Public Domain Hi-Eff Engine Design DIY

4/28/2003 | John Jamieson

[John Jamieson]

A Dual Mode, High Efficiency Engine, Based on a Standard 4-Cylinder Block

John R. Jamieson 4/28/2003

John R. Jamieson believes the engine configuration described in this paper is a unique and original idea. He hereby places this design in the Public Domain for the use of anyone who reduces the idea to practice. (Questions and comments may be addressed to JRJamieTX@wmconnect.com)

Background: For the past 100 years, engineers have known that high efficiency, internal combustion engines have two features that we rarely use in our current designs:

1. Close match between the normal load and max load. Such a design operates the engine at near wide open throttle most of the time. Current automotive design, however, is to use engines with 10 times the max load as nominal in order to provide brisk acceleration. The customers demand it. Efforts have been made (Cadillac in the late 70’s) to shutdown cylinders in large engines to increase the cruise efficiency. These efforts were only partially successful due to the fact that all of the friction loses in the unused cylinders remained and the control systems of the day were much simpler than today’s.

2. Much higher gas expansion ratios. The conventional designs require that the expansion ratio match the compression ratio, which is limited to 10:1 with modern gasoline. Beginning with the complex mechanical designs of James Atkinson in 1885-6 and continuing through the Wright Turbo-Compound aircraft engine of the early 1950’s, engineers have tried to increase the expansion ratio and although all of these engines demonstrated increased fuel efficiency, all suffered from cost, weight, or reliability issues and none became popular. Present day Miller cycle engines extend the expansion ratio to about 15:1 and are used in some of our most fuel-efficient automobiles. Even diesel engines, with their inherent 20:1 expansion ratio, can benefit from further expansion ratio increases, and a European engine manufacturer Scania is currently using turbo-compounding to do just that. That engine has a Specific Fuel Consumption (SFC) of .32 pounds/hr-hour.

3. The author experimented with 2-cylinder engines based on a 4-cylinder 1.9 liter Opel in the 1970’s. This car demonstrated about a 40% increase in fuel economy, but suffered poor horsepower performance, barely reaching the 55mph top speed of the day. Never the less, the car was driven to the Kennedy Space Center every day for over a year. About 2 years ago, the author started wondering if the two extra cylinders could be used for additional gas expansion, and the present idea was born. A 1987 Toyota Corolla was purchased and the conversion began, only to be never completed because of a combination of health issues, and more pressing time demands.

Concept: A dual mode engine based on existing 4 cylinder designs, and requiring only cylinder head and control system changes. In it’s simplest form, such an engine would have 3 valves per cylinder. A cross flow head would be used with 4 conventional intake valves, 4 conventional exhaust valves, and 4 new transfer valves. The 4 transfer valves would all connect to a single transfer manifold either located internally in the head (difficult to cast) or externally.

Mode 1: Cold start, on ramp acceleration, hills, high speed, high load, passing. 2 liter, conventional, 4 cylinder 100 horsepower @ 5000rpm Compression Ratio 10:1, Expansion Ratio 10:1 SFC .6 pound/hp-hour

In Mode 1, conventional operation at full power and rpm would use the 8 conventional valves, while the transfer valves remained closed. All four cylinders would supply power.

Mode 2: Warm start, idle, moderate city driving, level cruise to 70 mph. 1 liter, double expansion, 2 cylinder 33 horsepower @ 2500rpm Compression Ratio 10:1, Expansion Ratio 20:1 SFC .4 pound/hp-hour

Mode 2, low power, high efficiency operation would operate cylinders 1 and 4 in a conventional mode, except that their exhaust valves would remain closed and instead each cylinder would use it’s transfer valve, to route exhaust gases to the two center cylinders (2 & 3) for further expansion. 3 transfer valves would be open during the exhaust stroke of either cylinder 1 or 4. Cylinders 2 and 3 then act as a two stroke slave engine, providing about 33% of a normal power stroke. The engine would still have 4 power strokes, but two are weaker than the two main ones. At the completion of the slave power stroke and during the next intake stroke on 1 or 4, the center cylinders perform an exhaust stroke through their exhaust valves. The 4-stroke cycle has become a 5-stroke cycle with two power strokes.

The combined efficiency improvement due to the reduced displacement and 20:1 expansion ratio, of the engine in Mode 2, is estimated to be 50%. A small 4-passenger car that requires 12 hp at 60mpg or 15 hp at the engine, could be expected to deliver about 60 mpg at cruise.

Two Step Development Plan

The technological challenge of switching modes during operation is far and away the most difficult and should be saved until after a pure Mode 2 demonstration has been completed, through road test.

Prototype 1 Modify an existing 4 cylinder, 8 valve engine to Mode 2 operation. Basically requires the following modifications: 1. Permanently disable fuel and air intake on cylinders 2 & 3 by grinding off the appropriate cam lobes, leaving the valves in place. 2. Permanently disable fuel injection (if present) and ignition of cylinders 2 & 3, leave plugs in place. 3. “Twin” cylinders 2 & 3 by cutting a port between them in the head area separating the cylinders. Cylinders 2 & 3 should operate as a single double size cylinder for gas expansion. 4. Remove one exhaust valve from cylinder 2 or 3 and plug or weld it’s valve guide to reseal the combined chambers. Via a small external transfer manifold, route the exhaust gas from cylinders 1 and 4 to this port. 5. The remaining exhaust valve provides all exhaust gas exiting the engine and connects to the exhaust pipe. The camshaft has to be modified for this remaining valve so that it has two lobes at 180 degrees. 6. Modify any engine controls and software as required to get it running. Road test for expected engine efficiency improvements. Exhaust gas temperature should be much reduced; re-verify catalytic converter operation.

Note that only 5 valves are now used and only modest changes are required to the cam shaft. The Dual Mode engine obviously requires much more serious changes. (Estimated cost of Prototype 1 development and test: $100,000).

Prototype 2 Modify an existing or build a new 12 valve head for a crossflow 4 cylinder engine. Although purely mechanical valve controls might be possible, the prototype will be much easier to develop with electrically controlled valves (Sturman Industries has demonstrated such a camless valve train). A custom engine valve controller will perform mode switch over and all valve control. Road test for smooth mode transition and continued max performance with high cruise efficiency. (Estimated cost of Prototype 2 development and test: $1,000,000).

Note: The author expects the same idea will work on V8 engines, but not easily on other configurations.

[John Jamieson]

Please help me get the word around to those in the automotive biz or other interested parties.

Comments welcome.

John

[martin_fierro]

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[Orbiting_Rosie's_Head]

Interesting Idea. A 5-stroke 2-cylinder engine from a regular 4-cylinder, 4-stroke engine. But why the high cost to develop and test? Sounds like an operation that a friend of mine who use to build motorcycle racing engines could do in his well-equipped garage.

[John Jamieson]

Sounds like engine Guys and Gals, thanks.

John

[John Jamieson]

That's if the big boys do it. You and I could do it for peanuts. GM spent $1,000,000,000 on the Impact..... and then crushed 'em.

[bmwcyle]

bttt

[The_Victor]

Cool concept.

I would have thought the exhaust pressure would have been too low for a second expansion cycle. Obviously you have made the calculation do demonstrate otherwise.

Is the fuel efficiency calculation just an extrapolation based upon the effective expansion ratio?

[alloysteel]

OK, some of my latent engineering insight kicks in. Rather than using the two middle cylinders of a four-cylinder IC block, build a single double-acting piston, tied into the crank, using the exhaust portion of the cycle from one cylinder to drive the piston down, and the exhaust portion of the cycle of the other cylinder to drive the piston up. This scavenges a lot of the remaining energy in the exhaust stream, and gives up a lot of heat in the process. Thermal efficiency should be much improved. And rather than poppet valves, use slide or rotary valves, to reduce internal inertial resistance to opening and closing the various valves.

If you identify this as an adaptation of an external combustion engine using steam as a medium, that is correct. The engineering is about 80 years old, going back to the time of a fellow named Abner Doble. With a really good water vapor reclamation system, condenser and heat exchanger tank, the system was superior to any internal combustion engine of the time, and would be on a par with the most advanced engineering of an internal combustion engine of today. With minimal emissions.

[Consort]

How much will one of those effing engines cost?

[Jack of all Trades]

A full authority electronic valvetrain opens up a world of possibilties. How do you think the efficiency of your idea for increasing expansion compares to cylinder deactivation? With Sturman valves, you could do either or both.

I think you'd better add another zero to your proposed development cost. Sturman will want your million just to design the valve and build a few protoypes. Then you'll still have to D&B the cylinder head and engine control system. Then you'll need a dyno with emissions capability. At that point you'll be ready to start engine development.

Bosch, Delphi and a few others have deep pockets and buildings full of PHd's working on future IC engine configurations. If they are not working on this concept, why do you think that is? If they are working on it, how do you propose to compete?

[boris]

"3. The author experimented with 2-cylinder engines based on a 4-cylinder 1.9 liter Opel in the 1970’s. This car demonstrated about a 40% increase in fuel economy, but suffered poor horsepower performance, barely reaching the 55mph top speed of the day. Never the less, the car was driven to the Kennedy Space Center every day for over a year. About 2 years ago, the author started wondering if the two extra cylinders could be used for additional gas expansion, and the present idea was born. A 1987 Toyota Corolla was purchased and the conversion began, only to be never completed because of a combination of health issues, and more pressing time demands. "

My professor (mechanical engineering) at Cornell in 1971 experimented with this notion. He had a V-8 running on 6 cylinders and two as 'expanders'. I would not be surprised if he had a patent or two. My 51-year-old brain is refusing to give up his name but eventually it might.

--Boris

[boris]

High-compression ratio engines have been known to be good for a long time. The government basically outlawed them because of pollution concerns. If you look at a curve of Nox emissions versus compression ratios you will see what I mean. The "Muscle Cars" of the 60's and early 70s ran at much higher compression ratios than do today's engines because there were no Nox emission standards.

Nobody had heard of catalytic converters, and the notion of an engine that would not start unless its computer was working right would have been thought insane.

--Boris

[boris]

Ah HA! His last name was Booker. That was the prof's name. I'm still working on his first name.

[John Jamieson]

Yes, more area under the curve.

[Jack of all Trades]

The current model Acura RSX has a 2.0 liter 4 cylinder engine with an 11.0:1 compression ratio. Valve and ignition timing control along with combustion chamber design keep the engine from melting. EGR is used for Nox reduction. A 10:1 CR engine that runs on 87 octane gasoline is a common thing today.

[John Jamieson]

A lot less than a diesel upgrade ($1400) which pays off in 60k miles. And much less than hybrid ($5000) which never pays off.

Depends on the valve train costs, I would guess $200 to $600 extra. Payoff in 30k miles or so.

[John Jamieson]

You get both cylinder deactivation and exhaust expansion with this idea, no trade off needed.

The big boys keep their research secret.

[John Jamieson]

He was on the right track.

[John Jamieson]

This is not a high compression engine, just high expansion.

[boris]

"This is not a high compression engine, just high expansion."

Hey, I'm just a rocket engineer. In rockets you can 'overexpand', i.e., allow the exit static pressure to drop below ambient.

How do you do that in a car? A high expansion ratio kind of implies a high compression ratio, or am I missing something?

--Boris