16v Cylinder Head Facts
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  1. #1
    Member Tim Tech's Avatar
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    Icon10 16v Cylinder Head Facts

    Bx 16v Cylinder Head Facts

    I late December 1991 a quest by the Australian Citroen Racing Team was made to see what developments (improvements) could be made to the cylinder heads on their Citroen BX 16v Production Race Cars.

    A stock, used head with inlet and exhaust manifolds was sent to Yamaha Racing Australia for evaluation. Conducting the tests was renowned Yamaha Racing engineer Chris Dowed who has been at the head of Yamaha's GP Bike Developements for the past 10 years.

    The main objectives of these tests were to find if any performance improvements could be made to the head package whilst still using the cylinder heads stock internals (eg: cams, valves etc.) as per cams. regulations.

    The head was tested first on flow bench and also tested for Volumetric effeciency and valve duration. The head was returned with one simple comment ......"You will not find any better than that"!!

    The heads flowbench rating was 94%
    Flow restriction 11.6%
    Volumetric Efficency was 87%


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    Not bad for what is supposed to be a stock, de-tuned engine for road purposes

    As we all know there have been improvements done to these cylinder heads (ie: bigger inlets etc) but these test truely show testament to Citroen's engineering expertise and knowledge!!

    Tim Tech

    P.s: Throughout the use of the XU9J4 motor within 2litre sportscar racing internationally, not one team used anything but the stock Exhaust manifold proving its excellence in design and strength

  2. #2
    1000+ Posts PeterT's Avatar
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    Quote Originally Posted by Tim Tech
    Bx 16v Cylinder Head Facts

    I late December 1991 a quest by the Australian Citroen Racing Team was made to see what developments (improvements) could be made to the cylinder heads on their Citroen BX 16v Production Race Cars.

    A stock, used head with inlet and exhaust manifolds was sent to Yamaha Racing Australia for evaluation. Conducting the tests was renowned Yamaha Racing engineer Chris Dowed who has been at the head of Yamaha's GP Bike Developements for the past 10 years.

    The main objectives of these tests were to find if any performance improvements could be made to the head package whilst still using the cylinder heads stock internals (eg: cams, valves etc.) as per cams. regulations.

    The head was tested first on flow bench and also tested for Volumetric effeciency and valve duration. The head was returned with one simple comment ......"You will not find any better than that"!!

    The heads flowbench rating was 94%
    Flow restriction 11.6%
    Volumetric Efficency was 87%


    Not bad for what is supposed to be a stock, de-tuned engine for road purposes

    As we all know there have been improvements done to these cylinder heads (ie: bigger inlets etc) but these test truely show testament to Citroen's engineering expertise and knowledge!!

    Tim Tech

    P.s: Throughout the use of the XU9J4 motor within 2litre sportscar racing internationally, not one team used anything but the stock Exhaust manifold proving its excellence in design and strength
    I didn't realise Citroen were responsible for the design of the XU9J4 head.

    '92 205 Mi16
    '90 Mi16x4

  3. #3
    1000+ Posts Dave's Avatar
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    Thanks for that Tim, that validates much of the discussion we have had here on the board about the 16 Valve heads ability in standard form.

    Keep up the good work,



    Dave


  4. #4
    Cal
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    Quote Originally Posted by PeterT
    I didn't realise Citroen were responsible for the design of the XU9J4 head.


    Thanks for the thread though. Interesting indeed.

    Cheers,

    Cal.
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  5. #5
    1000+ Posts Dave's Avatar
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    From what i have read in the past the Xu9J4 head took 6 years to develop and is an evolution of the 205 T16 head. Dont know the accuracy of this info, i will let you know if i find otherwise.


    Dave


  6. #6
    Fellow Frogger! sproose16v's Avatar
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    I didnt have a clue either but have done some reading around and actually had my head taken off when i did the head gasket, sent it to a mate who is an engine fabricator and he said that he could really port or polish it. Well he could of but like only a tiny tiny bit. They are an anwsome head, i love good head.
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  7. #7
    1000+ Posts PeterT's Avatar
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    Quote Originally Posted by sproose16v
    I didnt have a clue either but have done some reading around and actually had my head taken off when i did the head gasket, sent it to a mate who is an engine fabricator and he said that he could really port or polish it. Well he could of but like only a tiny tiny bit. They are an anwsome head, i love good head.
    The Mi16 head is so good in fact, that without the aid of a flow bench, you'll probably go backwards. I wouldn't let mine anywhere near your average head shop.

    '92 205 Mi16
    '90 Mi16x4

  8. #8
    Moderator Alan S's Avatar
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    Peter,

    I think (my) Brad may have told you & I know I actually posted the results of his head when it was tested up here by a guy who does a few of the top V8 supercars and a few of the top dragster engines that when he put it on the flow bench, it showed figures better than most V8 supercars heads after they've been put into race trim.
    They are a brilliant piece of engineering. (To quote him; who'd never seen one before.)


    Alan S
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  9. #9
    Member senthil16V's Avatar
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    Hey guys,

    How about the XU10J4 head....does it flow as well as the Mi16 head? Will this engine be a good starting point for turbocharging?

    With Rgds,

    Senthil16V

  10. #10
    1000+ Posts PeterT's Avatar
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    Quote Originally Posted by senthil16V
    Hey guys,

    How about the XU10J4 head....does it flow as well as the Mi16 head? Will this engine be a good starting point for turbocharging?

    It's basically identical.

    '92 205 Mi16
    '90 Mi16x4

  11. #11
    Budding Architect ???? pugrambo's Avatar
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    Quote Originally Posted by PeterT
    It's basically identical.

    so how different is the 10J4RS head compared to the 10J4 head ?

    or is it just down to cam shafts ?
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  12. #12
    1000+ Posts PeterT's Avatar
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    Quote Originally Posted by pugrambo
    so how different is the 10J4RS head compared to the 10J4 head ?

    or is it just down to cam shafts ?
    The RS head has 6mm valve stems rather than 7mm. There could be others, but I don't know.

    '92 205 Mi16
    '90 Mi16x4

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    Budding Architect ???? pugrambo's Avatar
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    Quote Originally Posted by PeterT
    The RS head has 6mm valve stems rather than 7mm. There could be others, but I don't know.

    that would just be in the guides though wouldn't it ?

    could you put the RS valves and guides into the J4 head ?

    i know looking at the parts manuals they have different camshafts but it's a bit hard to flow test the pictures on the CD's to find any differences that way
    3 x '78 604 SL

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  14. #14
    Member senthil16V's Avatar
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    Icon14

    Guys,

    So can the XU10J4RS head be bolted onto the XU10J4 block? Does the XU10J4R flow as well as XU10J4? Are these heads interchangeable?

    So if these were same....then there should not be any problem bolting on the XU10J4R inlet manifold with XU10J4 heads?

    I thought of changing my inlet manifold to the XU10J4R manifold as i believe there is no ACAV system on this engine.....will there be problems if i do this?

    With Rgds,

    Senthil16V

  15. #15
    Member senthil16V's Avatar
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    Icon14

    Guys,

    Hey guys,

    How about the XU10J2 head....whats the flow rate for this head?what modifications can i do to increase the flow rate?

    Any suggestions?

    With Rgds,

    Senthil16V

  16. #16
    1000+ Posts PeterT's Avatar
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    Quote Originally Posted by senthil16V
    Guys,

    Hey guys,

    How about the XU10J2 head....whats the flow rate for this head?what modifications can i do to increase the flow rate?

    Any suggestions?

    They flow a tad better than a worked XU9J2 head, but nothing like a 16V head.

    '92 205 Mi16
    '90 Mi16x4

  17. #17
    Member senthil16V's Avatar
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    Dear PeterT,

    What kinda of cfm are we looking at for the XU10J2 head?

    How about the inlet manifold (XU10J4R) modification with no ACAV on the XU10J4 head? Is this possible...will there be problems if i do this?

    With Rgds,

    Senthil16V

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