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Old 11-09-2017, 03:07 PM   #31 (permalink)
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Originally Posted by serialk11r View Post
The toughest standard is something like 0.02g/mile NOx (need to check on that again), which works out to something in the tens of ppm depending on how much fuel you burn in a mile.

I think if you drop the combustion temperature by a little bit it is easy to go below 100ppm (which should be able to squeak by the minimum standards on a smaller engine car). HCCI supposedly should be able to control the burn speed so that maximum temperature is lower.

I am not sure exactly how this works, but my hunch is that they use a lot of hot EGR to control the charge temperature (to induce autoignition) and reduce the burn temperature, and somehow avoid knock.
Cooled EGR, plus intercooled supercharging. Gives you a nice, dense, temperature controlled mix in the cylinder that's primed to go off when the small ball of "rich" air-fuel mixture around the plug ignites.

I bet they're using supercharging so they can keep using the long-tube scavenging header of the naturally aspirated SkyActiv G. But I haven't seen the engine fully dressed yet, so I could be wrong.

SkyActiv X is going to be wild. And it won't be using unobtanium engine internals, stratospheric injection pressures or ridiculously fast and expensive knock detectors.

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Old 03-23-2018, 06:01 PM   #32 (permalink)
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Guys the numbers are conflicting here but look promising. Skyactiv X is targeting "27% better thermal efficiency"... Don't quote me on this but isn't their current engine around 36.5% thermal efficient. Thats a boost to 46.4% thermal efficiency which agrees with whats currently possible with ICE on the cheapest energy currently available to run a car aka 87 octane.
Imagine a 2016 Mazda 3 gets 33 mpg combined that could result in 42 mpg combined and 51 highway. I'd also assumme if they're going to these lengths to bust EV and Hybrid balls they will probably drop the cd down to at least 0.23. Seems neat in 2800 pound car.
(https://pdfs.semanticscholar.org/226...3adda2e15f.pdf)
(Mazda Skyactiv-3 Engine to achieve 56% thermal efficiency)
Think of the hypermiling for the love of god. lol
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Old 03-23-2018, 08:58 PM   #33 (permalink)
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The only question is when will they put HCCI in the Mx5/ Miata.
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Old 04-03-2018, 12:03 AM   #34 (permalink)
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As long as they run port injection as well (only way I've seen to keep the intake valves clean).
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Old 04-03-2018, 04:25 AM   #35 (permalink)
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As long as they run port injection as well (only way I've seen to keep the intake valves clean).
My understanding is that there is a small in cylinder injector for providing a richer mixture in vicinity of spark plug and a port injector for fuel to rest of cylinder. i.e stratified combustion
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Old 04-03-2018, 11:37 AM   #36 (permalink)
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Having re-read Mazda's literature, it would appear that there is 1 direct high pressure injector per cylinder.

https://insidemazda.mazdausa.com/pre...s-information/
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Old 04-11-2018, 05:08 PM   #37 (permalink)
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Adding back to the list it looks like Mazda isn't just targeting peak thermal efficiency by using compression ignition and lean burn, they are also using it to increase thermal efficiency to a much greater amount under higher loads where a Prius would say be less efficient than a Bmw m3 (see top gear test) unless its in its peak small operation window. So it sounds like it should hit the Miata.

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