Lynn,
The question was on inlet velocity for a Mazda rotary at 7,500 rpm
- if you happened to have some info on that.
Everyday cars have 450' per sec and race cars 125' per second,(
suggested on a carb site) Ed's calculations used 176' per
second which indicated a bigger inlet diameter. I was thinking about 300
to 350' per second would more like it, but I have no real hard
data!
Well then let me speculate.
The engines have two RPM where they wander above 100% VE. These are
too low to help us much but the car designers use this and stretch it
out a bit looking at the pipe organ intakes.
Just off idle and about 2,000 RPM. This confuses the idle and
transition circuits in the Weber and you get a
nice Rumppp...Rumppp...Rumppp. Breathing is very good compared to a
piston engine, and runner diameter is small for any HP output. The stock
intake manifold gasket in my engines (Daryl Drummond) is barely enlarged
at all. The new engine may have more than two such RPM.
Porting extends the intake open time and makes for a more turbine
like flow. Even a street port can nearly double the stock HP, and that
would require nearly double the stock airflow. Down low the race or even
street ported engine has little advantage over the stock engine. For any
RPM the air flow determines the HP output, so where (RPM) you are
interested in output there will need to be dramatically improved
airflow.
So generally, the displacement times the RPM minus some percentage
for inlet restriction based on TP size or carb choke size and or runner
length and diameter will be the stock situation and one CFM value.
And in a modified intake system with longer runners of slightly more
diameter which will favor the same RPM as the stock example
engine will have very much more power than a stock engine at the same
RPM, indicating a much higher than stock (CFM) air flow. Maybe not over
100% VE but much closer to that number than the stock engine.
There is no cheating possible here. So if your example engine is
compared to any other engine with more power at the same RPM. The higher
power output requires very much more airflow, not less.
Something is amiss Watson.........I can feel it!
Lynn E. Hanover