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BDC:what's the purpose of going straight instead of back cutting it?

Ha no flaming on this thread!. The ports look good, thinking about the back cutting as the port starts to open there is only a small volume between the housing and the rotor so the flow has to basically come through 90 degrees so it is parallel to the housing surface, to me it would seem that to get the best flow here you would want as smaller radius as possible while still keeping the flow attatched to the inside radius of the port wall. further through the inlet cycle the flow does not have to bend around as much as so back cutting may be benificial to flow towards the top of the port. there is also the consideration of how the flow from the bridge port interacts with the extended primary as opposed to to a full bridge port.



now bear in mind that these are only my theories so may be completely wrong

If doing half bridge is not for flow, what is it then for? For sound?

The ports work dramatically well without doing any backcutting just like this, guys. If you don't believe me, do them yourselves and you'll see. https://www.nopistons.com/forums/pub...IR#>/smile.png



B

are there any advantages to not back cutting? or do you just feel that its indifferent whether or not back cutting is done?

I've been thinking about this bridge port without the back cutting alot lately. From my view is that it probably doesn't matter a whole lot when it comes to engines running boost simply because the air is getting stuffed into the engine regardless and air will be forced through that hole whether it is back cut or not. I always back cut my bridge ports but these all have been for N/A motors and the difference in flow with N/A ports might be more noticeable when not back cut. From memory BDC is making some good HP numbers with these ports and they are not back cut so he must be doing something right. Also a question for BDC have you done any full bridge turbos? I'm thinking of doing one in the future small bridge towards the top of the port and minimize the overlap.

excellent work. should make quite a fun motor. i can't wait to see the results.

i am especially fascinated with the exhaust ports. how do you get the sleeves so smooth? if this is something you're not comfortable discussing, i understand, but if you don't mind, please do tell.



thanks.

[quote name='diabolical1' date='Aug 19 2005, 06:26 AM']i am especially fascinated with the exhaust ports. how do you get the sleeves so smooth? if this is something you're not comfortable discussing, i understand, but if you don't mind, please do tell.



thanks.


[/quote]



I just mainly cleann them up by sanding them down, then scuffing them, then usually polishing them afterwards.



B