14 replies to this topic

[Speedman]

Hello

I search photos from a VW oval piston diesel- engine

This was a prototype-Engine in the 80th years.

The photos was in the magazine "Auto, Motor und Sport" in the 80er years.

This piston is not to compare with Honda-oval-piston


best regards

Speedman

[perfectelise]

"1990 VW 2.3L diesel 4-cylinder engine with oval pistons: exterior view and engine block comparison with the standard 1.6L unit." http://www.ibiblio.org/tkan/audi/

[rhm]

What was the idea, just to increase displacement without lengthening the engine?

[Speedman]

Thanks for the pictures.

best regards

Speedman

[McGuire]

Originally posted by rhm
What was the idea, just to increase displacement without lengthening the engine?

exactly.

[Fortymark]

Originally posted by McGuire


exactly.

Why ain´t nobody using it? Like in a Porsche boxer engine?

Too expensive? Or are there other disvantages?

[Speedman]

Oval cylinder/piston is very expensiv.

You can make this parts only special machines.

[Terry Walker]

There was a burst of interest in oval pistons in the motorcycle gp world a few years back. In practice, I recall, the advantages weren't quite there.

[Wuzak]

The oval piston in the motorcycle GP world was Honda's last 4-cycle stand in the 500cc GPs. The 2 strokes had all but taken over by the late '70s, and early '80s.

The FIM had introduced a limit to the number of cylinders, which for the 500cc GPs was 4.

Honda wanted a V8 - needed a V8 - to compete with the 2 strokes. But they weren't allowed. So they designed and built the oval piston NR500.

The idea of having an oval piston was to enable them to have 8 valves per cylinder, 32 valves all up.

Unlike the VW Diesel oval pistons, the Honda NR500 (and the NR750 road bike) pistons had their long axes parallel to the crank axis. Each piston had two connecting rods too.

There is probably a picture in the Crazy Racing Engines thread.

[soubriquet]

There certainly is:



It would have been fun fitting the rings on this. I guess they would be two-part, so I was interested to see that the VW rings are single piece.

[Speedman]

The System from VW Ovalpiston engine is better as Honda Ovalpiston engine.

The Honda ovalpiston make problems with piston ring.

[Halfwitt]

I've got one question: how is it possible to finish the bores of the cylinders on these engines?

I've never seen an oval honing tool. Is it possible to do this?

[desmo]

I suppose one could do a probably poor job of it easily enough with one of those "brush" type hone/glazebreakers. They work reasonably well on brake cylinders and for cleaning the remains of piston sticks from 2-stroke engine bores after the highly technical pretreatment of dilute HCl on a Q-Tip.

[McGuire]

Originally posted by Halfwitt
I've got one question: how is it possible to finish the bores of the cylinders on these engines?

I've never seen an oval honing tool. Is it possible to do this?

Sure, to bore and hone these cylinders you will need a tool with an orbiting spindle. Shouldn't be terribly difficult but it will be slow.

[McGuire]

Originally posted by Halfwitt
I've got one question: how is it possible to finish the bores of the cylinders on these engines?

I've never seen an oval honing tool. Is it possible to do this?

To bore and hone cylinders like these you could also use a fixed spindle and orbit the table. Depending on your equipment that might be the easier way. That's how I think I would do it if I got stuck with one. Locate the elliptical centers, fabricate a cam lobe and use it to reciprocate a fixture.