4686Re: [hreg] What is holding back American car companies?
- Aug 3, 2006Yesterday, Ariel Thomann wrote:
> Thank you, yes, that was it. For those who are curious about this Scuderi engine, hereFor those of you who don't quite get what's different about this engine, let
> is their own website: : http://www.scuderigroup.com/
me attempt an explaination.
First, a normal engine uses a four-stroke cycle.
Piston movement: down up down up
Action happening: intake compression power exhaust
In other words, as the piston moves down, it takes in a fuel/air mixture.
The valves close, and the piston moves up, compressing the air (and fuel).
The piston gets (almost to) the top of the stroke, and the spark plug fires,
igniting the air/fuel mixture, and starting the power stroke. The expanding
gasses push the piston down, providing power. The piston moves back up, and
the exhaust gas is released.
What happens in the Scuderi engine
(http://scuderigroup.com/technology/images/scuderi_piston2.jpg) is that the
air/fuel mixture (or possibly just the air, and the fuel is injected later)
flows from the first piston (on the left) to the second piston (on the
The second piston acts like the piston in a normal engine (performing the
four phases I listed above). The first piston is ganged to the second, so
they move (roughly) in phase.
Every time the second piston moves down (on intake and power), the first
piston does too, filling up with air. Every time the second piston moves up
(on compression and exhaust), the first on does too, pushing air into the
chamber between the pistons.
What this means is that with a normal engine, a piston can take in the
volume of one cylinder every cycle. With the Scuderi engine, the piston (the
power piston on the right, that is) takes in the volume of two cylinders
I don't honestly know if this is really any better than a standard
supercharger, since that's all this really is. (A supercharger uses a
compressor turbine driven directly off the engine to compress incoming air
to get more in the cylinder. A turbocharger, BTW, does the same job, but is
driven from exhaust gas pressure.)
I also question the wisdom of a four-cylinder engine (that according to the
website produces as much power as a six-cylinder engine) that only fires on
two cylinders. The problem here, especially if it does produce as much power
as a six-cylinder engine, is that it means the power cylinder is doing three
times the work (and producing three times the heat) of a cylinder in a
regular car. That points to the potential for heat-related problems.
There is potential here, though. Using a piston to compress the incoming air
is probably cheaper (in terms of mechanical efficiency) than a supercharger.
And it would produce much higher boost. A standard turbocharger (I can't
give you numbers for superchargers, 'cause I don't know as much about them)
produces around 8lbs(per square inch) of boost. Performance modders rarely
jack them up past 12lbs because of reliability issues, and 15lbs (which is a
full atmosphere) of boost is pretty much the max you can run them at without
a high risk of failure.
By doubling the amount of air going into the power cylinder, they're
effectively doubling the atmospheric pressue, which would be like 15lbs
boost from a turbo/super-charger.
Their website mentions being able to fire the spark after TDC (top dead
center), and having a superfast burn. In a normal engine, the spark is fired
before the piston is done compressing the gas, so that it's burning well
by the time the piston is moving down. That's inefficient. So being able to
produce a complete burn after TDC is a win.
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