Hi Paul & Group,

I worked for some years on Rotary engines, development testing and
manufacture.

I am looking for some data, to verify my Excel spreadsheets, formula for
working out the CR on the Wankel engines, combustion pocket capacity in
particular.

We use to (in the early days 1968 ) place plasticine in the rotor
combustion
pocket, smooth it level with the flank and they measure the fluid
displacement, form this we would work out the CR , knowing the Rotary
engine
geometry of course.

So, if any one can borrow a small amount of plasticine from the little
one,
and carry out the experiments, I would be grateful.

Differing sizes of engine would be good (Rotary of course)

The formula that I have converted from GWBasic to Excel takes into
account,
flank clearance between housing and rotor, side seal losses due to the
rotor
side clearance gap.

Once proven I will gift the Spreadsheet to the group if  you feel that it
could be useful.

I see a lot of comments about Mazda engines and one thing you perhaps
already know is that the combustion pockets changed over the years, from
precision cast to machined.

I visited Mazda for a week when we had our race machine winning (JPS
Norton)
Mazda and Norton exchanged ideas, as  we at the time where getting
more BHP
per CC than the Mazda 24 hour Engine. I do remember one international
incident!  At Mazda they had beautiful petite young women guides,
dress in
white jackets, really smart, and after a few days in Japan for some
reason I
also started to bow my head, as you do, as we entered the Lift to go
to our
meeting I bowed, She bowed, heads collided, She sat down for a few
moments
whilst she regained her composure, the Mazda guys and technicians
would not
let me live this down. We dined with the Vice President on the last
night of
our meeting and even he had heard about the incident, but after few
drinks
all was well.

Anyway I digress back to the CR .

It seems to me that as part of the blueprinting of the engine on
assembly,
then the Compression Ratio would be one of the data checks to make,
this is
something that we logged on every build, we also did static pressure
test,
with the rotor at TDC have air pressure bleed into plug hole (a
drilled out
spark plug, was used for the adaptor)

From memory we had two gauges one monitoring incoming pressure and the
other
the leak pressure,  compared against a known bleed hole.

However if we had to get the motor back together in a hurry, (race
starting
in 55 minutes) we would feel the engine by cranking it around with a
spanner, and our mechanics could sometimes by feel an engines build
quality
better than any Technical approach. Oh and we made the start line and
after
only one lap warm up, we chalked up another win.

Paul some one did say that CR  request was answered, so I do apologize
if I
seem to be repeating myself, but I was not sure how to get the e-mail
replies from you, and now read most of the e-mails.

Robert Rowley

I take it you have the Ansdale book. That is all I know about the
subject.

Paul Lamar


Robert, see Message of 29 Dec. 2009, 2:14 PM  (29/12/2009 2:14 PM)
Title: Compression Ratio Data. [ was Re: Calculating chamber volume for
intake close angle]
Regards
Rolf

-------------------------------------------------------------------------

Compression Ratio Data. [ was Re: Calculating chamber volume for intake close angle]


Steve

In a peripheral port engine like the RX7 you simply use the formula for
the trochoide:

X = e * cos (3 alp) + R * cos (alp)
Y = e * sin (3 alp) + R * sin (alp)

Here we are only concerned with the dimension X from centreline of the
trochoide.

Remember, angle (alp) refers to the angle of R, and the angle of the
eccentric shaft is (3 alp). When you compare the port timing of the
Rotary with the that of the RPE, the ratio is 3/2.
In other words, if the inlet at the rotary opens at 60 degrees BTDC, it
would be equivalent to the RPE of 40 degrees BTDC.

For a chamber to be at TDC position the angle alp for R is 30°, and for
e = 90° (3*30)

I we assume that the inlet opens at (alp) 55° BTDC, (3 alp) would be
165°.
The opening edge of the port from center would be:

X = 15 * cos (165) + 105 * cos (55) = 45.74 mm from center of the
trochoide.

The timing with reference to e would be 165° - 90° = 75° BTDC.
In terms of the RPE that would be 50° BTDC.

We can simply double the angle (alp) for the equivalent RPE timing, (55
-- 30)*2 = 50°


The BDC position of a chamber occurs at (alp) = 60° and (3 alp) = 180°.

Say the inlet closes at (alp) = 40°, (3 alp) for e would be 120°.
(All with reference to the original shape calculation of the trochoide).

The timing with reference to e would be 120° - 60° = 60° ABDC.
In terms of the RPE that would be 40° ABDC.

X = 15 * cos (120) + 105 * cos (40) = 72.94 mm from center of the
trochoide.

The port would be 72.94 -- 45.74 = 27.2 mm wide measured along the
x-coordinate.

The same calculation works for the exhaust port in reverse rotation.

For some reason In feel that nobody cares about that. One can't change
the porting anyway.

Regards
Rolf Pfeiffer