STi Intake Maniflod length??
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  1. #1
    Fellow Frogger! crosspug's Avatar
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    STi Intake Maniflod length??

    Well, I finally finished gettting everything I want off my wrecking 505 STi.

    Then I sat back and looked at all the bits, what a pain in the damn arse the entire design is.... moon whip

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    While trying to ignore all the black CRAP that was literally falling out of the intake manifold, and the airflow meter that looked like it had been spray painted black (with oil). dead (have photos for later, scary amount of crap in that engine)

    I noticed, is it just me or could someone basically slice off a good 10-20cm off the intake manifolds pipes that lead to the intake valves??? As in shorten the manifold by that much.... Is there a reason that it is as long as it is?? question better performance??

    Would make it a much easier place to work in if it was gone/shortened. deal

    Only reason I ask is now I have a spare manifold head and etc to play with and its more fun than uni work.....

    Jono
    1989 BX16Valve

    "Resting" 1983 505 STi

  2. #2
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    Generally, I have been led to believe that a long manifold produces more mid range power and torque whilst shorter manifolds are used on high revving high horsepower engines. Very vague I know, but its a start!!

  3. #3
    Guru davemcbean's Avatar
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    Yeah, the long length is to give it plenty of low down torque. Which is probably the best feature of the STI motor.

    I fully agree when you say "what a pain in the damn arse the entire design is"

    Dave
    NZ Fleet
    1976 504 Ti
    1984 205 GT twin carb
    1991 205 SI 1.6GTI motor
    1994 106 Xsi
    1996 Mondeo V6
    Aus Fleet
    1955 203C
    1997 Civic Cxi (great allrounder- revy, flexible, nimble, comfortable , economical, simple and durable )

  4. #4
    Gus
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    While what I understand agrees with the previous 2 posts, I can't help but wonder what effect would be due to the ridiculously large (from memory) plenum on the 505 STI.

    It's larger than the GTI plenum, which is big of its own accord.

    I don't know how plenum size, and runner length, interact... but I'd imagine some of the calculation is simply the volume of intake tubing after the throttle body (runner, plenum, or otherwise.) Or not?

  5. #5
    Guru davemcbean's Avatar
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    Gus:
    While what I understand agrees with the previous 2 posts, I can't help but wonder what effect would be due to the ridiculously large (from memory) plenum on the 505 STI.
    One effect may have been unwanted resonance noises at certain revs. Over the lifespan of the STI and GTI they were conastantly trying to make them quieter.

    The first 2 litre STIs in Europe had a plastic plenum, then they changed to alloy, then to the GTI type.

    The first European STIs had a 504 style exhaust back box, then they changed to the triple pipe betweeen the two mufflers style. The first STIs had normal engine mounts, then they changed to the fancy ones.

    They certainly kept trying new things to get them quieter and smoother.

    Dave
    NZ Fleet
    1976 504 Ti
    1984 205 GT twin carb
    1991 205 SI 1.6GTI motor
    1994 106 Xsi
    1996 Mondeo V6
    Aus Fleet
    1955 203C
    1997 Civic Cxi (great allrounder- revy, flexible, nimble, comfortable , economical, simple and durable )

  6. #6
    nJm
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    Was it only the STi and GTi that got the tripple pipe between the two boxes?

    Only reason I ask is my GR has that exaughst on it, while ever other GR/SR I've seen doesn't (and has a skinnier pipe at the end).
    Nick
    1983 Peugeot 505 GR


    "All of its cars from the 1.1 litre 205 through the ugly duckling 309 to the 2.2 litre 505 GTi had a rightness and a righteousness about them that turned every humdrum drive into a journey. Someone, I once wrote, in the bowels of Peugeot understands handling and how a chassis should feel." - Jeremy Clarkson

  7. #7
    1000+ Posts silverexec's Avatar
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    Take a look at <a href="http://www.bluep.com/~eai/PEUGEOT%20EXHAUST.html" target="_blank">European Auto Imports Exhaust page</a>. EAI have scanned their exhaust catalogue so you can see all the exhaust bits for Peugeots, as well as other cars if you go back a page (there are a lot of images so it may take a while to load).

    It would seem that all series 1 505s had the triple pipe setup except for very early GRs and SRD diesels which had the single pipe, and wagons which had a different setup again.

    Richard
    - Richard

    Now: 405 SRI D70 '93
    - 2.0L manual
    Earlier: 505 GTi Executive '85
    - hence "Silver Exec"...
    25 GTX '86
    - manual conversion

  8. #8
    Guru davemcbean's Avatar
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    silverexec:
    It would seem that all series 1 505s had the triple pipe setup except for very early GRs and SRD diesels which had the single pipe, and wagons which had a different setup again.
    That's my understanding too.

    I think the triple pipe may have been one of those things designed to help the STI, but was standardised across the range around the same time.

    Dave
    NZ Fleet
    1976 504 Ti
    1984 205 GT twin carb
    1991 205 SI 1.6GTI motor
    1994 106 Xsi
    1996 Mondeo V6
    Aus Fleet
    1955 203C
    1997 Civic Cxi (great allrounder- revy, flexible, nimble, comfortable , economical, simple and durable )

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