Alan,
I was wondering given the final diameter selection of the inlet

manifold,

what other diameters were tried ( to your knowledge) and what was the

result

of those trials.

The 2" on the Le-Mans definitely gives better breathing and more power

and

some heavier Aircraft may require this extra power.
The extra weight might mitigate the 'higher RPM on landing' effect.

However my concern is, as you say, this effect on lighter aircraft, in

that

it may cause float - when you don't want it!
There would be nothing worse than having to decide whether to cut the

engine

or not, if there was a possibility of  a need to go-around.

At the end of the day, everyone's opinion may be correct and it well may
just boil down to 'horses for courses'. The trade-off may be as simple

as

lower max power ( for take-off and cruise) for lower idle RPM

Do you have an opinion ?
George (down under)

Where did you come up with 'higher RPM on landing' effect. ?

If the P-port can idle as low as 2000 RPM and they can that is
714 prop RPM. My O-470 can barely idle at 700 RPM.

Also Allan was using mechanical fuel injection and staged electronic
injection is much better at controlling the engine at low RPM.
Tracy's engine will idle at 650 engine RPM and 230 prop RPM.

Paul Lamar

Paul,
Sorry - your right about the prop speed.
I'm thinking too hard and getting myself confused.
My apologies!!
George ( down under)

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