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| What are the advantages to a dual port intake? https://www.slantsix.org/forum/viewtopic.php?t=19041 |
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| Author: | Reed [ Sun Aug 06, 2006 9:02 am ] |
| Post subject: | What are the advantages to a dual port intake? |
I recently discovered dual port intakes and the claim that they offer better fuel efficiency that dual plane or single plane intake. True? False? Any other benefits to dual port intakes? Is it all lie? Thanks! |
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| Author: | AndyZ [ Mon Aug 07, 2006 3:57 pm ] |
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What does a dual port look like. I havn't heard of these. |
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| Author: | Reed [ Mon Aug 07, 2006 4:17 pm ] |
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I have only recently learned about them, and i have only found them for Ford inline sixes, Volkswagen air-cooled motors, and v-8s. Here's a link: http://www.offyparts.com/product_info.p ... 53bd63a562 Here's a picture:  The theory is that the primaries on the carb feed the smaller tubes, and the secondaries feed the larger. Supposedly this give better fuel economy and low end torque. B.S.? |
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| Author: | dakight [ Mon Aug 07, 2006 5:48 pm ] |
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I can only make an educated guess, but with the smaller runners the air/fuel mixture will maintain higher velocity which should help to keep the fuel from separating out of the mixture. The increased stream velocity should also help to better fill the cylinders during the intake stroke. |
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| Author: | JDS [ Tue Aug 08, 2006 11:36 pm ] |
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i had a ford/mazda V6 once that had a similar style intake, only the large runners actually had vacum controlled butterfly style valves to close them at low RPM and open at high, this was an EFI engine but with the valves ziptied open there was a huge difference on the bottom end.. |
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| Author: | AndyZ [ Wed Aug 09, 2006 8:02 am ] |
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Now that I see it, it looks familiar. Someone made this type for the Jeep Inline 6 and from what I remeber the reason was better throttle response at low rpm because of higher velocity through those smaller primary runners. I guess the trade off is smaller total runner volume which will hurt at higher rpm on racing engines. |
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| Author: | steponmebbbboom [ Thu Aug 10, 2006 6:20 pm ] |
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Quote: I have only recently learned about them, and i have only found them for Volkswagen air-cooled motors,
Not the same thing. Single versus dual port only referred to the opening on the cylinder head. On the single port, the intake ports were siamesed in the head, on dual ports they were siamesed on the intake runner. Single ports had better low-end velocity which resulted in better low-end torque, which especially suits them for a bus application, whereas the dual port has better high end velocity, which makes them ideal for a bug.
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| Author: | kesteb [ Thu Aug 10, 2006 6:56 pm ] |
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Those are Offy manifolds designed in the early '70s for the first gas shortage. Yes they worked, or at least the car magazine tests showed that they worked. I don't think one was ever developed for the \6. Edelbrock at one time made a SP2P style manifold for the \6. Long out of production. Same idea, differant design. |
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| Author: | SlantSixDan [ Thu Aug 10, 2006 7:02 pm ] |
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Quote: Edelbrock at one time made a SP2P style manifold for the \6.
Really?! Cool! Got any old ads or spec sheets or pictures...or maybe just a description? What was it, a 2bbl or a 4bbl or??
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