in this video we're going to be talking about

why the rotary engine died

and now hopefully we'll be coming back

with the Mazda RX vision

but nonetheless the engine disappeared

for several years as a result of some of its disadvantages.

So we're going to get into four of those major disadvantages.

Now, if you haven't yet checked out my video on how rotary engines work

you'd want to check that out before watching this.

So the first disadvantage we're going to get into

is that by design wankel engines tend to have a low thermal efficiency.

And part of this is due to the fact that they tend to have lower compression ratios

But it's also because of the shape of the combustion chamber.

So here we're gonna have our two spark plugs

and they're going to be igniting the air-fuel mixture

And so this is going to begin to rotate this direction

as the combustion occurs

So your flame is going to be starting here

and it's going to want to travel out and ignite that air-fuel mixture

So it has to travel a long distance in order to ignite

All of this mixture, and so by the time it gets to over here,

you know you're continually growing that and making it more difficult

to ignite that mixture, and then you get to the end

where it reaches the exhaust port, and some of that air and fuel

is going to be unburnt, and so

you're going to be sending that fuel out the exhaust

And so this is going to tend to be why

you may see rotary engines spitting flames out the exhaust

is because they're not going to be able to burn all of that fuel

within the combustion stroke here

And so, because of that they're going to have a lower thermal efficiency

They're going to get worse fuel economy and they're not going to have good emissions.

Another big challenge for the rotary engine

is how to keep it sealed.

And so you have to remember that you don't want to let any of the gas in this chamber

to get into this chamber or vice versa

and it could pass over this way or it could pass around this way.

And so because of that you have these apex seals

which try and seal it out this direction

and then you've got face seals and side seals

which go along here on the edges to try to prevent gases from coming in this direction

Now the challenge that occurs

results because as you can see,

Combustion is going to be occurring constantly on one side

That's why this area is darker and this area is lighter.

So this is where intake is always going to be occurring

This is where combustion is always going to be occurring

And so because of that you're going to have a huge temperature differential

Where this side is going to be much hotter than this side

and so you are trying to maintain a seal

But the temperature is different

and so you're going to have the metal expending in different ways on different sides of this housing

and doing that makes it very difficult to create a good seal

And because of that you can have mixture of some of the air in one pocket getting over into the pocket of another chamber

Now in order to help insure that there is a seal, you can see here this hole which injects oil into here

so you'll have oil getting injected directly into the combustion chamber

and do that's to help maintain the seal around the edges

and lubricate the edges to you don't have anywhere

Now that leads us to our 3rd disadvantage

Which is the fact that design, this engine is going to be burning oil because you're ejecting oil directly into the combustion chamber

So periodically you are going to have to check the oil levels

and fill that and make sure that you're running a sufficient amount of oil because you are going to be burning that as the oil runs.

Now here we have the oil pump which is going to be actuated with the throttle.