The Mazda MX-30 PHEV with a rotary engine is likely to land in about a year. We don’t write much about PHEV at CleanTechnica these days, this is going to be a very special plugin hybrid because it doesn’t follow the usual plugin hybrid formula. When used properly (occasional range extender use, which actually happens despite popular reporting to the contrary that’s based on a flawed study), a rotary range extender will make for a plugin hybrid that has all of the advantages of a PHEV, but with basically none of the usual drawbacks.
Why We Think It’s Coming in Early 2023
Before I review the advantages of a hybrid range extender, I want to explain why the guys at Motor 1 thinks we’re around a year out. They were told that the PHEV version of the vehicle would be coming during the second half of the fiscal year. We’ve only recently started the fiscal year (in March), so the current fiscal year doesn’t end until March 2023. With as much delay as we’ve seen with the PHEV version of the vehicle, we probably won’t see it until fairly close to the end of their estimations, and perhaps a little after.
More delays are always possible, though. Putting any new product to market takes time, and as I’ll get into in a minute, Mazda is right to make darn sure that they don’t have serious problems at launch as they have with rotary engines before.
Why Is the Mazda Rotary Engine Special?
I’ve written a long deep-dive about rotary engines in the past, which you can read here if you want the full details. In this article, I’m only going to hit the most important points.
The Wankel Rotary was invented by Felix Wankel, a man who was a Nazi in World War II. It’s easy to make the same argument people make against De-Ba’athification during the Iraq War and say that anybody who wanted to do anything important in Nazi Germany, including an engineering career, had to join the Nazi Party, even if they weren’t really involved in any of the party’s crimes. But, oddly enough this argument both applies and doesn’t apply to Wankel. He was a very extreme Nazi, but ironically his extremism actually saved him from a death sentence. He was too extreme for his fellow Nazis, and was thus relegated to doing things like designing valves, which wasn’t anywhere close to being a war crime.
But, despite his political and human rights stupidity early in life, he was a brilliant engineer who wanted to make a simpler internal combustion engine. His designs culminated in the Wankel Rotary, a 4-stroke engine with only a few moving parts. It is also light weight, compact, and produces very little in the way of vibration. It’s also very good at running on a variety of fuels, including kerosene, hydrogen, and almost any grade of unleaded.
Many other manufacturers have experimented with Wankel rotaries, but Mazda was more committed to it than any other manufacturer over the decades. Its last rotary car, the RX-8, is the car I’ve driven the fastest on public roads with (150 MPH). I can tell you this because the statute of limitations has long run out and I’ve grown up a lot since I was 18. The engine has also found use in a variety of non-automotive roles, including aircraft and boats, where its light weight and high output was a real asset.
Here’s a quick video illustrating how it works and why many people refer to them as “spinning Doritos”:
3D Printed Rotary Engine in Mazda RX-7
It’s also important to note that they’ve been improving the design over time since it last showed up in a car in 2012. The latest Skyactiv-X technology would likely be used in a range extender, meaning it would use even less fuel.
Why Does It Work Better In A PHEV Than Other Engine Designs?
The advantages listed further up include some of the same advantages of electric motors. It’s compact, doesn’t make much vibration, has very few moving parts, and doesn’t weigh much. It is these shared advantages that make it an ideal partner to an EV drive system.
Most PHEVs require fairly severe design compromises. Including a normal 4-cylinder engine, a transmission, and other things that take up a lot of space and weight. Because they take up so much weight, you can’t build an EV dedicated design from the ground up with a typical “skateboard” chassis that slings the batteries low for superior handling and interior room. Instead, you basically have to put the batteries into a normal car design and fit them wherever you can, even if it creates less-than-ideal outcomes.
A Wankel Rotary with enough power to turn a small generator can be far smaller than a normal piston combustion engine and weighs far less. So, you can basically build a normal electric vehicle (like the MX-30) and then put the range extender somewhere out of the way. When it runs, it could make a considerable amount of noise, but that’s something a good exhaust system can mostly mitigate. But, it doesn’t make any vibration and doesn’t intrude on anything otherwise.
Why Range Extending Is The Ideal Job For The Rotary
Normally, rotary engines have issues with longevity and fuel efficiency, which makes them a not very good fit for anything but an enthusiast car. But, most of the problems are associated with operating the rotary engine outside of its most efficient operating RPM and load ranges. That’s why some of the older rotary engines lasted so much longer than others (Editor’s Note: This is factually inaccurate. Older rotaries had much wider build tolerances that allowed for greater oil consumption, especially around the apex seals. Those had to be tightened up to meet stricter emissions standards, which made for less lubrication inside the trochoid that forced the introduction of more exotic materials in the seals, linings, etc. that jacked up costs beyond what RX-7/8 sales could recoup— as a generator that doesn’t directly power the wheels, the Wankel may may slip through a loophole that means it won’t be subject to those same strict automotive standards. If that comes to pass, the Mazda REX will be “allowed” to burn more oil and remove some of the reliability/cost issues.). The ones driving in the city had the most problems, while the ones that mostly did highway duty survived the best. (Literally true of any internal combustion car. —Ed.)
The great news? An engine working as a range extender can always work at one RPM/load range that works best for it. When done like this, it would likely get in excess of 60 miles per gallon when driving on gas power.
Another factor in longevity is how often the range extender actually gets used. There’s a lot of information floating around saying that people don’t plug in plugin hybrids. So, the argument goes, they’re bad because they will only be used as hybrids, so we shouldn’t support manufacturers who make them. But the problem with these past studies on whether people plug in their hybrids is that they were based on studies of company-owned vehicles that the employer would pay for gas but not electricity on. So, naturally, employees wouldn’t plug them in because they didn’t want to see a higher power bill.
In talks with some automotive executives (not necessarily from Mazda), I’ve been told that they have better data from users who pay for their own gas, and that they almost always plug the thing in for local driving. So, that argument (that people won’t plug their cars in) isn’t really supported by valid data. I’m going to share this data in a future article when I’m done collecting it, but wanted to share that little tidbit for now.
This is great news for the upcoming Mazda MX-30 plug-in hybrid, because that means it will be used very little and negates most of the longevity problems that would remain with a rotary engine.
All in all, we really have a lot to look forward to when it comes to range extender hybrids. This could be a game changer for plugin hybrids.
Featured image: A Mazda MX-30 (without the PHEV). Image by Kyle Field/CleanTechnica.