From my understanding the reason why there is a difference in the port size on the intake than the engine is due to trying to limit reversion. I read on the rx7club forum a while back: "Mazda left the intake manifold runners smaller than the block to help stop reversion of the intake charge back into the intake manifold. That tiny lip was actually designed for a reason."
That is what I read, too. It's a complex topic I don't fully understand, but from reading the forums, it sounds like it was to address reversion, and increase velocity on stock 12a setups. Although the difference I'm referring to isn't that small, it's considerable, about 20mm taller on the iron than the manifold - there's some footage in my porting video about it. I have read theories that the reversion and velocity loss arguments only apply to carburetors that actually have separate primary+secondary operation, which, I don't think the sniper does - AFAIK it's firing all four in unison, at least with the stock linkages. I do wish I realized that small manifold ports meeting up to big iron ports was a normal setup, as when I received my manifold I just saw it as a big setup mistake, not an intentional thing, and 'fixed' it without reading enough. It would have been nice to run it as-is to see if I was happy with it, but I guess we're just sending it lol This is what makes me feel a little better, from the forums... "I know when the subject of port matching comes up everyone says not to do it because of reversion and velocity loss. I have read those discussions with flow testing results by Paul Yaw, RotaryGod, Jeff20B and many others who I respect. But both RB and RaceCast tell me that doesn't really apply to Weber since they are "always on" and flowing through all 4 ports. The small primaries on a 4 bbl (which is what most port-match threads are about) affect low speed throttle response and vac secondary operation, but go out the window when using an IDA or DCOE"
@@nickshimondle2105 Of course, and hey, I don't even know if my understanding is correct so I appreciate the opportunity to chat about it! We'll see how well it works out in a few weeks when we fire it up. And thanks!!
Great video! I love how we've run into the exact same issues at almost exactly the same time haha I sent my sniper 2 back and went with a different unit. (It has a little more fine tuning in the software). I think I want to build a 13b in the future for myself as well. Subscribed!
awesome video!!!
nice one interested to see how it runs
From my understanding the reason why there is a difference in the port size on the intake than the engine is due to trying to limit reversion. I read on the rx7club forum a while back: "Mazda left the intake manifold runners smaller than the block to help stop reversion of the intake charge back into the intake manifold. That tiny lip was actually designed for a reason."
That is what I read, too. It's a complex topic I don't fully understand, but from reading the forums, it sounds like it was to address reversion, and increase velocity on stock 12a setups. Although the difference I'm referring to isn't that small, it's considerable, about 20mm taller on the iron than the manifold - there's some footage in my porting video about it. I have read theories that the reversion and velocity loss arguments only apply to carburetors that actually have separate primary+secondary operation, which, I don't think the sniper does - AFAIK it's firing all four in unison, at least with the stock linkages. I do wish I realized that small manifold ports meeting up to big iron ports was a normal setup, as when I received my manifold I just saw it as a big setup mistake, not an intentional thing, and 'fixed' it without reading enough. It would have been nice to run it as-is to see if I was happy with it, but I guess we're just sending it lol
This is what makes me feel a little better, from the forums...
"I know when the subject of port matching comes up everyone says not to do it because of reversion and velocity loss. I have read those discussions with flow testing results by Paul Yaw, RotaryGod, Jeff20B and many others who I respect. But both RB and RaceCast tell me that doesn't really apply to Weber since they are "always on" and flowing through all 4 ports. The small primaries on a 4 bbl (which is what most port-match threads are about) affect low speed throttle response and vac secondary operation, but go out the window when using an IDA or DCOE"
@@GilesVessey very good point. I realize my mistake as I have the carburetor mentality.
Thank you for your response, and your project is awesome!
@@nickshimondle2105 Of course, and hey, I don't even know if my understanding is correct so I appreciate the opportunity to chat about it! We'll see how well it works out in a few weeks when we fire it up. And thanks!!
Great video! I love how we've run into the exact same issues at almost exactly the same time haha I sent my sniper 2 back and went with a different unit. (It has a little more fine tuning in the software). I think I want to build a 13b in the future for myself as well. Subscribed!
Thanks man! By the looks of it I gotta check your channel out, I'm curious to see what you're up to!
@GilesVessey Hell yeah! Probably be struggling with trying to tune a rotary with a sniper efi or sniper like efi at the same time haha
How much for the air cleaner?