But unlike the guy who had no business taking an 8 a.m. class, Mazda has no choice but to electrify, and that’s a tough proposition for a small, independent automaker that isn’t flush with investor cash—one of the last, really. So can Mazda’s only EV (for now) be more than it is? It says yes, and one answer for now at least is bringing back the rotary engine as a range extender, not unlike the Chevrolet Volt or the BMW i3. And though a “new rotary engine” has been rumored since the Fast & Furious movies were still about street racing, Mazda’s confirmed it’s actually doing this. Now, via a patent scoop from CarBuzz, we can see how unusual this new rotary range extender for the MX-30 will really be. And the end result—all that stuff I listed in my lede, plus the magic spinning triangle engine—could make this the weirdest new car on the road. (Seriously, what could be weirder than this right now? I’ll wait.)
The site says this new Mazda rotary aims to be significantly more efficient than its notoriously not-so predecessors by adding something akin to variable valve timing. I’m just going to quote the article rather than screw this up by attempting to explain it myself:
However, the secondary port also interferes with low-speed efficiency, so Mazda added a throttle valve to close it off in low-power conditions. This has the same effect as altering the valve timing on a piston engine and improves the rotary’s breathing efficiency over a wider speed range. Following along? Good. Now the next part is where it gets confusing. Fascinating already. And that “next part” refers to the electric motor; it’s fed by the EV’s high-voltage traction battery and can speed up or slow down the rotary engine as needed to optimize the intake into the combustion chamber. [Ed note: The patent, US 20220381190 A1, actually mentions that the slowing or speeding of the rotary engine could happen via a separate “assist motor” independent of the generator, though this assist motor, the patent makes clear, isn’t needed and is likely only mentioned to cover the invention broadly -DT]. As that story notes, the rotary engine here is just used to generate electricity, not drive the wheels themselves. But it’s a unique application of something that’s historically important to Mazda, and while it’s not the same as a new RX-7, it’s great to see this company trying something so different. Here’s a basic description of the patent from document’s abstract: The patent breaks it down:
You can see at low RPMS, there’s positive assist torque, and at high RPMs, there’s negative assist torque. At that optimal RPM that will see high usage, the “assist motor” doesn’t apply a torque. The patent continues: If that’s still not clear, maybe this and the diagram below will help a tiny bit: I’m going to be honest: I’m a little bit confused by the way this patent is worded, so engineers please chime in. But it seems to me that optimal intake timing occurs at a given RPM (the one the engine will run at most of the time) but there are certain scenarios (presumably when the battery is at a really low state of charge and draws lots of load from the generator, or the opposite where the battery is full/regen?) that would operate that engine outside of its optimal intake timing point; an electric motor lowers or raises the load on the engine to bring intake timing closer to optimal — that’s how I read this, though again, it’s a patent document, so not the clearest on earth. And also, I’m no powertrain engineer! -DT] Images: USPTO via CarBuzz
Domino’s Pizza Will Have America’s Largest Electric Pizza Delivery Fleet
Mazda RX-7 FD, Buick Super Riviera, Honda CBR250RR MC22: Mercedes’ Marketplace Madness
Marvel At Nissan’s Weird Rebadges Of The Great Recession
The 2022 Mazda 3 Turbo Is An Anti-Hot Hatch In The Best Way Imaginable
Now Mazda is adding complexity… is it necessary? Am I totally wrong on this? With that in mind, this is basically a controls-level tweak to slow down or speed up the engine speed just during the intake stroke to effectively get the benefits of cam phasing to make the engine more efficient over that range of speeds and loads. The multiple ports is just background, and is equivalent to different cam profiles that can be switched between (and is old news for rotaries – they’ve been doing this since the 2nd generation RX-7 with 4-port turbo and 6-port NA engines). The Fisker Karma operated as a simple series hybrid and it got awful mpg (after it ran through its EV range). The Volt’s ability to switch between pure EV, series hybrid, and parallel hybrid modes was actually really slick engineering. It gave you better mpg. I think this is some good lemonade that Mazda is making out of the market transition to EV lemons the market has served them. Assuming they don’t take forever to release them and don’t have too many glitches at launch (something something never buy v1 of a new technology). At least that’s how I read it. And I want one of these. Badly. It sounds like they’re using the assist motor torque as a proportional controller to make up the difference between the torque the engine would otherwise produce and what’s required to maintain a steady engine RPM (and max. efficiency). Either way i have huge doubts the intake tricks will make the rotary more economical than a piston engine.It’s starting point is far too low. And i hope i’m wrong of course! My guess is that the discussion on ports is just background, while the novel part of the invention being covered by the patent is using the electric generator to selectively slow down or speed up the engine during the intake stroke to get a cam phasing-type effect in addition to the switchable valve profile effect (similar to VTec, yo!) that the different ports allow. and even though it handles well, the title’s brand all to hell But you’ll never hear a sound quite like 9,000 rpm and more! So she’s a bit of a fixer-upper so she’s got a few flaws It’s peculiar engine, the need for high revving that requires breaking traffic laws So she’s a bit of a fixer upper, but this were certain of you can fix this fixer upper with a little bit of love! My English teacher would probably be appalled at my run-on sentence. Sorry Mrs. Z. While the CX-30 makes little sense to most people with its minuscule range, it did sell out in the US. That should tell everyone an electric Mazda will be very attractive, when even an imperfect one sells this well. I’m an engineer. Previously worked on range-extended electric vehicles (REEV). Imagine you plug in your EV every night, and do all your daily driving in EV mode, then a few times a month/year you need to do a 600 mile road trip. That’s when you use your range extender. You can live with the inefficiency of the Wankel if it’s small and light enough to be a more efficient solution than a piston ICE you’d be lugging around all the time instead. I’ve been in prototype REEVs when the piston RE starts up, it’s an NVH nightmare. A Wankel cuts the vibration way down (I had an FC RX7 for a while, sooo smooth) so that’s a lot of space and money saved on NVH. You’ll want a nice big muffler, but that’s crushable so can live in a crumple zone, which you can’t use as space for batteries, motors, fuel or people. It’s a smaller, lighter solution that is more energy efficient over the life of the vehicle. But only if your daily use is within battery range (which it probably is for most people) and you actually plug it in to charge. Of course we’ve all heard the old trope of why EVs are no good because you can’t take that 600 mile road trip once a year. Many people drive much more vehicle than they need just for that once of twice a year when they tow a boat or take a long road trip. People should buy and drive what they like of course. “You can live with the inefficiency of the Wankel if it’s small and light enough to be a more efficient solution than a piston ICE” Wankels don’t have the ability to burn fuel as efficiently as a piston engine, meaning lower power density and high emissions. They can make great power for they’re physical size, but the wankel being a light weight engine is a myth. It would likely weigh more than a piston engine at the same power level. Don’t get me wrong, I love and appreciate Wankels, I just think there is a lot of myth surrounding them. The NVH is a great point, as that’s really a big part of my disdain for range extenders. A Chevy Volt or i3 with the range extender running is a miserable thing. Thanks for sharing your insight. I still don’t like it, but I’m no crossover enthusaist anyway. Hopefully people will buy this and then Mazda will have more money for Miata-like things. Getting a serious Jones here. I do think that PHEV’s time is not over, if a hybrid can achieve over 60mpg it’s approaching fossil fueled power plant levels of efficiency all on it’s own, with less weight and cost than a full on battery EV, and a decent heater too. Until this fusion thing really starts going, BEVs are still tethered to their power generation. Maybe not at home for the solar or those that can pick their providers, but definitely with public charging.
