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
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