Mi16 cam timing - which way to turn?
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  1. #1
    Fellow Frogger! WRX2PUG's Avatar
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    Mi16 cam timing - which way to turn?

    Hi guys,
    My Mi16 motor has adjustable cam verniers and I have heard from Peter T and others that advancing inlet cam timing by 3-4 degrees is worthwhile.

    Silly question but which way do I rotate the vernier to advance the timing. The picture below (sorry about the resolution - had to use the phone as the digicam was flat) shows the cam timing gear looking at the motor from the LHS cambelt end. Do I rotate clockwise or anti-clockwise?

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    Cheers
    Steve
    Renault Clio F1R27 road car and Supercharged Lotus Elise track car

  2. #2
    Fellow Frogger! WRX2PUG's Avatar
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    Sorry one more addition to my question I think a previous post mentioned advancing inlet timing by 4 CRANK degrees and that this translates to 2 or 2.5 cam degrees. Pardon my mechanical ignorance but is this correct?

    Cheers
    Steve
    Renault Clio F1R27 road car and Supercharged Lotus Elise track car

  3. #3
    1000+ Posts PeterT's Avatar
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    Couldn't see the picture, but looking from the drivers side front wheel, you need to rotate the outer 2 pulley degrees, which will equal 4 crank degrees, for a low compression XU9J4Z engine. That's not much, approx. 1mm from memory.

    But how do you know where it is now? When installing vernier pulleys you need to set up some external reference marks BEFORE you take the std. pulleys off. The std. pulleys are setup by installing dowel pins to lock them into the head, and a third to lock the crank to the block.

    '92 205 Mi16
    '90 Mi16x4

  4. #4
    1000+ Posts PeterT's Avatar
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    Whoops, that's wrong. Rotate the inner, which of course makes the valves open earlier that what they should.

    '92 205 Mi16
    '90 Mi16x4

  5. #5
    Fellow Frogger! WRX2PUG's Avatar
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    Thanks for the reply Peter and once again I should preface this with the fact that I'm a software person and a bit of a mechanical ignoramus.

    Just so that I make sure I understand - with reference to the following rough diagram

    Adjusting the Inlet Cam Pulley. The outer part of the pulley in red attached to the belt has markings as shown (actually 0 to 10 on either side). It has a few allen-key bolts going through slots allowing the adjustment.

    1) Just confirming that what I do is loosen the bolts and then actually rotate the internal part (which I'm assuming is connected directly to the inlet camshaft) whilst keeping the outer part still - How do I do this?
    2) One of the guys on the Peugeot Sport forum indicated that I will need to turn the camshaft - clockwise whilst holding onto the pulley. He also mentioned that I need to be careful that I dont get valve overlap though as there isnt much room between inlet and exhaust. Does this match your understanding re what to rotate and how?
    3) What are the consequences if I do get valve overlap ie what is actually happening - will I just get misfires because both are open simultaneously or is there a possibility of mechanical damage?
    4) I guess the other question is re reference points - Are you saying that the 0 indicator on the outer pulley is not necessary 0 in terms of advance/retard? How do I tell?

    <img src="http://www.yambay.com/www/steve/diagram.jpg" alt=" - " />
    Renault Clio F1R27 road car and Supercharged Lotus Elise track car

  6. #6
    1000+ Posts PeterT's Avatar
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    Much better picture. The markings are a reference for retard/advance. You will have to measure the outer diameter of the inner, to determine whether they're in crank or camshaft degrees, using a bit of maths.

    You also need to identify which engine you have. If it's a XU9J4 (with no Z) don't do anything! The inlet cam is already in the right place. If the engine was in an AUS. delivered car, it will be a Z model. So proceed.

    Just loosen the bolts enough so the two parts will move, by rocking the engine with the car in 5th gear. Don't do it in neutral. If you loosen the bolts too much, the cam will rotate very quickly the wrong way (out of your control due to spring pressures) and you may hit valves to pistons.

    Without external reference marks, you would have to assume that "0" is the std. position. But for what? Remember that these pulleys most likely originated in UK were the std. poistion is what you're trying to achieve. I would assume they're already in the right place. Without comparing the inlet pulley with a std. pulley you can not be certain. I would only advance the inlet cam 2 crank degrees max to begin with. If the performance improves, go another two, but no further. Be realistic though. Do 3 timed runs on a level road from 60-100 in 4th. You can also experiment with the exhaust too. Advance up to 5 crank degrees. This should improve the top end. So do timed runs that utilize 5000-7000 rpm.

    The cams are very mild. If you stay within the range suggested, you will not have a problem with overlap or mechanical interferance.

    Have fun!

    '92 205 Mi16
    '90 Mi16x4

  7. #7
    1000+ Posts PeterT's Avatar
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    As the other guy said, hold the outer still and move the inner clockwise to advance. You can do it by youself in 5th gear. Stand in front of the pulleys, then rock the car forwards or backwards to adjust.

    '92 205 Mi16
    '90 Mi16x4

  8. #8
    1000+ Posts PeterT's Avatar
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    Also, make sure you hold the pulley retaining bolt with a suitable size ring spanner whilst doing the adjustment. Otherwise you'll loose control.

    '92 205 Mi16
    '90 Mi16x4

  9. #9
    Fellow Frogger! WRX2PUG's Avatar
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    Thanks for all the info Peter, that helps heaps..

    Armed with that info what I think I will do is try and get it back on the dyno so the changes and results are more measurable. I'll let you know how I go.

    Got a GE short-shift kit which is going in tomorrow - looking forward to that

    Cheers
    Steve
    Renault Clio F1R27 road car and Supercharged Lotus Elise track car

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