Mazda’s engine tech lives up to the hype
FRANKFURT, GERMANY— Has Mazda come up with a new engine technology which might extend the life of internal combustion engines by another several decades?
Or is their upcoming “Spark Controlled Compression Ignition” (thankfully shortened to SPCCI) engine simply a reworking of the century-and-a-half old four-stroke intake-compression-power-exhaust (or “suck-squeeze-bang-blow”) petroleum-fueled power plant which has been the backbone of personal and goods transportation for most of that time frame?
I figured a smallish company like Mazda, which has a reputation for innovative engine technology (hello, rotary Wankel engine) and which, despite a recent tie-up with Toyota, doesn’t have a ton of money to blow on PR stunts, wouldn’t have invited journalists from around the world just for a dog-and-pony show.
We had heard rumours that it was a gasoline engine without spark plugs which operated more like a diesel, which ignites fuel spontaneously when the rising temperature caused by the increased internal pressure is sufficiently high to ignite the air-fuel mixture.
But when we saw the engine, there were the spark plugs. One rumour scotched.
Yes, at first blush, the new engine, dubbed SKYACTIV-X, looked like a conventional supercharged gasoline-fuelled four cylinder. What was so new?
When Ichiro Hirose, managing executive director in charge of powertrain development for Mazda, took us through the explanation of the new engine, we learned that the compression ratio — the degree that the air-fuel charge is squeezed during the engine’s “compression” stroke — was 15.0:1, a higher number than gasoline engines can typically handle, and that it runs on regular fuel. This is indeed something different.
Nominally, gasoline engines run at a14.7:1 air-fuel mixture — the socalled “stoichiometric” ratio. The new Mazdas can run as lean as 50.0:1, thereby saving considerable amounts of fuel.
How do they do this without the engine “knocking,” i.e., without the air-fuel mixture spontaneously starting to burn under the higher pressure this engine develops? Severe knocking or pre-ignition can destroy an engine in minutes. The devil, as they say, is in the details.
Combustion in the SPCCI engine is, you should pardon the expression, sparked by the spark plug, but the majority of the actual burning is initiated by the heat rise due to the higher compression, like a diesel.
To get the higher volume of air needed to make this all happen, the engine has a supercharger, although Mazda prefers to call this a “highresponse air supply” or “air assist.”
I asked if the difference was that a supercharger increases the volume of both the air and the fuel, whereas this device only blows more air into the cylinder to create the ultralean mixture.
“Exactly!” was the reply. Still, if it looks like a duck, walks like a duck and quacks like a duck . . .
To illustrate how this new engine works in the more-or-less real world, Mazda provided each of us with a pair of next-generation Mazda3 hatchbacks, due here in 2019, which will feature an ultra-stiff body, revised suspension, new seats and brake-by-wire brakes, but were draped in the bodywork of the existing car to fool the spy photographers. And of course, these cars had this new engine.
One car had a six-speed manual transmission, the other a six-speed automatic. We ran each car around a predetermined route which involved city streets, highways and a couple of no-speed-limit Autobahn stretches. Not your usual fuel econ- omy run. Our fuel usage was carefully measured, and the results posted for all to see.
I’m proud to say that the four Canadians on this event, which also included Americans, Japanese, Australians and Brits, collectively topped the charts.
I blush to mention who had the overall best scores, of 5.2 L/100 km with the automatic transmission and 5.7 with the manual, while also recording the highest top speed on the Autobahn (164 km/h). Er, yes, that would be me.
But any way you slice it, these represent excellent real-world numbers. Can’t wait to see how well they score on the formal Transport Canada tests. Incidentally, those numbers for the current Mazda3 2.0litre are 8.4 city, 6.4 highway and 7.5 combined. Given the Transport Canada test procedure involves much lower-speed driving, this makes the numbers we recorded even more impressive.
There are still a few bugs to be worked out in this system. On light throttle, there was still some knock or “pinging” detectable from these engines.
The brake-by-wire system, which still has to be approved by governmental regulatory agencies in some countries, needs a bit more development to achieve world-class pedal feel. But with a year-and-a-half to sort these issues out, it seems Mazda has once again come up with some unique new engine technology.
Internal combustion engines have been ever-more-carefully studied over the past 30 years or so, as engineers look for ways to improve fuel economy and reduce emissions. Surely somebody else has looked into this concept?
They have. Buried deep in my brain is a fragment of memory of (I think) General Motors working on engines that sounded vaguely like the SKYACTIV-X concept, but nothing has reached production.
What has Mazda discovered that others have not? Apparently, that you never give up.
Speaking of never giving up, what about that screaming, ultrapowerful, rotary Wankel engine? Mazda engineers won’t say anything formal, but they always grin like assassins when we ask them about future applications.
We can only hope.