Public Domain Hi-Eff Engine Design

[XNASA]

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 [email protected])

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 losses 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.

[ivymike1031]

I'd appreciate it if you would post a copy of this at the following site:

http://autos.groups.yahoo.com/group/highefficiencyvehicles

http://autos.groups.yahoo.com/group/...ciencyvehicles

[XNASA]

Done, I think!

Thanks, John

[dovatf]

Hi John and Ivymike,
What happened to this interesting idea ? No answer at all neither here nor on yahoo ?

[ivymike1031]

I never got a chance to analyze it (even in a rudimentary fashion). I'll get to it sometime when my workload is lighter.

[dovatf]

Nice to meet you again here. I wonder what Greg, Patprimmer and the others think about it. PJGD wrote me he feels the losses in the transfer ducting would be too high. But I think it is a much better way than simple cylinder deactivation because at least the friction losses in the deactivated cylinders would not be lost uselessly.
I didn't understand why this thread was removed from eng-tips. I complained to the administration of the website and the reply was that advertising and posting of such papers was prohibited.

Cheers
Aorangi

[ivymike1031]

Aorangi,

Good to see you here as well. Have you stopped by the yahoo group yet ( http://groups.yahoo.com/group/highefficiencyvehicles )? Pat and Greg regularly haunt that particular venue.

My guess is that PJGD is probably looking in the right direction, but I don't know yet.

Regards,
Isaac

[dovatf]

Yes, I had stopped by the yahoo group and saw there was no answer neither to the post of John. Today I registered and read some more posts. I understood that you launched that forum. It's very interesting, congratulations. I hope to participate in the discussions some day, but it's often outside my field of competence.

Cheers
Aorangi

[ivymike1031]

yeah, I started that group so that non-engineers could have discussions about high efficiency vehicles w/o fear of being ejected (Eng-tips is for work-related discussions between engrs). Competence is not required in the yahoo group - feel free to post / ask /etc. Many of our members are completely clueless when it comes to engines, physics, etc., and that's okay.