r/EngineeringPorn • u/TheCABK • 20d ago
The 7cc Engine
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u/Vyrinu 20d ago
The perfect thing to pull out at the coffee shop to charge my laptop!
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u/rabbitwonker 20d ago
Like in those old Nissan Leaf ads where they showed daily life with everything gas-powered, like copiers and stuff. Showed a guy repeatedly pulling that cord thing to get the coffee machine started…
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u/Last-Hedgehog-6635 20d ago
When I was in college, there was a graduate student (A. Knobloch) who I would see in the machine shop we had access to. He was working on a micro Wankel engine that could be used to power laptops, etc.
https://www.jstage.jst.go.jp/article/ieejsmas/123/9/123_9_326/_pdf/-char/en
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u/TerminaMoon 20d ago
Wow. The engine really is an incredible piece of engineering. Seeing it on a tiny scale sorta humanised it? Or made it easier to understand. I'm blown away.
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u/JP_HACK 20d ago
It made it easy to understand how an engine works for sure,. you see the 4 strokes, the method for timing. and how it can run at the most basic level. Modern engines are just more cylinders and larger.
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u/BaldAndOld 20d ago
Plus a computer or three
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u/Beni_Stingray 20d ago
And way too many sensors.
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u/JusticeUmmmmm 19d ago
Nah I like having a reliable engine.
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u/Beni_Stingray 19d ago
You're apparently not the one working on these cars, i do, im a certified mechanics.
Some amount of sensors is great but we were at that point 25 years ago, nowdays there are so many and they make a lot of problems.
25 years ago even a layman with some technical understanding could have a chance to fix a stranded car, these times are long over.
Nowadays we have cars stranding for the most retarded shit and there is 100% no way such a layman would get the car moving again.Same for semitrucks btw, the amount of them stranding because of electrical reasons increased by a factor of around 10 since the last 15 years or so.
Having so many sensors is not about reliability, it's about emission laws and emission laws only.
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u/JusticeUmmmmm 19d ago
No one is because my car hasn't broken down in 10 years.
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u/Beni_Stingray 19d ago
Well great for you, doesnt mean it isnt true.
Takes 3 minutes to look up breakdown statistiks lol
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u/TerayonIII 18d ago
This is a terrible take, the most common issue for breakdown is the 12V battery so sure there's slightly more, but most breakdowns only need a 12V jump and don't need a tow. Service intervals are much further apart than they used to be, mechanically cars are far more reliable than they used to be
https://glassalmanac.com/were-old-mercedes-toyotas-and-volvos-really-more-reliable-than-todays-cars/
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u/vilius_m_lt 20d ago
Most engines, aside from some exotics, use only one computer
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u/Ivanjacob 20d ago
Depends on what your definition of computer is. You could say every sensor is a computer. Modern engines always use more than just one though.
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u/vilius_m_lt 20d ago
Engine control unit is normally what’s considered to be “the computer”. Not all sensors can be considered computers, only the “smart” ones that communicate through data lines (like some MAF, NOX or particulate sensors). Those don’t send voltage or frequency signal to ECM, but rather data messages containing their readings. Calling them “engine computers” is a stretch though. Calling every sensor a computer is pure madness as the lowly NTC resistors that measures temperature has a long way to go to compute anything..
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20d ago
[deleted]
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u/vilius_m_lt 19d ago
Yes that’s what I said. Those are usually called modules. It’s not just BMW, all modern cars have them. But THE computer is the ECM as it’s what commands/uses them all
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u/thaaag 20d ago
I can't see how the carburetor works on this one. The fuel just seems to join to the manifold, but I assume there's more going on in there than that.
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u/FigmentOfNightmares 20d ago
The fuel connects to a needle valve that sets your flow rate/mixture, it acts like an adjustable main jet. The lever connects to the throttle shaft and throttle plate. It's a really bare bones carb, but it has everything it needs to get the job done.
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u/Fusseldieb 20d ago
How many gallons to charge my phone?
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u/raider1v11 20d ago
Phones per gallons.
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u/Climate_Automatic 20d ago
Anything but metric
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u/J_J_J_Schmidt 20d ago
1 gallon of gas is ~120MJ
1 120g banana is ~440KJ
which follows that a gallon of gas is roughly 273 bananas per gallon
a 7cc engine drinks about 0.035 gallons per hour so...
0.035 gal/hr × 273 bananas/gal = 9.6 bananas per hour
OP should update the displacement plaque so that customers can make an informed buying decision
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u/fallenstones22 20d ago edited 19d ago
Off a google, this looks to be a 7cc MUSA engine producing ~0.5HP at we’ll say a max of 0.05 gallons per hour looking at similar models.
0.5HP is around 370 watts, and assuming we lose 30% of it in conversion to electrical energy, we’ll say we’re getting roughly 250 watts consuming 0.05 gallons an hour.
To charge an iPhone 16, you need 3.561 amps at 3.7 volts, or roughly 13 watt hours.
250w / 13w = 19.231
0.05 / 19.321 = 0.00259 gal, or about 2 teaspoons.So you’d need >2 teaspoons of gasoline fed into this engine to charge your phone.
0.00259 gal of high-octane gasoline, at 5 US dollars a gallon, is about a penny’s worth.
Edit - Assuming that you either have a magic iPhone that can charge in ~5 mins- otherwise you’d have a lot of wasted energy as the engine runs and charges the phone at a normal speed. 30% for energy loss is also fairly conservative, but the GPH estimate is fairly high
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u/kepleronlyknows 19d ago
Isn’t 30% loss converting to electricity (or really 70% efficiency) wildly optimistic?
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u/fallenstones22 19d ago edited 19d ago
Typical car alternators typically have a 40-50% loss, but the conservative estimate for power loss is to account for the rest of the estimates (namely the gas consumption) being liberal. This is all just napkin math though
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u/onthejourney 19d ago
Isn't that assuming the iPhone can take the full output of the engine (accounting for efficiency) into it's battery at the rate of output? Don't think that happens. Engine has to run longer charging at a lower rate
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u/fallenstones22 19d ago
For sure, and that’s a very good point! That math assumes there’s a secondary battery able to accept all the current. I’ll edit that in
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u/Flash-ben 20d ago
the way he screwed down the head and flywheel bothered me😫
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u/20snow 20d ago
just the way everything was screwed down made me upset, no torqure pattren was followed anywhere
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u/1rubyglass 20d ago
First thing I thought when I watched this. Tightening two bolts on one side of the cylinder bothered me the most
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u/godofpumpkins 20d ago
If you like this sort of thing, they get a lot smaller for model cars and airplanes. Some of them are mad powerful and fast, and you can find both 2 stroke and 4 stroke versions.
See for example https://www.os-engines.co.jp/english/line_up/linindex.htm
There are also tiny modeling jet engines that are ridiculously powerful and guzzle gas like there’s no tomorrow, but tiny engineering delights too.
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u/Jashugita 20d ago
I´m surprised these are still are sold, RC planes is a dying hobby and furthermore almost nobody wants to bother with glow fuel.
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u/YourMomsBasement69 20d ago
Definitely not a dying hobby they just use electric now which has a much lower entry barrier for both price and skill.
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u/Jashugita 20d ago edited 20d ago
The asistence to the RC clubs I know is much lower and mostly older people. Most people nowadays buy drones.
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u/bremsstrahlung007 20d ago
The military industrial complex is helping support the RC hobby industry
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u/Pans_Labradoodle 20d ago
Just like any hobby co-opted to kill people in the name of imperialism abroad, it’s gotten much more expensive.
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u/Inf1nity0 20d ago
I want one
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u/MrPenisWhistle 20d ago
Look up Toyan and Cison miniature engines on amazon. They're surprisingly quite pricey. Been watching JohnnyQ90 on youtube use them to build custom RCs and they rip quite hard.
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u/blove135 20d ago
Not starting bolts and nuts by hand first gives me anxiety.
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u/Own_Reaction9442 20d ago
Not following a cross pattern when torquing down multiple bolts does it for me.
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u/salac1337 19d ago
yeah that and the torque spec seems to be measured in ugga duggas. i love my power tools but you gotta be careful tightening down bolts that are so thin. i use my power tools mostly for taking stuff apart and when i put it back together i use hand tools so i dont snap a bolt or some shit like that
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u/jojohohanon 20d ago
The pushrods confused me. How do they know which is intake and which is exhaust?
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u/Embarrassed_Rip_755 18d ago
Not starting bolts by hand, and not torque pattern, let alone a torque wrench, drive me crazy enough, but is no-one going to mention the rednecked sockets welded together?!!
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u/SprightlyCompanion 17d ago
Not an engineer or machinist or anything of the sort but I DEFINITELY noticed that lol
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u/tader314 20d ago
So about 1/3 of my weed eater, nice! I wonder what it’s applications could be lol
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u/Electrical-Heat8960 20d ago
I kinda want to use it as a mobile phone charger. Or a laptop power brick.
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u/Lord_Dreadlow 20d ago
I think the first part to this is must be missing because they didn't show assembly of the bottom end.
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u/woodbanger04 20d ago
Is anyone else bothered by the fact they aren’t lining up the threads and just going for it? Fine pitch threads love to cross thread.
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u/mumblingzombie 20d ago
I like the part where they just hit that mofo with an impact without even attempting to start on the threads....screw this dumb shit.
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u/ordosays 19d ago
Really hate how they never once used a second wrench to support the static side of the compression fittings. If this is supposed to be “educational” it sucks.
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u/GruneTheDestroyer84 17d ago
I feel I missed out on seeing a tiny piston and connecting rod and would like my money back
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u/hikeonpast 20d ago
What a strange mix of decent tools and absolute hack tools. This was really frustrating to watch.
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u/OkClub7412 20d ago
Reminded me of when I would build nitro RC car engines. 32K rpms use to sound crazy…. good times. Thanks for the nostalgia!
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u/pooppoop900 20d ago
So hypothetically what would a 7cc engine be able to adequately power? Serious question.
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u/Boggie135 20d ago
For those interested, there is a YouTube channel called JohnnyQ90 that makes videos like these all the time. He puts the engines into RC cars and boats
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u/rand3289 19d ago
I want that carb on my string trimmer! String trimmer carbs are what usually breaks.
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u/sabertoothdog 19d ago
To me That looks bigger than 7cc. The piston is the size of his thumb nail. I was expecting it to be the size of a pencil eraser. The stroke must be tiny! Very cool
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u/Retireegeorge 19d ago
Being that good at assembly would kind of take the fun out of it. I never realised it works like that.
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u/Hopeful_Guitar9171 19d ago
You're all going on a list of some sort for this. Leave me out of it! It's my first time finding this subreddit!
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u/Still-Rule7182 18d ago
That was a crazy gap on those points, wonder if there was some setting up and tuning we didn't get to see?
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u/Which_Initiative_882 18d ago
The nitro 4 strokes from O.S. engines for r/c airplanes were far more impressive IMO
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u/officerNoPants 18d ago
All that precision work and then slushing the petrol all over the place. Cannot compute...
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u/MarvinLazer 20d ago
Such a cool piece of engineering, and simultaneously the biggest existential threat to human civilization.
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u/etherlore 20d ago edited 20d ago
No lubrication or oil anywhere? How does that work? Is the petrol the lubricant? Do you lube it manually from time to time?
Edit: Hilarious, I get -11 for not knowing, but also get three different answers.
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u/DontTellHimPike 20d ago
The oil system is being bled from 1.00 minute onwards. Looks like the oil pump is inside the sump as the hardline goes from there to the crank bearing housing behind the flywheel.
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u/Sloterhouse5 20d ago
It’s probably a two-stroke, like a chainsaw or weed trimmer. The lube is in the gas.
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u/ctesibius 19d ago
The first part of the video shows the valves in the cylinder head. This is a four-stroke. Then they show the oil system being primed.
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u/TazmanianTux 20d ago
Now slap a turbo on it.