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Old 12-04-2010, 11:13 PM   #121 (permalink)
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Note that back in the old days (100 years ago) engines did have quite low compression ratios, like 4:1. And in conventional engines anyway, the more squeeze you put on the mixture, the more bang you get when it ignites, and the more power it makes. So the traditional relationship has been more C.R.=more power.

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Old 12-05-2010, 02:17 AM   #122 (permalink)
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Quote:
Originally Posted by Frank Lee View Post
Note that back in the old days (100 years ago) engines did have quite low compression ratios, like 4:1. And in conventional engines anyway, the more squeeze you put on the mixture, the more bang you get when it ignites, and the more power it makes. So the traditional relationship has been more C.R.=more power.
This also seems to hold true for the turbine engines as well. Something has to pressurize the air, be it a piston or a supercharger, to get efficient work from the fuel.
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Old 12-05-2010, 03:15 AM   #123 (permalink)
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Originally Posted by Old Mechanic View Post
After all this BS you admit that DCB.
No, I've always appreciated the appropriate application of hydraulic regeneration, %70 for regen is awesome, and many of us are indebted to you for persevering in that regard. But as a series transmission it kinda sucks in the peak efficiency department at %83 percent.

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I don't think so, and I have gambled a lot in hope of succeeding.
I am aware of this too, having read your posts carefully.
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Old 12-05-2010, 07:33 AM   #124 (permalink)
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In the spring of 2006 when I drove to Detroit Ryan Waddington at Next Energy said that development was at 78% and the threshold for a breakthrough was 80% regeneration efficiency.

The most basic flaw in the EPA design was running the pump at prop shaft speed, which kills the efficiency at higher sustained speeds, while running the pump at wheel speed as is done in the INNAS design eliminates high RPM pump operation.

Back to engines and my belief that they can reach 60% efficiency.

No one has discussed the cooling system, which is a one size fits all configuration. While some here are advocates and some opponents, blocking the air flow through the radiator reduces heat dissipation in cold climates.

Make that automatic with a dual thermostat radiator where coolant bypass the radiator to maintain a constant (and higher) coolant temperature of the coolant reentering the engine.

Engines run more efficiently at higher operating temperatures. The coolant exiting a radiator at temps below freezing can be 75 degrees colder than the same coolant in mid summer.

I have read of claims of 10% improvement in mileage. In extreme climates a hypermiled car can keep the engine cool using only the heater core. The radiator and cooling system need to be able to cool the engine but a "same size fits all" radiator cools to much in 95% of the driving conditions.

Having followed engine design for 4 decades, I have seen many new designs and configurations that seem to hold promise. Has anyone here actually seen a thorough breakdown of the losses attributed to individual systems?

Neil I did look over your proposed design in the first few posts. I believe one of the disadvantages of engines that have opposed cylinders like the old air cooled VW was that I have not seen one of that design that was terribly efficient in the first place.
I think disc type valves are an improvement over poppets in theory, but I am not sure if they have the ability to last and be low maintenance.

Every car manufacturers nightmare is to build some significant departure from their proven designs, only to find out that they have made a huge mistake when some poor design characteristic makes them the target of lawsuits and could possibly bankrupt their business.

Autoteach. I liked the Aprilla design, and my original thoughts were in the direction of Orbital and injecting air and fuel into the cylinder with ports for exhaust. It seems like a significant amount of EGR (Like Edison did in the X prize) may be a solution, to the point of even controlling engine power levels through the amount of EGR applied. At this point EGR is a necessary evil, but I also believe in the future, with the computational ability available today that HCCI will become practical with combinations of ultra high pressure multiple sequential injections during the combustion stroke.

I always felt, from the beginning when they started hanging pollution components on old engine designs, that the real solution was to fix the engines design deficiencies instead of adding stuff to solve the problem. Nissan and Honda tried to do that with fuel injection in 1976 for Nissan, and stratified charge engines in the Honda CVCC civics and Accords about the same time.

The 1977 Accord I rebuilt for Pop was a heck of a nice car. He drove it up and down US1 in the Florida Keys and averaged 40 MPG, and that stretch of road is one of the worst anywhere for efficient driving. The Accord weighed almost exactly the same as my VX and had the same size engine.

Both the Nissan and Hondas in 77-80 time frames did not need catalytic converters to pass emissions because they tried to make the engines inherently cleaner. WE may see that happen again when the true capability of precision ultra high pressure, sequential injections, while combustion is occurring, becomes perfected, which will go far to mitigate the poor leverage referred to in Neil's first posts.

I am not sure that you really need any more than two valves. Honda's ISDI engine uses only two, but the are not directly opposing each other and Honda uses two spark plugs to create good efficiency. They claim it is the equivalent of the old VX lean burn engine without the NOX issues that killed lean burn designs.

If you consider the engine only and use a systematic approach I think the can get close to 60% if you consider development as open ended with no time limitations.

It will require:
Fuel improvements
Variable compression
Multi point and multi sequence fuel injection with fuel heated to a super critical state
Low speed engine operation at only best BSFC rates
Possible some reconsidering of many of the performance improvements that have become common recently (as in the Honda ISDI design which seems to revert to a 2 valve configuration)
I like electric supercharging because it can be configured as a system that does not require constantly driven components like supercharging or turbocharging.
The reason I like the electric supercharging option is because you can significantly downsize the engine, with increased efficiency, while having the very low percentage burst of power available for the very small percentage of time you may actually need that power.
When you drive a car with a instant fuel economy bar graph (mine is factory) you learn a lot about what the cost of acceleration is in fuel consumption.
There are 5 states of operation in a car, acceleration, deceleration, coasting, braking, and idling.
Hypermilers gain mileage by accelerating at peak BSFC, coasting is done with engine off to achieve best mileage. The other 3 are where most of the energy is wasted, and while they are not specifically improvements to the engine, their elimination is a crucial factor in increasing fuel economy.

Also Neil my post 116 just before your request to stay on topic in 117 clearly stated that it has to be a systematic approach. Engine efficiency improvements must be tailored to the power train that is applying the engines power to the wheels, and specific development pathways will evolve when the power train issues are resolved. EPA stated in 2005 that an 80% improvement can be obtained through power train alone. Engine refinements could increase that figures by another 40% to a total of 120%.

A lot of work has been done with engines and they are a greater source of focus, while the real key is a power train that takes advantage of any improvement.

I think if you consider the engine as only running to add energy to the system, and is not designed for drag racing versus fuel economy you will see much resistance from the performance enthusiasts. I once was one of those who wanted power over economy, now I want some power, but would gladly sacrifice that for extreme economy and that may be a difficult prejudice to overcome.

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Old 12-05-2010, 03:49 PM   #125 (permalink)
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Old Mechanic -

Quote:
Originally Posted by Old Mechanic View Post
...

Neil I did look over your proposed design in the first few posts. I believe one of the disadvantages of engines that have opposed cylinders like the old air cooled VW was that I have not seen one of that design that was terribly efficient in the first place.
I think disc type valves are an improvement over poppets in theory, but I am not sure if they have the ability to last and be low maintenance.

...
Can you comment on liquid-cooled Subaru boxer engines? Frank Lee has stated that there have been experiments with VW engines where they remove 2 opposing cylinders out of a 4 cylinder VW engine and it stays balanced. It made me think that boxer engines are "naturally inclined" to have cylinder deactivation. I know that means extra weight and extra friction, but I was wondering if this was a "perk" that boxer engines could provide in the quest for greater MPG.

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Old 12-05-2010, 04:07 PM   #126 (permalink)
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Boxers could very well be better candidates for cyl deac. I wonder why sooby doesn't have it?
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Old 12-05-2010, 06:02 PM   #127 (permalink)
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If I had to choose. I would choose two smaller engines working together or separately over one larger engine with cylinder deactivation.

Alfa Romeo did that in the 8C grand prix engine developed before WW2. In 1950 the engine was a pair of 4 cylinder engines bolted nose to nose. All accessories were gear driven, no fan belts. One engines output flange ran a two stage supercharger while the other drove the car.

90 cubic inches and 390 horsepower @ 2 MPG.

Not a good reference for high efficiency, but the idea of two 45 cubic inch blocks working together for power with one disabled for economy is appealing.

The road racing rivalries between Mercedes and Auto Union prior to WW2 are also a fascinating study in competition between in line and horizontally opposed engines. The old Ford Flathead was basically two engines siamezed at the crankshaft with separate cooling systems, water pumps, and thermostats for each 4 cylinders. Only the radiator was a common unit.

EPA proposed a V8 that was two 4 cylinder engines that could operate in unison and separately. Maybe two 2 cylinder engines placed in an opposed piston with either side capable of being disabled to provide two cylinders for cruising and 4 for power.

While the thought process is fun, I came to the conclusion based on the capacitive storage IVT power train, that trying to make the engine more complicated is really unnecessary. I went in the other direction, more like a pressure washer engine. The 5 HP Honda in my pressure washer runs at 3600 RPM and uses something like a quart of fuel per hour. Needs no throttle control, and is fairly low stressed at 9 cubic inches and only 5 horsepower. Torque is the real objective as long as its BSFC is optimized, and I have doubts that you actually would need any more complicated design than the Toyota Corolla engines of the 70s which were beautiful little push rod staggered valve hemis.
Sophisticated multi valve engines follow the racing traditions and get more fuel and air in the engine for more power, but that may be like the old Alfa grand prix engine where sure, you are getting 4 HP per cubic inch, but at 2 miles per gallon.

I read somewhere that Toyota had actually managed to get their Corolla engine to run at open throttle and power was controlled by timing and fuel delivery without any throttle restriction. I think that is the way to go with gasoline fueled engines when you have the computational capability to inject fuel through 4 different orifices at 5 different sequences in every power stroke in an engine.

EPA also had a design for a puck in the top of th cylinder that could be elevated using oil pressure to vary the compression ratio while the engine was running.

With some of the latest improvements, Mazda has introduced an engine with compression ratio of 14 to 1. Unthinkable in the past, this is very close to the compression ratio of Indy car engines running pure alcohol. Precision control of direct fuel injection both from multiple points on the injector and at multiple points during the combustion stroke make this practical, something that was impossible on a couple of years ago.

We can only guess at what they have in their top secret research developments for IC engines, but looking at history as well as really studying the latest developments in precision control, that has only become possible with today's data processing and sensor capabilities allow only what was dreamed about very shortly ago.

Supercritical preheated fuel, injected at pressures approaching 30,000 PSI would actually spontaneously ignite without any spark ignition necessary.

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Old 12-05-2010, 06:14 PM   #128 (permalink)
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A good friend of mine who used to race go-carts told me something once that I will never forget. They dynoed a 5 HP Briggs and Stratton engine at 18 HP on alcohol. They put a brace that clamped the head to the block, a girdle to keep the head from blowing off the engine at 100 MPH on a dirt track.

When they finished the race you could put your hand on the cylinder head and it would not burn you, but the exhaust would fry you in a heartbeat.

I guess that might mean the actual peak heat from combustion was much later due to the alcohol fuel. No cooling system other than air cooled, no pressurized lubrication, just a splash feed.

He never got past the 10th grade as far as any formal education, but the family business is worth millions. His father was one of 12 sharecroppers children who left home at 16.

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Old 12-05-2010, 06:48 PM   #129 (permalink)
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I have a suspicion that eliminating the throttle plate won't cut pumping losses, if it's done by manipulating valve timing, cuz then the restriction that the piston sees on the downward stroke would be caused by the intake valve. However if Toyota is doing something else then good.

BTW my friend has an old Starlet- the car is a totally rotted out, smashed up, beaten to a pulp POS with an estimated 400,000 miles on it, but that engine still sounds like a sewing machine at idle!
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Old 12-05-2010, 07:12 PM   #130 (permalink)
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I wish someone would do the two engine (for efficiency, not performance) experiment already. Oh wait, that is what burt rutan already did

Use them both for takeoff and initial flight then shut down the larger one for cruise
Rutan Voyager - Wikipedia, the free encyclopedia

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