Theory: not just disabled cylinders, but a power/compound cylinder engine

[mechman600]

A lot of theories float around this site, mine included, and a lot of time nothing ever comes to fruition, as mods cost money - enough money to prevent the fuel savings offset from benefitting anyone, especially if testing proves that the mod doesn't work.

But, I have another one to ponder. I doubt I'll ever actually try it, but it's an interesting thought. It stems off of the thread where someone wanted to disable half of the cylinders on his engine.

As a side note, engineers have designed ways of capturing lost exhaust energy for quite some time. Turbochargers are one example, but more specificially, using turbo-compounding.
Turbo-compound engine - Wikipedia, the free encyclopedia

It is true that when the piston is nearing BTC and the exhaust valves open, there is still a lot of pressure left over in the cylinder. It is released into the exhaust manifold and basically wasted, because it has simply "run out of time" to produce effective energy. Turbo-compounding was used in WW2, where exhaust gasses would spin a turbine, much like in a turbocharger, but this energy was used to physically help turn the crankshaft, unlike a turbocharger. Currently, the DD15, a heavy duty truck engine, also employs such a design. This engine has a VGT turbo for supplying boost pressure, and also a compound turbo that physically drives the gear train at the back of the engine to supply an extra 50 "free" horsepower. Interesting.

My idea combines the disabling half the cylinders with compound-turbocharging. As an example, I will use my motorcycle, a 400cc four stroke parallel twin.

One cylinder will run normally. It will be called the "power cylinder." The other cylinder will be turned into the "compound cylinder." With some fancy welding and machining, we will add two bumps 180 degrees away from the normal intake and exhaust bumps on the cam lobes, so the valves open twice during one camshaft rotation, turning it into a 2-stroke "air compressor" of sorts, giving it twice the capacity of the power cylinder. The exhaust from the power cylinder is routed through an increased diameter "accumulator", necessary because of mismatched timing between the two cylinders, and then into the intake port of the compound cylinder. The exhaust port of the compound cylinder exhausts to the normal exhaust system.

How it works. Exhaust from the power cylinder, builds pressure in the pipe between the power cylinder exhaust port and compound cylinder intake port. When the air/fuel in the power cylinder is ignited, it expands to maybe five times its volume. The double capacity compound cylinder takes advantage of a higher volume, lower pressure exiting the power cylinder and turns it into energy to drive the crankshaft.

A four cylinder car could be turned into a 2/2 power/compound cylinder engine. Or a V6 into a 3/3. Would it work? Probably. Well? Who knows. I can see compound piston cooling being a big issue, since there would be no cool intake charge to moderate temps. Most importantly: what would we call it? A catchy name is mandatory. Maybe THIS is the question I need to ask!

[bgd73]

I was just reading up on a drag race/veteran/engineer named ed donovan, makes racing aluminum engines.

he made a four cylinder to have 5 main bearings, four bolt main caps...because it needs all of it. today, all four cylinders inline are that design...but with two bolt caps or insane japanese mitsubishi types, still committing suicide to performance...anbd 25psi boost too much..just to make up for its own wobbling mass, like a jackhammer..

Aside from having my last name.. it occured to me. They are all crazy.

leave that darned inline four alone..not even a v-twin harley with momentum keepers can keep an engine going for long. An inline for is extremely set and proprietary with balance.. it is hopeless. Save time and money, and leave it alone with all four banging, ya know, up and down up and down with a hopeless hollow backside already....

I have said it time and time again..the ONLY four cyl that can run on two cylinders and survive.. is a 3 main bearing boxer, with one timing belt removed...and ya know..that is just plain ol ridiculous... a four cyl takes the linear to a revolution at a zero degree loss..that is as small as it can get to maintain fantastic efficiency.

I do not type this to be mean to ideas.. given my own path and past.. it is just outright ridiculous to ponder.

[dcb]

personally I always liked the idea of just having a couple small engines, i.e. an opposed two cylinder for each drive wheel, and you can shut one off when cruising. with separate paths to the ground you would have ultimate reliability and have a more optimal sized engine for cruising and have twice that much for accelerating. I don't think most current disabled cylinder schemes go far enough, the pistons are still moving, and moving air and causing friction.

[mechman600]

Originally Posted by bgd73

An inline for is extremely set and proprietary with balance.. it is hopeless.

I'm not talking about removing pistons or anything, so the primary balance would remain the same. And I'm not talking about getting rid of half the power either. This design, while removing half of the combustion events, would add twice as many expansion cycles. If all went well, there would only be a 30% or so loss of power. And of course, increased efficiency.

Just an idea.

[fatman57]

I like this idea.

I have looked at turbo-compund too, which is a really good technique.

There is a guy in india who is currently working for a forklift company. he has strapped a smaller engine next to the bigger ones and the only intake are exhaust gases and fresh air. the result is extra power off the exhaust gases as well as lower emissions.

there is a big issue about fuel burning time (whatever fuel you may be using) and wasted energy.............without looking at the technical details i like the idea.

[chuckm]

I don't think most current disabled cylinder schemes go far enough, the pistons are still moving, and moving air and causing friction.

The problem with stopping the cylinders altogether would be the massive imbalance. You'd shake the engine right off the mounts.

[dcb]

not, as I was suggesting, if they are separate engines, but this might be a hijack in progress.

Edit: moving two engine discussion here:
http://ecomodder.com/forum/showthrea...tml#post170570

[Peter7307]

Originally Posted by mechman600

As a side note, engineers have designed ways of capturing lost exhaust energy for quite some time. Turbochargers are one example, but more specificially, using turbo-compounding.
Turbo-compound engine - Wikipedia, the free encyclopedia

It is true that when the piston is nearing BTC and the exhaust valves open, there is still a lot of pressure left over in the cylinder. It is released into the exhaust manifold and basically wasted, because it has simply "run out of time" to produce effective energy. Turbo-compounding was used in WW2, where exhaust gasses would spin a turbine, much like in a turbocharger, but this energy was used to physically help turn the crankshaft, unlike a turbocharger. Currently, the DD15, a heavy duty truck engine, also employs such a design. This engine has a VGT turbo for supplying boost pressure, and also a compound turbo that physically drives the gear train at the back of the engine to supply an extra 50 "free" horsepower. Interesting.

My idea combines the disabling half the cylinders with compound-turbocharging. As an example, I will use my motorcycle, a 400cc four stroke parallel twin.

One cylinder will run normally. It will be called the "power cylinder." The other cylinder will be turned into the "compound cylinder." With some fancy welding and machining, we will add two bumps 180 degrees away from the normal intake and exhaust bumps on the cam lobes, so the valves open twice during one camshaft rotation, turning it into a 2-stroke "air compressor" of sorts, giving it twice the capacity of the power cylinder. The exhaust from the power cylinder is routed through an increased diameter "accumulator", necessary because of mismatched timing between the two cylinders, and then into the intake port of the compound cylinder. The exhaust port of the compound cylinder exhausts to the normal exhaust system.

How it works. Exhaust from the power cylinder, builds pressure in the pipe between the power cylinder exhaust port and compound cylinder intake port. When the air/fuel in the power cylinder is ignited, it expands to maybe five times its volume. The double capacity compound cylinder takes advantage of a higher volume, lower pressure exiting the power cylinder and turns it into energy to drive the crankshaft.

A four cylinder car could be turned into a 2/2 power/compound cylinder engine. Or a V6 into a 3/3. Would it work? Probably. Well? Who knows. I can see compound piston cooling being a big issue, since there would be no cool intake charge to moderate temps. Most importantly: what would we call it? A catchy name is mandatory. Maybe THIS is the question I need to ask!

You might want to have a look at the Comprex Supercharger developed by Brown-Boveri (Switzerland) and now made by ABB which uses pulse waves to do what your "Compound cylinder" is meant to do IF I am reading your post correctly.

By the way the unlimited development of the turbine to add power to the crankshaft lead to the demise of the piston engine for commercial aircraft !

When the main aim is to use expanding gasses to provide power a turbine is a much more efficient method of doing so.

Peter.

[gone-ot]

...the Wright R-3350's on our Lockheed Constellation EC-121's used 3 each "power-recovery turbines" (PRT's) that recovered energy from the exhaust from 6 cylinders (3 x 6 = 18 cylinders), to boost total horsepower from 2900 hp up to 3400 hp...that's 500 hp just from exhaust gases at 2,900 engine rpm!

[dcb]

yup, but to Peters point, it wasn't long before they got rid of the piston engine that was between the supercharger and the turbine.

But I'm sure there is work left in standard car engine exhaust fwiw. Problem is extracting the additional heat energy without undue back-pressure (which makes the pistons not want to come back up).