snips..

 PLANK is not really a means of predicting pwer, it is just a

relationship.

 If you can predict the pressure then you  have predicted the power

(less

friction
 if you use IMEP) normally the equation is reversed using stated power

to

 compute the BMEP (Brake meam effective pressure) . This is often used
 as a reality check on advertised power of normally aspirated engines
 (with boosted or nitro'd engines you can dial any amount of power
 you want - right up to distruction) - I once wrote an article for

Contact

 magazine titled "Seperating the BS from BHP with BMEP"
 Wankels are pressure/area/volume expansion engines like all the
 rest, and the same rules apply - Vance

Norman DeBoer writes:

Thank you Vance for your response.  Yes, all that you say is correct.

The

first item P = 146 is the predicted pressure (IMEP) for the Zoche Aero
Diesel engine.  All the rest of the parameters are given or are claimed

(300

HP).  Could something like the PLANK/33000 formula be developed for the
Rotary Engine?

As inferred above, all the same basic rules apply to any form of positive
displacement
expansion engine. Since we do not have classic bore and stroke, the
equivalent is
the swept volume of an individual cylinder/chamber   cubic inches, divided
by 12
(this is our LA)  NK then becomes the number of expansion completions (power
strokes) per turn of a reference shaft times the rpm of that shaft. The
Wankel output
shaft turns 3 times for each turn of the trochoid rotor, and each of those
turns makes
3 complete 4 stroke cycles (3 power" strokes") for each of the two rotors in
a
Mazda 13B. so there are 2 power expansions per each turn of the output
shaft.
Each expansion displacement is half the "rated "1.3 liter displacement, or
39.65 cubic inches  thus with 133 psig bmep (typical normally aspirated
value
for a  production automobile engine), and 6000 rpm we have:

133 psig * (39.65/12 ) * 2 per rev * 6000  rpm  /   33000 = 159.8 hp

Which is about what a late model stock RX7  engine will do.
Vance

Excellent Vance :-)

Paul Lamar

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