Self Supercharging engine
Self Supercharging engine
(OP)
Last night during a bench racing session, some friends and I discussed a concept that was new to us. I assume that it has been tried somewhere by someone (as almost everything has thanks to Smokey). Anyone please speak up, as this is probably tragically flawed.
There is a class that limits engines to four cylinders and forbids turbochargers and superchargers, but does not specify Natural Aspiration strictly. What if you took a V8 engine and used the exhaust charge from four cylinders to compress the intake charge for the other four cylinders? Let me explain a little more. It would have to be direct injected, the 'compressor' side would have no ignition, just air in, compression, and release compressed air thru a one way flow control of some sort into a chamber to be used in the intake charge of the other four cylinders. Understanding that there would be energy wasted in running the piston thru the power stroke without actually making power, do you think the power increase from the charged intake would overcome the power losses of swinging that heavier mass(8 cyl VS 4 cyl) and the wasted power stroke of the compressor side.
There is a class that limits engines to four cylinders and forbids turbochargers and superchargers, but does not specify Natural Aspiration strictly. What if you took a V8 engine and used the exhaust charge from four cylinders to compress the intake charge for the other four cylinders? Let me explain a little more. It would have to be direct injected, the 'compressor' side would have no ignition, just air in, compression, and release compressed air thru a one way flow control of some sort into a chamber to be used in the intake charge of the other four cylinders. Understanding that there would be energy wasted in running the piston thru the power stroke without actually making power, do you think the power increase from the charged intake would overcome the power losses of swinging that heavier mass(8 cyl VS 4 cyl) and the wasted power stroke of the compressor side.





RE: Self Supercharging engine
RE: Self Supercharging engine
RE: Self Supercharging engine
There is a thread about SBC compressors, where half the motor is a compressor for air, while the other half powers it.
I dont think that normal head/piston/valve geometry is a very efficient way to compress things. There is way too much dead space at the top of the stroke. (You could modify the head to eliminate these problems.)
Interestring thought, though I dont know how well a SI motor would handle 2x the air from 0rpm till whenever the rpm's are too high for the whole second bank compressed intake air to move across.
Nick
I love materials science!
RE: Self Supercharging engine
There is a unit that kinda does this called GasJack from Compressco. The compressor side doen't seam to make enough air though when I looked at the curves.
RE: Self Supercharging engine
Certainly not impossible, but not terribly practical, and absolutely not going to be allowed by any racing sactioning body in a "limited" class.
-Tony Staples
www.tscombustion.com
RE: Self Supercharging engine
RE: Self Supercharging engine
It is a supercharger, so it would be illegal. A supercharger is a device to compress the inlet charge before it enters the cylinder.
Regards
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RE: Self Supercharging engine
RE: Self Supercharging engine
RE: Self Supercharging engine
I know were not about rumors here, but I thought the theory was interesting anyway.
RE: Self Supercharging engine
RE: Self Supercharging engine
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RE: Self Supercharging engine
Cheers
Greg Locock
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RE: Self Supercharging engine
you are absolutely correct. I was assuming one stroke per each. If you added the reed valves, then you could get boost by using two pumps of the "compressor" cylinder, for each four stroke cycle. Then the problem becomes one of how to route air. To me, the smart option would be to use the "exhaust" valves as inlets for the compressor cylinders, letting the compressed air into the common intake via the normally "intake" valves.
Still, frightfull to implement, but fun to toss the idea around.
-Tony Staples
www.tscombustion.com
RE: Self Supercharging engine
While in its death throes, Triumph Motorcycles (the old one) came up with a piston having two skirts, the second much larger and attached at the bottom to the first. The engine was a twin, and the cylinders supercharged each other. There were, of course, two concentric cylinder surfaces for each cylinder, too. Given the extra complexity, the difficulty of making annular cylinders and annular pistons, and the difficulty of cooling and lubricating the combustion cylinder's walls, the idea probably didn't stand a chance, but it was a clever thing to have been exploring, in a company that was _not_ in dire financial straits. Given the company's business situation, I thought it was an irresponsible distraction, or maybe a last gasp.
Mike Halloran
Pembroke Pines, FL, USA
RE: Self Supercharging engine
Have a Google for:
Comprex Pressure-wave supercharger
United States Patent 5799641
Bill
RE: Self Supercharging engine
In Smokey's three book series there is a brief description of a bellhousing supercharger. He said he welded fittings onto the housing, then filled it with expandable foam. When the engine was started it cleared a passage through the foam, and once the outlet was cleared of foam he claimed it produced positive pressure. My memory is foggy on how much it was able to produce or what sort of difference it made.
Thanks,
Jack
RE: Self Supercharging engine
RE: Self Supercharging engine
Cheers
Greg Locock
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: Self Supercharging engine
Static pressure -- no flow (?)
Bill
RE: Self Supercharging engine
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RE: Self Supercharging engine
RE: Self Supercharging engine
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RE: Self Supercharging engine
RE: Self Supercharging engine
"Now I have everything clean inside and stick a bottle of urethane at a hole and press the button, everything inside gets full of foam. Let it harden. Now crank engine up and cut a path for the rotating parts. Then...opened the entrance and exit areas up with a knife, then cut room for throwout bearing and fork. Then run engine up to 7000 rpm AND FIND OUT YOU GET 10 PSI OF PRESSURE, AND ARE PUMPING 800 CFM WITH NO PARASITIC LOSSES."
800CFM at 10 psi????? Jeez, that's a lot of air. I don't buy it. Unless he left out the part about building the engine with a special turbine shaped . . .. Aw, never mind.
-Tony Staples
www.tscombustion.com
RE: Self Supercharging engine
With all that foam insulation, I guess you'll need an adiabatic clutch & t/o bearing that can really "take the heat"!
RE: Self Supercharging engine
Mike Halloran
Pembroke Pines, FL, USA
RE: Self Supercharging engine
Regards
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RE: Self Supercharging engine
I think I can understand (maybe) the use of the flywheel ring gear teeth as a pumping mechanism. After all, a lot of current electric fuel pumps do just about the same thing - peripheral toothed wheels rotated at high speed.
To get these things to work with any sort of efficiency, you have to use very fine tolerances and have the 'turbine' shaft running at quite high speed to generate the sort of peripheral speeds where the pump works best.
I can imagine the foam providing these sort of close-fit conditions, but as to how wide a speed range that would provide a useful boost....?????
What happens when the crank end float gets so that the foam is worn away from the flywheel.....efficiency drops/dissappears.
Bill
RE: Self Supercharging engine
I have been involved with a project that uses crankcase pressure as a source of forced induction. The mixture is pulled into the crankcase as the piston rises and expelled as the piston drops, airflow is controlled by a rotary valve running at crank speed, so you get two displacements per power stroke. This feeds a plenumn which feeds the inlet to the cylinder. In terms of psi boost the figures were low compared to more traditional forced inductions, but required very little in the way of extra moving parts, and the figures were obviously higher than a NA engine. The fuel was mixed 50:1 with stroker oil for lubrication of the bearings and rotary valve. The majority of the engines built were only small capacity for use in an Ecomarathon car, but a larger engine was still born when the UK motorcycle speedway authority got wind of it and banned the concept before the prototype was finished, let alone running. Without a market the research ended. Only works if the engine is a single or has seperate crankcases.
RE: Self Supercharging engine
Hmmm.....isn't that just a traditional 2-stroke ?
Bill
RE: Self Supercharging engine
RE: Self Supercharging engine
RE: Self Supercharging engine
Many large bore 2-stroke, x-head,slow speed Marine diesel engines use under piston compression to supercharge the air manifold. This concept has been around for many years. The drawbacks are large accumulation of sludge in the air manifolds over time and danger of fires in this area.
RE: Self Supercharging engine
1891
http://www.lindsaybks.com/arch/backus/index.html
1930s
http://en.wikipedia.org/wiki/Bourke_engine
Cheers
Greg Locock
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: Self Supercharging engine
The Triumph project you mentioned was a two stroke 500cc twin called the Norton Wulf. (Norton Viliiers Triumph by then, no matter).
The concept was to develop a two stroke engine with low emissions. Because the crankcase was sealed with regard to the combustion chambers, it could be lubricated by pump and return tank as a 4 stroke, rather than by the usual total loss / burn it and blow it out system.
It looked fairly conventional from the outside with carbs on the rear of the two cylinders. I recall it looked like a cross between an Ariel Square four and a Suzuki twin. However, the intakes were crossed over, so that a mixture adjustment on the left cylinder was made at the right hand carb.
There may be some merit in the concept even now. Like all the other good ideas from that factory, such as the Bandit and Fury modular bike engines, they were sadly strangled at birth due to the foolish refusal of the mangement to reinvest in the business in the face of new and rapidly emerging technology from the far east.
The prominent engine designer for Norton at the time was Bernard Hooper, who, I understand, is still experimenting with this type of engine.
I read all this almost as it happened, at school in the early 1970s from my smuggled in copies of Motorcycle Mechanics, whilst supposedly reading Shakespeare in English literature lessons. Consequently, I know a little about British bikes but I still don't know my Puck from my Bottom.
RE: Self Supercharging engine
PEW - not knowing yer Puck from yer botteom.....could be nasty if you ever have to explain any pains to your doctor.
Bill
RE: Self Supercharging engine
How about a Puck from a Puch? The zenith of self supercharging...
h