The problem with the Wankel is and has always been apex seals. You need to rebuild it at least once during a vehicle lifetime. I would not say it is safe from this fate, even with modern seals and a hybrid application.
Mazda’s rotary engine in the age of the electric car
101–110 of 295 posts
Re: Mazda’s rotary engine in the age of the electric car
#102Does it produce more low end torque verses a traditional gasoline combustion engine? If not then why is it better suited for electrical generation? Is it more efficient with less load? The article mostly makes it sound like Mazda just loves the wankle and wants to find any possibly way to bring it back - even though it has “high” emissions… so coupling it with a hybrid electric motor makes it happen.. That can’t be t…
Low end torque tends to be the rotary's Achilles heel. I think the claim being made is that efficiency is better at high, steady RPMs, but tbh, I've always found that claim a bit dubious. If you love the rotary engine, this does have some nice perks as the electric motor basically fixes the rotary engine's main weakness. Having said that, I'd have been much more excited about this 10-15 years ago.
It really isn't. Go and drive a 13BT car. They make almost all their torque by 2500rpm and the curve is flat. They're more torquey than any 4 cylinder I've driven.
Re: Mazda’s rotary engine in the age of the electric car
#103Earlier quoted context omitted.
Several reasons. First, like most of the Japanese manufacturers, Mazda bet against electric vehicles. They focused R&D on improving engine efficiency and getting their engines to run on hydrogen. If Mazda wants to make electric vehicles now, they have to play catch-up, or license key technologies from other manufacturers. Second, batteries are heavy. For sedans and mid-size crossovers, this isn't much of a problem. E…
It would be theoretically possible to have a small battery ("just a 60 mile/100km range, or even smaller) combined with a generator, but I don't know if markets would appreciate that.
This company Toyota started a pretty popular line of hybrid gas-electric cars, maybe 20 years ago, called Priuses. I think they sell pretty well. I see a lot of them running as taxis. The new ones can plug in and drive a few miles on the highway on pure electric before starting the gas engine.
Re: Mazda’s rotary engine in the age of the electric car
#104Earlier quoted context omitted.
Then you may as well use a gas turbine, which is pretty much better in every way that matters for generating purposes.
Apparently they really don't scale well. I found this reddit post explaining it better: > Gas turbines scale extremely poorly. They rely on small clearance between the rotating blades and the housings for efficiency. The smaller the turbine, the greater the relative clearance and the more energy is lost. Gas turbines, at least with established technology, make very little sense below 300ish HP. As a real life compari…
Thank you, I've wondered for years why we didn't have tiny gas turbine engines...
Re: Mazda’s rotary engine in the age of the electric car
#105Earlier quoted context omitted.
> Does it produce more low end torque verses a traditional gasoline combustion engine? If not then why is it better suited for electrical generation? What does low end torque have to do with electrical generation ?
It's not a direct connection. You do want efficient horsepower to drive a generator. More low end torque means the HP comes at lower RPM, which should mean less fuel consumption. Sibling says the achilles heel of the Wankel rotary is low end torque, but you don't take the direct output from the engine, it goes through gear reduction for final drive output. The real achilles heel is the awful emissions. It's more or l…
The side-port exhaust used in the rx-8 generation RE substantially improved the emissions situation, but the fuel efficiency is still trash by modern ICE standards.
It's been awhile since I gave a damn about wankels (or ICEs in general), but ISTR there being a relatively low limit to achievable static compression ratio due to the fundamental geometry of the swept volume. Modern ICE engines are largely exploiting the combination of direct injection and the high compression ratios it enables to improve their thermal efficiency. Between the relatively low compression ratio and sub-optimal combustion chamber shape and the fact that it migrates around the housing with the power stroke, the wankel is pretty much doomed in a world that cares about efficiency.
disclaimer: I've worked hard to discard all my gearhead knowledge, but went fairly deep down the rx-7 rabbithole in my 20s-30s. Take the above with a big grain of "I may be senile and overconfident in stale once-deep knowledge" salt.
Re: Mazda’s rotary engine in the age of the electric car
#106Earlier quoted context omitted.
I don’t understand why Mazda doesn’t just make a drift-tuned electric car. You could do amazing stuff with software focused on that driving style. A true electric successor to the RX-7 would capture so much attention.
Several reasons. First, like most of the Japanese manufacturers, Mazda bet against electric vehicles. They focused R&D on improving engine efficiency and getting their engines to run on hydrogen. If Mazda wants to make electric vehicles now, they have to play catch-up, or license key technologies from other manufacturers. Second, batteries are heavy. For sedans and mid-size crossovers, this isn't much of a problem. E…
The McMurtry Spéirling is claimed to be under 1000kg. A lightweight electric car may not be an oxymoron after all. Just some concessions to make.
Re: Mazda’s rotary engine in the age of the electric car
#107The problem with the Wankel is and has always been apex seals. You need to rebuild it at least once during a vehicle lifetime. I would not say it is safe from this fate, even with modern seals and a hybrid application.
I thought it was the horrible compression and oil burning. Apex seals seem to last if you don’t do silly things to them but you can’t solve inherent issues with the cycle design.
For comparison, rotaries get about 100psi of compression, a modern gas car can more than double that. More compression, more efficient burn.
Re: Mazda’s rotary engine in the age of the electric car
#108Does it produce more low end torque verses a traditional gasoline combustion engine? If not then why is it better suited for electrical generation? Is it more efficient with less load? The article mostly makes it sound like Mazda just loves the wankle and wants to find any possibly way to bring it back - even though it has “high” emissions… so coupling it with a hybrid electric motor makes it happen.. That can’t be t…
> Does it produce more low end torque verses a traditional gasoline combustion engine? If not then why is it better suited for electrical generation? Is it more efficient with less load? You've got it backwards. The Prius's Atkinson engine makes low-end torque *worse*, and then relies upon the EV Motor to drive the car at low speeds (0mph to 10mph) before the ICE kicks back in. If ICE is operating, its at higher RPMs…
It's not like the ICE doesn't do anything at low speeds, HSD uses the two motor-generators like a gearbox
Re: Mazda’s rotary engine in the age of the electric car
#109Earlier quoted context omitted.
Then you may as well use a gas turbine, which is pretty much better in every way that matters for generating purposes.
Gas turbine cars have been built, but they tend to set anyone on fire if they walk behind the car. https://bandimere.com/previewing-the-brakes-plus-jet-car-nat...
Oh! The Batmobile!
Re: Mazda’s rotary engine in the age of the electric car
#110Earlier quoted context omitted.
The reason jet engines have that sort of exhaust is because the primary purpose of the gas turbine there is to dump all the excess energy into the exhaust to make it go fast (so that the plane can be pushed ahead by the reaction force). They produce very little power, just enough to power the Auxiliary Power Unit (that manages the plane electronics, air-conditioning etc.). If you want to use a gas turbine for produci…
Depending on the plane and engine. Big jetliners have high-bypass turbines where they do intentionally produce a lot of torque, to spin a large compressor fan, but most of the fan air does not go through the combustion step, it's just used to react off of.
It's ironic how propeller airplanes evolved into jets for for thrust and back to propellers.
(A ducted fan is still a propeller.)