Mazda Brought Back The Rotary Engine!

hello everyone and welcome after 10 years the rotary engine is back and it's coming in the Mazda mx-30rev now there's a lot that's really cool about this engine and there's some clever tricks that Mazda has employed there's also some disappointing news that goes along with it now I have plenty of videos explaining how rotary engines work so let's compare this new engine versus Mazda's last rotary engine which they produced which was used in the RX-8 so I'll put the specifications up on the screen and as you can see some of the disappointing news right off the bat this is a significantly lower revving lower power it is just a single rotor rotary engine rather than the Dual rotors on the RX-8 so you know this isn't quite the same thing that we used to get with this super high revving really neat unique engine experience now we have something a bit different now one of the most notable changes of this engine is that you are now directly injecting fuel in to the combustion chamber rather than in the intake Port like was done previously so Mazda says there's two real benefits to this first of all the location of where you're injecting that fuel keeps the fuel in the main area of that combustion chamber and also you have better atomization because you're using higher pressure and a finer mist of fuel being injected which is helpful at low temperatures such as startup now there's a pretty fascinating quote in the press kit about this so they say when fuel is injected into the ports on a conventional rotary engine a lot of the air fuel mixture ends up at the back of the combustion chamber not fully combusting and eventually being expelled as unburned gas this has a negative effect on both fuel economy and engine output so Mazda is saying directly in their press kit that a lot of the fuel in the conventional rotary engines just goes out the exhaust I think that's pretty incredible to see in a press kit because let's go back to 2008 and see what Mazda said about the rotary engine through the incredible efficiencies of a rotary power plant the renesis engine delivers smooth linear power on a grand scale so you can see they play with words a little differently there the new engine is also Now using exhaust gas recirculation which Mazda says helps with efficiency at low loads and low RPMs because it helps contain some of the heat within this engine so Mazda engines inherently have a lot of heat loss because of so much surface area within this rotor housing and so they say using EGR they can help reduce some of that heat loss we're now using aluminum side housings versus Iron Mazda says this is good for 15 kilograms of weight savings and they're also using a spray-on plasma ceramic coating that they're applying to those housing sides for better wear and better friction they also now have wider Apex seals up to 2 2.5 millimeters a 25 increase which they say gives better wear resistance okay and the big kicker and the kind of disappointing news here of this new engine being introduced is that it's simply used as a range extender so the engine spins up a generator that generator provides power to go to a battery or to an inverter which then Powers an electric motor which is powering the vehicle so there's no direct link between the engine and the driven wheels so if the rotary engine is just being used to power a generator what's the point of using a rotary engine at all well Mazda says the big Advantage here is that the engine is compact so if you compare the 0.83 liter making 74 horsepower versus BMW's inline two-cylinder used in the I3 as a range extender that's just using 34 horsepower with a 0.65 liter so you know fairly similar in displacement yet wildly different Power numbers and a big reason for that of course being that a rotary engine for each rotor has three active combustion Chambers which are all happening simultaneously but there's also a big problem with rotary engines and yet Mazda has come up with a very clever solution so here we have our classic internal combustion engine using a piston and cylinder and there's a technology called variable valve timing that is very common in today's engines which are using piston cylinders so how does this all work well basically what you need to know is this intake valve which opens and closes in order for you to pull in that fresh air to use with combustion if you close it too early well you don't let enough air within the cylinder right and then if you leave it open for a really long time well then you let some of that airflow go back into the intake and eventually that piston starts moving up and pushing more of that air out effectively reducing your compression ratio so if you open it too short you have problems if you leave the intake valve open too long you have problems there's some ideal that falls somewhere in between and it's dependent on the airflow coming in and that airflow coming in changes depending on your RPM so as this engine is operating at different speeds when you want to open and close this intake valve varies okay so that's no problem with internal combustion engines using piston cylinder vices we have variable valve timing and we can change it throughout that RPM range so can you do that with a rotary well not exactly right because we have this simple port and that Port whenever it's exposed to the intake chamber here within our combustion chamber that's when you can pull air in and then once that rotor covers up that valve well then you can't pull in any more air right you don't really have control over when this is open so you do have control over how you design this overall engine and you can optimize it for one specific RPM but you can't optimize it throughout the whole range unlike what you can do with piston cylinder engines so I found a study looking at rotary engines and they talked about you know what is ideal and so at low RPM much like with an internal combustion engine using piston cylinder you want to have that intake valve close early you want less time to have the maximum amount of air ever come in to the cylinder as you get to higher RPM you want more time you want to be able to let that air to pack its way in for more time as your engine is going really fast so there's this variance in how much time you want these intake valve open for Optimum volumetric efficiency meaning putting as much air as you possibly can within that cylinder and the same is true for rotary engines that's what this study showed as you have that RPM go higher you want to leave the amount of time that that intake air has to enter the chamber a bit longer so you can get more air in it well how do you do this with a rotary engine if the timing is fixed because that whole opening is a fixed location well a Mazda patent from December of 2022 answers this question so first let's understand the vehicle layout based on this patent which is very similar to how it is actually laid out in the mx-30 so we have a battery pack that battery pack sends energy to an inverter the inverter sends the energy to a motor the motor rotates a gearbox that gearbox ultimately rotates your driven Wheels in this case it is front wheel drive so you also have a rotary engine which Powers a generator and that generator can be used to either send power to that motor powering the wheels or it can be used to send power to recharge your battery pack great now one of the options Mazda describes in this patent is that they add an additional electric motor that's going to be directly linked to The Eccentric shaft of your rotary engine in order to manipulate the speed of your rotor's rotation so why would you want to do this well again remember for low RPM we want less time for our intake to be open for high RPM we want more time for our intake open so we can get more air into the engine so here's a little chart that shows the logic of how this electric motor is going to work basically the way we're going to set up the engine is so that at the RPM that we use the most and keep in mind as a generator there's is going to be like one set nice efficient RPM where this thing's cranking out a good amount of power so we're going to pick that RPM where we're efficiently generating power that we think the engine will sit at the most frequently and that's going to be our zero assist spot meaning this motor is doing absolutely nothing to Aid the rotation of this rotor but if we're at a lower RPM then we're going to help speed up that rotation and if we're at a higher RPM we're going to slow down that rotation for a portion of it so if we look at our intake stroke here for the rotary engine this little Dorito here is going to rotate and that's going to cause our eccentric shaft to rotate 270 degrees well throughout that rotation that's the total amount of degrees of rotation that we have for our intake stroke so for the initial bit we're not going to do anything we're not influencing in any way but right at the end we're going to use our electric motor to change the speed of that rotation and and that speed change is dependent on where our RPM is so again if our RPM is really low then we're going to add a positive assist of torque that motor is going to help speed up the rotation so that you have less time for intake and then if you're at a really high RPM meaning this speed right here is really fast well then you slow down that rotor very briefly at the end of its intake stroke in order to give it more time for air to come in then you turn that assist off again and it maintains its rotation at a higher RPM but it slows it down just for that little bit at the end so you can get more air within the engine now you might reasonably say wow that's complicated we've got an extra motor and an extra inverter we're adding this complicated Mass to this already complicated powertrain and also is the efficiency gain of rotating that rotor just a little bit faster for these different portions actually worth the added energy to power this motor and so is there a way that we can eliminate this motor and this and inverter yes yes you can okay option two as described by the patent and this is extremely clever because instead of using this additional motor and inverter we're going to Simply use the generator to do that job now one of the key differences here previously we designed an engine such that the most frequently used RPM gave us our maximum intake charge air efficiency so the overall design of the engine is designed for one specific RPM and at that specific RPM we have our maximum intake charge efficiency and thus we don't need to use any assist from the motor now our most efficient RPM for intake charge efficiency is the highest RPM we're going to use so in other words like the engine's Redline the highest RPM we ever will use is going to be our maximum intake charge efficiency and then anything less than that we're going to have to provide some positive torque in order to speed up the rotation of the rotor in order to shorten the duration of that intake again we want the longest duration for our highest RPM so that is the location where we provide no assist and so how do you provide a torque boost with a generator that you're using to generate electricity well basically what you're doing is you're using this generator like a brake when it's generating electricity this generator acts like a brake it's providing a torque that this engine has to overcome for a brief moment you can basically shut that off you can reduce the torque requested there's an electricity generation torque and you're reducing that request by a certain amount so in other words it's like for example if you were to be driving a manual transmission have your foot on the gas and you're in let's say sixth gear and then you push in the clutch you take off that load from the engine and so the RPM just flies up you're doing the same thing here you're generating a bunch of electricity then you're saying hey reduce the amount of generation and suddenly there's nothing resisting this engine from spinning up really fast so it increases its rotation thus shortening the duration of time that your intake is open Super clever so that is what you're doing as you're using lower RPM and if you were to be at the maximum rpm then you're simply not requiring that generator to change its load at all okay so as a quick review there's a certain duration of time that is ideal in order to maximize the amount of air we get into this engine and thus maximize power and efficiency and so we can influence how much time this rotor has for its intake Stroke by using a generator and taking that generator to change the amount of load it is placing on the engine and thus how fast that engine rotates and so by doing this we're you know it's a very simple solution we're eliminating that extra motor and inverter and we're not powering an extra motor right and so the only thing you might wonder is well aren't we going to have some weird Vibrations by changing this RPM constantly as the thing is going along well your engine isn't actually connected to the wheels so you don't really care that much you can isolate the vibration of this engine because it's not going to the driven wheels and thus you're not feeling that pass along you know through your drivetrain to you instead it's maintained within this rotor and its generator right so it's just simply sending power to the battery pack and it doesn't necessarily mean that all these crazy vibrations are going to be passing to you so it's a really neat solution I don't know if it's actually used within the mx30 or not but this patent just came out conveniently when the mx-30rev is coming out and so it seems likely that this is something that Mazda has been thinking about with this vehicle thank you all so much for watching and if you have any questions or comments feel free to leave them below

Channel: Engineering Explained

Views: 1,527,151

Keywords: rotary engine, mazda, mazda wankel engine, mazda rotary engine, mazda 13b, mazda renesis, mazda rx-8, mazda rx-7, mazda mx-30, mazda mx-30 r-ev, mx-30, mx-30 r-ev, engineering explained

Id: -3gzQVGEqF4

Length: 14min 7sec (847 seconds)

Published: Fri Feb 17 2023