Aggressive street port effect on vacuum and compression?
On a stock engine that produces let's say 17 inHg at idle, what will the vacuum be after the street port?
What will be the effect on cranking compression? 5%, 10% drop? |
mine seems lower than most at about 105 110 on used housings and sideplates. Normaly it seems like it is more around 120 but who knows. There are so many different factors that can be affecting things. Oh and my vac is only 13 at a grand or so, Definitely low but the compression is good hmmm.....
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Originally Posted by yourmom23
(Post 10519165)
mine seems lower than most at about 105 110 on used housings and sideplates. Normaly it seems like it is more around 120 but who knows. There are so many different factors that can be affecting things. Oh and my vac is only 13 at a grand or so, Definitely low but the compression is good hmmm.....
Mine is an FC-TII and producing ~78 psi cold. But from the sound of the pulses, doesn't seem it's cranking over 200 RPM. Spec when warm is ~85 psi @ 250 RPM.(Recently, I took a reading w/ the upper manifold off and I swear I saw ~105 psi being hit. Now I think I was hallucinating!!) Is the stock compression spec @ op-temp on the FD > 120 psi? Or is 120 what others are seeing w/ the aggressive street port when cold? Regardless, if op-temp spec is > 120, it's amazing when compared to the spec of the FC-TII w/ just 1/2 point lower compression ratio. I wonder if the cranking RPM is considerably higher on the FD? |
That was warmed up. If you think about it technicaly the compression shouldnt change no matter what port it is, cuz the compression is not even near the intake or exhaust?
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Originally Posted by yourmom23
(Post 10520450)
That was warmed up. If you think about it technicaly the compression shouldnt change no matter what port it is, cuz the compression is not even near the intake or exhaust?
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yeah compression stays the same check out this
https://www.rx7club.com/showthread.p...ession+numbers |
Originally Posted by yourmom23
(Post 10522231)
yeah compression stays the same check out this
https://www.rx7club.com/showthread.p...ession+numbers |
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