cool that the motors can be used for things other than moving the vehicle. It reminds me of how ESCs for RC vehicles use the motors to generate audible chirp tones to indicate status.

Motors are multi-purpose devices!

[dralley]

My understanding is that high-end residential heat pumps (e.g. Mitsubishi HyperHeat) will do this at lower temperatures as well. If the temp drops into the zone where the heat pump starts losing effectiveness (which on such systems is still pretty low, supposedly mine provides the full heat rating down to around 0F), they can run the blower motor in a less efficient regime to supplement the heat pump with a bit of resistance heating, without needing to fall back to a true "auxillary" heat source like heat strips or a furnace. That can extend the effective range down to a few degrees below zero (Fahrenheit).

Since I live in the southeast, that's more than good enough to skip installing any auxillary heat source in the first place.

[xg15]

I find it interesting that you can find stuff like this even in biology: When you shiver in cold weather, your body is basically doing the same.

[joshspankit]

This is an aside, but as a native of winter cold: shivering is an excellent strategy to avoid death, but it’s a terrible strategy for actually feeling warm. (Better is moving, relaxing, and massaging the ears/hands/feet to promote blood flow.)

[xg15]

Sort of makes sense to me. From what I understood from the wiki [1], you can compare the temperature regulation (very) roughly to a thermostat: There is a "target" temperature that the body "wants" to reach and a "current" temperature that the body senses it currently has.

If "current" is higher than "target", the body invokes several mechanisms to bring the temperature down, such as turning up sweat production and making you feel hot; if "current" is lower than "target", it does the same to raise the temperature e.g. by shivering and making you feel cold.

(Fever also works by changing the target temperature of that regulation system, which is why you feel cold at the beginning when the target was raised to the fever temperature and hot at the end when it was lowered back to the normal body temperature)

So it makes sense to me that shivering doesn't make you feel warm, because both, the feeling and the shivering are efforts by the body to raise the temperature.

[1] https://en.m.wikipedia.org/wiki/Thermoregulation_in_humans

[joshspankit]

Easy upvote.

I think there’s something else mentioned on that page that is a major contributor to feeling cold: redirecting blood flow away from the skin and in to the muscles (/organs)

[Angostura]

> shivering is an excellent strategy to avoid death, but it’s a terrible strategy for actually feeling warm.

Sounds like an excellent survival strategy - saves you, but leaves discomfort so you have an incentive to get somewhere safer.

[gambiting]

Don't know about high end - I literally have the cheapest unit from Midea and it does exactly this when it's cold.

[dosshell]

Interesting, that does not sound efficient? How much more efficient than using electrical heating directly instead?

0F ? That can't be right?

My Mitsubishi gives heat to around -31F (MSZ-RW Sumo)

[londons_explore]

The efficiency of electrical resistance heating is exactly the same whether you use motor coil resistance or resistance wire.

However, they simplify their system design a little (fewer contactors, fewer wires, fewer components to buy/test)

[stavros]

It's not the same if you generate the heat outside and bring it inside, though. I don't know enough about where the fan is located to know if that's what you mean, but that would be different.

[londons_explore]

air/air heat pumps have a fan on both the inside and the outside. In modern designs, both those fans will be brushless DC, which enables deliberate heating through software.

Note however that both fans will typically be ~150 watts - which means that when heating they can't produce orders of magnitude more heat than that. So heat produced by the fan motor, even when run to generate as much heat as possible, probably won't be a very significant contributor to overall system heat output.

[raccoonDivider]

Logically you'd keep as many parts as possible inside, where the temperature is easier to control?

[bogeholm]

Maybe if you expect the heat pump to mainly move heat in, the heat generating parts should be on the inside, and reverse if you’re mainly moving heat out (A/C).

Don’t know if this is considered during installation?

[jon-wood]

> It reminds me of how ESCs for RC vehicles use the motors to generate audible chirp tones to indicate status.

Super Mario Wonder from Nintendo recently uses the vibration motors in your controller to play sound effects in some places which I thought was an incredibly neat trick.

[Waterluvian]

I always thought about this growing up. How the engine’s heat is used directly to heat the cabin and there is no heater.

Also my gaming PC in the winter. It feels like free compute given I’m heating anyways.

[jacquesm]

A gasoline based ICE is so incredibly inefficient it needs to shed heat or it would melt down. It makes more heat than that it makes motive power (the thing it is designed to do...). A 50 KW engine makes 200 KW(!!) of heat (at full throttle). Most of that heat energy exits the system through the exhaust gases but there is plenty that gets stuck in the body of the engine and you need to remove it from there somehow before it causes damage. That's where your cooling system comes in, a coolant (typically: water or glycol or a mixture) passes through its own channels in the engine around the thermally loaded parts such as the cylinder and head walls to remove the heat. This coolant is pumped around in the engine using the coolant pump to a radiator, usually located at the front of the car in the airstream to help reject the heat to the environment. The interior heater of a car basically just re-routes a bit of that heat in the cooling system into the cabin through a miniature radiator with a fan connected to it that doesn't vent into the environment but into the cabin.

So there is plenty of waste heat to go around. Some diesels got so efficient though that they needed an extra in-line heater to have enough heat for the cabin in specific operating domains (low power engine, low revs).

It is effectively co-generation: you get two different kinds of energy (motive and heat) and you use them for different purposes.

[dmix]

I always wonder how you know so much about so many topics to make quality comments on a wide variety of topics on HN. Truly a jack of all trades.

Maybe it's like how I spend so much time reading random Wikipedia articles on topics because I need to know how everything works.

[jacquesm]

Hm... too many projects :)

And that list is only getting longer, I think I'll pass it on to my kids.

Right now (and for the past couple of years) it has been mostly music but also still some more interesting tools to play with. Currently making a set of super realistic traffic lights for my youngest including pedestrian crossing and automatic cycle influencing (road coil pickup to detect car presence in front of the lights) for his model cars. Green wave, the works.

I've mostly stopped writing up the projects, but still have a bunch of posts pickled that I probably should finish. Most recent software bit: ear training module for pianojacq.com is work in progress (press low 'A' on an 88 key keyboard to enable the secret menu that will enable the ear trainer, it is not quite ready for mass consumption yet but it is getting there).

[rebuilder]

Even more off-topic, but something I’m struggling with personally: how do you find the time for projects, with kids in the picture? Me, I can just barely eke out a truncated workday, then it’s kids and housework until the kids go to sleep and maybe 1.5 hours of time until bed, which mostly I spend with my partner.

So I see people with diverse interests and kids and I just wonder: how!

[jacquesm]

Hm, that's a hard one. I try to involve my kids in them, this doesn't always work, but when it does it is fantastic.

I'm also an insomniac (it's 7:20 am here and I'm still awake...) so I have a ton of time when everybody is asleep (that's when I do most of my coding and reading), and when everybody is off to school I catch up on sleep. Not ideal but it mostly works. Another nice-to-have is that I can make ends meet with a relatively small fraction of the year spent on work (and that simply means I'm not reducing my savings, if I want to grow my savings I'd have to work more than that).

[dmix]

Oh cool, not to further derail this thread but the music direction is interesting. I've also just gotten (back) into music production using an MPC One+ and I used https://www.audiblegenius.com/ for music theory+ear training. A frequent theme I've noticed in Youtube tutorials is a ton of >35 software engineers mentioning they are getting into music and feeling the need to say how old they are, as I guess the meme is learning music is for naive 20yr olds.

[jacquesm]

For me it was COVID that drove me back to music, I had a ton of time on my hands and we'd just bought an old (and really crappy) piano so I decided to get more serious about it. Long way to go though before I'll be satisfied with it, and I doubt I ever will be. Not giving up, it is just too much fun.

Thank you for that link!

[jacquesm]

So, you're officially an influencer now, I bought the course. Very high quality material, a ton of work must have gone into that. I hope to get my own stuff up to that level of polish, it certainly sets an example.

[sbierwagen]

>Some diesels got so efficient though that they needed an extra in-line heater to have enough heat for the cabin in specific operating domains

I live on the top of a hill, so the first seven minutes or so of me driving anywhere is coasting at minimum engine power. Once air temp gets below 10C it's a long, slow painful wait for the vents to start blowing warm air. Especially unfortunate when you're waiting for the defroster to start doing something. I've considered installing a block heater, even though it wouldn't be needed to start the engine at all, just to warm the coolant up!

[jacquesm]

Such a slow warmup is probably also bad for your engine (the oil will be super hard to pump around so you'll have very little lubrication and very high oil pressure until it warms up a bit) so that block heater may well be useful in more ways than one.

You may want to look into oil that flows better at low temps in winter based on what temperature your engine eventually reaches when it is fully warmed up. There is a good chance that your engine will work better with different oils for winter and summer, also if you have an older car you may get some mileage out of blocking off a piece of the radiator.

[sbierwagen]

It's supposed to run 5W-30 but for the cold months I do 5W-20. After watching the Project Farm metal on metal wear tests of 0W oils, and the fact I'm not running the engine at -20C, I'm not eager to go any lighter: https://www.youtube.com/watch?v=xtSwaF2evTU

[literalAardvark]

Do 0w-30 not Xw-20. The number on the left is cold temperature performance, where cold temperature =not at operating temperature.

The number on the right is in the manual and you only change it when you go to the track.

Atm you're running a lighter oil than your car is designed to use and it's very likely to be a bad idea.

In the video you linked the only oils you can compare in the way he is comparing them are the 0w-20 and the 5w-20.

Later edit: I've watched that and since the tests the oils only at cold temperature it is entirely inconclusive wrt protection at operating temperature.

And cooking test is just dumb. Your oil rarely above operating spec. The only oil exposure to above spec temps is the oil in the top side while the engine is cooking after being stopped, and the oil in the burn chamber which burns and is then filtered out.

If you want to know how your oil is doing collect it after a service interval and send it to be tested.

[jacquesm]

Definitely go for the 0W-30 if you're doing cold runs even if it isn't at -20C. I use it myself in the winter on an older engine for very similar reasons. That video is ... questionable ....

[Roark66]

Maybe check if your EGR is operating properly? Also the resistance heater if equipped.

Most diesel cars equipped with EGR also detect its (frequent in older cars) failures, but I suppose it's possible to have a fault without it being detected.

EGR is responsible for recirculating exhaust gases back into the intake primarily to increase efficiency, but a nice side effect is that it heats up the engine a lot quicker.

Also, many diesel cars sold around here since 2000 or so are equipped with a resistance heater that kicks in when the engine is cold. Perhaps that's different in other markets.

[almostnormal]

> EGR is responsible for recirculating exhaust gases back into the intake primarily to increase efficiency, but a nice side effect is that it heats up the engine a lot quicker.

Efficiency does not need EGR. EGR only helps to keep NOX down when running efficiently. In some (many) vehicles EGR is disabled at cold temperatures.

[semi-extrinsic]

Better than (or in addition to) a block heater is to have an AC cabin heater. Defa makes some really nice stuff, it's more or less "standard extra equipment" here in Scandinavia.

[queuebert]

I'd like to add that ICEs need to run hot to minimize cylinder wall heat losses and allow more of the explosion to be converted into work instead of heat, although too hot and they break of course. Ideally the engine block would be at the same temperature as the combustion temperature, but we don't have the materials to achieve that yet.

[jacquesm]

There have been some experiments with uncooled diesels that almost made it.

[akira2501]

> It makes more heat than that it makes motive power (the thing it is designed to do...).

Sure.. but try running that same engine when it gets too cold, which is why "block heaters" exist and get used in certain parts of the world. The operating temperature of the engine _is_ part of the design criteria.

[jacquesm]

Absolutely, but to get it there it has to work first or you'll have to pump in heat from some other source. Starting a large diesel in sub-zero temps can be quite challenging.

[afavour]

Unfortunately I have a vivid memory of the opposite: driving an extremely decrepit old car through the south in July, had to crank the heat to max to try to direct the heat away from the engine. No AC in the car, naturally.

[JoBrad]

I also have this memory. The A/C is a heat pump that just pulled heat to/from the radiator, which is used for both the engine and the A/C. So turning on the heat causes the thermostat to be tripped faster (or so I was told), moving heat away from the engine. You had to be moving for this to work well, especially if your thermostat was going bad.

[bigyikes]

> Also my gaming PC in the winter. It feels like free compute given I’m heating anyways.

Totally. If it's cold and you have an idle rig, you might as well use it to run a crypto miner before reaching for an actual heater.

[xur17]

Assuming you use electric resistive heat. The math changes a bit for gas or heat pumps.

[Rebelgecko]

Actual heating systems can be better than 100% efficient, while crypto mining or cinebench or whatever is <100%

[josephcsible]

How can anything be <100% if producing heat is the goal? Where would the rest of the energy be going?

[stephen_g]

I’m not sure what they mean about crypto miners or computers (mentioning cinebench), basically all the energy going in should be turned into heat so that should be near enough to 100% efficient. Where else would the energy be going? Sure, there will be a bit of RF power (Wi-Fi and some EMI) and depending on the device, a bit of light (LED indicators, monitor backlight) but that should be tiny compared to the energy that will end up as heat…

In terms of heating systems though, it’s normal for fuel based systems to be <100% because you need to vent exhaust, and a lot of your heat your fuel produced can be rejected away from where you want it with that. For example, older gas boilers might only be 80% efficient or so, and even the much more efficient condensing boilers are still only in the low 90s.

[crashmat]

Won't light heat things up by bouncing around anyway?

[wardedVibe]

They mean a heat pump. You apply work to transfer heat, getting more inside than if you had just turned the energy into heat directly; the outside gets colder of course.

https://en.wikipedia.org/wiki/Heat_pump#Principle_of_operati...

[josephcsible]

Yes, heat pumps are over 100%, but isn't turning the energy into heat directly exactly 100%?

[Rebelgecko]

I think you lose some to RF, photons (with a monitor), sound waves, etc. Some of those losses can be reabsorbed and turned into heat, but some stray photons and radio waves will go out the window, never to return.

The majority does go to heat but you'll never hit the 100% threshold like other methods of heating can meet (or exceed)

[quesera]

Using a cryptominer or GP computer at full tilt for the purpose of making heat is less than 100% efficient, because some of the input power gets used on computing.

A pure resistive heater is also less than 100% efficient, but it's very very close.

[jffry]

Where does the energy "used on computing" go? The power consumption of a CPU is dissipated as heat.

[amluto]

Your computer is not doing work (in the thermodynamic sense) that gets stored anywhere in the computer, and it is not transmitting a significant amount of energy out the Ethernet port either. (It is moving some energy out the port, copper or fiber, but it’s likely receiving an almost equal amount back, and the power is question is negligible.)

[koverda]

what do you mean?

[vGPU]

Heat pumps can provide an “efficiency” of some 300-400%+. The “trick” is that they use electricity to move heat instead of creating heat, which is why heat pumps stop working well under a certain temperature.

They kinda work like a reverse refrigerator. A fridge takes heat out from the inside and moves it to the outside. A heat pump does the opposite.

[stephen_g]

You’ve completely failed to answer their actual question, it was the claim of less than 100% efficient heating they were asking about…

[kalleboo]

Heat pumps which use energy to move heat around are more efficient than using energy to generate heat directly.

[jowea]

Won't you damage your GPU faster by doing that?

[anikan_vader]

It's free electricity, but a computing device still makes for a pricey space heater.

[spike021]

I have a relatively analogue car (Subaru BRZ) and there are times when you shut it off on a warm day and then randomly about ten mins later a radiator fan kicks on. I guess it's to help cool down but I don't remember exactly what the manual says.

Basically it's cool how cars do things largely on their own sometimes to stay within certain parameters.

[bb123]

This is due to a phenomenon called heat soak which is where the engine temperature increases above normal for a time after it has been switched off due to the lack of coolant flow. The fan is coming on to aid cooling the engine/engine bay to reduce the effect of heat soak. With carburettor fed engines it is sometimes advised by the manufacturer to allow the engine to idle for some time after running it at high RPM. This is because the effect of heat soak can be significant enough to boil all the fuel off in the carb, making the engine hard to restart when hot.

[op00to]

I had an old Volvo that would “vapor lock” on short trips. It’s amazing how reliable cars are now compared to 20 years ago.

[rootusrootus]

In my experience it was more than 20 years ago that this happened. It was when most cars switched to fuel injection. Late 80s, early 90s. Treating a car as an appliance and having it 'just work' became so much easier when fuel injection was invented.

20 years ago was 2003, which is practically yesterday [in my mind...].

[bratwurst3000]

To my knowledge it is because the the oil and water needs the motor on to move through the engine and cool certain parts . If the motor is shout down to early and those can’t circulate anymore following could happen

-turbocharger overheats

-oil overheats And the things you stated and much more …

Better to let the motor run while standing is to run it the last kilometers in low rpm

[l33tman]

same issue with projector lamps, the fan is kept on for a while after you shut them off

[HPsquared]

And ovens.

[almostnormal]

And some PC power supplies.

[krallja]

My portable induction stove runs its fan for a minute after I shut off the coil.

[actionfromafar]

Also turbo charged engines can greatly benefit from running idle for a minute. I learned the hard way. (Had to replace the turbo.)

[rainbowzootsuit]

There have existed "turbo timers" that keep the engine running for a short time after the key is off to help avoid this. Not sure if that works with modern cars as easily.

[rootusrootus]

Modern turbo designs (most anything in the last 25 years, at least) use water cooled turbos and convection keeps the water flowing after the engine is turned off. This is why we don't use turbo timers any more.

[gambiting]

And also even back then it affected almost no one, there were loads of tests done on this by automotive magazines of the era and found out that usually the last 1-2 minutes of gentle driving to your driveway/garage is more than enough to cool down the turbo properly, the only people affected were those who due to either aggressive driving or circumstances of their location would drive at high rpm, stop, then immediately shut down their engines.

[FireBeyond]

I have a 2021 twin turbo car (Audi RS 5). It runs the radiator and pumps adaptively on engine shut off to bring things down.

[throwawaaarrgh]

The fan is triggered by a relay, triggered by the ECU, which uses coolant sensors (the thermostat sensor that is iirc not always the mechanical thermostat) to adjust when to cool the radiator. That temp is much higher than the ambient air will ever get, so if the fan comes on after the car is turned off then either it was just about at the temp that would have turned on the fan, or something could be slowly going wrong with the car to trigger the fan unnecessarily. A car is a system of systems so many different things can cause it.

If it happens a lot (when turned off) I'd think about having an inspection done. Worst case scenario, engine ends up overheating, warps or explodes, and you need a new one. Coolant system is one of those "oh shit" systems that you need to pay close attention to.

[sgc]

Car engines heat up when you park, because the air cooling and circulation of the coolant keeps it cooler while driving. It seems completely within the common laws of physics that when you are at not so uncommon temperatures, the coolant closer to the engine heats up well above standard operating temperatures once the car is off, and then convection currents bring enough of this overheated coolant to the sensor to trigger the fan. I have seen this behavior on many cars over the years, without any underlying concern in any of them. If it is not running hot while driving, I personally would not worry about it.

[JasonSage]

This is 100% correct.

For those curious, the coolant around the engine block can boil and flow upwards after the engine is off, and the coolant circulation system is designed to handle this pattern. You can observe this yourself if you overfill your coolant and take it out on a hot day, the excess hot coolant will bubble up and run out for a good while after the engine is off.

I second the advice that if the engine isn’t overheating while running, everything is likely working as intended.

[londons_explore]

It's also a common cause of breakdowns... The fan normally cools the radiator, but the temperature sensor is on a coolant hose. Since the engine is stopped coolant isn't flowing so the fan isn't cooling the same thing the sensor is sensing, which means it can end up running for 30 mins or more. Since the fan can be 20 amps or so, you can easily kill old car batteries due to this effect. User comes back after an hour shopping to find their car battery is dead.

If I was a car manufacturer, I would wire the fan into the ignition circuit so it can never run with the ignition off - it's fairly useless to have a fan blowing on a radiator when the coolant isn't flowing anyway.

[pests]

Isn't that feature the exact one being discussed in this threads in order to not overheat the engine though?

[throwawaaarrgh]

If it goes on for 15 minutes or more, it could be one of seven different problems: https://mindofmechanic.com/fan-still-running-when-car-is-off...

Cars are like people. Sometimes a quirk is normal, and sometimes it means your bottom end is gonna fall out. Gotta get regular checkups and hope you catch it in time.

[pests]

> Car engines heat up when you park, because the air cooling and circulation of the coolant

A further reason is no movement = no wind speed. I used to have an old Pontiac grand am with the ram air. I had overheating issues sometimes that were literally solved by going faster.

[bb123]

I don’t think this is true - this is completely normal behaviour. The cooling fan is coming on due to a phenomenon called heat soak which is where the engine temperature increases above normal for a time after it has been switched off due to the lack of coolant flow. The fan is coming on to aid cooling the engine/engine bay to reduce the effect of heat soak.

With carburettor fed engines it is sometimes advised by the manufacturer to allow the engine to idle for some time after running it at high RPM. This is because the effect of heat soak can be significant enough to boil all the fuel off in the carb, making the engine hard to restart when hot.

[kiksy]

I have the same car, it does this too. As have most if not all of my other cars I've owned. I've always put it down to the fact there is no cooling from the forward motion of the car passing air towards the radiators so the engine slowly heats from the already generated heat from driving. The temperature hits the limit the sensor has set and the fan turns on until it's below that set temperature.

[c0nsumer]

Because it was designed with Toyota I don't know if the BRZ does it, but a number of other Subarus will kick on an recovery pump ~6 hours after ignition. It sounds sort of like a small/quiet compressor.

Before I looked up what it was, I kept hearing a gentle noise coming from the garage in the late evening. Figured it was noise from outside... Then one day I was out there and heard it start, realized it was the car, and looked it up.

[rootusrootus]

That is the evap leak testing pump. It pressurizes the tank briefly to test the effectiveness of the cap.

[twisteriffic]

This confused the hell out of me the first time I heard it. Taking the garbage out in the middle of the night and hear whirring coming from under a vehicle that hasn't moved in hours.

[rpmisms]

My Kawasaki Ninja 500 will do the same thing, and it's a bike with very old tech. It is air-cooled, so it's probably a safety feature. Still cool.

[akira2501]

Supposedly one of the arguments for lane splitting in California was the propensity for bikes to overheat out here when stopped in traffic. My 650 did not have a fan but it did a good enough job heating up my crotch to a nearly unbearable degree on a hot day without it.

[IgorPartola]

I have certainly experienced overheating due to traffic on my air cooled bike. Now I am thinking about adding a fan to my oil cooler that would either be on a switch or even on a proper thermostat.

[rpmisms]

I have as well, and it's why I'm getting a liquid-cooled bike.

[rainbowzootsuit]

Back when I watched more F1 racing they had a musical performance where they used the telematic systems of some cars, with their high revving motors, to play notes ie the telematics selectively. I couldn't readily find a reference but remember the event.

[NextHendrix]

https://www.youtube.com/watch?v=XRXwWbo_mX0

Maybe this is what you're referring to. There are similar examples where people do this with old disk drives and printers too.

[rainbowzootsuit]

I'm pretty sure this is exactly it. Thank you!

[NextHendrix]

https://www.youtube.com/watch?v=kCCXRerqaJI

The floppotron

[wrycoder]

It's on YouTube. Star Wars, as I recollect.

[bitwize]

> Super cool that the motors can be used for things other than moving the vehicle. It reminds me of how ESCs for RC vehicles use the motors to generate audible chirp tones to indicate status.

> Motors are multi-purpose devices!

In WALL-E, one of the robots following the title character, lacking any audio output, spins its motors at different rates to play the tune from Hello, Dolly! that it had learned from WALL-E.

See also the Floppotron: https://www.youtube.com/watch?v=oGfkPCZYfFw

[yonatan8070]

This reminded me of the SmartKnob View I saw on YT a while back, it's a knob built on a burshless motor that's controlled to provide the user with software defined feedback like tactile clicks and end stops

https://youtube.com/watch?v=ip641WmY4pA

[queuebert]

The Car Care Nut talked in detail about the multi-purpose design of Tesla's heating systems: https://www.youtube.com/watch?v=7HC72p2gfuQ

[pests]

This was def a noticable thing in the M3 before they added the dedicated heat pump.