Understanding Porsche's New Six Stroke Engine Patent
Porsche has just patented a revolutionary six-stroke Before we get started: PORSH? Some people say you should be pronouncing it the original German: Porsche Hast du mein Porsche gesehen? And they're very strict about this. Now, I personally believe it's more important that we understand each other rather than how somebody pronounces something And although I'm not American, it's easier for me to say Porsche And it's my video so I'm going to be saying it Porsche for the rest of the video There you go, I just saved you from commenting your pronunciation preferences that nobody cares about So Porsche has just recently patented a revolutionary six-stroke engine And according to them, it has the power benefits of a two-stroke while having the durability and emissions cleanliness of a four-stroke. Sounds almost too good to be true Now, as you probably know, a traditional four-stroke which powers virtually every car, truck, and motorcycle on the road, today does intake, compression, combustion, and then exhaust A six-stroke adds one more compression and one more combustion event into the mix So it goes: intake, compression, combustion, compression, combustion, exhaust It almost does a little DJ loop on the compression combustion So intake, compression, combustion, fk fk, compression, combustion, exhaust That was so unnecessary Now what we're going to do in this video is that first we're going to see how is that even possible by explaining in detail how this engine actually works And then we are going to discuss its benefits, its drawbacks, and its potential to become mainstream or mass-produced at least, in the near future, because why would Porsche be patenting this now when there's going to be an allegedly ban of sales of new combustion vehicles starting with 2035 Okay, so if we go into the Porsche patent drawings, we are going to find this image And here we can see this large ring gear Inside the ring gear we have another gear: a planet gear What's important about this planet gear is that it has an element on it that is offset from the center So it's eccentric So here we have our ring gear, our planet gear, and our eccentric element on the planet gear If we observe the rotation of the planet gear, we can see that the center of the planet gear of course follows a perfect circle But the center of the offset, the eccentric element does not follow a perfect circle Instead, it follows along a path that looks something like this and this is known as a hypocycloidal path We can see this same hypocycloidal path in the pattern drawings too Now observe what happens when we connect a connecting rod to the eccentric element When the eccentric element is in this position, it allows the piston to reach the highest point in the cylinder We will call this our first top dead center. As the eccentric element continues to rotate, it will reach this point As you can see, the piston is now a bit below top dead center We will call this point our second top dead center The same thing happens on the bottom dead center When the eccentric element is here, it allows the piston to reach this point in the cylinder We will call this our first bottom dead center. As the eccentric element continues to rotate, it ends up in this position where it allows the piston to end up even lower in the cylinder And we will call this point our second bottom dead center So as you can see the eccentric element on the planet gear and the fact that the connecting rod is attached to it gives the engine two top and two bottom dead centers As you will see, this is absolutely critical and it is what allows the engine to perform the six strokes It's also important to note that the crankshaft rod journal is attached centrally to the planet gear, so that the crankshaft can follow a perfectly circular path It's only the big end of the rod that goes onto the eccentric element and is forced into a hypocycloidal path Something else that the patent mentions is a worm gear that meshes with the teeth on the outer side of the ring gear This allows us to manipulate the outer ring gear while the engine is running which makes it possible to have complete control over a variable compression ratio and also to deviate from the path we showed, which opens up various possibilities The final piece of the puzzle are these ports which we can find between the first and second bottom dead center The distance between the first and second bottom dead center is equal to the height of the ports and this is of course equal to the offset in the eccentric gear These ports at the bottom of the cylinder allow fresh air and fuel to enter into the engine when the piston uncovers them And the piston starts to uncover these ports only when it goes below the first bottom dead center And finally, we also have conventional intake and exhaust valves at the top of the engine Now let's observe the full working cycle of the six-stroke engine Our first stroke is intake and it begins at the second top dead center During this stroke the intake valve opens and air and fuel comes in, as the piston goes down The intake stroke ends at the first bottom dead center due to the position of the eccentric element which keeps the piston from reaching further down in the bore This also means that the bottom ports or the scavenging ports remain closed by the piston Now the compression stroke starts The piston goes up and compresses the air-fuel mixture As the eccentric element rotates around, it now allows the piston to reach the first top dead center and fully compress the air-fuel mixture Just before the piston reaches the first top dead center, the fuel mixture gets ignited and the compression stroke ends. The combustion stroke now begins Combustion pressure acts on the piston, creating torque as the piston travels down As the piston is going down, the eccentricity now allows the piston to reach the second bottom dead center As it does so, it uncovers the ports. At the same time, an exhaust valve opens on the top and the
pressurized exhaust gases from the completed combustion now escape through the exhaust valve and leave a vacuum behind them because they rapidly vacate the cylinder This vacuum pulls in a fresh air-fuel mixture through the bottom ports Now this only works if the exhaust gases are pressurized enough which doesn't really usually happen at idle So at idle we might need the help of forced induction to push the fresh air-fuel mixture into the combustion chamber and force the exhaust gases out As you can see the bottom ports are fairly short in relation to total engine stroke So they're open only for a brief period of time, which means that they're likely unable to replace all the exhaust gas with a fresh air-fuel mixture Instead what we likely have at the beginning of our second stroke is a mixture of fresh air and fuel and some exhaust gas So something similar to what we have when the EGR or exhaust gas recirculation valve allows some exhaust gas back into an engine So now begins our second compression which starts at the second bottom dead center and ends at the first top dead center The air-fuel and exhaust mixture is ignited creating the second combustion stroke which likely creates less torque due to the presence of the inert exhaust gas But torque is still created as the piston moves down Our second combustion stroke ends at the first bottom dead center again due to the effects of the crankshaft gear eccentricity And finally, the piston moves back up to push the exhaust gas out through the exhaust valve Our exhaust stroke ends at the second top dead center which ends the cycle and begins a new cycle and a new intake stroke which again of course starts from the second top dead center That's how it works Now let's talk about first the benefits Benefit No 1. This relies on 100% conventional mechanics and technology The gears, the crankshaft, the connecting rod, the piston, even the little ports at the bottom It's all very conventional. By the way, this arrangement where we have ports which are known as scavenging ports on one side of the cylinder and conventional valves on the other is usually known as uniflow scavenging. Because the gas moves through the cylinder in a uniform fashion
and this is very common on two-stroke diesels in ships and locomotives and other industrial applications The six strokes, also they don't really make a problem for the camshafts We do need to change some things. Instead of rotating at half the crankshaft speed the camshafts now need to rotate at one-third the crankshaft speed So we need just a slightly larger cam gear and we need an additional exhaust lobe on the exhaust cam So that's pretty much it So what this means is that because we have very conventional technology we do not need massive investments into research and development to get this engine to market Benefit No 2. is that this does make more power than a traditional four-stroke If we observe the first 720 degrees of rotation then it doesn't really make any more power because we just have one power stroke, one combustion event during the first 720 degrees of rotation just like a traditional four-stroke But we have another combustion event starting right at 720 degrees A traditional four-stroke cannot do this. It can only do the second combustion event at 1080 degrees So we need more rotation from a traditional four-stroke Now if we observe let's say 7200 degrees of rotation then a traditional four-stroke is of course going to do 10 combustion events A six-stroke is going to do 13.34 combustion events so that's a 33.4% potentially more power
Now, it is definitely not in two-stroke territory because during 7200 degrees a two-stroke is going to do 20 combustion events and that's going to be 20 proper full combustion events Remember in the six-stroke every other stroke is a bit weaker because it's going to have a lot of inert exhaust gas in it which means that we're probably not looking at 33.4% power increase but let's say something like 25% power increase but 25% more power with conventional technology and traditional four-stroke reliability and emissions friendliness is a big deal Something else that a six-stroke allows is to run very very high boost and still be pretty emissions-friendly. When you run crazy high boost, let's say something like three bar or 45 PSI, you need to run a very rich mixture and excess of fuel to prevent knock When you burn such a rich air-fuel mixture, you're going to have leftover fuel in the exhaust gas If you send that fuel out into the atmosphere, you're going to have horrible emissions But remember in the six-stroke we don't send all that exhaust gas into the atmosphere We just sent a little bit of it when the bottom ports open just a little bit escapes, the rest remains in the cylinder and gets compressed and burned again which means that you have another chance of burning your unburned fuel which means much better emissions so massive boost and government approval The next benefit is efficiency But I think that at cruising conditions this design does not significantly improve efficiency Becuase cruising, low rpm, low load, whatever, we're usually running something close to a stoichiometric air-fuel mixture which means that we have a clean burning combustion and really no unburned fuel in the exhaust which means that there's not much energy, or any significant quantity of energy to be harnessed from the exhaust gas and the second combustion, or every other combustion stroke in a six stroke depends sort of on what's in the exhaust gas So if there's nothing significant to be harnessed from the exhaust gas then there are no significant gains in efficiency In other words, where this engine can improve efficiency is high load, high rpm, high boost where we potentially have unburned fuel in the exhaust, and here we can sort of harness some of that energy Recover it during that second combustion stroke The final benefit is compactness and simplicity And for what it is, this design is pretty simple and compact We're gaining the ability to do six strokes while only marginally increasing engine size, weight and complexity The ring gear is the main culprit behind a potential increase in engine size And that too is kinda design friendly, you can somehow stick it into the engine block without increasing the size of the engine block too much. It's a round shape, usually easy to design things around it and it's very thin so it doesn't increase engine length In terms of mass and complexity we're really just adding three more parts Ring gear, planet gear, worm gear and that's per crankshaft because you can add one planet gear to a single multi-cylinder crankshaft and do the same thing as the single cylinder example in this video So we're gaining 25% more power and improving efficiency at high rpm, high load But we're definitely not increasing engine size and mass by 25% And now the drawbacks. The first drawback is of course the gears, very obvious. Introducing gears to anything is creating a parasitic loss which reduces efficiency, which is another reason why I don't think this design is primarily focused on efficiency The second drawback is that for this engine to function as it functions in the patent drawings We need a very long piston with a very long skirt and that's because when the piston is at top top dead center, the first top dead center it needs to be tall enough to still close off the scavenging ports at the bottom which means that the piston ends up being pretty much half of the entire stroke of the engine and that's a very tall piston. A very tall piston has a lot of mass
And a piston with a lot of mass is going to create a lot of vibrations which is going to limit maximum rpm I think that realistically in the final design, if this ever sees the light of day we're not going to see a locomotive style piston like this one, especially on something that could be a Porsche engine What I think I more likely solution would be in reality is to control the access of air to the scavenging ports Because there's another port or intake duct or whatever brining air to the scavenging ports If we can control that with some sort of valve than we might not need such a giant piston The final drawback, and this is probably the most significant one is engine balance it's not horrible, but it's not ideal either if we take this graph of the running cycle of the engine we can also use it as a primary force graph for a single piston Because it's pretty much the same thing If we take one more piston and offset it by 180 degrees to balance the pistons out, which works well in traditional four stroke designs we can see that in the six stroke it doesn't work we have uneven stroke lengths so the two pistons don't fully balance each other out then we have a resulting force creating some vibrations Similar things happen with secondary force where the pistons again cannot fully balance each other out The resulting vibrations are pretty small, but they're still there and should be mentioned The next issue with balance we have is the planet gear It rotates around pretty quickly as the engine is running so it's creating its own forces which have the possibility to produce vibrations on the engine And then we also have the offset, eccentric element on the planet gear which creates its own forces as it's spinning around and another little source of potential vibrations And the final issue with balance we have is that the eccentric element misaligns the big end of the connecting rod against the crankshaft counterweight so we can't use the crankshaft counterweight to fully balance out the big end of the rod This misalignment is small and the big end of the rod is still in the general counter position to the counterweight But part of it is from time to time outside the area where the crankshaft counterweight can balance it out they point in different directions, so this too creates a little source of potential vibrations So as you can see, we have multiple sources of very small vibrations Although none of them are individually significant vibrations I gues that they do add up However, it is likely possible to mitigate these vibrations with a different cylinder count and engine configuration and Porsche does mention this in the patent saying that this design, the six stroke is most suitable for engine cylinder numbers which are multiples of 3 So 3, 6, 9 and 12 Of cours the 6 is what matters here because as we know 911s are all about flat sixes So it is possible that this cylinder configuration, perhaps together with some mechanical devices can render these vibrations to a non-significant level So overall I have to say that I like this, this design It is elegant, it is clever and very much Porsche-like if that makes sense and it's good because it brings significant benefits to the table without any major, unresolvable drawbacks And as a final note let's talk about why patent this now if there's going to be a ban on Ice Vehicles starting with 2035 in the EU and I think some other parts of the world uh well here's the deal, there's not going to be an actual full complete ban of ice vehicles in the EU starting with 2035. The people who still think that and spread this information are allowing mass media headlines to shape their opinions and I'm pretty sure that most of these people haven't really made it to this point in the video they're probably in the comments down below regurgitating some sort of contextless snippet of information they picked up during their many aimless journeys through the world wide web so what I'm about to say probably won't reach them but that's okay On March 25th of 2023 the EU actually reached an agreement with Germany whose industry very much depends on the production of vehicles and they reached an agreement which says that new ICE Vehicles can be sold and registered after 2035 provided that they are fueled by E-fuels or environmentally friendly, carbon neutral fuels. Right now the production of such fuels is... I don't think it's sufficient to sustain anything, it's very expensive, but some people claim that it's going to ramp up a lot before 2035 and so this gives ice vehicles, you know, a potential to keep existing for a long time into the future. New ICE Vehicles. So what Porsche is actually doing here is that it is taking preventive measures which are going to allow it to produce a very high power emissions friendly engine that still fits into the back of a 911 in case that e-fuel production ramps up By patenting this they're preventing anyone else from implementing this design without paying fees to Porsche. So that's pretty much it, again a very rational and clever decision. So will this
happen, are we going to see it in the future? It's anybody's guess. If e-fuel production does indeed ramp up I think that it is very likely that Porsche is going to greenlight some sort of project an actual research and development project on this. Will e-fuel production ramp up? Who knows Is it going to be expensive? I'm pretty sure it is going to be expensive, the e-fuels. But I don't think that's a major issue for Porsche buyers. So there you have it, the six stroke engine. as always As always, thanks a lot for watching I'll be seeing us soon with more fun and useful stuff on the D4A channel
2024-10-04 11:51
