snip
To me that's like calling a 650 cc 2-stroke a 1300 cc engine.
What is wrong with this picture? I don't get it.
Regards,
Gordon.
Ah well you have touched on the solution.
The rotary is not a two stroke. It is a four stroke.
Lets turn it around. How much air would a 2.6 liter two cylinder
TWO STROKE engine pump in one revolution?
As far as HP is concerned the ONLY thing that matters is how much
air a four stroke engine pumps in ONE REVOLUTION at 100% VE.
Not the physical displacement of x number of chambers.
The definition of displacement, as far as engines are concerned,
is only valid in context with the type of stroke.
Here is what Ansdale has to say about that.
13B rotaries are raced in the 2.6 liter class world wide
for a good reason. The only reason they generate more power
than a 2.6 liter four cylinder engine is they turn faster
and breath better. Lately that is less true as the piston
engine RPM has been raised by detail development and the
use of high strength to weight ratio materials like titanium.
Also four valves per cylinder has improved the breathing.
It is very rare for any 2 valve cylinder to have a VE over one.
The RX8 engine is just over one and P-ports are typically
1.2.
Formula One (2.5 liter as I recall) V8 engines are now
turning 19,000 RPM. At least four valves per cylinder with
a very short stroke so larger valves can be used for a given
physical cylinder displacement. You will not find the details
of a competitive Formula One engine anywhere. Its a well
kept secret. However I would not be surprised if the VE's were
well over one. Applying the RPM difference to a 2.6L p-port rotary
making 340 HP at 10,000 RPM would make the Formula One engine
about 19,000/10,000 times 300 HP or 655 HP which is about
right for a Formula One engine.
Paul Lamar ...No rotor no motor.
I'm sorry I ever brought it up. I just wanted to know what turbo would
work best on my 20B.
Don
No need to be sorry Don. I certanuly don't mind. Each time
I explain it I get better and better at it:) If you hadn't
somebody else would sooner or later. I need to add this
stuff to the web site.
Paul Lamar ...No rotor no motor.
Paul,
Regarding the F1 engines, the 'rule book' says that the ratio of stroke
to piston diameter can not be less than 0.4.
Two years ago they were still running the V10 engines of 3 litre
displacement. Now its down to 8 cylinders, total of 2.4 litre displacement
or 300 cc per cylinder. Assuming the S/D is 0.4, we would have 98.5 mm
(3.877") piston diameter and 39.4 mm (1.55") stroke.
Yes, the large piston diameter allows very large valves. Fuel efficiency
is the pits, but power is at its maximum.
At 19,000 rpm the displacement / sec at 100% VE is 380 l/s. At a piston
mean effective pressure of 16 bar results in 608 kW or 815 hp, which is
what they are producing nowadays, even 850 hp are being reported.
In imperial measurements:
2.4 liter * 61 = 146.5 cuin. Multiply that by 19000 /120 = 23,200 cuin /
sec.
The mean effective pressure is about 232 psi, so 23200 * 232 / 6600 =
815 HP
Regarding the Wankel displacement we sure must distinguish between 2
stroke and four stroke engines.
The Wankel is a four stroke, so its displacement should be counted at
two crankshaft (eccentric shaft) revolutions.
The Germans (NSU) did that, Mazda counts the displacement at only one
revolution which is the reason for the difference and confusion.
By rights, as a four stroke, the designation should be twice of what
Mazda says it is. On the other hand, Mazda argues that it has no valves
and it is ported like a two stroke. I personally find that a week argument.
I agree Paul, the explanations are getting better, even mine, I think. :)
Rolf Pfeiffer
Thanks Rolf. I forgot about the F1 compression ratio difference.
They are probably running something like 14:1 while 10:1 is
about max for a Mazda.
Paul Lamar ...No rotor no motor.
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