281–290 of 295 posts
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> Mazda is BlackBerry No, they're not. Go test drive a Miata. They make the most fun cars to come out of Japan. And also have one of the better design languages.
As much as I love Mazda, if the only thing they'll have for them is fun, they are dead as a mass manufacturer.
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Yep I've seen it on his YouTube. The "EcoJet" https://www.youtube.com/watch?v=10q9_pB6unU He said that they had to put really big brakes on it. I guess for some reason you can't just have a clutch. Personally if I was going for eco I'd want something more clever than "bigger brakes" but maybe building something like a Hybrid Synergy Drive is harder than building a turbine.
> He said that they had to put really big brakes on it. There's no compression braking (engine braking) with a turbine engine.
The EcoJet is just one of many examples of his cars that have been improved in this way.
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Low end torque tends to be the rotary's Achilles heel. I think the claim being made is that efficiency is better at high, steady RPMs, but tbh, I've always found that claim a bit dubious. If you love the rotary engine, this does have some nice perks as the electric motor basically fixes the rotary engine's main weakness. Having said that, I'd have been much more excited about this 10-15 years ago.
It really isn't. Go and drive a 13BT car. They make almost all their torque by 2500rpm and the curve is flat. They're more torquey than any 4 cylinder I've driven.
But even if it was, that was the most powerful stock configuration made and it topped out at ~184 lb/ft. :)
Torque was never the strength of this motor.
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The same reason we don’t use two strokes anymore? They’re environmental disasters and wildly inefficient.
The comment I replied to said a rotary couldn't have variable timing and so I was simply refuting that claim. I'm not trying to make a case for either engine here.. there's clear reasons why four cycle piston engines won out for the most part (other than a few powersport and power equipment niches).
As for two strokes being "less efficient", efficiency is in the eye of the beholder. We see on the recent key bridge collapse lore that indeed these mammoth cargo ships run two stroke engines, in this case, two stroke turbodiesels which formerly were the mainstay engine of american trucking. The humble weed eater or chainsaw also tends to use two-stroke - why? because they're far more efficient, almost twice as efficient, in power-per-pound of engine i.e. in applications where lightweight is needed. An added benefit is mechanical simplicity. The double-power notion follows from the name, these engines give power every two strokes versus every four strokes. Two strokes are also really interesting in that exhaust manifold geometry interacts with the engine stroke with pressure waves, look at any two-stroke dirtbike and some will have these goofy-appearing exhaust manifolds for this reason. Granted the major challenge of two-strokes is dirty/pollution and being oil-burning by their nature.
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The comment I replied to said a rotary couldn't have variable timing and so I was simply refuting that claim. I'm not trying to make a case for either engine here.. there's clear reasons why four cycle piston engines won out for the most part (other than a few powersport and power equipment niches).
I completely agree, there's no reason any engine can't have VVT. I believe that famous northern european supercar guy, I think "Keurig" or something like this is is name - he took an old beater car 4 cylinder engine and superpowered it with some pneumatic / AI controlled valves - I think it's called "FreeValve" or something like this. As for two strokes being "less efficient", efficiency is in the eye of the beholder…
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A hydrogen-oxygen flame (this is what happens naturally since you're burning hydrogen in open atmosphere) burns closer to 2800C, and also has the fun property of causing embrittlement (which is especially worsened at higher temperatures where metal expands and becomes more porous.) Your steel pots and pans are essentially toast under a hydrogen flame. People think "Fire is fire" and no, no it is not.
When I was doing a bit of research, I was coming up with 2050C or so for hydrogen open flame (in air; with pure oxygen it was 2600C), and about 1950C for methane in air. Natural gas is mostly methane and has a pretty similar flame temperature, but it does not melt our pots and pans. Why would hydrogen? It is hotter, sure, but not dramatically so.
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And, of course, Mazda had been selling LIVC engines for years before the Prius appeared. Like all of Mazda's other weird engines they were expensive, bad, and unreliable.
I was gonna say, pretty sure the millenia? Had some sort of Miller cycle
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That's not what they're saying. They're talking about things that couldn't be done due to performance issues but are now possible thanks to improved hardware.
Software developers rarely question the hardware they are developing on/for. Unless you were developing in the pentium and earlier era, it has almost definitely not been true for you that “the hardware is not capable of running this idea” (ignore certain obvious high performance sectors).
The AI boom is almost entirely a thing due to advancements in hardware. You simply couldn't build ChatGPT with 2014 hardware.
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I completely agree, there's no reason any engine can't have VVT. I believe that famous northern european supercar guy, I think "Keurig" or something like this is is name - he took an old beater car 4 cylinder engine and superpowered it with some pneumatic / AI controlled valves - I think it's called "FreeValve" or something like this. As for two strokes being "less efficient", efficiency is in the eye of the beholder…
That hasn't been true for a long time. Two strokes barely produce more power per CC, and the emissions are not compatible with any modern standards. They're used in yard tools becuase they're CHEAP.
The cost argument probably is the main driver for yard tools (Honda makes a great 4 stroke string trimmer for instance) but Endurocross bikes, trials bikes, and mountain snowmobiles especially still use two strokes for the power to weight advantage. The BRP snow machines even have direct injection which really helps emissions, though obviously they still have total loss lubrication so they're dirtier than a four stroke.
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The comment I replied to said a rotary couldn't have variable timing and so I was simply refuting that claim. I'm not trying to make a case for either engine here.. there's clear reasons why four cycle piston engines won out for the most part (other than a few powersport and power equipment niches).
I completely agree, there's no reason any engine can't have VVT. I believe that famous northern european supercar guy, I think "Keurig" or something like this is is name - he took an old beater car 4 cylinder engine and superpowered it with some pneumatic / AI controlled valves - I think it's called "FreeValve" or something like this. As for two strokes being "less efficient", efficiency is in the eye of the beholder…
Because they use forced induction, they don't use the crankcase for scavenging and thus have a "normal" four stroke style oil sump.
Since the total loss lubrication system isn't used, they aren't actually any dirtier on principle than a four stroke.
The big ship engines also turn very slow so a lot of the physics behind it is different, and different fuels are used compared to road going diesel (different grades of bunker fuel).
You are correct that GM used to make a two stroke diesel for over the highway and medium-sized equipment use but they were phased out because they weren't competitive on fuel consumption and their crude superchargers were incredibly loud. Growing up my Dad owned a compactor with one and I'd have to wear ear plugs under my ear muffs to not be deafed by "the screaming jimmy" (Detroit 471, IIRC).