Originally Posted by Twibs415
(Post 1505495)
the short turn is so bad
It's my intention to do a minimum of blending from the bowl to the port on the floor side. |
Also miata valve sizes could be bigger but then you need to cut out and knock in new seats and double check piston to valve clearance... money people dont want to spend
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Originally Posted by Twibs415
(Post 1505503)
Also miata valve sizes could be bigger but then you need to cut out and knock in new seats and double check piston to valve clearance... money people dont want to spend
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Originally Posted by burdickjp
(Post 1505491)
I took a casting of a VVT head and then laser scanned the casting. Here it is: https://a360.co/2JKtHkp
Rounding out the flat roof from the injector pocket through to the bowl looks to me like one way to achieve the appropriate change in cross section through the length of the port. Even with filling the floor as an option I didn't see the shape up top as being good. It doesn't look like it has an appropriate change in cross section through the length of the port. So I asked Keegan to do a head with velocity in the lifts we were using as first priority. Ignore peak CFM. The result kicked ass. It also opened up new flow regimes that lead to further experimentation. That led to the +2 exhaust CNC head that we offer now. Let us know how your experiment works out. Meaning, post A/B dynos with no other changes. |
Originally Posted by emilio700
(Post 1505515)
I had the same questions. Our earliest heads (2004) were just cleaned up, bowl blended. Then we started removing material. Several years of failure to improve with several port designs later, I noticed our best area under the curve was with the old cleaned up but basically stock head. Studied more and realized the BP's rod ratio plays a key role in determining intake gas mass hysteresis, peak velocity, avg velocity and ultimately, total flow. Greatly over simplified, high rod ratio (long rod) engines have a sine wave of intake velocity gradients with shallower ramps.
Originally Posted by emilio700
(Post 1505515)
Let us know how your experiment works out. Meaning, post A/B dynos with no other changes.
I appreciate you sharing your approach. |
Originally Posted by emilio700
(Post 1505515)
I had the same questions. Our earliest heads (2004) were just cleaned up, bowl blended. Then we started removing material. Several years of failure to improve with several port designs later, I noticed our best area under the curve was with the old cleaned up but basically stock head. Studied more and realized the BP's rod ratio plays a key role in determining intake gas mass hysteresis, peak velocity, avg velocity and ultimately, total flow. Greatly over simplified, high rod ratio (long rod) engines have a sine wave of intake velocity gradients with shallower ramps. The BP is short, sharp. Turns out it's easier to suck the gas and fill the cylinder through a smaller, higher velocity port than a larger, higher peak flow but lower velocity port. I'm not "engine guy" but the white papers and old school knowledge backed up my speculation.
So I asked Keegan to do a head with velocity in the lifts we were using as first priority. Ignore peak CFM. The result kicked ass. It also opened up new flow regimes that lead to further experimentation. That led to the +2 exhaust CNC head that we offer now. Let us know how your experiment works out. Meaning, post A/B dynos with no other changes. |
Originally Posted by concealer404
(Post 1505538)
What does this actually mean?
Hysteresis = slinky. Someone that knows more about it can dig up the correct terminology. The point is short rods need port and cam designs that do not work with long rods. This is again, something I learned by failing a lot by trying to apply tech optimized for longs rods to the BP. Once I went back to square one and got my fundamental understanding more accurately aligned with the platform, we started seeing breakthroughs. My favorite stuff is the tiny mod/big gain experiments. How we get 170whp out of stock cams and intake manifold kind of thing. |
Originally Posted by burdickjp
(Post 1505504)
Funny enough, Mazda BP and Honda B VTEC heads have the same valve sizes.
I would bet a bp with a reworked floor to decrease the cc of the ports and fix the short turn radius along with as big of valves as possible would make great power. |
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You need one of those supertech heavy double slinkies.
--Ian |
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Valve inclusion angles have also narrowed. The BP has a 50 degree valve inclusion angle, which is rather wide. Narrow inclusion angles create smaller combustion chambers and better squish. They also allow for straighter, taller ports.
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Originally Posted by 18psi
(Post 1505488)
unnatural aspirations
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