"Giffen A. Marr" wrote:

Paul
That's what I thought, but you finger must have slipped on the 3rd rotor as
it is aligned with the second at 210 deg.
Giff

-----Original Message-----
From: root@mxsf19.cluster1.charter.net
[mailto:root@mxsf19.cluster1.charter.net] On Behalf Of ACRE
Sent: Sunday, December 12, 2004 1:01 PM
Subject: Tuning engines

Here is how to relate piston engine tuning to rotary engine
tuning. Basically the equivalent rotary port timing to a piston
engine is the rotary opens its port roughly half as often so the
runner length is roughly twice as long. Roughly speaking the
piston engine port is open 90 degrees while the rotary port is
open roughly 270 degrees. For all practical purposes the rotary
port is always open 80 or 90% of the time while the piston port is
only open about 25% of the time. The same port  feeds three rotary
combustion chambers but the piston port only feeds one combustion
chamber.

The thing that frequently fools the piston engine guys is going to
a smaller runner lowers the RPM at which peak torque occurs. This
they like as they need torque down low. In fact it actually
narrows the torque band slightly.

If you were experimenting on a dyno the only adequate way to tune
the engine properly is with three different diameters of runners
and three different lengths of runners. That is nine combinations.
Other than the car manufactures none of the after market tuners
are doing this to my knowledge. I am certain Mazda did it with the
Lemans engine and choose 2 inches as the largest dia. pipe they
could get in there.

The chart below only shows six possible combinations and no pipes
at all.


Paul Lamar

Can ram air be ignored since it is the same in all combinations?

I will build two intakes for side by side testing.   Problem is I don't
have a dyno.   Static performance should tell something.    Jerry

Which two have you decided to try?

I don't know what you mean by "ignored". It is like flying below sea
level
:)

Static performance will only tell you what the HP is at static RPM.
Not what you want to know  unless you fly out of short fields all the
time.

In fact good static performance probably implies less than good
performance at climb or top speed.

Paul Lamar

"Giffen A. Marr" wrote:

How does the chart change for a 3 rotor? I assume that the port timing
would now be split between the 3 rotors. Giff Marr

Which chart is that Giff. The Bill Marvin Timing gif?
Assuming that is what you are talking about I cut and pasted it to a 3 rotor
form with the rotors equally spaced around the eshaft at 120 degrees.

If you think the two rotor is smooth you should feel a three rotor :)

Paul Lamar

"Giffen A. Marr" wrote:

Paul
That's what I thought, but you finger must have slipped on the 3rd rotor as
it is aligned with the second at 210 deg.
Giff

Opss. Paint does not have lines. This is approximate.


Paul Lamar

 
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