5 Stroke Engine

[Mr Twisty]

https://youtu.be/u0uPmrSRM7w

How much thermal energy is lost in a modern 4 stroke?

[DGthe3]

Originally Posted by Mr Twisty

https://youtu.be/u0uPmrSRM7w

How much thermal energy is lost in a modern 4 stroke?

Probably not much less than would be lost in a near-future 5 stroke

[Mr Twisty]

Heat lost is unused potential energy but it seems it would only be efficient if there was a large temp difference between the cylinder and the exhaust gasses.

Once the cylinder is heat soaked would efficiency drop to near nothing?

[DGthe3]

Originally Posted by Mr Twisty

Heat lost is unused potential energy but it seems it would only be efficient if there was a large temp difference between the cylinder and the exhaust gasses.

Once the cylinder is heat soaked would efficiency drop to near nothing?

I'm in slightly over my head here (its been quite a while since Thermo & Heat), but I'll give it a whirl ...

an engine works because hot gasses push against a piston. In doing so, they expand. As they expand, they cool.

It would seem to me that a cold cylinder would rob heat from the expanding gas -causing it to lose pressure faster, therefore producing less force against the piston (causing less torque, and by extension less power). Conversely, a hot cylinder would allow for more heat to be used to push the piston.


Now, as for the 5 stroke ... its interesting, but an alternate solution exists: leave the intake valve open for a bit on the compression stroke. The net result is more or less the same, but it requires essentially 0 extra parts.

[Mr Twisty]

Originally Posted by DGthe3

I'm in slightly over my head here (its been quite a while since Thermo & Heat), but I'll give it a whirl ...

an engine works because hot gasses push against a piston. In doing so, they expand. As they expand, they cool.

It would seem to me that a cold cylinder would rob heat from the expanding gas -causing it to lose pressure faster, therefore producing less force against the piston (causing less torque, and by extension less power). Conversely, a hot cylinder would allow for more heat to be used to push the piston.


Now, as for the 5 stroke ... its interesting, but an alternate solution exists: leave the intake valve open for a bit on the compression stroke. The net result is more or less the same, but it requires essentially 0 extra parts.

I'm in way over my head here but I always enjoy watching another person think outside the box... Like this 5 stroke engine.

I'm thinking expanding hot gas in a cool cylinder does cool but cool air (or carbon monoxide) is more dense. Probably way off base, but anyways.....

Allowing pressure into the intake from the cylinder would be the same as retarding timing wouldn't it?

They're claiming there's enough energy left in spent exhaust gas to do more work. According to wiki, modern gas engines are still pretty inefficient.

[Jason@JacFab]

Originally Posted by Mr Twisty

They're claiming there's enough energy left in spent exhaust gas to do more work.

I used to sit around and think of another way to reinvent the wheel (engines) all the time when I was younger... I think the test they've done is feasible, and it's cool to see it in action. The 3 cylinder engine is absolutely perfect for this setup.

What's a typical avg exhaust gas temp? Say 1000-1200 degrees under load? There could be some energy there to capture maybe?

Originally Posted by DGthe3

It would seem to me that a cold cylinder would rob heat from the expanding gas -causing it to lose pressure faster, therefore producing less force against the piston (causing less torque, and by extension less power).

I do agree, it would probably be weaker than the cylinders firing on fuel, but another thought comes to me based on what you said... Assuming the middle cylinder was sealed up well, If the cooling of the exhaust gas happened fast enough, it's possible that it could form a vacuum in the cylinder to pull the piston back up prior to the final exhaust valve opening?

But then again, as previously mentioned heat is energy. It appears they are robing energy from the turbo in this case?

Originally Posted by DGthe3

Now, as for the 5 stroke ... its interesting, but an alternate solution exists: leave the intake valve open for a bit on the compression stroke. The net result is more or less the same, but it requires essentially 0 extra parts.

What exactly does this achieve? Which cylinder(s)? I guess I'm not following you there?

I'm just going out on a limb here thinking outside the box...

[Mr Twisty]

Originally Posted by Jason@JacFab

I used to sit around and think of another way to reinvent the wheel (engines) all the time when I was younger... I think the test they've done is feasible, and it's cool to see it in action. The 3 cylinder engine is absolutely perfect for this setup.

What's a typical avg exhaust gas temp? Say 1000-1200 degrees under load? There could be some energy there to capture maybe?



I do agree, it would probably be weaker than the cylinders firing on fuel, but another thought comes to me based on what you said... Assuming the middle cylinder was sealed up well, If the cooling of the exhaust gas happened fast enough, it's possible that it could form a vacuum in the cylinder to pull the piston back up prior to the final exhaust valve opening?

But then again, as previously mentioned heat is energy. It appears they are robing energy from the turbo in this case?



What exactly does this achieve? Which cylinder(s)? I guess I'm not following you there?

I'm just going out on a limb here thinking outside the box...

Your egt number is probably close enough.

I guess they're working with the fact that exhaust gases are still expanding from unfinished ignition, and expanding into the third cylinder. It makes sense just from watching an engine throw flames out of the exhaust manifold. Those flames are from incomplete ignition, so.....

[rebelyell22]

Still won't smell as good as a 2 stroke...