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Old 08-30-2017, 02:46 AM   #1 (permalink)
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Mazda's SkyActiv X... uses spark-controlled knock! (maybe)

Figured some here would get a kick out of this article:

Nerd Alert! Mazda

The real meat, however, is on the final page:

Quote:
Picture this: the spark plug sparks causing the detonation of the air:fuel mixture right around the plug. The flame front forms and spreads out and away from the central ignition point. The flame front burns the fuel and air in the cylinder as it moves through the mixture. This flame front increases the pressure and temperature of the unburned mixture in front of it. Sometimes, the pressure increases enough to cause combustion in the mixture before the flame reaches it creating knock.
In other words, instead of creating enough pressure via compression to cause auto-ignition, the engine can create *almost* enough pressure via compression, and use traditional spark ignition of a very tiny amount of air-fuel mixture concentrated around the plug (basically, the way all direct injection engines do now to lean-burn) to push the mixture over the edge.

Very speculative, but I like the idea. Sort of the combustion equivalent of how we race in the rain... don't wait for the car to slide, push it over. Makes it more controllable.

Betcha this makes the calculations much simpler than in other HCCI systems.

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Old 08-31-2017, 01:15 AM   #2 (permalink)
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That might be safer to operate with a wider range of octane ratings, or with ethanol, and also gaseous fuels such as CNG and biomethane. Honestly, even though gasoline and regular Diesel fuel are eventually going to be outdated at all, it doesn't seem so likely that the internal-combustion engine would have the same fate in a mid to long term.
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Old 08-31-2017, 04:38 PM   #3 (permalink)
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Very interesting article... He gives a good explanation of a lot of their existing technology (I hadn't heard about their SPCCI engine before) and how it is likely leveraged with the HCCI engine.

Unfortunately, the real interesting bit is just a lot of educated speculation. Anyone closely following this engine would have already made most/all of the same assumptions. I'd be very interested to get more details directly from someone at Mazda.
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Old 09-01-2017, 08:47 AM   #4 (permalink)
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Quote:
Originally Posted by darcane View Post
Very interesting article... He gives a good explanation of a lot of their existing technology (I hadn't heard about their SPCCI engine before) and how it is likely leveraged with the HCCI engine.

Unfortunately, the real interesting bit is just a lot of educated speculation. Anyone closely following this engine would have already made most/all of the same assumptions. I'd be very interested to get more details directly from someone at Mazda.
They're very tight-lipped about it. Very frustrating!

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As Dave Coleman works at Mazda and is a good friend of the people at MotoIQ, I reckon they've probably run these guesses past him, so they may be very good guesses.

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