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.
Years back I was an intern in a bio lab whose ultracentrifuge achieved spin rates similar to a turbopump. On its titanium head was a bar code used to regulate the speed via a beam of light. Unfortunately the manufacturer issued some with the wrong bar code, causing them to overspin and, at one lab, undergo "rapid unexpected disassembly", sending chunks of flying titanium through concrete walls. Fortunately it was at night and no-one was hurt, but the salespeople travelled out to every customer site the next day to implement the product recall.
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.
> 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
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.
I did a stint back in the day at the IBM Cottle road site sputtering hard disks. All the tools had roughing pumps that would bring the tool to near vacuum before the turbo pumps would kick in as anything even remotely close to atmosphere would just rip the blades apart. Then the older huge tool, the Ulvac had a cryo-pump which was just a big chamber that would cool a sponge to 20 kelvin and molecules would just come in contact and slow down...
What diameter was the part that spun at that speed? Also do you have some idea of the maximum forces exerted on it? It might not be much higher (as in, less than on order of magnitude) than the peak forces exerted on some parts of a reciprocating engine. And the turbine doesn't have to constantly switch between tension and compression, which I think should help a lot when designing a part that moves quickly.
Yes it does, it matters a lot. With smaller dimensions, tip speeds remain manageable. As soon as parts of the thing get supersonic, everything gets much more complicated.
But even with 244 Hz the engine running at 9000 rpm or 150 Hz will not even give you two frames per revolution, about 221° of rotation per frame to be precise. If you want a somewhat smooth animation, say 10° per frame, you want to look for a 5400 Hz monitor.
Yup, 240Hz here make even idling look more like something glitching than moving fast.
At 1/4th the speed idling moves fine, but the individual pixels don't have time to reset properly and some artifacts can be appreciated (1ms refresh time 27" IPS panel)
I don't think it's overly pedantic or even really pedantic at all as there's only one reason for any author to make such assumptions knowing full well that it won't hold for the entire audience. (The reason being editorializing the title to make it sound more appealing than it might otherwise be)
What's wrong with "9000 RPM is faster than my screen refreshes" or "9000 RPM is faster than most screen refreshes" or "9000 RPM is faster than an average screen refreshes"?
"Shocking" news that is anything but. "Little known facts" that are widely known. "Mistakes your making with ..." that you've never once made. It's all just trying to get you to consume the content.
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.
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.
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.
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.
> 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.
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.
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.)
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.
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.
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.
> 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.
> The downsides of idle stops are, however, that they tend to put a lot of load on the engine
While I don't doubt that it seems like this is essentially a solved issue. Priuses are some of the most reliable, long-lasting cars out there despite experiencing considerably more start-stop cycles than a traditional ICE with start-stop would.
Hybrids likely have more engineering around the start-stop cycles than full ICEs with start-stop bolted on to meet emissions requirements.
The prius style dual motor/generator planetary gear arangment avoids concerns about starter motor longevity. But the engines and how they're managed is tuned for their use case.
I'm sure ICE with start-stop will get there eventually, but the automotive industry tends to learn to build reliable drivetrains through a history of failure. From my experience with a couple rental cars a year, on user experience, start-stop is all over the map from really annoying to noticable but unobtrusive ... I imagine how design challenges around lubrication are met is also all over the map.
> Hybrids likely have more engineering around the start-stop cycles than full ICEs with start-stop bolted on to meet emissions requirements.
What evidence is there for this? The Prius was around for 12 years before Toyota brought their first production start-stop ICE to market, surely they (and other mfgs whose hybrids predate start-stop) didn't just throw away all of that knowledge to haphazardly "bolt on" a start-stop system. They didn't, which is why start-stop equipped card have things like low-friction coatings on their crankshaft bearings.
> The prius style dual motor/generator planetary gear arangment avoids concerns about starter motor longevity
Redesigned starter motors with improved longevity also avoid these concerns. In start-stop systems, the starter motor is a safety critical item and they are engineered to a much higher standard. As far as I can find, there's only one start-stop starter related recall in the US (Honda) and it wasn't even a mechanical issue.
> From my experience with a couple rental cars a year, on user experience, start-stop is all over the map from really annoying to noticable but unobtrusive ... I imagine how design challenges around lubrication are met is also all over the map.
I think this captures exactly why people fixate on these systems. They assume that because they can be janky to use (they often can be), that they must be jankily designed. I can't prove a negative, but I just haven't ever seen meaningful evidence that start-stop cars fail faster or fail in the ways critics suggest they should. Surely we would see some evidence of the extra spun bearings, sparkly oil, and premature starter replacements that this almost 20 year old tech has has wrought by now, right? The only evidence I've seen are slightly more expensive batteries needing to be replaced slightly more often.
> As far as I can find, there's only one start-stop starter related recall in the US (Honda) and it wasn't even a mechanical issue.
A start-stop starter issue seems more likely to be handled quietly with Technical Service Bulletins rather than a recall, IMHO. Unless the issue is a critical safety issue or is likely to affect every vehicle, manufacturers seem to prefer TSBs that have much less visibility than a recall. If you're lucky, the dealer will take care of it at your next scheduled service; but many TSBs are only taken care of if you specifically ask about trouble you're having and the dealer is aware of the TSB and you bring it up during the TSB period... my Ford hybrid had a major bearing issue and they replaced the whole motor/generator/transmission assembly under the TSB but only because I happened upon the TSB and brought it in specifically complaining... they had it for scheduled maintenance while it was exhibiting symptoms but it wasn't bad enough for me to complain and they didn't mention anything ... had I known to ask, I would have gotten a new replacement rather than a remanufactured, but oh well.
> They assume that because they can be janky to use (they often can be), that they must be jankily designed.
I think it's a fair assumption, because cars tend to be jankily designed or at least designed around the edge of viability. Most of the modern vehicles I've owned have had successful class actions about drive train problems that almost always come down to running things close to the edge to meet emissions requirements.
There's this one for start-stop https://www.carscoops.com/2025/08/honda-paying-millions-to-s... but there were a lot in the 2000s related to oil leaks etc related to running thinner oils for emissions. It's a consistent pattern; push the envelope for emissions, deal with the powertrain problems via class action.
> almost 20 year old tech
It's closer to 10-15 years old for the North American market, discounting systems used for hybrids because they tend to be significantly different.
> It's a consistent pattern; push the envelope for emissions, deal with the powertrain problems via class action.
Sure, I can definitely see that being a pattern, especially for things like modern Diesel emissions systems that are notoriously unreliable. I just haven't seen that pattern materialize for start-stop. You found the same recall I did, which for the mast majority of people was fixed with just a software update. Where are the class actions for these shoddily designed systems?
A Prius isn't taking off from a stop under strictly ICE power. The electric motor in the transmission lowers the load on the ICE, certainly enough to let the engine oil pump generate operating pressure before it's really under load.
Up to 2022 the Prius' ICE barely had 70 kW of engine power, and (IIRC, take with a grain of salt) neither turbochargers nor compressors. The less capacity the engine has, the more abuse it can tolerate, and it likely was ridiculously overspecced in tolerances and thicknesses.
In contrast, your 100 kW+ average vehicle? Probably built for maximum profit margins.
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.
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.
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.
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.
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.
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