Some years ago I developed a theory relating to measuring the efficiency of balanced systems or nearly balanced systems (according to the laws of physics ).
It was not until later, I realized that the combustion engine of a motor car was in itself a balanced system. Or rather the individual pistons within cylinders were systems within the overall system of the engine! (They could be considered individual motors making up a part of the total motor)
Anyway getting back to the theory - This required the monitoring of the system over a time frame of five timing points and at the end of that time to come to a logical conclusion as to whether the system was operating as efficiently as it could be or if there should be a small adjustment made!
This theory could then be applied to each cylinder of a combustion engine. There would be one timing point at top dead centre, a second at the bottom of the downstroke and three others in between.
The monitoring of the system would be via the compression ratio at each timing point per cylinder. Those five readings could be linked to get an overall picture of the performance of each cylinder.
ie.
1 - 2
1 - 3
1 - 4
1 - 5
2 - 3
2 - 4
2 - 5
3 - 4
3 - 5
4 - 5
These figures can be fed into a computer for analysis of exactly how much fuel that particular cylinder required injecting.
I am convinced this theory would work and would result in -
1. Greater fuel economy.
2. Greater horsepower for size of motor.
3. Greater Torque.
4. Smoother throttle for all loads.
5. Less maintenance costs.
6. Less emissions.
7. Cooler running.
I also am convinced that much of the present gadgetry on modern engines would not be required and would remain obsolete. With the cost of fuel rising exponentially the further we get into this Century, I believe it is imperative that we run smaller cars with more efficient engines.
In creating this article I wish it to be known that I am a layperson with very limited access to working on motor engines. All of my theories have been derived from logic! Excuse the pretty rough explanation involved!
With Kind Regards,
taurus26
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I'm no super engineer but I'm on my way to a degree there, and I see where you are getting at with a totally balanced system. The pressures involved during combustion change rapidly depending up where the engine is in the combustion cycle. The compression ratio can only be established between the maximum cylinder volume and the minimum. You could however read the cylinder pressure at different points in the cycle though I would have thought that a balanced reading at a fixed interval of 2pi/5 rads (or 72 degrees) would be somewhat easier to implement.
The current engine management systems continously monitor such systems in feedback loops anyway to ensure that the engine is running at it's most efficient. Be that running at Stoichiometric ratios for the operation of a three way Cat, or in lean burn mode. The real issue is that there are times when you want a huge engine to do rapid overtaking and times when you want a small engine that just keeps you going.
A couple of years ago a proposal, the Mayflower e-3 ( www.sae.org/automag/techbriefs/01-2002/page2.htm ) was put forwards, the idea being to have a high capacity long stroke engine for power that became a shorter stroke small capacity engine when less was being demanded. I haven't heard anything about this recently but the reasoning behind increasing the angle at which the piston/crank/conrod are connected at point of ingnition makes sense.
Another proposal that has been around a while is the six stroke engine ( www.sixstroke.com/ ) The idea being using a dual pair of pistons in the cylinder with the top piston acting as the valve gear but also on a two stroke cycle for more power while the bottom piston operates in a four stroke cycle. These have been used to limited effect in a few trials as detailed.
As far as your theory goes, I would be interested to see you develop your thoughts further. Points 2 and 3 are inexorably linked given that power is a function of torque, increasing the balance of the engine should improve smoothness and also reduce loss in the engine leading to better fuel economy so I can follow that too. Cooler running may not necessarily be a benefit, as a certain level of heat is needed around the combustion to avoid energy loss due to heat conduction.
I'd nominate that driving a fuel efficient vehicle is the way forwards, but the biggest impact is not the engine but the driving style. Today's engines are capable of phenominal efficiency, witness it's possible to get 40mpg from a 3 litre diesel automatic 4wd executive saloon (Audi A8) without trying, similarly one can get 15mpg from the same car by driving it exceptionally hard. Same engine, two drivers, one using roughly 1/3 of the fuel.
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Thanks very much for your contribution cjehuk.
You are spot on by your suggestion that the timing points should be 72 degrees. We now have a near perfect balanced system.
I first produced copyright material on this subject on the 6th of August, 1996.
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The trouble is they don't want 'simpler' and true 'greater efficiency', the global economy is driven (or propped up) by continuous-obsolescence and over-complication required by legislation.
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Seems to me that what taurus26 is suggesting is an engine management system as fitted to many contemporary motor vehicles.
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By far the biggest contributor to reduced petrol engine efficiency surely, is the action of the throttle?
It reduces the compression ratio, except when on full throttle, and in so doing reduces the energy that is extracted from the burning of the fuel. Efficiency involves consideration of the heat of burning gases minus the heat blown out of exhaust etc.
The use of several engines of different size may be impractical but would be more efficient. Each one being used at its optimum power output. Or use one engine and charge a battery, as does one well known car.
I shall now go and have a lie down and let you mechanical engineers fight it out.
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There are petrol engines with no throttle, I think BMW have made one which uses electropneumatically actuated valves which can be opened and closed without being dependant upon mechanical connection to the rotating parts, thus they can be used as throttles, probably in conjunction with tunable air intakes.
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