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Tuned intake length

Discussion in 'Normally Aspirated Forum' started by RobT, Jan 16, 2007.

  1. RobT

    RobT Full throttle trip

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    different from airbox resonance - this is about length of intake from a rampipe to valve

    http://www.eng-tips.com/viewthread.cfm?qid=165529&page=3

    for an excellent selection of articles

    ballpark calculation is

    90 / (rpm/1000) = tuned length

    eg. torque peak at 7000 rpm, 90/7 = 12.86" or 321mm

    my DTH TB setup is 270mm = 10.8" so theoretically tuned for 8300rpm - could do with being a lot longer to bring tuned length of intake into play in normal operating rev ranges but is restricted by bonnet clearance

    it would be nice to have a slug of extra torque at about 5000rpm but for this the length would have to be 450mm....increase of 180mm over now....no chance
     
  2. R French

    R French Full Member

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    Hi Rob,
    Had a think about this for a while and all the kit cars ran with a front mounted air intake via what I am assuming TB's. See photo on link: http://www.rallycarsforsale.net/photos/p38827n3.jpg

    So - do you think this looks OE enough to get away with the "maintain the standard plenum chamber and throttle body" bit in the blue book??????
     
  3. RobT

    RobT Full throttle trip

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    not a chance mate - the kitcars dont have a plenum chamber as such, but like you say are single tb per cylinder
     
  4. F2 Stu

    F2 Stu I. Am. Legend.

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    eng-tips.com is a great site of all sorts of randon stuff!

    I have 2 plots on different rollers which are .03 within each other on HP but torque figures way different

    Awesome's plot peaks at 7k whilst AMD's peaks at just before 5k, If I stick to AMD's plot my runner length would be 18"!
     
  5. ibizacupra

    ibizacupra Jack-RIP my little Friend
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    in my experience, the longer I made my induction tract the more torque it made and from lower rpm.
    120mm airhorns, + 45mm spacers on the DTH bodies, with my airhorns cut and welded to duck under the bonnet line so additional length could be accomodated

    300mm was what I was told by a guy I met years ago as a good guide starting point.. from back of valve to end of rampipe.

    testing will confirm, and engine specs with vary this
     
  6. Suti

    Suti Guest

    thanks for link, really useful
     

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