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Euro ZC timing belt 124 vs 129

Discussion in 'Civic and CRX - EW' started by ankhati, May 2, 2011.

  1. ankhati

    ankhati New Member

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    Hi all I have a 1987 model CRX 1.6, 125hp, I take it the engine is ZC1.
    From reading on the pages I learned that the proper belt should have 124 notches, but when referencing my car at spare parts resellers here in Sweden I am offered this:
    Kamrem - 48-5170XS
    It's a 129 notch belt.
    Gates 5170X

    confused now?
     
  2. jlicrx

    jlicrx Senior Member

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    87 ZC1 engine uses same timing belt as 86-89 USDM Integra D16A1 which has 129 teeth - camshaft timing gears should have 40 teeth, like this:

    [​IMG]

    88-95 JDM DOHC ZC and 88-91 D16A8/D16A9/D16Z5 use the 124 tooth belt and camshaft timing gears which have 34 teeth
     
    Last edited: May 2, 2011
  3. ankhati

    ankhati New Member

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    Thank you Jlx, that was good to hear.
    On another note, why would Honda use bigger gears? To lessen the load on the belt, to compensate for higher lifts, and then to reconsider and find out it wasn't necessary, and go back?
     
  4. jlicrx

    jlicrx Senior Member

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    they started out with the larger gears on the first DOHC ZCs in the JDM 1g CRX Si and JDM 3g Civic Si and used the same gears in the 86-89 Integras, both JDM ZC and USDM D16A1 - in 1988, the 2g CRX and 4g Civic cars with the DOHC ZC, D16A8, D16A9 and D16Z5 engines were all switched to the smaller gears - just guessing, but i assume they went to the smaller gears in order to lower the top of the timing belt cover to get more hood clearance - if you have ever installed one of these engines in the 2g CRX or 4g Civic you will know that even with the smaller gears, the timing belt cover hits the underside of the hood - the factory 88-91 cars with the DOHC engines had a bubble in the hood to provide even more clearance
     
  5. ankhati

    ankhati New Member

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    Makes sense Jlx, this is why my CRX have a "power bulge", but this bulge is uncommon in the US it seems. Here in Sweden 125hp DOHC was the only option for 1gen CRX's
    The idle when cold is about 2200RPM, but it comes back down as temperature increases. Isn't this a rather high idle speed for a cold engine?
     
  6. jlicrx

    jlicrx Senior Member

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    i agree that it seems a little high - the factory specification for idle speed on the cold engine is 1250-2250 rpm - check for vacuum leaks which will cause high idle - been a while since i worked on the ZC1 engine, but if memory serves me, it has a fast idle valve on the back of the intake manifold which may not be working properly

    [​IMG]
     
  7. ankhati

    ankhati New Member

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    this is tricky JLx

    there is a black box on the firewall, it holds several selenoids, among them is the "idle control selenoid valve" then on the manifold you have the "fast idle valve" I read the factory manual, but can't understand why both would be there?
    Fast idle valve is a wax motor operated with the temperature of the coolant.
    idle control selenoid valve is electrically operated

    Am at a complete loss...
    Fast idle valve=cold start?
    Idle control selenoid valve=coasting valve and fine tuning? by coasting valve i mean somthing to prevent too much vacuum in the TB when you close the throttle at high RPM.
     
  8. ankhati

    ankhati New Member

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    did some research.

    when engine is hot, fan came on twice as stated by the manual. If I apply a fuel line clamp to the vacuum hose #10, then I get a destinct drop in RPM (100-200RPM)

    According to this document.
    [​IMG]
    Then the valve should only by open in EXTREME conditions. Coolant below -10C, if this is right then I should not be able to measure any change in RPM when clamping the hose?
    Could it be the high RPM is cumulative effect of the 2 idle valves being open? one correctly, and the other incorrectly.
     
  9. jlicrx

    jlicrx Senior Member

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    the page from the manual that you posted appears to be from the Factory Service Manual for the 91 USDM CRX Si with D16A6 engine which uses an electronic controlled FICV which receives a signal from the ECU at low temperature causing the valve to open which allows air to bypass the throttle plate into the intake manifold which causes the idle to increase (like having a vacuum leak) - it is not a thermowax operated valve and has no coolant connections - i must admit that i am only familiar with the JDM ZC1 and am not sure if the European version is the same - does your intake manifold have the Fast Idle Valve on the back like the picture that i posted? it is controlled by the temperature of the coolant passing through it and is the thermowax type

    back to your other question - yes, the Fast Idle Valve increases the idle when the coolant temperature is low and the idle drops as the coolant temp increases - it should only increase about 200rpm - the idle control solenoid valve increases the idle slightly at start-up and controls the idle speed with regard to load on the engine, such as when you turn on the lights, A/C, etc. which causes more load on the alternator and tries to drag the engine down

    generally speaking, high idle is usually caused by a vacuum leak - if your engine has the Fast Idle Valve like the picture, here is how you check it:

    (Note: the valve is factory adjusted and should not be disassembled)
    1. start the engine when it is cold (coolant temp below 30*C, 86*F)
    2. remove the cover on top of the Fast Idle Valve (2 screws)
    3. place your finger on the valve seat area and make sure that there is air flow with engine idling.
    4. if no air flow, the valve is bad.
    5. allow engine to warm up to normal operating temp (cooling fan comes on)
    6. as coolant temp increases, the plunger inside will rise.
    7. check that the valve is completely closed. if it is not closed, an air suction sound can be heard in the valve seat area.
    8. if any suction is heard, the valve is leaking and needs to be replaced.
     
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