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Mazda reportedly introducing sparkless gas engine—How is this different from a diesel?

Mazda reportedly introducing sparkless gas engine in 2018

The automaker is reportedly set to introduce the first modern gasoline automobile engine that works more like a diesel, using compression to ignite its fuel mixture, rather than an electronic spark.

The question is, is this just a diesel under a different name? But tuned to run on gasoline?

It IS just a diesel but it isn’t, Confusing? Yeah. Gas can be compression combusted like diesel fuel can but the results can be spectacularly bad. The greater volatility of gasoline mean the ignition can start too early in the compression stroke on a running engine plus the more rapid combustion can shove the crank out of the block. That’s why we haven’t seen compression ignition gas engines before now.

With the advent of direct fuel injection at very high pressures for both diesel and gas engines, we now have the technology to squirt fuel in at any point in the cycle. Gas squirted into the combustion chamber near TDC when it is more than hot enough to light off the mixture means the spark is eliminated. Multiple squirts can create a localized area of 14.7:1 air-fuel when the overall combustion chamber is lean, means the engine will run fine and give good MPG’s. Cold engines may still require spark plugs, much like the need for diesel glow plugs.

We’ve already gotten to 11:1 compression ratio engines that run on regular gas. How about 18:1? or 22:1? Promises greater efficiency with the lower emissions of a gasoline engine.

The reason I know a bit about this is a buddy of mine was working on exactly this for another manufacturer and we’d had many conversations about this and how it’s possible.


Presumably the gasoline powered compression ignition engine won’t fall flat on it’s face at 3500 RPM or require a turbocharger to get acceptable performance out of it :slight_smile:


Yup, and when it does in a conventional engine it’s called preignition… or pinging when it’s a slightly different mode of self-combustion.

I’m unfamiliar with this Mazda initiative, but I suspect there’ll be some issues yet to work out, perhaps ignition timing for one. But hey, I’m just speculating. :grin:

That buddy WAS working on engines that had both a supercharger AND a turbocharger. The exhaust gas was almost too cold to light off the catalytic convertors at times!

Really precise management of the events in an internal combustion engine is becoming possible, I guess. Energy is still being wasted a lot in a running engine with the heat being exhausted, so there’s obviously a lot of room for change. What a great time to be a gearhead.

There must be a lot of very good programmers out there, that are good at real time programming and have a very detailed knowledge of how IC engines work.

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'Won’t fall flat on its face at 3500 rpm" The early diesel tractor trailers I drove before the 60s had an operating range of 300 rpm. Minimum of 1800, maximum of 2100. That is why they had so many gears, 10 to 16, many with two transmissions, some wit 2 transmission levers. If you missed a shift going up hill. you and to stop, put it in 1st low and start all over again.

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That’s true. I still think that in another 10 years almost all of the new vehicles on the market will be very-high-mileage hybrids, and in 20 years most of the new vehicles on the market will be EVs. IMHO Mazda almost seems to be working toward something that’ll become obsolete quickly. Makes me wonder why.

I agree, but other car companies have also announced questionable projects that turned into…nothing.
Am I the only one who recalls Nissan’s announcement many years ago that they were developing some sort of Freon-based propulsion system for cars that would use less gasoline, and would revolutionize the auto industry?
A few years later, Freon was banned.

Nissan also claimed at one point that high-tech ceramics would soon be the material from which their engine blocks would be manufactured.
While this may have been much more feasible than the Freon propulsion concept, this project also never saw the light of day, and I believe that Nissan made that claim at least 20 years ago.

Until someone develops a way to transmit electric power through the air (without frying ourselves in the process) there may well be a need for some sort of fueled engine to power generation of electricity. The Chevy Volt technology seems more likely to have long term life than the Tesla model. So far at least, high powered, long life batteries pose problems with weight, size and heat generation, as well as significant environmental impacts in their manufacture and reuse. I expect to see a split in technology between urban, short distance transit and long haul runs. A highly efficient, diesel like gasoline engine might solve some of the particulate production issues of diesel, but will likely produce some other dangerous by-product that we haven’t heard of yet.

Stay tuned for the next exciting episode.

That is absolutely true and a good point. I wish I had a dollar for every exploratory design project that I’ve read about over the years that never came to fruition. Heck, I’ve gone down that road myself a few times. Maybe even more than a few times. :grin:

A normal part of R&D. Far more efforts fail than succeed. The difference is most companies do not go public until they are in the final stages of commercialization. The fact these companies came out with big splashes tells me they were out for some temporary gain, like a bump in stock price or trying to generate a buzz with the buying public to boost sales in the short term.

How true that is. :relaxed:

I read an article not to long ago, I forget where, but that Mazda, and some others, were also working on a variable compression ratio engine. I don’t know if it is related to this engine but possibly this engine could operate in both modes. It would use a lower compression ratio and spark plugs under certain conditions and then switch to the gas diesel mode when that would be the better option.

Available for public consumption as soon as 2018 @keith

SAAB developed one about the time they were closed.

Cool stuff!

With compression ratios at 20:1, maybe E85 will be a viable option

I still think this or a variation of this is the ultimate ICE and will eventually replace todays engines. Its much simpler but will require a lot of computer programming.

Perhaps. But I’ll put my money on EVs replacing ICEs before camless engines become practical. Solenoid operated valves with various modes of activation, pneumatic, hydraulic, and electrical, have all been played with before over the years without any real success. EVs, on the other hand, are actually becoming viable.

I guess we’ll all get to watch the future unfold together. Perhaps something neither of us has thought of is being designed in some lab somewhere that’ll transcend what we expect. I, for one, will enjoy seeing whatever it is transpire.

Camless engines are just a part of the puzzle, the Mazda engine is much more than that.