Honda and their oval pistons
 

Im guessing here that most of you have heard of hondas oval piston which finally got realeased as a road going machine in 1992 in the guise of the NR750. Well this bike is really getting on my nerves, not really in a bad way but because i want one! With 125bhp over 10 years ago, 15+ more than the GSZ-r back then (and apparently it was still limited) 15,000 RPM red line (also limited) It must have been a beast!

I dont have the money to buy one £40,000+ second hand, bit out of my budget, but im wondering if anyone has read any where about Honda doing something with the technology? I have seen an interview with an Honda bigwig and he says there is a "chance" the technology may be used because the engine is easier to engineer with modern technology!

If you have any info at all please post!! N' for those of you that have no idea about all this subject please look on Google for "NR750" (pictures too) and prepair to be amaized (if you like the technology side to biking...)

Cheers

What you mean this?

http://upload4.postimage.org/432464/1069777136_1_.jpg

BEAST! I've heard of this technology,not sure if it was ever used on any of Honda's other bkes!?

there are rumours of them using it in wsb then doin it for the next gen or road bikes but the cost loads to make so may never happen

£40K? Rather have a RC30 £32K cheaper.

From what I recall it came about as a result of trying to get round the limit on number of cylinders. What they did in effect was make 2 cylinders into 1 by "taking away" the bit in between. The combustion system, valving, stroke and thus RPM capability operated effectively as though it was 2 small cylinders.

There's no real technical advantage in having oval cylinders if you can have 2 round ones instead, and the mechanical challenges of machining the bores and making rings work properly (gas sealing and oil control, not to mention what happens when the ring gets hot and expands) really make it a nightmare.

An interesting technical oddity, but of little real value.

the concept was to gain cc's displacement can reduce thg friction of cylinder wall.

1 oval piston had more than the displacement of the 2 regular pistons it replaced and less cylinder wall area and more room in the head for valve opening

the piston required 2 rods

The pistons are on the front page of HRC's website.

http://world.honda.com/HRC/

...but I thought they were limited on displacement and no. of cylinders anyway.

An oval shape has a lower volume/surface ratio than a circular one, they would have been better off with a round cylinder except that to get the power (= revs) they needed such a short stroke/large bore that the combustion would go to pot, so to make it work at high revs they made the chamber effectively look like 2 small ones (as far as the gas was concerned anyway) which would work at those speeds. Valve train control was also a limitation for the bigger valves in a "single" round cylinder compared to the smaller ones in a "double" small cylinder.

I think it was a reflection of the technology of the day really, very short stroke large bore cylinders are now working well in F1 (19000rpm), and the valve gear materials and control is developed to a reliable state to allow those speeds with bigger diameter valves.

If you don't think the combustion technology has progressed much, just compare today's Fireblade with a CB750 etc of the 1970's.

Not quite, in essence Honda were trying to create a V8 in a class of racing that only allows four cylinders - in GPs. Honda were for a long time pushing the four stroke ethic when all of the competitive GP racing was two stroke.

It didn't have any success despite a stupendous amount of money being spent and some quality riders being persuaded to give the bike - the NR500* - a go, as I recall it never finished a race, not only was it way off the pace it went bang with regularity too.

And eight valves per pot too.

The NR750 is actually not that powerful, some of the numbers that have been thrown around are inaccurate to say the least, not through restriction exactly it's simply built to make the power it makes, the idea was to showcase the technology - it was never intended to be a serious production use of the idea, anyway not new when Honda had a go at it, the first oval pistons were a British creation in the 1920s, I forget who did it.

*Unkndly - but accurately - usually referred to as the Not Right500 or Never Ready500.

I read something from Honda a while back saying they may be bringing them in for their bikes (including road bikes) in the next few years as manufacturing methods have come on a lot since they first tried this. Still more expensive than round pistons but if you're stuck with a figure you have to conform to, on number of cylinders, capacity, etc. then every little helps.