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intakes

 seperate intake for each valve
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was thinking that as each intake valve on a four valve head is seperate could some advantage be from seperate samller throttle bodies so each one could flow faster and still have the area of one large one. would the valves not benifit from different injector pulse length or even different intake stacks?
—philandpa, Nov 02 2009

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       so widely baked. its a trade off and generally speaking the separate runner design is not able to produce higher total HP, just more torque and higher fuel economy. As to separate injectors: Yes you can achieve more power with twin runners and twin injectors but there is a sacrifice in economy. Not sure how using different resonance for the different valves plays out, everyone seems to use similar runners with different size valves and timing. If you would like to look closely at an engine that uses separate runners for multiple intake valves the Nissan ca16de and ca18de used them with a throttle system to close one runner (the one without the injector) at low load. In my experience fiddling with it made a dramatic difference in fuel economy so it did "work".
—WcW, Nov 02 2009
   

       Yes, toatlly Baked for correct applications (-). The early Taurus SHO motor and one of the Vettes (and probably dozens of others) had valves that would actually switch between single or combined intake runners based on engine RPM and throttle position.   

       The key to best air flow is to get the air velocity just up to a sweet spot of air velocity based on RPM. I used to actually know the number as I designed engines for a crazy guy with a rotary valve patent. I reverse engineered it from looking at dozens of engines. The reason is that you want to match the harmonic of the air which acts like a spring between valve openings. The air rushes forward and then the valve closes and the air compresses against the closed valve then bounces back till it hits the open manifold and bounces again. If designed correctly the compression wave will again hit the valve just as it opens.   

       This leads you to want long narrow intake runners at low RPM and short wide runners at high RPM. So if your engine can flow enough air at high RPM, separate runners are used.
—MisterQED, Nov 02 2009
   

       bone [21Q]'s anno assuming non-English language poster. bun if it is.
—FlyingToaster, Nov 02 2009
   


 

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