RONIN FC

I just wanted to document the difference in runner size between the 13bt and the Cosmo RE. I know that most havent seen the 2 side by side.



Also noted is the upper dowel casting is double that of the S4 TII...

sen2two

damn!!! never seen them side by side!



i need an RE!!!!!!!!

1Revvin7

lol...



believe it or not, the port timing of the the intermediate plate is the only real advantage to those irons...



Even a 13BT's intake ports flow 70% more than the exhaust ports in stock form, talk about the wrong stuff...

RONIN FC

Those sound like made up numbers..



I think alot of people really, Really, miss the objective to runner and manifold design. Not everything is about "flow". Its only part of the puzzle.



And I know this tread will bring controversy...

C. Ludwig

The RE runner is bigger for sure but the picture doesn't tell the whole story. The runners on the RE and REW intersect the manifold flange at an angle while the TII port intersects the manifold flange at a right angle. So while the RE runner is larger is area when measure in a perpendicular plane than the TII runner. It is not as much larger as the pictures make it appear to be. The REW runner is actually pretty close to the same area as the TII in this regard though they look much bigger when viewed in the same manner as these pictures suggest.

RONIN FC

I agree with that for the most part. The angle of the port makes it look larger than it is. But the perpendicular angle isnt THAT great like a 45degree. That hole isnt an unreasonable representation of the runner size.



My scientific way of measuring, was that I can stick three of my fat fingers in the secondaries. I suppose I can insert some dowels to get an accurate comparison. Or maybe even some clay. But i can confidently say that its at least 25-30% larger than the TII.

RONIN FC

DUH!! Or I can use my hole gauges!! I just remembered I own and have yet to utilize.



I will have a measurement soon...

ColinRX7

Flow is sweet but I'm also a huge fan of velocity

mazdaspeed7

Flow is nothing without velocity. Ideally, you want just enough flow to keep the velocity below supersonic. In reality, keeping the velocity that high may cause the pumping losses to be high, so the most power will be found at a velocity lower than that. Ive seen numbers here and there, but they were often based on experience and the numbers varied widely.



Heres some pertinent reading:



https://www.nopistons.com/forums/index.php?...st&p=813881

https://www.nopistons.com/forums/index.php?...st&p=711211

https://www.nopistons.com/forums/index.php?...st&p=711615

RONIN FC

Hmm, me too! Well how about that?... We should start a club.







The same reasons Mazda built the engine that way, are the same reasons I want it that way... Ever consider the combined runner volume of the 6-port Renesis?



And heres a tidbit for some of you to gnaw on, Port timing, size, and duration have just as great effect on velocity as does runner diameter. Runner size isnt the only way to manipulate inertial effects.



But back on track, I would like to keep this thread as just a physical comparison between motors. Not particularly interested in theories on what is great and what is not. Cause ive (and im sure most everyone else has) read them all, and then some.



It would be much appreciated if anyone has any runner measurements to contribute to the thread. From wall to wall, floor to ceiling. Primary and secondaries.