New Honda Engine

[csmutty]

A friend sent me a pic of this...pretty damn wild if you ask me. Would cooling be less efficient?

[Danz19899]

man that looks fricken bad ass lol very strange concept

however the valve adjustment on that would be a BITCH lol

[rg500]

That is far from new, but very cool.

http://en.wikipedia.org/wiki/Honda_NR

[ssg]

Very very expensive too (now), although I haven't seen one for sale in awhile.

[KawiSmurf]

That is far from new, but very cool.

That's the old NR500 GP motor (at least components of it) that's on display in the Honda Collection Hall at Motegi.

[csmutty]

Whoops my bad haha.

[brady]

I'd heard of the oval pistons, but didn't know they were THAT oval! or used two con-rods?

[Paul_E_D]

I didn't know they put it in a streetbike! How many HP did that thing make? Looks way ahead of its time design wise. The motor didn't catch on.

[spicy]

that's because it was ludicrously hard to manufacture and didn't have all that much to offer given such an expense over more conventional engines

[nt650hawk]

Honda NR 750
125.00 HP (91.2 kW)) @ 14000 RPM

[KawiSmurf]

I didn't know they put it in a streetbike! How many HP did that thing make? Looks way ahead of its time design wise. The motor didn't catch on.

The NR500 motor made 130 hp @ 20,000 rpm. It was never put in a streetbike. The picture of the motor that csmutty posted is from an NR500. The picture of the bike rg500 posted is the NR750 (usually just denoted as the "NR"). The NR500 looked like this:



The difference in the engines (besides the obvious displacement difference) was that the NR500 piston heads were flat on the long sides (as shown in the OP's pic), and the NR750 had curved sides, with a more elliptical shape.

The motor didn't catch on for a few reasons, a major one was that it was extremely unreliable. The monocoque frame of the NR500 also made it very difficult to work on. Not to mention the sheer cost to manufacture it.

[obsolete]

Talk about ice skating up hill.

[Tabby]

The reason they went that route, was to get around the cylinder count rule. The FIM had a four cylinder limit. The "NR" was essentially a siamesed V8. That way they could get the valve area for breathing, and really short stroke that kept piston speeds within reason at 20,000rpm, that a more conventional V8 would have. All this because of their pride in making 4 strokes instead of 2 strokes.

[brady]

IIRC it was also banned from racing pretty quickly.

[TLRMan]

We called it NR... "Not Ready" for racing....
Cool concept, they just couldn't keep the engine in one piece.

[a13x]

There is a guy in the Bay Area that rides his NR750 to bikes nights and Alice's sometimes. CRAZY.

[gmdboston]

The most difficult engineering challenge was ring seal. Think about it.....

[Paul_E_D]

The long, straight section being the challenge? I'm gueesing it would want to flex and allow a lot of blowby.

[Tabby]

Yup, that would be my guess. I'm sure if they attempted it today, they could do a better job, but at what cost. I wonder if they could take anything from some of Mazda's rotary apex seal technology.

[obsolete]

I don't even get how you would install a ring that shape on that piston. Where is the gap and how do you get the ring to stretch around the piston with out kinking.

[gmdboston]

Installation was not the issue, they would go on like any circular ring. The challenge was ring seal pressure. With a circular bore there is (in theory) even ring seal pressure at all points around the ring. With the oval design, ring seal pressure was highest at the semi-circular ends and almost zero along the straight sections. Honda tried gas porting, variable ring thickness, and a host of different alloys, even the "quad-oval" bore, but nothing worked. May be in the future some new technology will allow the NR (not ready) to become the NR (Now it's Ready) lol.

[spydah]

Its interesting how the pistons are configured on the crank. Its like a V8 that pulses as a twin. Must have stupid torque.

[stoinkythepig]

Its interesting how the pistons are configured on the crank. Its like a V8 that pulses as a twin. Must have stupid torque.

It would pulse like a V4, the pistons go up and down together on each side, but fire on every other stroke, 360 degress apart.

Torque is mostly a function of displacement, so it would have the peak torque of a typical 500 or 750, just like a V-twin has about the same peak torque as a 4 cylinder of the same displacement.

Torque, for given displacement, unlike HP, is very hard to increase without supercharging. HP is "easy" to increase, just add RPM, which was the whole point of these engines.

[spydah]

It would pulse like a V4, the pistons go up and down together on each side, but fire on every other stroke, 360 degress apart.

Torque is mostly a function of displacement, so it would have the peak torque of a typical 500 or 750, just like a V-twin has about the same peak torque as a 4 cylinder of the same displacement.

Torque, for given displacement, unlike HP, is very hard to increase without supercharging. HP is "easy" to increase, just add RPM, which was the whole point of these engines.

In that case, kind of stupid to have all that mass moving around for nothing. Why wouldn't they offset it like a car engine?

I'm no expert, but my though was that given the same displacement a twin has more available torque through out the rpm range. Had this fired the way I thought it did, it would torque like a twin.

[Tabby]

In that case, kind of stupid to have all that mass moving around for nothing. Why wouldn't they offset it like a car engine?

I'm no expert, but my though was that given the same displacement a twin has more available torque through out the rpm range. Had this fired the way I thought it did, it would torque like a twin.

There is more to torque than cylinder count. Firing order has a bit to do with it. I did high gear{!!} roll ons against a TL1000R with my 93 Suzuki GSX1100G {Shafty, approx. 90 rwhp, 65 ft/lbs torque, 600+lbs wet!!}, from 35 mph. I sucked his headlights out until the other side of 80mph. So much for twins being the mighty bastions of torque. The current advantage of twins isn't more torque, but how it is laid down. The huge space between firing events, allows the tire to hook up sooner. That is only an advantage IF the rider is on the gas hard enough to break the tire loose. If he isn't,,, then it isn't an advantage at all.