First.... thank you all for joining in... 
The HLA is 17 mm in diameter, making the HLA hole 17.0something in diameter, but surely under 17.1mm... so subtracting 17.1 from 24.5, that leaves us about 7.3mm of unnecessary splitter width. What we don't know is how evenly set the HLA bore is in relation to the two bow-legged intake ports.
Exact HLA placement inside the splitter is as yet not fully determined by me, or a photo or some other evidence I've been able to find. The cut away shown a number of posts above doesn't include the HLA
The view below kind of shows it, and yet it isn't specific. What you can tell in the view below is the HLA does interfere on the intake side, while it appears to not be an issue on the exhaust side.
So, by mathematics there is SOME room along the splitter for removing some material to help "straighten" the port, and remove some of the bow-leg the ports follow. This will help, but my little home made calipers found another problem....
no guessing on this one.... we know the valve is 34mm, the bowl/seat @ 29mm, and now....
Originally Posted by ost
A stock intake port is approximately 27mm (+ or - .25mm) and 100mm long @ that diameter
Think about that for a moment... the port = the throat for nearly 4" of length. The "throat" in an intake port is the narrowest point inside the port, it is designed to help speed up airflow a short distance from the valve. This narrowing also limits reversion(the air/fuel charge "bouncing" off the closing valve and moving back up the manifold). Often times, especially in performance engines, the throat is preceded by a gradually tapering section that goes out to the flange, and it either connects to an intake plenum, or an ITB. The tapering section is similar in principle to a velocity stack. The SR20, having a "throat" 4" long only chokes down the air volume by having a set diameter through this part instead of a tapered diameter. So if, along with straightening out the air passage we can add a taper to each port, in theory, we should be able to see noticeable gains in volume, with minimal loss in velocity.
So lets move on to what all this means.... Intake port - 4 panel as it transitions from stock to "within the lines" = inside "stock" openings - note I have not increased the opening size, I've worked within the original casting, and at no time have worked beyond that. The outermost green dotted crescent highlights that the area just inside the ports edge got the majority of the work, and not the edge itself
Look carefully... in the 2nd view down I diagram what I'm doing. Note the orange dotted line, it shows where I worked the splitter at its widest point. It shows I changed the shape, that I removed a bit more material from the roof and floor of the splitter while taken only a minimal amount from the splitter wall. Remember our measurement of 24,4mm, that is at the narrowest point at the center of the splitter, but do to the extreme arc of the port, the splitter at the roof and floor are closer to 40mm, and with care offer up a LOT of material that can be removed if done carefully... as shown by the time you get to the bottom view.
The other green dotted line/arc show additional areas of material removal. They also begin to highlight the narrowing, and shaping of the splitters leading edge.
So... why did I leave a large section of the port walls untouched?
more to come......
PS - over the next couple of weeks I'll be trying to keep up here, but I have a family issue I need to pay the most attention too... so if I'm not on for a day... 2 or gosh darn even 3... I'm just handling family issues.... I'll be back shortly
The HLA is 17 mm in diameter, making the HLA hole 17.0something in diameter, but surely under 17.1mm... so subtracting 17.1 from 24.5, that leaves us about 7.3mm of unnecessary splitter width. What we don't know is how evenly set the HLA bore is in relation to the two bow-legged intake ports.
Exact HLA placement inside the splitter is as yet not fully determined by me, or a photo or some other evidence I've been able to find. The cut away shown a number of posts above doesn't include the HLA
The view below kind of shows it, and yet it isn't specific. What you can tell in the view below is the HLA does interfere on the intake side, while it appears to not be an issue on the exhaust side.So, by mathematics there is SOME room along the splitter for removing some material to help "straighten" the port, and remove some of the bow-leg the ports follow. This will help, but my little home made calipers found another problem....
no guessing on this one.... we know the valve is 34mm, the bowl/seat @ 29mm, and now....
Originally Posted by ostA stock intake port is approximately 27mm (+ or - .25mm) and 100mm long @ that diameter
Think about that for a moment... the port = the throat for nearly 4" of length. The "throat" in an intake port is the narrowest point inside the port, it is designed to help speed up airflow a short distance from the valve. This narrowing also limits reversion(the air/fuel charge "bouncing" off the closing valve and moving back up the manifold). Often times, especially in performance engines, the throat is preceded by a gradually tapering section that goes out to the flange, and it either connects to an intake plenum, or an ITB. The tapering section is similar in principle to a velocity stack. The SR20, having a "throat" 4" long only chokes down the air volume by having a set diameter through this part instead of a tapered diameter. So if, along with straightening out the air passage we can add a taper to each port, in theory, we should be able to see noticeable gains in volume, with minimal loss in velocity.
So lets move on to what all this means.... Intake port - 4 panel as it transitions from stock to "within the lines" = inside "stock" openings - note I have not increased the opening size, I've worked within the original casting, and at no time have worked beyond that. The outermost green dotted crescent highlights that the area just inside the ports edge got the majority of the work, and not the edge itself
Look carefully... in the 2nd view down I diagram what I'm doing. Note the orange dotted line, it shows where I worked the splitter at its widest point. It shows I changed the shape, that I removed a bit more material from the roof and floor of the splitter while taken only a minimal amount from the splitter wall. Remember our measurement of 24,4mm, that is at the narrowest point at the center of the splitter, but do to the extreme arc of the port, the splitter at the roof and floor are closer to 40mm, and with care offer up a LOT of material that can be removed if done carefully... as shown by the time you get to the bottom view.
The other green dotted line/arc show additional areas of material removal. They also begin to highlight the narrowing, and shaping of the splitters leading edge.
So... why did I leave a large section of the port walls untouched?
more to come......
PS - over the next couple of weeks I'll be trying to keep up here, but I have a family issue I need to pay the most attention too... so if I'm not on for a day... 2 or gosh darn even 3... I'm just handling family issues.... I'll be back shortly
Last edited by oldeskewltoy
on 2014-10-12
at 21-31-39.
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