So I'm a gearhead since day one, but new to the rotary scene. Not because I own one but because I would seriously consider dropping one in a Porsche 914 (a project I'll probably never actually build). Would like to see the 20b twin turbo in a 914 'oh momma'.



But then I began to daydream about all the possiblities, many of these I'm sure have already been touched on:



Rotary diesel? Fuel probably too slow burning, correct? But imagine the boost you could run....



Rotary Propane, already seen a post on here with a guy in Australia doing it...looks pretty simple really.



Rotary diesel and/or propane hybrid: Hello Mazda, Time to jump on the Ecotrain. Mazda+Toyota=Love. "The Neeewwww Prius-RX"



Rotary direct injection: If Mazda wants to stay in the game, I see this as the next move. Would help lower emissions too. I saw this idea briefly brought up in another post.



I did a search on the diesel and didn't find anything in particular refering to changing one over. Would probably be pretty easy really, mostly with a turbo. Though realisticly, I doubt anyone would do that because of the RPM limits.



Enough of me babbling.

rolls royce played around with the rotary diesel idea without much success. But it would be an interesting concept to revisit if it were possible, due to the high compression though it seems tough. the next gen rotary engine is said to have direct injection, and in japan there is a hydrogen powered rotary engine. the cool thing about the whole green thing now is that it is really pushing the automakers hard to look into and try new things.

A true Diesel uses heat of compression to ignite the fuel. So, minimum compression ratio starts at about 16:1. Injection is generally very fast because of burn time of the cheap ass low octane fuel, and the burning must take place downstream of the injector body. So, stresses on Diesel engines are very high. It is close to a detonation event stress wise in just normal running. Remember GM making a Diesel out of a regular Chevy engine? Broken cranks and webs pulling out of the blocks.

They put 2 or 3 engines in each car. And you thought GM was stupid????



There is far more to a Diesel than high compression.



There are some gags you can use to operate with lower octain fuel. Notice first that the diesel idea was once popular because Diesel fuel was far cheaper than is now the case. Not very popular now. Even Diesels getting better fuel mileage is no longer a feature of value. In any case, there are some engines called spark assisted Diesels, thay are not Diesels at all.

(or it wouldn't need a spark plug)

More like a stratified charge engine running on crap. So low octain fuel is injected into a chamber, not unlike the trailing plug hole in a rotary. A long running spark plug lights the fuel and the engine runs as normal. This may come back into favor with the new Piezio injectors that can produce 32,000 PSI injection pressure. You don't need no stinking spark plug at 32,000 PSI.



http://www.physorg.com/news3952.html



The new 16X rotary has the injector in the top center of the housing. (BDC intake) It will start injecting after the intake port is close to the closing position. So, the fuel mixture will be rich down the centerline of the rotor and be easy to light. Tuning just an air column with no fuel mixed in it will be more effective, and so on. To make a real Diesel out of a Mazda rotary would require massive strength improvements along the combustion side of the housings. Not likely to come about.



Picture is the 16X engine. Note the injector locations. Sorry. I am unable to upload pictures.



Lynn E. Hanover

There was an extended string about diesels on the RX-7 list.



http://www.rx7club.com/showthread.php?t=538892



I have the book but that Rolls Royce picture does not scan well enough to use.





Lynn E. Hanover