Featured Rotary returns

I bought a Mazda RX2 for my wife (maybe 1972) I told her she had 2 weeks to learn to drive a stick, as I was going away to RCA school for several weeks. Teaching her never worked before, but she learned well before the allotted time ran out. I knew she could do it! Anyway, we both LOVED the car and fortunately traded it in on a Toyota Mark II before the apex seals (and maybe the side seals) started to wear! BTW, the bad fuel mileage could EZly be addressed by direct injection. Don't know about fixing the seals problem though.

 

My understanding is that the seals issue is mostly due to the fact that a rotary undergoes uneven heating.

The heat comes from burning the fuel. With a piston engine, there is just one space for combustion in the cylinder that is getting squeezed and released as the piston travels. The fuel is burned there, but the exhaust is also pushed out, and air and fuel pulled in. This allows the cylinder to cool down before the next burning of fuel.

In the rotary, the rotor has 3 lobes forming 3 spaces for combustion, and these spaces moves through 3 areas. The fuel burns and pushes the rotor around until a space comes to the area were the exhaust is sucked out. Then it to moves to the area where the fuel and air come in, and finally back to the first area where combustion. All the heat generating is happening at confined location of the engine block.

To put it another way, a piston engine naturally distributes the heat it generates through the engine block. The rotary produces it all in one spot of the block. That means its block doesn't evenly expand and contract, and that eventually wears out the seals. The fix is to have a cooling system that does its job unevenly in order to get even heat dissipation in the block.

 

I already knew all of this in 1972. I addressed the fuel mileage issue with direct injection (SkyActive) in Mazda's case. I know why there is wear, my question was, what are they doing to address the issue. I even built the Visible Engine model of this as well. I don't remember now if it was one or two lobes though. Probably two. I might even have it squirreled away somewhere.

 

Rotaries have problems other than the injection system, as far as efficiency, though.

The problem is that they're not good at getting all of the expansion out of the burning air/fuel mixture, and there's geometric constraints on how much compression that they have. Basically, they share the expansion problem with 2-strokes - the combustion products still have lots of energy in them when the exhaust ports are opened.

 

But not everyone reading this.

As for if there was an actual fix, are apex seals still an issue on the engine in the RX-8?