Just one of my random thoughts. Anyways it would seem to me that the higher the compression ratio the higher the air velocity would be in the intake ports. Take the comparison of a motor with a 4:1 compression ratio and one with a 10:1 compression ratio as an example.

With the 10:1 compression ratio motor the vacuum would be created more quickly by the downstroke of the piston than on a low compression motor. So if an aluminum head motor can have a one point higher compression ratio than the port velocity would be slightly higher than on a comparable iron head motor.

So if this is true than a aluminum head motor could run a slightly larger port size and still retain the same port velocity as an iron head motor. Time for another beer.

 

I'm going to throw more variables your way like RPM and piston speed. What effect will that have on pressure in the cylinder?

How about valve timing and how that plays on static compression.

Lastly, when does the compression stroke occur in relation to intake valve opening and closing?

What is the basis of your thought?

 

Make that "two beers".

Purse-in made some points you should really start thinking on.... maybe after the beer wears off.

-Mindgame

 

I agree variables would play a role. However if everything was kept the same except the cc's of the combustion chamber hence compression ratio it would seem to me that the smaller the size of the combustion chamber the higher the intake port velocity for any given rpm.

IMHO opinion this would give a slight advantage of the aluminum head over the iron head because of the ability to run a higher compression ratio without detonation. This would allow the aluminum head to have the same port velocity as the iron head but with a slightly larger size intake port. So more horsepower.

 

Your thinking along the right lines.... but it's not compression it's cubes that you are thinking about.

Then throw in how fast that all happens.

Bret