OT: This could make a few windmills redundant

[Adrian]

Are you sure about that?

[dennis]

Is one valve any better than the ones with no valves?

[The Natural Philosopher]

i've had lots of engines with no valves at all

I thik they are called 2-strokes

[Adrian]

As have I.

There are even engines around with odd numbers of valves.

But... one?

[The Natural Philosopher]

It might be that harry made one with one valve, but it didnt work....

[Nightjar]

The Rover P6 had a 3.5 V8 engine option, but a Mercedes E 250, with a two litre four cylinder petrol engine, although 27% heavier, is three seconds quicker from 0-60.

Colin Bignell

[The Other Mike]

WTF are you on about?

[The Other Mike]

I'm sure Harry will be along shortly.

We are talking about high efficiency engines in 'harrys world' where it's all related to the 'compression ratio' and 'nothing to do with bore/stroke ratio'

[The Natural Philosopher]

The problem is that harry is an ill educated armchair theorist, has googled a little on 4 stroke engine cyles, and come up with one factoid: that high compression engines are slightly more fuel efficeint than low, all other things being equal.

But he has no idea of what all those other things are, or how equal they are in the real world, raher than the woolly fantasy he inhabits.

The reality of post war engines, using crude coils contact breakers and distributors with centrifugal and vacuum advance, and crude carburettors with poorly defined fuel flow curves augmented by accelation pumps, dampers and multi-jet barrels, plus fixed overlap non variable valve timing, was that it was easy to achieve reliably low fuel air ratios and reliably high compression ratios with the breathing profile of a longer stroke engine.

Which could be usefuly employed with lead loaded petrol to give a greater MPG and a nice tractability due to the higher torque.

what they couldnt do, was rev, so racing engines went a different route and threw petrol into short stroke precision made screamers. using wild cam profiles to dump volumes of unburnt fuel into the exhaust, and destroying any ability to run at low RPM at all, or indeed to even START in many cases.

[John Williamson]

Name one. All the 4 stroke, Otto cycle engines I've ever seen have had

*at least* two valves per cylinder. One to let the gas in, one to let it out.

Two stroke engines have, IME, zero or two per cylinder. One is theoretically possible, but I've never met it/

[harryagain]

The Triumph V8 engine was pretty unreliable. I had a Stag, but didn't have a problem. Wonderful handling, 17mpg Many Stag engines were changed for the Rover engine which was in fact a Buick and in a very low state of tune back then. They didn't have a manual gearbox big enough in th early days untill they came up with the Getrag. So they de-tuned the engine for the Rover "2000 shape"

[harryagain]

Absolutely. The air and exhaust went in and out of the same valve.

They were common at one time. Some were diesel engines

[harryagain]

"Thik" is about right for you.

Just because they are two stoke doesn't mean they have no valves. Many large diesel two stroke engines have valves.

Some are double acting, ie use both side of the piston.

And even the motor cycle engine uses ports and the piston as a valve.

[harryagain]

Dopey as ever TurNiP

You really think you know it all. Do you never think to check before you open your big mouth?

[harryagain]

Thousands are made every years for large trucks and ships. The inlet is by a port, the exhaust is by a single poppet valve. Much improved scavenging and gas flow.

But some used the same valve for inlet and outlet

This was a French one.

There was some American ones as well. Diesel I think. The air goes in the same valve as the exhaust comes out so preheating it. Also a single valve fits well into the circular cylinder head space

[Tim Streater]

I don't think the mantle manufacturers adopted the fascist tactics ("direct action") and the like that our eco-fascist friends look to when there is any danger to their world view.

[Nightjar]

I got 19mpg with a modern 5 litre V8 and it pushed a 2 tonne 4x4 from

0-62 in 6 seconds. It didn't have a much higher top speed than the Stag, but that was because it was limited to suit the tyre speed rating.

My point was that engine size alone is not much use in determining performance. An idea of the 0-60 and top speed you got out of the car with that engine in it would be far more interesting.

Colin Bignell

[Adrian]

Well, well, well. Live and learn. Interesting.

[The Natural Philosopher]

Sadly though harry, this was a two valve per cylinder engine. One was just hidden in the piston crown.

"Instead, a single exhaust valve on the cylinder head was operated by a pushrod that opened the valve when the pressure dropped at the end of the power stroke. A pressure-operated inlet valve, which was balanced by a counterweight to equalize the centrifugal forces, was placed in the centre of the piston crown, where it opened to allow the fuel?air charge to enter from the engine's central crankcase."

[The Natural Philosopher]

that was a 2 valve engine.

If you are going to call me dopy for saying that 2 strokes have no valves, then you are as dopy for saying that had only one.

Which is neatly hoisting you by your own petard.