The four steps are like this:

1) The piston starts at the top, the intake valve opens, and the piston moves down to let the engine take in a cylinder-full of air and gasoline. This is the intake stroke. Only the tiniest drop of gasoline needs to be mixed into the air for this to work. (Part 1 of the figure)

2) Then the piston moves back up to compress this fuel/air mixture. Compression makes the explosion more powerful. (Part 2 of the figure)

3) When the piston reaches the top of its stroke, the spark plug emits a spark to ignite the gasoline. The gasoline charge in the cylinder explodes, driving the piston down. (Part 3 of the figure)

4) Once the piston hits the bottom of its stroke, the exhaust valve opens and the exhaust leaves the cylinder to go out the tailpipe. (Part 4 of the figure)

My questions:
1) What opens the intake valve? What moves the piston down?
2) What moves the piston back up?
3) Now I see that the piston moves down because of the explosion.
4) What moves the piston back up? And what opens the out valve?

Your thread title specifically refers to diesel engines and yet your description talks about gasoline and a 4-stroke gasoline cycle instead of the diesel cycle which uses the heat of compression to ignite the fuel-air mixture (and is frequently a two-cycle design, but not always).

Have you bothered to do a Google search to try to answer any of these questions?

 

The idea of effectively removing cylinders from the engine is decades old. I remember see car commercials from the 70's or 80's where they touted how the car would reduce the number of cylinders from 8 to 6 to 4 to achieve really high fuel economy. Since it seemed to be a passing fad, I concluded that the increases in economy, if any, were marginal and the increase in maintenance or initial investment outweighed any savings.

It was the Cadillac North Star Engine. One of the most durable GM engines ever made, if you changed the engine oil frequently - about 8 quarts! I think it was the workhorse engine on Cadillacs for about 20 years.

 

Your thread title specifically refers to diesel engines and yet your description talks about gasoline and a 4-stroke gasoline cycle instead of the diesel cycle which uses the heat of compression to ignite the fuel-air mixture (and is frequently a two-cycle design, but not always).

Have you bothered to do a Google search to try to answer any of these questions?

2-stroke diesels were an oddity (Detroit Diesel) of the past and research projects for engines of the future (Renault and others).

Most diesels are 4-stroke designs with camshaft and valves.

 

It was the Cadillac North Star Engine. One of the most durable GM engines ever made, if you changed the engine oil frequently - about 8 quarts! I think it was the workhorse engine on Cadillacs for about 20 years.

That name definitely sounds familiar, but I had thought it was called something like V8-6-4 and I thought there were all kinds of reliability problems with it because the control electronics of the day just weren't up to the challenge.

 

2-stroke diesels were an oddity (Detroit Diesel) of the past and research projects for engines of the future (Renault and others).

Most diesels are 4-stroke designs with camshaft and valves.

I tend to think of smaller engines and also non-diesel two strokes like motorcycle and model airplane engines (man, talk about simple, simple design!). So I forget that most production diesels are four stroke.

 

That name definitely sounds familiar, but I had thought it was called something like V8-6-4 and I thought there were all kinds of reliability problems with it because the control electronics of the day just weren't up to the challenge.

Maybe in the first years. They were used until 2010.

 

Maybe in the first years. They were used until 2010.

I just did a quick search and I didn't find anything that indicated that the Northstar engine turned of cylinders for fuel economy. I did find that it had a "limp home" mode that alternatingly cut of fuel to one bank of cylinders and then the other to let the cutout cylinders air cool in the event of loss of coolant.

I also found that they did, indeed, have an engine they called the V8-6-4, but don't see anything that relates it to the Northstar engine.

 

I believe marine diesel engines (really big ones) are two stroke!

 

I just did a quick search and I didn't find anything that indicated that the Northstar engine turned of cylinders for fuel economy. I did find that it had a "limp home" mode that alternatingly cut of fuel to one bank of cylinders and then the other to let the cutout cylinders air cool in the event of loss of coolant.

I also found that they did, indeed, have an engine they called the V8-6-4, but don't see anything that relates it to the Northstar engine.

Hey, you are right. I thought 8-6-4 was called "North Star". They are two different engines.

I had remembered the 8-6-4 then discussed "Displacement on Demand" when I was visiting GM. I was under the impression that they were re-configuring how the old system worked. I didn't realize that the current system on North Star was only a "limp home" feature instead of the legacy 8-6-4. I just looked and found that GM dropped the North Star before implementing the feature. They have added it to several engine platforms - marketed as Active Fuel Management.

More and more companies are using some version of this idea - Honda especially on the big 3.5 L Pilot and Odyssey motors.

 

Your thread title specifically refers to diesel engines and yet your description talks about gasoline and a 4-stroke gasoline cycle instead of the diesel cycle which uses the heat of compression to ignite the fuel-air mixture (and is frequently a two-cycle design, but not always).

Have you bothered to do a Google search to try to answer any of these questions?

Yeaaah, I already said I have basic knowledge (or non-existent) in this.
I did google, but I also asked here. More sources of info, the better.

 

The idea of effectively removing cylinders from the engine is decades old. I remember see car commercials from the 70's or 80's where they touted how the car would reduce the number of cylinders from 8 to 6 to 4 to achieve really high fuel economy. Since it seemed to be a passing fad, I concluded that the increases in economy, if any, were marginal and the increase in maintenance or initial investment outweighed any savings.

In the 50s, someone decided that OHC would sap more power than it gained.

 

The GMC/Detroit Diesel truck engines were 2 stroke starting in 1938. A "uniflow" design similar to uniflow steam engines. The 471 and 671 roots style blowers used in drag racing came off of them. They blew out the exhaust on the GMC but super charged the intake on drag engines.

All of the major car makers use a form of cylinder cancelling now days on their bigger engines. A camshaft inside a camshaft hydraulically controlled on many of them. Though the Cadillac 4-6-8 was among the first, but didn't have enough sophistication to work well.

 

Thanks.

I'm not reading the following sentence the right way to figure out what you meant, though:

They blew out the exhaust on the GMC but super charged the intake on drag engines.

 

That was in reference to the Roots type blowers. In the GMC/DD engines the cylinders exhaust was pushed/blown out of the cylinder at the bottom of the stroke. There was a port on both sides of the cylinder at the bottom. One side open to the blower, the other side open to the exhaust manifold. With out the blower, there was a large amount of spent gasses that stayed in the cylinder. And contaminated the next intake charge. That style engine is not like a 2 stroke in a chainsaw or weed whacker, that type use ports to feed the intake charge. A GMC/DD had an intake valve like a 4 stroke engine, to let in the fresh charge of air, So the blower helped scavenge all of the spent gases out. And since the fuel is injected near the top of compression stroke, the more fresh air in the cylinder equals more power output.

 

@WBahn, my description of how the GMC/DD engine works was wrong, ~40 years and two strokes sometimes cloud my memory. The engine uses a exhaust valve and the ports are intakes at the bottom of the cylinder. As the piston gets toward the bottom of the stroke the ports are uncovered and the exhaust valve opens. The blower pushes/scavenges the spent gases out through the open exhaust valve. The valve closes and the blower then charges the cylinder with a fresh charge of air, at higher than atmosphere pressure. As the piston goes up it compresses the air until near top dead center when the fuel is injected into the the cylinder and it ignites and starts the power stroke, then the cycle is repeated again. But the blower is still used to force the exhaust gasses out of the cylinder. Sorry for the confusion.

 

I believe marine diesel engines (really big ones) are two stroke!

Like this one.

 

Like this one.

Damn. What is the inertial force of a 3 foot diameter piston with an 8 foot stroke at 100 RPM? Talk about potential vibration!