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