Variable cylinder stroke

[Ayahuasca]

Do any car engines use this?

Is it even a thing?

Reason I ask is I have a little model Sterling engine. The kind you power by the heat from a cup of tea.

I noticed that the length of the stroke can be adjusted by sliding the piston up or down the connecting rod. With a short stroke the engine seems faster, with a long stroke it seems slower.

What are the implications of a variable length stroke in a car IC engine?

[TooLateForAName]

Honda have one.

Infiniti VC-T variable displacement engine

[spookly]

https://www.youtube.com/watch?v=UczuQYf2V6Y

[Truckosaurus]

Toyota (and Lexus) simulate a variable compression stroke by keeping the exhaust valves open longer than they traditionally would.

https://en.wikipedia.org/wiki/Atkinson_cycle

[Mr2Mike]

Ayahuasca said:

Do any car engines use this?

Is it even a thing?

Reason I ask is I have a little model Sterling engine. The kind you power by the heat from a cup of tea.

I noticed that the length of the stroke can be adjusted by sliding the piston up or down the connecting rod. With a short stroke the engine seems faster, with a long stroke it seems slower.

The length of the stroke is determined by the crankshaft, sliding the piston up and down the conrod won't change the stroke.

[TooLateForAName]

Nanook said:

TooLateForAName said:

Honda have one.

Infiniti VC-T variable displacement engine

Pretty sure that's Nissan? Unless I'm missing something.

Sorry - I was being stupid. You are correct of course.

I was confusing Acura and Infiniti.

[Ayahuasca]

Mr2Mike said:

Ayahuasca said:

Do any car engines use this?

Is it even a thing?

Reason I ask is I have a little model Sterling engine. The kind you power by the heat from a cup of tea.

I noticed that the length of the stroke can be adjusted by sliding the piston up or down the connecting rod. With a short stroke the engine seems faster, with a long stroke it seems slower.

The length of the stroke is determined by the crankshaft, sliding the piston up and down the conrod won't change the stroke.

You are of course absolutely right. I realised that after I posted. It just changes the volume of gas underneath the piston; in my little engine it alters the 'engine volume' - that might account for the extra speed.

This is an engine like mine, you can see the piston clearly.

https://m.youtube.com/watch?v=SCZwur5MIo0

[227bhp]

Ayahuasca said:

What are the implications of a variable length stroke in a car IC engine?

Getting it to work reliably for hundreds of thousands of miles.

As per above, you probably mean variable CR (compression ratio) and yes it's a very useful thing on a turbo engine if you can make it work. Have a look for Saab variable compression engine.
I'm not sure how your example is adjustable though and why or which piston/conrod you are referring to as there are two.

[Mr2Mike]

Ayahuasca said:

You are of course absolutely right. I realised that after I posted. It just changes the volume of gas underneath the piston; in my little engine it alters the 'engine volume' - that might account for the extra speed.

This is an engine like mine, you can see the piston clearly.

https://m.youtube.com/watch?v=SCZwur5MIo0

I have exactly the same engine. Minimising the unswept gas volume in a stirling engine is important for performance since this determines the compression ratio which is directly related to efficiency. You want the power piston as far down the cylinder as possible whilst ensuring it doesn't hit the displacer.

[rev-erend]

SAAB made a prototype variable compression engine

https://en.wikipedia.org/wiki/Saab_Variable_Compre...

http://www.spannerhead.com/2013/03/13/interesting-...

GM killed it due to costs.. but it was a very interesting technical solution that would have moved the petrol engine on a stage.

[Ayahuasca]

Mr2Mike said:

Ayahuasca said:

You are of course absolutely right. I realised that after I posted. It just changes the volume of gas underneath the piston; in my little engine it alters the 'engine volume' - that might account for the extra speed.

This is an engine like mine, you can see the piston clearly.

https://m.youtube.com/watch?v=SCZwur5MIo0

I have exactly the same engine. Minimising the unswept gas volume in a stirling engine is important for performance since this determines the compression ratio which is directly related to efficiency. You want the power piston as far down the cylinder as possible whilst ensuring it doesn't hit the displacer.

Have you managed to get yours to work with cold rather then heat? Mine goes like the clappers on a hot cup of tea, but refuses to budge on a cup of ice water in a hot room.

[Mr2Mike]

Ayahuasca said:

Have you managed to get yours to work with cold rather then heat? Mine goes like the clappers on a hot cup of tea, but refuses to budge on a cup of ice water in a hot room.

You can achieve a much higher temperature differential by applying heat rather than cooling. For example with the engine sitting on a cup of tea at say 80C with an ambient temperature of 20C, the engine has a 60C delta to work with. In the same situation, sitting the bottom plate on a block of ice (i.e. 0C) will only give you a 20C delta, barely enough to make it work.

With mine on ice it will only run backwards if I warm the top plate a bit e.g. with my fingers, and even then it's sluggish.

[227bhp]

https://www.pistonheads.com/gassing/topic.asp?h=0&...

Are we being used to do the writers research for them?