7 ms·

9000 RPM is faster than your screen refreshes

69 points by Mojah 15d ago

Danieru 15d ago
No wonder idle stop is so important. Idling at 900rpm or 15cycles per second is a tremendous waste. Somehow I always assumed it was slower. 0.9k RPM is way too fast to be the low end of a machine.
- Grombobulous 15d ago
  True, idling is wasteful, but at the same time “spinning fast” does not necessarily equate to “high energy consumption.” The CPU fans in my computer spin at about 1000 RPM all day long but that doesn’t mean they’re consuming a lot of electricity.
- huijzer 15d ago
  Well.. as so many things in engineering: it’s a tradeoff. Mechanically, it’s also very important to let the engine warm up and cool down before and after heavy load. Primary reasons for warmup are that the oil is more fluid on higher temperatures and metal is also less fragile when 50 or so degrees above freezing. Cooldown is especially important on turbo engines as the turbo on hundreds of thousands revs per minute and high temperature needs oil to be pumped through the bearings. If you turn it off after heavy load on engines that do not keep the oil running after motor shutdown, there is a chance that oil burns and gets stuck in the bearings, degrading performance or worst case breaking the turbo.
  - huijzer 15d ago
    Also for the warmup case, tolerances inside the engine are designed assuming a hot engine. At lower temperatures, the metal hasn’t expanded yet causing also more stress on various parts such as the piston (seals). And for the turbo I forget to mention that if you leave a turbo engine idle for a few minutes that this allows both the temperature and speed of the turbo to reduce. Many trucks have a sticker in the dashboard saying “do idle engine x minutes before shutdown to avoid turbo damage”. (But also do not idle for extended periods which I’m not 100% what’s the reason. I guess it’s due to diesel engines in some cases getting too cold while idling.)
    - fwlr 14d ago
      When a combustion engine is idling, it’s usually not burning anywhere close to 100% of the fuel that it draws, which means higher quantities of unburnt fuel are reaching downstream parts of the engine system (like the exhaust system) that are only designed to be moderately resistant to fuel.
- mschuster91 15d ago
  At idle, it doesn't take that much fuel to keep the engine alive. Idle stops are more important for noise abatement and local toxic exhaust gas emissions - a lot of exhaust gas treatment depends on the exhaust gas having a minimum amount of thermal energy. The downsides of idle stops are, however, that they tend to put a lot of load on the engine, especially from the lack of oil pressure at the very few first strokes [1], and that the low temperature deposits all kinds of gunk in the exhaust pipework instead of transporting it outwards. If you run an engine with idle stop, it really really is important to properly take care of the engine, including preventative maintenance and regular oil changes. [1] That is even more of an issue in large engine blocks, hence that high pitched noise you hear from ships and locomotives for a while before they start up - that is an ancilliary oil pump, priming the entire oil pipework until all air is gone and full oil pressure is present at all ports in the system.
  - dragontamer 15d ago
    Unless you have a hybrid vehicle, like the Prius. Which basically switches to electric during idle stops and barely has any downside.
  - SoftTalker 15d ago
    Yeah I disable idle stop on my cars, for exactly those reasons. If I'm going to be stopped for more than a minute or two, I'll let the engine idle so that temperatures can normalize, then shut it off manually. Back when turbochargers became common on passenger cars, there was even advice to be sure you let the engine idle for a minute or two before shutting it off, so that the turbocharger could cool. Otherwise the oil in the turbocharger would get baked into a goo. Modern synthetic oils, and turbochargers, handle this better today but I still like to give any hot spots a chance to cool off.
    - tristor 14d ago
      > Back when turbochargers became common on passenger cars, there was even advice to be sure you let the engine idle for a minute or two before shutting it off, so that the turbocharger could cool. Otherwise the oil in the turbocharger would get baked into a goo. Modern synthetic oils, and turbochargers, handle this better today but I still like to give any hot spots a chance to cool off. Yes, it was common to install a "turbo timer" that would leave the engine running at idle for a time after you shut off the ignition to let your turbo cool. I drive a 2024 factory turboed vehicle and it still recommends idling for 30 seconds to 2 minutes after parking before shutting the vehicle off and it continues running an electric cooling fan on a timer after you shut off the ignition. The same set of challenges still exist in 2026 as did in 1986 for a turbo, for the most part.
- deleted 15d ago
  [deleted]
- bob1029 15d ago
  Idle stop == cam death rattle. The externalized consequences of drivetrains failing faster (or being abandoned because they give the perception they might) easily offsets whatever gains are achieved with this nanny tech. Auto start/stop is a great example of weirdly aggressive nerds failing to explore nuance, which is found everywhere.
  - MisterTea 15d ago
    In the early days it also killed starter motors as they weren't rated for that duty cycle. I feel these kinds tech are more symbolic than functional and exist to simply check off boxes to obtain environmental ratings. I would even guess the environmental ratings are also short sighted and exist as symbolic gestures of environmentalism. Basically, environmentalism performance theater.
  - margalabargala 15d ago
    > easily offsets whatever gains are achieved with this nanny tech That's a matter of opinion, which may not be shared by anyone living near places that have seen decreases in noise and air pollution due to idle stop.
    - bob1029 15d ago
      Starting a motor is much noisier than idling a motor. It's "idle start/stop". not "idle stop". At some point the light will turn green.
      - margalabargala 14d ago
        Having stood next to many cars starting after an idle stop, the start is barely louder than the idle. The area under the curve is far smaller for idle start/stop than it is for leaving the vehicle running.
- PreownedPlaid 15d ago
  [dead]
dpoloncsak 15d ago
I'm being incredibly pedantic, but 244Hz monitors would refresh faster than the revolutions, right? Or do I misunderstand Hz
- phoghed 15d ago
  Not pedantic enough because we have 500Hz monitors already. Don’t think that’s the point the author was trying to make though.
  - Sohcahtoa82 15d ago
    Once you go above 144 hz, the returns really start to diminish. Going from 60 to 144 hz in games was great. Certainly noticeable. Going from 144 to 240, it's much more subtle. I'm not sure I'd even notice 500 versus 240 unless I had them side-by-side.
  - willx86 14d ago
    Not pedantic enough https://www.lg.com/uk/monitors/gaming/25g590b-b/ https://www.lg.com/uk/monitors/gaming/25g590b-b/
- deleted 15d ago
  [deleted]
- OGWhales 15d ago
  You’re correct, would be equivalent to 150Hz. I was curious too since my monitor is 360Hz :)
- zokier 15d ago
  But combustion engines go also much faster than 9000 RPM; afaik bike engines can reach 18000 RPM or more.
  - topspin 14d ago
    The fastest reciprocating ICEs I've ever heard of are small, two stroke model engines. Some of those can approach 30K RPM, but that is rare, and I don't know if anyone still manufactures those. ~20K isn't rare for these small engines. Back in the pre-history of Radio (before and during WW1,) electro-mechanical alternators were used to generate low frequency RF in powerful transmitters. Some of those designs would spin at 20K RPM.
AlfredBarnes 15d ago
i like going to https://makermotor.com/rpm-visualizer/ https://makermotor.com/rpm-visualizer/ and bumping up the rate to multiples of my refresh rate and seeing the pattern change.
ssuds 15d ago
In a past life I worked on a rocket engine turbopump that spun at 160,000 RPM. It’s crazy to visualize how fast that is. The stresses in the metal are so high that we needed speciality alloys made exclusively for us. The parts are literally ripping themselves apart.
- MisterTea 15d ago
  High speed turbo machinery is certainly an odd area -- like you said, its on the verge of ripping itself apart. The Leybold turbo molecular vacuum pump on my bench at home is rated to spin at 60,000 RPM. In the old days of metal fabrication you'd have two specialty precision machines to locate, drill and bore holes -- the jig bore and jig grinder. Once you bored a hole, if the part was heat treated there was almost certainly a need to touch up the bore from slight deformation so a jig grinder, a jig bore base with a 100,000+ RPM pneumatic grinder, is used to perform the final precision machining.
  - scoot 15d ago
    > like you said, its on the verge of ripping itself apart They didn't say that - they said "the (exclusive speciality alloy) parts are literally ripping themselves apart". That sounds like a seriously flawed design to me
    - xenadu02 14d ago
      It's just hyperbole. When parts spin that fast centrifugal force becomes a serious problem. Everything is a spring, nothing is actually 100% solid. Anything you make that spins that fast will at minimum grow larger in the direction of centrifugal force and shrink in perpendicular axis. If you don't account for that stretching and shrinking things like turbine blades will end up scraping the walls of the enclosure at speed. Even minor variations in weight get multiplied and create exponentially higher stresses on the part. If you don't have the right alloy with the right hardening/annealing parts will rip themselves apart from attempting to support their own weight against the centrifugal force. There's a reason modern high-bypass turbofan jet engines use monocrystaline blades because growing a single crystal of such size is the opposite of easy or inexpensive. Plus in the core you are dealing with so much heat no alloy exists that can withstand it for long so you have to machine cooling channels inside the blades (which have complex curves) to keep them from getting soft and flying apart.
Knork-and-Fife 15d ago
It is awe-inspiring to think about the metal internals of a combustion engine moving so quickly because they're so heavy and complicated. But in some ways it's more impressive to think about a $40 Dremel 4000 that can plug into a 120v electrical socket and spin at 35000 RPM
maerF0x0 15d ago
Also there's a honda that revs to 20k RPM - https://www.youtube.com/watch?v=2FOGOUkxcTQ https://www.youtube.com/watch?v=2FOGOUkxcTQ
- MaxikCZ 15d ago
  Cant be bothered to skim trough the video to see if he even revs it that high. None of the comments give any timestamp, but quite a few have the same complaint I do.
- tass 15d ago
  My first bike! It was an absolute cop magnet because it always sounded like you were speeding.
bitwize 15d ago
I just tried it and it does that thing where because it makes nearly, and then more than, one revolution per frame, the pistons and crankshaft appear to slow down and stop, then go in the other direction.
rconti 15d ago
The thing that always gets me is that a top fuel dragster's engine only rotates something like 540 times in an entire quarter-mile run.
t0mas88 14d ago
The visualisation is nice to compare with different engine types as well: https://random.ma.ttias.be/boxermotor https://random.ma.ttias.be/boxermotor My only complaint would be that there is no inline-6 while that does have some interesting properties in terms of balance compared to an inline-4 or V6.
rconti 14d ago
Related; I've owned a number of inline 6 cylinder motors and currently have a flat 6 (boxster). I believe the math says the I6 is smoother than the boxer 6, but my perception is that the boxer is vastly smoother. I don't know how to account for that -- maybe because of where the motor is physically located, maybe it's due to the lack of a central driveshaft, or maybe it's something else entirely.
- topspin 14d ago
  > I believe the math says the I6 is smoother than the boxer 6 Both designs (I6 and boxer) can have perfect primary and secondary balance. An I6 should be a smooth ICE, but there are other sources of vibration in these systems beyond inherent balance of reciprocating components.
ifwinterco 14d ago
People take it for granted how insanely good modern internal combustion engines are after 150 years of continuous improvement. A modern petrol engine is a miracle in terms of reliability, performance, smoothness and (relative) lack of harmful emissions
ramshanker 14d ago
A simple framing for reference. Electrical Grid Frequency: 50 Hz = 3000 RPM. 60 Hz = 3600 RPM. So, for Gaming Monitors 144 Hz = 8640 Hz.
hn_acc1 13d ago
I'm even more impressed by purely mechanical engines of the 50s and 60s that revved that high without any help from microprocessors/fuel injectors/coil packs. Porsche built a 9000 rpm race engine that had beveled gears (I had to look it up) to ensure good timing. The 550 Spyder (and apparently later 356 "hot" versions) revved up to around 8000 rpm.

69 points by Mojah 15d ago

No wonder idle stop is so important. Idling at 900rpm or 15cycles per second is a tremendous waste. Somehow I always assumed it was slower. 0.9k RPM is way too fast to be the low end of a machine.

Grombobulous 15d ago
True, idling is wasteful, but at the same time “spinning fast” does not necessarily equate to “high energy consumption.” The CPU fans in my computer spin at about 1000 RPM all day long but that doesn’t mean they’re consuming a lot of electricity.
huijzer 15d ago
Well.. as so many things in engineering: it’s a tradeoff. Mechanically, it’s also very important to let the engine warm up and cool down before and after heavy load. Primary reasons for warmup are that the oil is more fluid on higher temperatures and metal is also less fragile when 50 or so degrees above freezing. Cooldown is especially important on turbo engines as the turbo on hundreds of thousands revs per minute and high temperature needs oil to be pumped through the bearings. If you turn it off after heavy load on engines that do not keep the oil running after motor shutdown, there is a chance that oil burns and gets stuck in the bearings, degrading performance or worst case breaking the turbo.
- huijzer 15d ago
  Also for the warmup case, tolerances inside the engine are designed assuming a hot engine. At lower temperatures, the metal hasn’t expanded yet causing also more stress on various parts such as the piston (seals). And for the turbo I forget to mention that if you leave a turbo engine idle for a few minutes that this allows both the temperature and speed of the turbo to reduce. Many trucks have a sticker in the dashboard saying “do idle engine x minutes before shutdown to avoid turbo damage”. (But also do not idle for extended periods which I’m not 100% what’s the reason. I guess it’s due to diesel engines in some cases getting too cold while idling.)
  - fwlr 14d ago
    When a combustion engine is idling, it’s usually not burning anywhere close to 100% of the fuel that it draws, which means higher quantities of unburnt fuel are reaching downstream parts of the engine system (like the exhaust system) that are only designed to be moderately resistant to fuel.
mschuster91 15d ago
At idle, it doesn't take that much fuel to keep the engine alive. Idle stops are more important for noise abatement and local toxic exhaust gas emissions - a lot of exhaust gas treatment depends on the exhaust gas having a minimum amount of thermal energy. The downsides of idle stops are, however, that they tend to put a lot of load on the engine, especially from the lack of oil pressure at the very few first strokes [1], and that the low temperature deposits all kinds of gunk in the exhaust pipework instead of transporting it outwards. If you run an engine with idle stop, it really really is important to properly take care of the engine, including preventative maintenance and regular oil changes. [1] That is even more of an issue in large engine blocks, hence that high pitched noise you hear from ships and locomotives for a while before they start up - that is an ancilliary oil pump, priming the entire oil pipework until all air is gone and full oil pressure is present at all ports in the system.
- dragontamer 15d ago
  Unless you have a hybrid vehicle, like the Prius. Which basically switches to electric during idle stops and barely has any downside.
- SoftTalker 15d ago
  Yeah I disable idle stop on my cars, for exactly those reasons. If I'm going to be stopped for more than a minute or two, I'll let the engine idle so that temperatures can normalize, then shut it off manually. Back when turbochargers became common on passenger cars, there was even advice to be sure you let the engine idle for a minute or two before shutting it off, so that the turbocharger could cool. Otherwise the oil in the turbocharger would get baked into a goo. Modern synthetic oils, and turbochargers, handle this better today but I still like to give any hot spots a chance to cool off.
  - tristor 14d ago
    > Back when turbochargers became common on passenger cars, there was even advice to be sure you let the engine idle for a minute or two before shutting it off, so that the turbocharger could cool. Otherwise the oil in the turbocharger would get baked into a goo. Modern synthetic oils, and turbochargers, handle this better today but I still like to give any hot spots a chance to cool off. Yes, it was common to install a "turbo timer" that would leave the engine running at idle for a time after you shut off the ignition to let your turbo cool. I drive a 2024 factory turboed vehicle and it still recommends idling for 30 seconds to 2 minutes after parking before shutting the vehicle off and it continues running an electric cooling fan on a timer after you shut off the ignition. The same set of challenges still exist in 2026 as did in 1986 for a turbo, for the most part.
deleted 15d ago
[deleted]
bob1029 15d ago
Idle stop == cam death rattle. The externalized consequences of drivetrains failing faster (or being abandoned because they give the perception they might) easily offsets whatever gains are achieved with this nanny tech. Auto start/stop is a great example of weirdly aggressive nerds failing to explore nuance, which is found everywhere.
- MisterTea 15d ago
  In the early days it also killed starter motors as they weren't rated for that duty cycle. I feel these kinds tech are more symbolic than functional and exist to simply check off boxes to obtain environmental ratings. I would even guess the environmental ratings are also short sighted and exist as symbolic gestures of environmentalism. Basically, environmentalism performance theater.
- margalabargala 15d ago
  > easily offsets whatever gains are achieved with this nanny tech That's a matter of opinion, which may not be shared by anyone living near places that have seen decreases in noise and air pollution due to idle stop.
  - bob1029 15d ago
    Starting a motor is much noisier than idling a motor. It's "idle start/stop". not "idle stop". At some point the light will turn green.
    - margalabargala 14d ago
      Having stood next to many cars starting after an idle stop, the start is barely louder than the idle. The area under the curve is far smaller for idle start/stop than it is for leaving the vehicle running.
PreownedPlaid 15d ago
[dead]

dpoloncsak 15d ago

I'm being incredibly pedantic, but 244Hz monitors would refresh faster than the revolutions, right? Or do I misunderstand Hz

phoghed 15d ago
Not pedantic enough because we have 500Hz monitors already. Don’t think that’s the point the author was trying to make though.
- Sohcahtoa82 15d ago
  Once you go above 144 hz, the returns really start to diminish. Going from 60 to 144 hz in games was great. Certainly noticeable. Going from 144 to 240, it's much more subtle. I'm not sure I'd even notice 500 versus 240 unless I had them side-by-side.
- willx86 14d ago
  Not pedantic enough https://www.lg.com/uk/monitors/gaming/25g590b-b/ https://www.lg.com/uk/monitors/gaming/25g590b-b/
deleted 15d ago
[deleted]
OGWhales 15d ago
You’re correct, would be equivalent to 150Hz. I was curious too since my monitor is 360Hz :)
zokier 15d ago
But combustion engines go also much faster than 9000 RPM; afaik bike engines can reach 18000 RPM or more.
- topspin 14d ago
  The fastest reciprocating ICEs I've ever heard of are small, two stroke model engines. Some of those can approach 30K RPM, but that is rare, and I don't know if anyone still manufactures those. ~20K isn't rare for these small engines. Back in the pre-history of Radio (before and during WW1,) electro-mechanical alternators were used to generate low frequency RF in powerful transmitters. Some of those designs would spin at 20K RPM.

AlfredBarnes 15d ago

i like going to https://makermotor.com/rpm-visualizer/ https://makermotor.com/rpm-visualizer/ and bumping up the rate to multiples of my refresh rate and seeing the pattern change.

ssuds 15d ago

In a past life I worked on a rocket engine turbopump that spun at 160,000 RPM. It’s crazy to visualize how fast that is. The stresses in the metal are so high that we needed speciality alloys made exclusively for us. The parts are literally ripping themselves apart.

MisterTea 15d ago
High speed turbo machinery is certainly an odd area -- like you said, its on the verge of ripping itself apart. The Leybold turbo molecular vacuum pump on my bench at home is rated to spin at 60,000 RPM. In the old days of metal fabrication you'd have two specialty precision machines to locate, drill and bore holes -- the jig bore and jig grinder. Once you bored a hole, if the part was heat treated there was almost certainly a need to touch up the bore from slight deformation so a jig grinder, a jig bore base with a 100,000+ RPM pneumatic grinder, is used to perform the final precision machining.
- scoot 15d ago
  > like you said, its on the verge of ripping itself apart They didn't say that - they said "the (exclusive speciality alloy) parts are literally ripping themselves apart". That sounds like a seriously flawed design to me
  - xenadu02 14d ago
    It's just hyperbole. When parts spin that fast centrifugal force becomes a serious problem. Everything is a spring, nothing is actually 100% solid. Anything you make that spins that fast will at minimum grow larger in the direction of centrifugal force and shrink in perpendicular axis. If you don't account for that stretching and shrinking things like turbine blades will end up scraping the walls of the enclosure at speed. Even minor variations in weight get multiplied and create exponentially higher stresses on the part. If you don't have the right alloy with the right hardening/annealing parts will rip themselves apart from attempting to support their own weight against the centrifugal force. There's a reason modern high-bypass turbofan jet engines use monocrystaline blades because growing a single crystal of such size is the opposite of easy or inexpensive. Plus in the core you are dealing with so much heat no alloy exists that can withstand it for long so you have to machine cooling channels inside the blades (which have complex curves) to keep them from getting soft and flying apart.

Knork-and-Fife 15d ago

It is awe-inspiring to think about the metal internals of a combustion engine moving so quickly because they're so heavy and complicated. But in some ways it's more impressive to think about a $40 Dremel 4000 that can plug into a 120v electrical socket and spin at 35000 RPM

maerF0x0 15d ago

Also there's a honda that revs to 20k RPM - https://www.youtube.com/watch?v=2FOGOUkxcTQ https://www.youtube.com/watch?v=2FOGOUkxcTQ

MaxikCZ 15d ago
Cant be bothered to skim trough the video to see if he even revs it that high. None of the comments give any timestamp, but quite a few have the same complaint I do.
tass 15d ago
My first bike! It was an absolute cop magnet because it always sounded like you were speeding.

bitwize 15d ago

I just tried it and it does that thing where because it makes nearly, and then more than, one revolution per frame, the pistons and crankshaft appear to slow down and stop, then go in the other direction.

rconti 15d ago

The thing that always gets me is that a top fuel dragster's engine only rotates something like 540 times in an entire quarter-mile run.

t0mas88 14d ago

The visualisation is nice to compare with different engine types as well: https://random.ma.ttias.be/boxermotor https://random.ma.ttias.be/boxermotor My only complaint would be that there is no inline-6 while that does have some interesting properties in terms of balance compared to an inline-4 or V6.

rconti 14d ago

Related; I've owned a number of inline 6 cylinder motors and currently have a flat 6 (boxster). I believe the math says the I6 is smoother than the boxer 6, but my perception is that the boxer is vastly smoother. I don't know how to account for that -- maybe because of where the motor is physically located, maybe it's due to the lack of a central driveshaft, or maybe it's something else entirely.

topspin 14d ago
> I believe the math says the I6 is smoother than the boxer 6 Both designs (I6 and boxer) can have perfect primary and secondary balance. An I6 should be a smooth ICE, but there are other sources of vibration in these systems beyond inherent balance of reciprocating components.

ifwinterco 14d ago

People take it for granted how insanely good modern internal combustion engines are after 150 years of continuous improvement. A modern petrol engine is a miracle in terms of reliability, performance, smoothness and (relative) lack of harmful emissions

ramshanker 14d ago

A simple framing for reference. Electrical Grid Frequency: 50 Hz = 3000 RPM. 60 Hz = 3600 RPM. So, for Gaming Monitors 144 Hz = 8640 Hz.

hn_acc1 13d ago

I'm even more impressed by purely mechanical engines of the 50s and 60s that revved that high without any help from microprocessors/fuel injectors/coil packs. Porsche built a 9000 rpm race engine that had beveled gears (I had to look it up) to ensure good timing. The 550 Spyder (and apparently later 356 "hot" versions) revved up to around 8000 rpm.