85rotarypower

Converting to diesel rotary=$20000+

Not good for your wallet.

BrianHeston

That "top-mounted silver thingie", would be the alternator.

Actually, technically on a diesel, it would be a generator.

vipernicus42

iTrader: (4)

I bring this thread back up to the top because I've been pondering it ever since it came up...

The more I think about it, the more I realize that it would be a cool (albeit expensive) project for someone to do, and I started thinking of ways to make it work. So I figure what the hell, I'll dump my random smatterings of thoughts here in hopes that some day some guy with money will be able to use them.

I know some of the basics behind burning diesel. Basically get air, compress the living crap out of it, inject diesel and repeat... (in uber-simplified form). The rotary engine as it is has very low compression compared to our piston counterparts, and EXTREMELY low compression when compared to the kind of pressure you'd need to make in order to properly burn diesel.

Now you could make a spark-assisted diesel engine (which the guys who are making the engines for the Skycar have toyed with), but that pretty much kills the whole point of it.

Nah, what I'm thinking, is that there's gotta be a way to increase the pressure in the chamber to the point where it would ignite diesel. So I got to thinking "how can we jam more air into the chamber, and make it compress harder?". Not knowing exactly how much extra compression would be needed, I figured that some sort of turbocharger or supercharger might be able to provide sufficient boost. (not at startup, but I'll get to that in a sec).

So the inside of the engine would have to be rebuilt to handle massive amounts of pressure (obviously). Some of the turbo guys have made advancements in that area, and I'm sure that if you completely prepped the engine for high amounts of power (like Jesus Padilla's 13b must have been making) you should be okay.. You know, custom apex seals, stationary gears, e-shaft, the works.

Depending on how much extra air would have to be jammed in there, maybe an electronically-assisted supercharger like the one they're thinking of for the Hydrogen powered Rx8 could provide enough extra pressure for diesel ignition. The electronic assist would help for when you're starting the car. You turn the key and the supercharger revvs up, pounds massive amounts of air into the chamber, then a really strong starter turns the engine, compressing the air even more, and then you add diesel.

I figure plug the trailing plug holes and use the leading ones for diesel injection. I mean you don't need spark plugs anyway, and using the leading ones makes sure that when the fuel is introduced into the chamber and starts to burn, it pushes the rotor in the right direction.

You'd need a totally custom fuel computer to match the amount of diesel to the amount of air in the chamber and still be able to account for the longer duration of spray you'd need to get even combustion through the whole chamber area...

So totally rebuild/boost-prepped engine, diesel injectors where the leading plugs are, electronically-assisted supercharger, extremely strong starter to overcome the higher compression, custom fuel computer.... maybe change the size/shape of the recess in the side of the rotor (smaller would allow for higher compression)... and of course the nightmare of trying to make it all work together in tandem...

What do you think? What did I miss?

I would expect that it would produce a hell of a lot more power, if not necessarily *usable* power. You have to figure that if you are cramming a lot more air, and introducing more fuel (or at least, more volitile-burning fuel), you've gotta have more power. How much, nobody can say.. I would just love to see this funky project come to fruition.

Jon

85rotarypower

I've been thinking about the "pinging" that a diesel makes. Its sort of a "signature" sound of a diesel. We had a Diesel powered chevy in the shop at co-op today. I asked my supervisor what makes that pinging sound. He said its SPARK KNOCK due to it either running too rich or too lean, can't remember which. But a diesel's engine speed is controled by the amount of fuel thats put into the engine. There is no throttle body. Everything is controled by how much fuel is being put into the combustion chamber.

Now, the extra fuel is of course going to create more power to turn the engine faster. Now that I think of it, the pinging is caused by a rich condition that causes hot spots and therefore detonation at idle, and only at idle. This is BAD for a rotary. Detonation destroys apex seals. If there was a way to get rid of the detonation I think it would work. But that is something that I don't think you can get around unless you control the air intake to get rid of that rich condition at idle, or input less fuel while still letting the engine run, but I don't think thats possible.

Its true that the rotary would make loads of power if it was powered by diesel. It would also have a lot more torque. But I just don't think you would be able to get rid of the detonation at idle and be able to compress the air enough to detonate it. If I am correct, you would need something like 30 psi of boost to compensate for the lower compression ratio on the rotary. Mabey more, but I'm not sure.

I don't know if it makes any sence, but I just don't think it will work. If it does, I seriously doubt that the engine would last very long.

wdwflash

1

wdwflash

I have a '79 Kelmark that is powered by a '87 Mazda TurboII and run by a Haltech E6K. Last year I had it at a local every Wed. "show n' shine" and usually no one knows what a rotary engine is. Well, these two guys walk up and start talking about rotary engines and in particular diesel rotary engines.
It turns out they are techs/scientists for a company that makes diesel rotary engines up to 3000hp. Since I work on marine diesels up to 5000 hp and 16cyl, I found them very intereseting. It seems that in the county I live in there is a company that make a small patrol boat for the US Navy and they were trying this companie's rotary engines in them.
Their engine uses a preignition chamber like the '70s Honda CVCC used and it uses a spark plug. This way they don't have to have the high compression of diesel engine. They were having problems keeping spark plugs in the engines so I asked them if they had every tried a spark plug from a Pratt & Whitney radial engine. (they hadn't.)
I also asked them if they were using anything like a Haltech computer and they had never heard of it. There eyes light up when I got out my laptop and started to tune my engine and showed them the data log function.
I think the name of their company was "Rotary Internationial" and they have the patents from when "John Deer" was looking into diesel rotaries.

wdwflash

1

wdwflash

Sorry, web site wouldn't post reply than posted three at once!!

jhillyer

Yes, knock/ping is a high stress our seals won't tolerate, but a diesel engine need not be operated in the knock range. I also think an early ultra-lean pilot injection would prepare heat for the secondary local injection for the major push.

Yes, for auto-ignition by knock, we'd need a warm engine breathing 30psi to rely on knock to sustain ignition, but knock is not a necessity.



I think we can look at better points of injection, and better methods of ignition to create our diesel.

lovintha7

I dunno about the Diesel concept. Seems that diesels have a hard time revving due to stress issues. Granted they make big power numbers, IF, they're turbo, or supercharged. But say if you look at a smaller, non turbo piston diesel, say a VW, the power numbers are incredibly low. They are torquey, but I wouldn't expect a ton of hp, nor high rpm without turning the engine into a grenade.

Just my 2 cents