16v Exhaust problems
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  1. #1
    Member Tim Tech's Avatar
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    Icon10 16v Exhaust problems

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    16v Exhaust Systems

    Citroen Sport International was contacted throughout 1992 as to information concerning the standard exhaust system used on the Citroen BX 16v. As we all know the exhaust manifold is a work of art, but the Australian Citroen Racing Team was trying to work out why they were not able to develop more HP's when designing and testing new exhaust systems for their racing BX 16v's.

    Many attemps and long hours were waisted with experienced exhaust engineers on dyno's across sydney tyring to work out how the standard system was so good and why they were not making considerable gains in hp's

    Several different designs were tryed, such as:
    - 3 inch pipe from manifold (no cat) straight to rear of car
    - 3 inch pipe from manifold (cat) out the left side of car
    - 3 inch pipe from manifold (cat) straight to rear of car

    The head development engineer from Citroen Sport was contacted (who designed the 16v's exhaust) revealing that it took over 4.5 months of testing and design to create the perfect standard exhaust system. The secret lies in the centre pipe. This is a special progressive pipe which holds a "venturi effect" within its design. This pipe was specially designed to the exact length and diameter. The pipe is 4mm larger in diameter before the rearward 45degree bend than it is at the start of the manifold join.

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    Citroen Australia was told that in NO way were they to modify or replace that pipe. Being progressive the pipe created a venturi effect sucking the gasses from the system and whilst not disturbing the engines exhaust harmonics and gas flow. They were told that they could do whatever they like to the system past the centre pipe but nothing else.

    This was done by simply welding a joiner pipe by-passing the centre crossways muffler and using the stock tailpipe and rear muffler.
    To the amazement of the crew 8kW was gained and 12Nm of torque


    This shows once again the superiority of Citroen design and engineering and why the 16v will live on as a supercar throughout the years!!!!

    Tim Tech

  2. #2
    1000+ Posts PeterT's Avatar
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    Quote Originally Posted by Tim Tech
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    16v Exhaust Systems



    This was done by simply welding a joiner pipe by-passing the centre crossways muffler and using the stock tailpipe and rear muffler.


    Tim Tech

    You've lost me here. Are you saying they replaced the cat with a straight pipe? Or the resonator that sits behind the cat? My experience has been that the Mi16 pipe is twin skinned to reduce noise levels. Replacing the twin skinned pipe with a regular 2.25" pipe and resonator helps. Also, on Mi16's the std. exhaust was flattened considerably around the rear suspension. Replace this with a mandrel bent curve. The rear muffler needs to be a genuine 2.25", straight through, but 21" long and 6" diameter to avoid drumming. Get all this right, and you'll find the kW and Nm, with an acceptable non-ricey noise level.

    '92 205 Mi16
    '90 Mi16x4

  3. #3
    1000+ Posts parry's Avatar
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    Pete, any recommendations for my 205, what will help it breathe a tad better?
    90 205 Gti Cherry Red(Track Car)
    2009 207gti
    1985 505gti (Shitbox Rally) Sold

    PBs:

    Oran Park: 1:27:9
    Wakefield: 1:05.6 (July 2015)
    Eastern Creek: 1:54 (8v) 1:48 (16V)
    Mt Huntley: 34.44 (2004 stock 205)
    Ringwood: 35.06 (30/10/2005)
    Winton: 1:33.6 (2017)

  4. #4
    Budding Architect ???? pugrambo's Avatar
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    was it peugeot or citroen that designed this engine ??

    i know i have heard rumours that the XU10J4RS engine was a citroen engine that was shared between the GTi-6 and the Xsara but i thought the engine from the Mi-16 was a pug engine that was shared between the Mi-16 and the BX 16V

    i would imagine that both sides of the camp would have put the effort into getting whatever engine they were using to run nicely in either make and that they are one in the same company
    3 x '78 604 SL

    1 x '98 306 GTi6

    1 x secret project

    1 x '98 406 STDT troop carrier and i don't care if it stinks, i don't sniff it's arse Death by wank tank

    1 x '99 406SV 5spd wagon, time to burn more fuel

    1 x 1994 605 SV3.0


    WTD long range fuel tank for 605

  5. #5
    1000+ Posts PeterT's Avatar
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    Quote Originally Posted by parry
    Pete, any recommendations for my 205, what will help it breathe a tad better?
    You don't need any more power, but all's fair in love and war. Anything to topple the Wuillemins. Do it similar to your 205, but you'll have to use a different shape rear muffler.


    I always thought the XU9J4 was a Pug design too, with roots dating back to the turbo 205.

    '92 205 Mi16
    '90 Mi16x4

  6. #6
    Moderator Alan S's Avatar
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    The first couple of paragraphs of this kind of answers that question, but I won't give any clues as to who it was:

    http://www.citroenz.com/BX/twin.html


    Alan S
    If it ain't broke, use a 12" shifter.....that usually does the trick!!

  7. #7
    1000+ Posts bowie's Avatar
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    nice read..

    so if the inlet and exhaust manifold are so well constructed on these vechiles.. just how do you pull more power from them..

    Works: 2003 YV Commodore (That is Cecil to you)
    Playing: R12, SuperPos, thinks It's a race car and Sunny the R12 Lego set.
    Previous: SuperGrumpy fuel spitting 504ti(ish), SuperComfortable 505 STI, SuperDoper carried my groceries Mi16, Choo Choo'd Volvo S40
    Wanted Will hoard 12/15/17 Junk.

    "More and more of less and less" - Marina Abramović

  8. #8
    1000+ Posts bowie's Avatar
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    sorry dont bother replying to that... read all about those lovely Cams and cats.. lol

    Works: 2003 YV Commodore (That is Cecil to you)
    Playing: R12, SuperPos, thinks It's a race car and Sunny the R12 Lego set.
    Previous: SuperGrumpy fuel spitting 504ti(ish), SuperComfortable 505 STI, SuperDoper carried my groceries Mi16, Choo Choo'd Volvo S40
    Wanted Will hoard 12/15/17 Junk.

    "More and more of less and less" - Marina Abramović

  9. #9
    Fellow Frogger! sproose16v's Avatar
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    Dam right! Best car ever!
    1989 BX 16 Valve Mk1 - SOLD (And Missed)
    http://www.bx16v.cjb.net
    1992 R32 GTSt Skyline

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