Oddball engines and prototypes

[WilDun]

The absence of beautiful girls at the ball will make the ugly ones happy .

Yes Frits, but the reason for a lack of the beautiful girls you mentioned is often that they have a nasty habit of lying down, surrendering and becoming second best! (see the similaritiy with two strokes?).

We've had quite a few uniflow two strokes here, but here's an oddball prototype from Ferrari, featuring exhaust poppet valves.

A lot of those have been tried on and off but none seems to have met with much success probably because they are as complicated and heavy as a four stroke with more marginal lubrication and pollution .......... that's what I think anyway.

Yes Marquez is brilliant but much more aggressive and falls off trying to ride a bike at 110% (which really isn't the best bike out there at the moment) !

[WilDun]

Is this thread going? .....going ....... going ....... gon ........ hang on a minute, one more bid coming up!
It seems that Mazda have decided to actually put an HCCI engine into production next year (very brave move) but then they have always been game, those guys! They have (wisely) also kept some of their range on conventional engines. Also they haven't ventured into HCCI two strokes which are still only "pie in the sky" - unless somebody else knows differently! - can't remember where I saw the link but I'll look for it.

There you go:- http://www.motorauthority.com/news/1...engine-in-2018

[EssexNick]

Good find. I don't think this thread's dead yet, just resting.

[Michael Moore]

Once you've posted about all the historic oddball engines you've got to wait for new ones to be built, which doesn't happen overnight.

[WilDun]

Good find. I don't think this thread's dead yet, just resting.

Yes, guess it's resting - it often does! but even so, it has actually got to the 100th page - there has been quite a lot of interesting stuff come up, a lot of it historic interesting stuff of course, which was bound to run out eventually. ( Michael, you and I must have been typing at the same time and came up with the same thing! but I went to make a cup of coffee!).

HCCI is relatively new and if it reaches the motorcycle scene then I guess it will fire up here again (or at ESE depending on what the hot subject there is at the time).
The Ryger created quite a stir or at least the promise of the Ryger did! (in the Kart racing scene anyway), but Mazda is a large successful company who bravely plodded on with the Wankel engine, which they more or less appear to have given up on now - No doubt they wanted to concentrate on the HCCI project instead.
There are also some other companies who are making use of normal engine design practice, with important new additions in the area of the transition of power from the piston to crankshaft, technology which, if "meshed" with HCCI could produce some interesting and much more favourable power curves than the "normal" engines of today can produce.
No doubt we'll see this all in action reasonably soon!

[Frits Overmars]

...Mazda is a large successful company who bravely plodded on with the Wankel engine, which they more or less appear to have given up on now - No doubt they wanted to concentrate on the HCCI project instead.

I wouldn't be surprised if Mazda started looking into HCCI because of their Wankel engine.
Wankels suffer from a horrible combustion chamber shape and an accordingly mediocre flame speed and extended combustion duration. But with HCCI that wouldn't matter because combustion would start in all nooks and crannies simultaneously without the need for a flame to travel to the farthest corners of the chamber.
The ultrafast HCCI combustion would also somewhat counteract the high heat losses due to the bad chamber volume / surface area ratio of a Wankel.

I've got a GIF comparing combustion speeds in HCCI, spark ignition and diesel systems. It's too big to attach it here but you can view it on Facebook:
https://www.facebook.com/groups/1055...98668946694411

Food for thought, isn't it?

https://www.facebook.com/frits.overm...7380387468294/

[WilDun]

I wouldn't be surprised if Mazda started looking into HCCI because of their Wankel engine.

...........Food for thought, isn't it?

I was thinking that too! but as I don't know a lot about the Wankel then I'd better not say too much! (probably don't know a lot about anything really! but then we're still allowed to think a little and opinions aren't a crime!)
I seem to remember that someone wrote about the Wankel being suitable for Hydrogen as the combustion chamber shape would be compatible with that fuel and thought, what about Wankel/HCCI/Hydrogen?
Don't think they ever completely eliminated the sealing problems in the Wankel though and someone somewhere on the net pointed out that just at the beginning of the ignition/power stroke there is actually a reversing force on the rotor, I didn't study that very closely at the time though.

[husaberg]

I was thinking that too! but as I don't know a lot about the Wankel then I'd better not say too much! (probably don't know a lot about anything really! but then we're still allowed to think a little and opinions aren't a crime!)
I seem to remember that someone wrote about the Wankel being suitable for Hydrogen as the combustion chamber shape would be compatible with that fuel and thought, what about Wankel/HCCI/Hydrogen?
Don't think they ever completely eliminated the sealing problems in the Wankel though and someone somewhere on the net pointed out that just at the beginning of the ignition/power stroke there is actually a reversing force on the rotor, I didn't study that very closely at the time though.

Mazda experimented extensively with Hydrogen as the wankel is most suited to its application, as it has slow combustion and separate areas for its cycles.

[Frits Overmars]

I seem to remember that someone wrote about the Wankel being suitable for Hydrogen as the combustion chamber shape would be compatible with that fuel and thought, what about Wankel/HCCI/Hydrogen?

Hydrogen mimics HCCI in a couple of ways: it burns very fast and it is largely indifferent to the fuel/air ratio; ratios that would be too rich or too lean for petrol spark-ignition, will still ignite and burn happily when the fuel is hydrogen.

Someone pointed out that just at the beginning of the ignition/power stroke there is actually a reversing force on the rotor.

That is not different from any conventional piston engine, wherein combustion already starts to create a pressure rise before TDC. If we would ignite at TDC, a large part of the combustion proces would take place when the piston is already well on its way down again.
This is one more advantage of HCCI: whereas normal spark combustion duration may take more than 50 crank degrees, HCCI combustion may elapse ten times as fast,
or even faster, judging by the combustion modes comparison that I posted above. So with HCCI we can afford to let combustion begin at TDC, so avoiding any negative combustion force on the piston. This, together with the more complete combustion and the lower heat losses, gives HCCI its good efficiency.

[WilDun]

Hydrogen mimics HCCI in a couple of ways: it burns very fast and it is largely indifferent to the fuel/air ratio; ratios that would be too rich or too lean for petrol spark-ignition, will still ignite and burn happily when the fuel is hydrogen.................. So with HCCI we can afford to let combustion begin at TDC, so avoiding any negative combustion force on the piston. This, together with the more complete combustion and the lower heat losses, gives HCCI its good efficiency.

Mazda will then have a very distinct advantage in developing HCCI especially if the Wankel does turn out to be useful after all, both from their previous Wankel experience and present piston HCCI experience.
I think that I turned against the Wankel engine when in the earlier stages of its development (in the NSU) when I saw a dismantled engine with some pretty serious ripples in the bore. Also when all the young "boy racer" types got their hands on the RX Mazdas and butchered them till they became very noisy, lumpy smelly and unmanageable fire breathing monsters - sad end to a basically promising idea!

I'm told that they are exceptionally smooth and compact, and I must say that rotary motion appeals to me more than reciprocating motion with its 'power robbing'' reversals (has worked well for a long time though) - it's a pity the rotaries didn't tick as many boxes from the word go, as the piston engine did.

[WilDun]

.......... a large part of the combustion process would take place when the piston is already well on its way down again............
This is one more advantage of HCCI: whereas normal spark combustion duration may take more than 50 crank degrees, HCCI combustion may elapse ten times as fast, ......... we can afford to let combustion begin at TDC, so avoiding any negative combustion force on the ........together with the more complete combustion and the lower heat losses, gives HCCI its good efficiency.

I know that in practice it isn't the case, but to cause less power there must be another reason we need to have advance - at say 10 to fifteen degrees after tdc (in a normal engine) there must be some very unnecessarily heavy and unproductive forces on the rod and bearing instead of turning force?? yet it appears to be totally necessary to have this advance, maybe if I study it more carefully I'll find that question has already been answered!

[Frits Overmars]

I think that I turned against the Wankel engine when in the earlier stages of its development (in the NSU) when I saw a dismantled engine with some pretty serious ripples in the bore.

NSU made the mistake of putting an immature engine in series production. It gave the Wankel a bad reputation and killed NSU. The only good it did for us, was Nikasil, which was developed to combat the rattling marks in the Wankel housings.

I'm told that they are exceptionally smooth and compact, and I must say that rotary motion appeals to me more than reciprocating motion with its 'power robbing'' reversals (has worked well for a long time though) - it's a pity the rotaries didn't tick as many boxes from the word go, as the piston engine did.

If you look beyond the ancilliaries, a Wankel is a very compact engine. But it was in its initial stage, up against the reciprocating piston engine that had already seen many decades of development, so ticking the boxes from the word go was hard to do.
Below is the Mazda 787B, a 700 hp naturally-aspirated four-rotor engine (yes, with trombone inlets). Feel free to compare its size with any other engine type that produces the same power.


http://www.spannerhead.com/2012/10/0...s-mazdas-r26b/

And listen to it. Turn up the volume http://www.youtube.com/watch?v=9jAngoCbOMg#t=0m8s

BTW, those power robbing reversals in the conventional piston engine aren't all that bad. It does take power to accelerate a piston away from TDC, but that same power (minus some friction losses) is delivered back to the crankshaft when the piston has to be slowed down as it nears BDC.
Still, I too am charmed by the Wankel. I think that, had it been developed before the reciprocating piston engine, the latter would never have become the main type of internal combustion engine.

[eldog]

I was told Wankel engines were more suited to higher speed constant rpm operations,
how true is that opinion?

[tjbw]

I was the proud owner of an NSU RO80. Loved it, very smooth comfortable drive, but heavy on petrol consumption.

NSU thought the answer to tip seal problems was to make the seals harder, but then the housings got worn instead, resulting in reduced compression. Mazda did a much better job with their seals.

[tjbw]

The Triumph Rocket III may, or may not, be an oddball bike, but this advert for it is definitely oddball:

https://www.youtube.com/watch?v=n0LSh97AbMw