How Mazda's Compression-Ignition Gas Engine Runs Like a Diesel Without Blowing Up

[enzo1]

Mazda's Skyactiv-X engine is the first in the world to burn gasoline using diesel-style compression ignition. The result? Amazing power and economy.






Yesterday at the Tokyo Motor Show, Mazda released new info on its highly anticipated compression-ignition Skyactiv-X engine. It's all a bit daunting if you're not an engineer, but helpfully, Mazda put together a short video explaining exactly how this revolutionary engine works.

Essentially, this gas-powered engine can run like a diesel, using compression ignition to burn its fuel. Mazda calls this Spark-Controlled Compression Ignition (since a spark plug is still used to initiate combustion), and it's the first engine that can switch seamlessly between compression and spark ignition, depending on load.

This engine also uses a new, split fuel injection system, and an in-cylinder pressure sensor to keep combustion stable and heat in check. Here's how Mazda explains it:

The SKYACTIV-X controls the distribution of the air-fuel mixture in order to enable lean burn using the SPCCI mechanism. First, a lean air-fuel mixture for compression ignition is distributed throughout the combustion chamber. Next, precision fuel injection and swirl is used to create a zone of richer air-fuel mixture—rich enough to be ignited with a spark and to minimize nitrous oxide production—around the spark plug. Using these techniques, SPCCI ensures stable combustion.
You can read a lot more in-depth coverage on this tech on Mazda's website, but we bet you just want to know the results. Essentially, a 2.0-liter Skyactiv-X engine provides up to 30 percent more torque, sharper throttle response, and a 20-percent improvement in fuel economy compared with Mazda's current 2.0-liter gasoline engine. And Mazda says that at low speeds, the Skyactiv-X can get even better fuel mileage, thanks to its ability to run a super lean fuel mixture.

Skyactiv-X promises the best of both worlds—diesel fuel efficiency with gasoline emissions and drivability. It'll reach production in the 2020 Mazda 3, whose design was previewed in the new Kai Concept that debuted at Tokyo.

If it all works out, this technology could help internal combustion engines stay relevant even with increasingly stringent emissions and economy regulations... How Mazda's Compression-Ignition Gas Engine Runs Like a Diesel Without Blowing Up

[Borders Reivers]

Kinda like how above 12,000rpm an ignition system is not needed on a gasoline engine. Heat of compression does the trick. Dieselish.

[onewhippedpuppy]

Super cool stuff. Mazda is an awesome company, the smallest of the major Japanese manufacturers but still building the most innovative, highest quality, best looking, and most fun to drive cars. I'll be very interested to see how this new technology works in actual application in the 3. Now if they would just produce the RX Vision concept in a rotary coupe.....

[JD159]

Does this change the type of fuel being used??? With a lot of motors now going forced induction, will gas companies be selling higher octane gas at the same prices??

[onewhippedpuppy]

This is essentially intentional, controlled detonation. It's part of what makes the concept work.

[GH85Carrera]

I hope that engine design works as advertised. It would be a great step forward for the internal combustion engine.

I do worry about the reliability. Really high compression ratios like that obviously work in diesel engine. But diesel is a lot different fuel in many ways.

Mazda tried for decades with the rotary. It makes power like crazy but getting more than 100,000 miles of use is a real challenge. And they sucked gas like crazy. And in my opinion no engine ever made sounds worse the a rotary. Even a Honda ricer with a fart can exhaust is melodious compared to a rotary. Only a Harley with open exhaust "potato potato potato" racket is close. Just my opinion. Your opinion can be different, (but wrong)

[Nickshu]

Very cool. The ICE engine isn't dead...yet.

[RKDinOKC]

Mazda was already varying the charge and compression with valve timing. This looks like it is allowing them to get even higher compression without pre-detonation being an issue. Bet their motors get even smaller.

[dan79brooklyn]

How are Mazda’s Diesel engines as far as reliability goes? I only know one person that has one. He had some carbon issues that were taken care of under warranty.

[berettafan]

just here to say x2 on the horrible sound of a rotary.

[porsche4life]

Very cool. I can everybody close to buying a cx3 when I bought my escape.


Will be interesting to see the economy and power numbers.

[ben parrish]

Seriously cool...

[onewhippedpuppy]

Hey Glen, if you’re ever up in KS you can swing by and drive my FD RX7. I think it will change at least some of your rotary opinions. I agree that they sound like crap with a big open exhaust, hence why you don’t install a big open exhaust.

They don’t all sound bad.

https://youtu.be/81zhOQ5PvaE

[OK-944]

I'm suddenly reminded of a demolition derby I watched years ago...guy lost his radiator fluid...car seriously overheats...guy gets out of still-running car, lifts hood, reaches in and rips out spark plug wires, gets back in and drives off!

[slow&rusty]

Originally Posted by onewhippedpuppy

Super cool stuff. Mazda is an awesome company, the smallest of the major Japanese manufacturers but still building the most innovative, highest quality, best looking, and most fun to drive cars. I'll be very interested to see how this new technology works in actual application in the 3. Now if they would just produce the RX Vision concept in a rotary coupe.....

Agreed!

[RKDinOKC]

Saw a newer RX7 at an autocross being pushed hard. Thought it sounded cool. Sounded like a jet instead of a car.