Two-in-one engine

General Discussion
1

I guess I’m a glutton for punishment. I’m sure I’ll get it for sharing the novel Idea I just came up with.

In recent years variable cylinder management has had some success with the help of computer management, but gains are limited because the inactivated cylinders still have friction losses and then there’s the issue of oil migration into the “dead” cylinders.

Suppose we had a V6 block with the crankshaft split in two, with a solenoid clutch and locking pins.
Under light load above a certain engine speed the crankshafts unlock and half the engine comes to a standstill, running on 3 cylinders.
To re-engage the clutch quickly brings the still half up to speed and the pins lock the shafts together in the proper orientation for engine balance.
Each half-a-crank would need a chain to drive its respective cam(s); and maybe a solenoid valve to cut oil pressure to the inactivated half.

Yes, it sounds complicated, but we’re in the era of the 9-speed automatic transmission.
How about an exotic Italian super car that could run on 4, 8 or 12 cylinders?

2

I think you are right. It will be limited to exotic cars. Other attempts to vary the number of cylinders operating have fallen by the wayside in many cars because the complexity doesn’t match the savings. The icE will keep churning new technologies to keep burn fossil fuels as long as possible. In some respects, that is a good thing as there are still some things that only ICE can do and there is a lot of "job support " for it. IMO, you subject is one of those instances.

3

A straight-6 maybe. I can’t see how you’d split the crank of a V-6.

4

You don’t need more than four cylinders in a family sedan.

5

If a cylinder is disabled so that it will not develop vacuum or compression it would likely have less mechanical drag than the cost of the added drag when the two crankshafts are mated. Two engines with separate drive trains might be more efficient.

Let me hopefully make myself clear here. The mechanical loss when the 2 crankshafts are connected would likely be significant and the cost of that loss might be significantly greater than the increase in efficiency when they are disconnected.

6

Why not just use a separate boost engine that could be started up for passing power or steep hills. They could share cooling systems so the main engine would already have the boost engine at operating temperature when you need to kick in the boost engine.
I’m thinking maybe a 60 horsepower main engine for most driving needs and cruising power and a 200 horsepower boost engine that could kick in when you just have to get ahead of that jerk who won’t let you merge. Since the boost engine only works intermittently, it could even be an outboard motor style two stroke since it probably will never even start during the EPA certification test.

7

One major problem with shutting down a crankshaft part time is that the cylinders that were shut down not only have to be brought up to speed when needed, but also timed properly with the continuously operating cylinders. That could add considerable complexity.

Actually, I like the hybrid system that some of the supercars are developing, a high performance gas engine that’s supplemented by the instant torque of electric motors. The gas engine could also be shut down in town and the vehicle just run on the electric motors until the battery gets low, whereupon the gas engine fires up again.

See the specs on the new LeFerarri. It’s really interesting.

8

You’re still lugging around a heavy engine every where you go. The reason for getting a V6 is displacement. Displacement is what enable you to take in more air and fuel. There are two other ways for a small engine to take in more air. The less popular way is ultra high rpm. The Honda S2000 with its 9k red line allowed it to take in more air than some V6s in its days; it made as much power as a V6 accord. The other, more popular way, is to use a turbo. Either way, you are not carrying a heavy V6 under the hoods, and you get the benefit of a smaller engine so long as you aren’t spooling up every few seconds. A small engine with a 9 speed that let’s you rev up the engine for power on demand is the trend

9

“Why not just use a separate boost engine that could be started up for passing power or steep hills. They could share cooling systems so the main engine would already have the boost engine at operating temperature when you need to kick in the boost engine.”

What I envisioned is essentially two separate engines, except they share the same cylinder block.

“that the cylinders that were shut down not only have to be brought up to speed when needed, but also timed properly with the continuously operating cylinders.”

“I can’t see how you’d split the crank of a V-6”

Add a couple inches between the middle two cylinders.

The clutch would slip and bring the second crank up to speed, then the locking pins would hold it in sync.

“You’re still lugging around a heavy engine every where you go.”

That’s true of all the variable cylinder schemes.

Does anybody remember back in the '80s someone added a second engine in the back of a Honda Civic?

10

That’s true, but my point is that we are seeing more and more turbo fours rather than six with cylinder deactivation because it is better not to drag along extra weight. New transmissions with wide gear spread multiplies the small engines

11

“I can’t see how you’d split the crank of a V-6”

Add a couple inches between the middle two cylinders.

A V6 has only three crank throws; can’t be split in the middle:

http://www.google.com/search?q=v6+crankshaft&client=safari&rls=en&source=lnms&tbm=isch&sa=X&ei=cnzzU9PkLMShogSulIKoBg&ved=0CAgQ_AUoAQ&biw=1030&bih=576

12

“A V6 has only three crank throws”

Then use two 2-throw cranks; each center rod would have its own throw.
Think two V3 setups.

13

Heres my idea, but several other things will be needed first. The system voltage will need to be much higher, somewhere between 36V and 60V. The only thing operated by a belt will be the generator, and it could be direct drive. The oil pump mechanical, but everything else driven electrically.

Now a V6 would have the exhaust system between the heads and the intake on the outside, just the reverse of how it is done now. The engine will need two exhaust valves. All the valves will be actuated by a solenoid that is controlled by the PCM.

The exhaust valves from each cylinder will fed into separate manifolds, one manifold will be direct exhaust, the other will be a plenum that connects all the other valves together but will have a separate gate valve to dump exhaust to the direct exhaust system.

The engine will operate in two modes, one as a 4 cycle that we know today with the gate valve in the plenum open to the exhaust system.

For light loads, the plenum exhaust gate valve will close and the engine will go into a 6 cycle mode: intake, compression, power, primary exhaust, expansion and then second exhaust. During the primary exhaust, only the exhaust valve to the plenum will open and the same valve on the cylinder in the expansion stroke will also open.

The exhaust from the first exhaust stroke will duct into the cylinder on expansion stroke and push that piston down, effectively nullifying the pumping losses. When the expansion stroke is finished, that cylinder will close the exhaust valve to the plenum and open the other exhaust valve to the cats and tailpipe.

The solenoid valves will also allow an infinite number of valve timing profiles to perfectly match to the load requirements for each revolution of the engine. Fewer gears would be needed in the transmission because the most efficient operating RPM would be so wide.

The engine would also have a high compression ratio but the intake valve timing could be adjusted so that the effective compression would be variable. Keeping the intake open part way in to the compression stroke would lower the effective compression ratio. This is called the Miller Cycle, short compression stroke, long exhaust stroke, but under the right circumstances, it could go full compression and operate as a gas diesel.

On the highway, a small displacement v6 with a turbo charger in 6 cycle, gas diesel mode, I could see some very high gas mileage numbers possible. Maybe even the elusive 100 mpg in a compact car like a Civic.

14

One more thing to add to that engine, the oil system would be primarily mechanical, but the oil pump could be made a little smaller but add an aux electrically driven oil pump. It would come on at idle if the pressure from the primary pump were to drop as it probably would with a smaller pump.

It would also come on and prime the oil system the same as the fuel pump during the start cycle and run for a minute or two after the engine shuts down. It is during a hot shut down that the oil trapped in the engine typically gets the most damage absorbing all the engine heat. With the oil pump running under those conditions, the flowing oil would be replenishing the oil in the block so that it doesn’t overheat. The oil and the engine would last a lot longer.

15

“This is called the Miller Cycle…”

Miller patented the addition of a supercharger to the Atkinson Cycle.

16

I stand corrected. Thank you.

17

@‌circuitsmith

Does anybody remember back in the '80s someone added a second engine in the back of a Honda Civic?

Yes!

But they were not operated concurrently. The front engine drove the front wheels for driving on the street. The rear engine drove the rear wheels for racing at the drag strip.

18
But they were not operated concurrently. The front engine drove the front wheels for driving on the street. The rear engine drove the rear wheels for racing at the drag strip.

Just because this car didn’t use both engines at once doesn’t mean it couldn’t be done. The rear engine wouldn’t even need an alternator or electric starter, just engage the clutch. Since it only gets used for passing or onramp acceleration, it doesn’t even need a whole lot of gears in it’s transmission, maybe a single ratio.
A small primary engine in front for small car fuel economy and then start the rear engine for muscle car acceleration.
The secondary engine could even share the primary engine’s coolant and lube oil. That way it would already be warmed up when called into action.

19

Just put a clutch between 2 small engines,the torque of most small engines isnt that great,some farmers used to hang a small engine on the front of their tractors and put a bet drive or somthing to the crank pulley on the main engine(gave em a bit more lugging power-Kevin

20

Ok, to stay close to the topic of this discussion, there are numbers of patents and paper on variable stroke engines. Some made it into SAE journal. These things are claim to vary the stroke, thus displacement, and compression ratio. And some even claim to keep the connecting rod close to vertical, which reduces the side thrust against the cylinder wall.