Old Grey

Here are some links to Airflow testing I did years ago, if anyone is interested.



The velocity graphs are calculated from the airflow passing through the runner area, the smaller the port, for the same airflow, will show higher on the graph



Flow of std primary ports

http://photo.livevideo.com/photo/allsize.a...AC6E&size=o



Velocity of std primary ports

http://photo.livevideo.com/photo/allsize.a...B18C&size=o



Flow of std secondary ports

http://photo.livevideo.com/photo/allsize.a...A508&size=o



Velocity of std secondary ports

http://photo.livevideo.com/photo/allsize.a...E007&size=o

PDF

Interesting. Its good to see some hard data with comparisons. Were the cosmo irons JC? If so, that would explain the low velocity. Where abouts in the port or runner was the air speed probe positioned? Was it the same position for every test?



You can really see the late port closing of the 6 ports.

You can also see why people had great success with 3B irons in the past.

Old Grey

The Cosmo was a sedan just before the S6, it's basically a S6 13B with very large runners, I think they are like the 20B. Mazda realised their mistake and made the ports smaller in the S6



The velocities are "calculated" from the CFM and the runner area. Pitot testing was not that common back then(10yrs ago), I've only started using pitots for velocities in the last 2yrs



Another point of interest is comparing the 3B RX3 small centre port to the very large(tall) RX5 centre. The RX5 centre is the same as the early RX7 large centre ports. I didn't have a std tall port centre plate and had to use a mild ported one. You can see from the graph it opens 10º before and closes 10º after the 3B plate .If you subtract these points and put it back to a std timing plate the flow would be the same as the 3B plate



Another point is the S2 RX7 port, the port has a very flat turn that directs the flow straight into the rotor face ,the rotor face hurts the flow, thats why the curve has a dip at the top. After this port Mazda made all their ports with large late turns to direct air 90º from the plate face so they are not shrouded by the rotor. Mazda's best flowing ports have the late large turn, S4, S6. The best of the 12A plates is the 12A Y Turbo plate, it has the best shape. It doesn't look that good on the graph because it closes at 40º if opened up to the std 50º closing point it would flow more than the S2 and not have a dip.

j9fd3s

very cool! so based on that, the best motor would be something like a 3b centre with 6 port outers?

Kenku

Not familiar with the 3B irons, what are they from other than the RX-3, or is there not that much of a difference from the S2-S3 stuff after porting? Also, would the earlier centers (S2-S3) still be superior to the later centers (S4-S5) even after both were ported? I suspect I know the answer to the second is yes, but wanted to throw it out. Finally, is the "6PI Aust" flows for both the aux and secondary ports on the 6 port irons, or just the aux ports? It looks like it pretty much has to be both, but want to be sure.



Thank you very much for posting this stuff; been wanting to see flowbench numbers, but as far as I know noone's ever posted this kind of data.

Old Grey

I would think 3Bs are close to S1



The 6PI is with secondary and aux ports



Here are some pictures of what ports look like inside



Primary centre plate

http://photo.livevideo.com/photo/allsize.a...C002FDD93609E7E



Secondary ports

http://photo.livevideo.com/photo/allsize.a...8B6752448AA2173



Notice how the S6 and Cosmo ports turn up in the plate to match the manifold making the turn more gradual and the actual port area is smaller than the large opening at the manifold suggests

j9fd3s

thats really neat.

Old Grey

Here is a flow graph of a PP Vs BP Vs std 12A turbo



http://photo.livevideo.com/photo/allsize.a...2378&size=o



Calculated Velocity in the runner



http://photo.livevideo.com/photo/allsize.a...8604&size=o



Looking at the PP flow graph you have to account for the BP and std 12A being only one(secondary) port. When you add the primary port the flow will go up about 80%, just imagine the curves are 80% higher and the same timing(width)



With the velocity graph when you add the primary port you have to imagine the curves to reduce in height by about 80% due to the extra area



Look at when the PP opens, even though the port opens at 100ºBTDC it takes 30º before the flow has the potential to start in earnest, even though it probably doesn't

Always remember the flow is mainly dictated by the rotor demand, even though the port can flow 270cfm @ TDC (T on the graph) the chamber will be at it's smallest and there will be little flow because the rotor is not asking for any flow. There will actually be slight flow due to pulse tuning etc.



With the PP the flow seems to be a direct correlation with area, ie increase area by 10% and flow goes up 10%



The BP EYE lines are tests on the size of the eyebrow notch in the Alum housing which uncovers the bridge of the BP, ie BP=4 EYE is a 4mm chamfer in the housing, 10 EYE 10mm chamfer

PDF

Nice. You must've done a fair few hours of testing! According to my gas velocity chart the PP diam is around 44mm. Close?

Ranzo

so by this test a bridge port does not increase cfm over std ports?? or am I just looking at this all wrong.