Skyactiv-X: Mazda's Revolutionary Engine Explained

Compression ignition in a gasoline engine has been seen as the holy grail of engine technology by many engineers and for 2019 Mazda has finally made it a reality. While some may say that SPCCI (Spark Controlled Compression Ignition) isn't true compression ignition I disagree. Mazda's engineers took a pragmatic approach to the issues surrounding compression ignition and instead of fighting the spark plug, they embraced it to solve the issues other companies encountered when trying to make this work. If all goes to plan this engine will be found under the hood of a Mazda you can actually buy next year.

[TheAdventureAuto]

You explained this engine technology better than anybody. I finally 100% understand how it works. Pretty dang cool, thanks Alex.

[kwangpark]

Alex’s reviews are not only the most useful in detail but also the most viewer-friendly informative. Thank you, Alex. I love you!!

[raymoreno]

Amazing reaching the compression stroke and raising the actual compression dilivering ignition on its way down makes sense and all the ifficiency in the world. Keep up the good work Mazda.

[tmwei]

Awesome. I currently have the 2.5L Mazda 3 and I just absolutely love it. I can't wait for the new Skyactive-X engine.

[slutica]

The feeding of lean air that won’t ping was the first thing our class thought of when learning combustion thermodynamics at uni 15 years ago. Emissions adds that layer of complexity that stopped everyone from doing so I guess.

[rhino]

I own since new a 2009 Mazda 3s hatchback 5 speed auto with 184, 000 miles. I have been dumping money lately for suspension parts at all four corners and a trans module. I just got back from a 2000 mile Marathon trip in 50 hours. Car ran like a champ. Did not burn a drop of synthetic oil.

[schoong]

What a lovely clear explanation of the technology.

[elit]

Love Mazda . Had many in the family for 20 years. Very reliable. This is Japan's best kept secret. Will keep on buying.

[rkalla]

“Ignitiates” - I... am going to start using that word!

Very cool EE style video Alex, love these!

[aerospacenews]

Alex - good job on a tough concept to explain. Another analog to the diesel engine would be the gas turbine (jet) engine. After using igniters to initiate (or what ever word you made up) :) combustion, compression is used to keep the fuel burning from that point on. Broadly speaking there are centrifugal and axial flow compressor designs. I've driven rental Mazda 3s and seen above 40 mpg on the highway. This would really push them into hybrid territory if they deliver. And are reliable. And don't leak oil (or anything else). Mazda is a company I really admire for pushing on the leading edge, even if things don't always work out.

[konasteph]

You need to get into octane numbers. Gasoline is the opposite of Diesel if it comes to Octane number. Diesel is using a different number, Cetane..Diesel is extremely eager to self ignite Gasoline very reluctant to self ignite That would be a good starting point for this video. This also explains the entire philosophy of diesel and gasoline engines. The increased efficiency and fuel economy is what is all important! I give it a thumbs up!

[bryan_ferrer]

This is what I am looking for!!! Great explanation. I hope there is a follow up to this as I have seen that the stop/start feature does wear your engine faster ( as told by mechanics). Although technically they are right I trust these car maker engineers that they have an explanation as to why their technology works better.

[brianpetersen]

I admire Mazda's engine technology, but my personal experience with a new 1990 M6 soured me on Mazda. With less than 17K miles I had a failure of the power steering system along with a failure of the catalytic converter. Both of these were in careful use of the car. I loved the design and ride of the car but these combined failures make me not want to risk another Mazda purchase. Mazda tried to get out of covering these items fully.

[TheDude]

As an owner of an e skyactiv x Mazda 3 I can tell you that its your best option if you want a very economical car which drives just like a good old naturally aspirated 2 litre 4 cylinder. No Turbocharger, no lag and power increases with your revs. Just like it used to be.

[craigrmeyer]

So here’s what I’m walking away with:

It achieves conventional ratio + spark mode without detonating by (somehow) prolonging the intake valve, this “wasting” some (pre-fuel) intake air back out the intake valve, thus “spoiling” the effective compression ratio to something conventional.

It achieves super-lean combustion mode by going SO lean that it just won’t auto-ignite. It then injects a last-minute “stoich ball” that the spark can ignite. The bump in pressure/temperature from the burning/expanding “stoich ball” then creates diesel-like compression and pow, the super-lean mixture then burns all at once.

Whew! Do you agree?

[guidedmeditation]

I loved this video. It makes the differences of engine types so easily understandable. Thank you.

[c.vdh.]

Very clear explanation. After a long search I finally understand how it works in detail!

[JackdeDuCoeur]

Very good explanation; clear and complete, and not overly wordy.

[TheKaisarwilhelm]

To some entheusists, this is old news. Many of us subscribe to Engineering Explained. On the other hand, I appreciate you helping get this out to the maasses to become common knowledge. I am holding out of my next vehicle to see if I can get a Mazda3 X.

[Dave-in-France]

Hi Alex, thank you very much for this video. If I understand this correctly, this engine is using some of the principles of the Atkinson cycle engine, to provide for variable compression ratios. Interesting but ultimately I believe we will all be driving battery electric cars very soon.