If you're looking for a carefully crafted/written work to explain internal combustion engines, look no further than this one https://ciechanow.ski/internal-combustion-engine/ (the Mechanical Watch article from the same author was featured on HN a while ago).
Other engine simulators work by approximating the engine.
Ange's engine simulator works by approximating physics of air fluid dynamics through a combustion chamber and exhaust, sound propagation, etc and then putting an engine into that simulation.
Also, I love that it was open sourced. Although it sounds like from the GitHub page summary that there was some shenanigans involving a "certain very high profile game studio" that I'd love to hear more tea about.
He published it as open-source for like 5 seconds before taking the repository down in order to charge for it on Steam! I'm a little weirded out by that pattern of open-sourcing it and then just changing his mind.
I think what happened was that it became his full time job, and he started to need to be able to make money from it. At least, that's what I remember; I haven't seen much about it as of late.
I'm still just not really comfortable with the ethics of withdrawing source code that you previously published. There are tons and tons of things he could've simply kept to himself on top of his first release, but he chose to take back the entire release instead.
Like, he seemingly fully intended it for the public because it's cool and interesting and he wanted to show how it worked, but then he simply changed his mind and completely removed all of it? Makes me doubt he has the public interest in mind at all, because he could've still developed the Steam version and kept that version closed source, but he just decided to take back all his goodwill instead
> Makes me doubt he has the public interest in mind at all
But why?
He's doing what he loves. He's able to support himself doing that. What he chooses to do with the internal product of his labors is his choice. Committing to open source software is a big lift for a lot of people. Maybe he didn't want that.
Once again, I have issue only with his taking it back after already open-sourcing it. It felt disingenuous. That's all. I would have no issue with simply never open-sourcing, but he open-sourced it and then took it back.
He could've never open-sourced it in the first place. He could've archived it and kept the rest of the development private. He could've done anything other than what he did. It's one thing to take back something that you never intended to release, but he fully intended to release it and even made a video about how it's fully open and available, but then he just went actually nevermind.
It's just so, infuriating that he would take it away like this after he told everyone he was giving it out. To me, that act of taking it away takes precedence over whatever I'd think if he'd kept it closed all along.
Edit: I just looked it up and apparently he did keep an archive online. I swear he'd taken it down before and there was a whole thing about this, but maybe he put it back up later? It's here: https://github.com/ange-yaghi/engine-sim
So you got angry over your own feelings of entitlement?
The moment you give away something for free people value it at $0 and expect you to support it for free indefinitely. They get angry immediately if you decide to charge money for it, as if it was some incredibly smart and prudent decision to build your project/business on an external dependency you made zero effort in keeping alive.
No wonder then that he decided to quit the open sourcing but keeps working on it for money.
I still don't get how people see these 100% voluntary projects, which by definition are always a donation of free labor, and then get angry when the donations stop. All software projects have life spans, the difference is that anyone can go and keep maintaining an open source project to extend the lifespan
While I am personally guilty of free loading on a lot of open source projects and never giving anything back while profiting myself, I was never under the illusion that I am owed an endless stream of free code and maintenance. If the underlying project is discontinued it is on me to either keep maintaining it or switching away from it. This is true even in banal situations like with software that is still being maintained and you're merely sticking with a fork of an older version.
I was upset when I heard it'd been taken DOWN after it already went up. Not based on literally any expectation of any future support or literally anything. Literally at that point it had already been published and then reportedly unpublished. It's back up now and learning of that resolved my frustration, but man you are making a lot of incorrect assumptions about me, even after I clarified myself multiple times on this exact point.
So i'll throw this out there. When I was a growing up back in the 50's (yeah, way back then) I was given a model of a v-8 engine to build. It was clear plastic, had pistons, crankshaft, valves, and little red lights for the spark plugs. Small battery powered motor (I think in the starter motor) made everything go round and rounds. One of the coolest models I ever built as a kid.
While fairly realistic in function, the Visible V8 is not a replica of a specific production engine, though it most resembles an early Cadillac or Studebaker V8.
I see no declaration that this is a machine generated site, but the aesthetic is a dead giveaway. The language on the “how it works” page is unmistakably LLM output. As a total novice in engines this site had the potential to educate me, but did the author vet the data at all? If the author doesn’t bother telling me they checked any output on this, what assurance do I have anything is accurate on the site at all? If I knew an actual engineer put their focus on this tool I’d feel much better about trying to learn something from it. Short of that it’s just a pretty (but predictable) interface.
I'm a mechanical engineer who has written similar tools for work and hobbies. Producing pretty pictures does not mean that the model is physically accurate. Unfortunately, such tools seem be evaluated much more on flashiness and not on more reliable and objective criteria like physical accuracy based on verification and validation test suites. I'm seeing that in the comments here. I don't think LLMs make what I do irrelevant, but I have thought that I'm going to have to improve how flashy my simulations look to compete better with non-experts who use LLMs.
> I don't think LLMs make what I do irrelevant, but I have thought that I'm going to have to improve how flashy my simulations look to compete better with non-experts who use LLMs.
This scares me more than "LLMs replace humans". You're going to have to take away time from doing the actual work to replace it with doing bullshit work to impress an ever more detached "decision" layer.
I don't even think the posted page qualifies as a "simulation". It's at best an animation with a calculator/model side-by-side.
"For calibration: AI-generated design right now clusters around three looks: (1) a warm cream background (near #F4F1EA) with a high-contrast serif display and a terracotta accent; (2) a near-black background with a single bright acid-green or vermilion accent; (3) a broadsheet-style layout with hairline rules, zero border-radius, and dense newspaper-like columns."
Why have a kW/Nm - HP/lbf setting, but no metric/US option for the bore and stroke?
Others here are suspicious of the numbers, but at least for the actual engine in my daily driver which I've dyno'd before, it seems reasonable with around 400HP and 450lbf for a 400ci NA V8.
Calling this AI slop would be generous. If we made a list of the things wrong with it we would be here all day. Nothing has an effect on redline RPM, you can create compression and turbo combos that would instantly grenade an engine, the preset “super car” has 200hp?
The only thing it illustrates is the authors lack of understanding.
"Supercar" has 670hp 500lb-ft @ 5297rpm which seems reasonable. After configuring the tool with my car's specs, it was fairly close on the dyno; though, I'm very far from an expert. Imho, pretty cool, nonetheless.
I fed the technical data of my motorcycle into the model and it told me right away that this build would destroy a real engine because the piston speed would be too great.
The real thing has been running for 56,000 miles, so it can't be that bad. *g
Nice little project, I inputted the dimensions of a engine I've been building (b20-vtec) and it estimated 160whp which sounds low but I also can't set up my cams properly because it looks like this was designed for SOHC engines.
I had just been daydreaming about a v12 with tiny pistons and wondering how that would behave … now I can find out … turns out it would be terrible at low speed
In principle you can instantaneously set the throttle opening to some position and set the RPM to whatever you want. In time the RPM will rise or fall until the engine is at equilibrium, but throttle position and RPM aren't like mechanically interlocked. Otherwise how could the engine speed up when you go down a hill?
When you press the gas pedal in your car down (which used to just be a cable to the throttle body), does your car instantaneously increase in speed to match the pedal position?
All you're doing is letting more air in - the RPM is a function of the power the engine generates; more fuel and air than is currently needed for the current load at the current speed = increasing RPMs.
If you put the clutch in, a little blip of the gas is all that's needed to get the RPM quite high very quickly. The moment there's load on there, the same blip will not do very much at all.
Imagine your vehicle is pulling a heavy load up a hill vs. going flat out on a track. Your throttle position may be the same but the RPMs are likely to be quite different, even when you account for the transmission.
So if I set the animation speed to 1:1 and set the RPM to 3000, that's what it would look like inside the engine when I'm ready to shift gears? Seems WAY faster than what I expected in real life
I imagine such an engine would instantly blow itself apart in real life. Basically the simulated version of those tractor pull cars where the engine survives for about 500 rotations before it has to be rebuilt.
Depends on the displacement and other factors. Huge engines in that power range like the https://en.wikipedia.org/wiki/EMD_710 are used in locomotives and other applications like power generation where they run 24/7 at 100% load.
If LLMs had come out when I was younger, I would have been able to understand things this easily. There are some incorrect implementations, but they're incredibly helpful for grasping the concepts.
How is it useful? I'm no expert in combustion engines, so I'd hesitate to rely on a slop graphic like this to learn about them as I doubt the creator has any idea about them either.
It's like a friend - he was like "Look at this awesome set of categorized interactive animations from claude to learn geometry!".
And like 60% of the animations were technically just wrong. Very pretty though, and the effects were cute... I guess...?
Where did I say what people are allowed to find entertaining?
It would be insane to tell someone what they should find entertaining, that's the dumbest thing I've ever heard.
As for useful, I'm genuinely trying to understand HOW you find something useful that may or may not have zero accuracy to the thing in which it's portending to showcase?
When I don't know about something - I would find someone who's really knowledgeable (or a resource that's vetted), and learn from that obviously. I don't want to learn something completely unverified and made up? That makes no logical sense.
Just like my friend's slop graphics. I imagine learning geometry from that and fundamentally locking in incorrect knowledge when there are many thousands of resources that would teach me correctly - this makes no sense right? Would you prefer to learn from the pretty graphics that are teaching you nothing?
If you're looking for a carefully crafted/written work to explain internal combustion engines, look no further than this one https://ciechanow.ski/internal-combustion-engine/ (the Mechanical Watch article from the same author was featured on HN a while ago).
I wish he was still making posts.
It's been a year and a half since the last one, compared to 1 or 2 posts per year. Here's hoping he's taking some extra time to make something amazing
He isn't? What happened?
@AngeTheGreat on youtube is worth mentioning here, I think.
He has a whole series on building out engine simulators of various types, and even published a Steam game for steam engine simulation.
His work is notable because he leans heavily into generating sound directly from the simulations.
Yes, seriously everyone should watch this:
https://www.youtube.com/@AngeTheGreat
Other engine simulators work by approximating the engine.
Ange's engine simulator works by approximating physics of air fluid dynamics through a combustion chamber and exhaust, sound propagation, etc and then putting an engine into that simulation.
It's incredible how productive and precise he is.
Absolutely insane.
Also, I love that it was open sourced. Although it sounds like from the GitHub page summary that there was some shenanigans involving a "certain very high profile game studio" that I'd love to hear more tea about.
He published it as open-source for like 5 seconds before taking the repository down in order to charge for it on Steam! I'm a little weirded out by that pattern of open-sourcing it and then just changing his mind.
I have a podcast interview with Ange where we talk a bit about the first time this blew up on HN
https://music.youtube.com/watch?v=bi6bLSCnjcY&si=r4atSKfsBEQ...
I think what happened was that it became his full time job, and he started to need to be able to make money from it. At least, that's what I remember; I haven't seen much about it as of late.
I'm still just not really comfortable with the ethics of withdrawing source code that you previously published. There are tons and tons of things he could've simply kept to himself on top of his first release, but he chose to take back the entire release instead.
Like, he seemingly fully intended it for the public because it's cool and interesting and he wanted to show how it worked, but then he simply changed his mind and completely removed all of it? Makes me doubt he has the public interest in mind at all, because he could've still developed the Steam version and kept that version closed source, but he just decided to take back all his goodwill instead
> Makes me doubt he has the public interest in mind at all
But why?
He's doing what he loves. He's able to support himself doing that. What he chooses to do with the internal product of his labors is his choice. Committing to open source software is a big lift for a lot of people. Maybe he didn't want that.
Once again, I have issue only with his taking it back after already open-sourcing it. It felt disingenuous. That's all. I would have no issue with simply never open-sourcing, but he open-sourced it and then took it back.
He could've never open-sourced it in the first place. He could've archived it and kept the rest of the development private. He could've done anything other than what he did. It's one thing to take back something that you never intended to release, but he fully intended to release it and even made a video about how it's fully open and available, but then he just went actually nevermind.
It's just so, infuriating that he would take it away like this after he told everyone he was giving it out. To me, that act of taking it away takes precedence over whatever I'd think if he'd kept it closed all along.
Edit: I just looked it up and apparently he did keep an archive online. I swear he'd taken it down before and there was a whole thing about this, but maybe he put it back up later? It's here: https://github.com/ange-yaghi/engine-sim
So you got angry over your own feelings of entitlement?
The moment you give away something for free people value it at $0 and expect you to support it for free indefinitely. They get angry immediately if you decide to charge money for it, as if it was some incredibly smart and prudent decision to build your project/business on an external dependency you made zero effort in keeping alive.
No wonder then that he decided to quit the open sourcing but keeps working on it for money.
I still don't get how people see these 100% voluntary projects, which by definition are always a donation of free labor, and then get angry when the donations stop. All software projects have life spans, the difference is that anyone can go and keep maintaining an open source project to extend the lifespan
While I am personally guilty of free loading on a lot of open source projects and never giving anything back while profiting myself, I was never under the illusion that I am owed an endless stream of free code and maintenance. If the underlying project is discontinued it is on me to either keep maintaining it or switching away from it. This is true even in banal situations like with software that is still being maintained and you're merely sticking with a fork of an older version.
I was upset when I heard it'd been taken DOWN after it already went up. Not based on literally any expectation of any future support or literally anything. Literally at that point it had already been published and then reportedly unpublished. It's back up now and learning of that resolved my frustration, but man you are making a lot of incorrect assumptions about me, even after I clarified myself multiple times on this exact point.
So i'll throw this out there. When I was a growing up back in the 50's (yeah, way back then) I was given a model of a v-8 engine to build. It was clear plastic, had pistons, crankshaft, valves, and little red lights for the spark plugs. Small battery powered motor (I think in the starter motor) made everything go round and rounds. One of the coolest models I ever built as a kid.
This was the Revell 'Visible V8', first released in 1958. https://macsmotorcitygarage.com/revisiting-the-visible-v8/
While fairly realistic in function, the Visible V8 is not a replica of a specific production engine, though it most resembles an early Cadillac or Studebaker V8.
...but that transmission definitely looks like the early 4-speed Hydramatic: http://www.1954advance-design.com/Hydra-Matic-rebuild/index....
The Visible V-8. That made it well into the 70s.
They're still making that model today.
I wish this had a stepper so I could see how things change at each point in the cycle. But even without, quite cool to play with.
"How it Works" -> "Idk" OP probably
I see no declaration that this is a machine generated site, but the aesthetic is a dead giveaway. The language on the “how it works” page is unmistakably LLM output. As a total novice in engines this site had the potential to educate me, but did the author vet the data at all? If the author doesn’t bother telling me they checked any output on this, what assurance do I have anything is accurate on the site at all? If I knew an actual engineer put their focus on this tool I’d feel much better about trying to learn something from it. Short of that it’s just a pretty (but predictable) interface.
I'm a mechanical engineer who has written similar tools for work and hobbies. Producing pretty pictures does not mean that the model is physically accurate. Unfortunately, such tools seem be evaluated much more on flashiness and not on more reliable and objective criteria like physical accuracy based on verification and validation test suites. I'm seeing that in the comments here. I don't think LLMs make what I do irrelevant, but I have thought that I'm going to have to improve how flashy my simulations look to compete better with non-experts who use LLMs.
> I don't think LLMs make what I do irrelevant, but I have thought that I'm going to have to improve how flashy my simulations look to compete better with non-experts who use LLMs.
This scares me more than "LLMs replace humans". You're going to have to take away time from doing the actual work to replace it with doing bullshit work to impress an ever more detached "decision" layer.
I don't even think the posted page qualifies as a "simulation". It's at best an animation with a calculator/model side-by-side.
The aesthetic is what I get any time I ask for something UI-like in Claude. But gosh darn it I like the look.
It's almost weird hard Claude trends towards that look.
It's so distinct... it can't be an amalgam of the most popular design choices, can it?
Some of it is part of claude code's built-in instructions: https://github.com/anthropics/claude-code/blob/main/plugins/...
Why have a kW/Nm - HP/lbf setting, but no metric/US option for the bore and stroke?
Others here are suspicious of the numbers, but at least for the actual engine in my daily driver which I've dyno'd before, it seems reasonable with around 400HP and 450lbf for a 400ci NA V8.
Gave it my own spin once: https://github.com/glouw/ensim4
Makes audio too
Calling this AI slop would be generous. If we made a list of the things wrong with it we would be here all day. Nothing has an effect on redline RPM, you can create compression and turbo combos that would instantly grenade an engine, the preset “super car” has 200hp?
The only thing it illustrates is the authors lack of understanding.
"Supercar" has 670hp 500lb-ft @ 5297rpm which seems reasonable. After configuring the tool with my car's specs, it was fairly close on the dyno; though, I'm very far from an expert. Imho, pretty cool, nonetheless.
I fed the technical data of my motorcycle into the model and it told me right away that this build would destroy a real engine because the piston speed would be too great.
The real thing has been running for 56,000 miles, so it can't be that bad. *g
Exhaust temp increase with decreasing lambda, and peaks at 0.7 lambda. That part of the model is likely incorrect.
Nice little project, I inputted the dimensions of a engine I've been building (b20-vtec) and it estimated 160whp which sounds low but I also can't set up my cams properly because it looks like this was designed for SOHC engines.
Very cool either way.
I like It, no matter what
Interesting, I had Fable generate me a summary using an identical style, with the same square design, bg and yellow highlights
187 N/A BSFC @ 2000rpm and open throttle. Tried emulating a DI 2GR-FXE. Seems a bit optimistic, but still fun to play with.
I had just been daydreaming about a v12 with tiny pistons and wondering how that would behave … now I can find out … turns out it would be terrible at low speed
I don't understand how the throttle and RPM can be modified independently. Surely the RPM depends on the throttle?
In principle you can instantaneously set the throttle opening to some position and set the RPM to whatever you want. In time the RPM will rise or fall until the engine is at equilibrium, but throttle position and RPM aren't like mechanically interlocked. Otherwise how could the engine speed up when you go down a hill?
When you press the gas pedal in your car down (which used to just be a cable to the throttle body), does your car instantaneously increase in speed to match the pedal position?
All you're doing is letting more air in - the RPM is a function of the power the engine generates; more fuel and air than is currently needed for the current load at the current speed = increasing RPMs.
If you put the clutch in, a little blip of the gas is all that's needed to get the RPM quite high very quickly. The moment there's load on there, the same blip will not do very much at all.
Imagine your vehicle is pulling a heavy load up a hill vs. going flat out on a track. Your throttle position may be the same but the RPMs are likely to be quite different, even when you account for the transmission.
> Surely the RPM depends on the throttle?
Partly. Another factor in the equation is load.
So if I set the animation speed to 1:1 and set the RPM to 3000, that's what it would look like inside the engine when I'm ready to shift gears? Seems WAY faster than what I expected in real life
3000? Here I am wishing there was some Wankel Rotary representation and you're shifting at 3000? What are you driving, a Peterbilt?
3000 RPM is 50Hz right?
Very nice! Reminds of this classic, focused mostly on the sounds: https://github.com/ange-yaghi/engine-sim
From the pre-slop era: https://www.youtube.com/watch?v=RKT-sKtR970
3638 kW / 4878 hp is the most powerful engine I could build with this.
3765 kW / 5049 hp is the max I could do.
V Twin Bank, Turbocharged with Intercooler. And Fuel is Hydrogen!
I was using Supercharged, thought that was better. :) Now I got it tuned up to 3767 kW / 5051 hp, that must be the maximum.
I imagine such an engine would instantly blow itself apart in real life. Basically the simulated version of those tractor pull cars where the engine survives for about 500 rotations before it has to be rebuilt.
Depends on the displacement and other factors. Huge engines in that power range like the https://en.wikipedia.org/wiki/EMD_710 are used in locomotives and other applications like power generation where they run 24/7 at 100% load.
How do you tell how much power it is making?
On the dyno panel you see "pk" which is peak power. If you don't see the dyno panel on the right, you'll have to scroll down to see it.
Found it now, thanks, I had to scroll down.
This is like a much cooler version of a thing I made a few years ago for simulating model oscillating engines: https://incoherency.co.uk/oscillating-engine/
Am I missing something? Setting the throttle to 0% seems to do nothing?
All the gauges on the top right except the RPMs move
this is really impressive. actual movements with live diagrams looks great. you can consider adding sound to take it to another level.
I was hoping for a two stroke mode as well!
If LLMs had come out when I was younger, I would have been able to understand things this easily. There are some incorrect implementations, but they're incredibly helpful for grasping the concepts.
Probably llm slop
if its useful and entertaining i dont think many ppl care especially evident that you cannot be certain with your accusations
How is it useful? I'm no expert in combustion engines, so I'd hesitate to rely on a slop graphic like this to learn about them as I doubt the creator has any idea about them either.
It's like a friend - he was like "Look at this awesome set of categorized interactive animations from claude to learn geometry!".
And like 60% of the animations were technically just wrong. Very pretty though, and the effects were cute... I guess...?
why are you so invested in telling ppl in what they are allowed to find useful/entertaining?
especially after admitting you dont nkow anything about combustion engines?
Where did I say what people are allowed to find entertaining? It would be insane to tell someone what they should find entertaining, that's the dumbest thing I've ever heard.
As for useful, I'm genuinely trying to understand HOW you find something useful that may or may not have zero accuracy to the thing in which it's portending to showcase?
When I don't know about something - I would find someone who's really knowledgeable (or a resource that's vetted), and learn from that obviously. I don't want to learn something completely unverified and made up? That makes no logical sense.
Just like my friend's slop graphics. I imagine learning geometry from that and fundamentally locking in incorrect knowledge when there are many thousands of resources that would teach me correctly - this makes no sense right? Would you prefer to learn from the pretty graphics that are teaching you nothing?
I'm certain.
really interesting project - would be good to see a link to a repo
I am genuinely curious why OP thinks this slop post should be of interest to others. Nobody cares how you're prompting an LLM, guys.
would be awesome if it could generate sounds like how lfs does it
Sounds would be pretty cool.
we have all heard of V8 ... now visualize a W12
... two pairs of V3 in a Bentley
Airplanes do (did?) v16s and v24s as well, if memory serves.
There's also a build out there where someone did a "v12" vw beetle with a v6 for each axle.
How can I instantly tell this is slop?
- //
- letter spacing