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  1. #1
    Resident electronics hacker UnityRacing's Avatar
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    Question about DI heads

    While i'm waiting for Watcon to finish up my cylinders i've been cleaning up my heads and found that my PTO head had some pitting where the o-rings seal it to the cylinder. That had me concerned to the point of looking for another.

    The cylinder that failed me was the PTO, so I want to ensure I don't have an issue again.

    I ran across this thread - http://www.greenhulk.net/forums/showthread.php?t=91517 talking about an update for the 99 Genesis.

    If i'm not mistaken (and i'll have to read the EMM to verify for sure) I'm running a 99 Genesis EMM and injectors. I'm pretty certain the heads i'm using are 02 TXi spec heads.

    Does anyone know the differences in the heads? I thought it had to do with the water cooling restrictor plates, but they appear to be on the other heads as well. Anyone have any more input on what the update disc does?


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    My current understanding assembled from info related to me from several others, goes as follows.

    The 1999 Genesis FFI (first model year Ficht) engine would sometimes burn down the PTO cylinder/piston when in customers hands. Polaris could not fully identify why this was happening only on some engines with some customers, but seemed just fine with others.

    As an interim fix the compression for the Ficht PTO cylinder was reduced by retrofitting the special PTO-only service replacement cylinder head. Along with changing the PTO cylinder head there was a floppy disc that reprogrammed the EMM. I do not know what exactly that reprogramming did but I suspect it made the fuel mixture richer and/or retarded the ignition timing.

    Bear in mind that the 1999 (and only for 1999) Genesis also had the under water exhaust system. This exhaust system created back pressure, and the amount of back pressure would vary depending on hull speed and whether on or off plane.

    The 2000 Virage and 2000 Genesis used the above waterline exhaust exit which continued through 2004. Still, some Ficht engines would suffer PTO failure yet others would be just fine. I think there was further experimenting with EMM updates and reprogramming.

    Eventually it became clear that under some Ficht engine operating conditions (cruising just off plane with a big bow wave?) there was unwanted exhaust back flow into the PTO which caused the piston damage. Polaris changed the interior casting design of the exhaust manifold to better direct exhaust flow away from the PTO cylinder. This change happened around 2003, and I think I have posted the actual manifold part numbers and dates elsewhere.

    I have been told the 'best' fix is to retrofit the latest version of the exhaust manifold. On a 1999 Genesis the special 1999 only PTO cylinder head may not be needed with the newer manifold. I have not tested this myself.

  3. #3
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    Quote Originally Posted by UnityRacing View Post
    While i'm waiting for Watcon to finish up my cylinders i've been cleaning up my heads and found that my PTO head had some pitting where the o-rings seal it to the cylinder. That had me concerned to the point of looking for another.

    The cylinder that failed me was the PTO, so I want to ensure I don't have an issue again.

    I ran across this thread - http://www.greenhulk.net/forums/showthread.php?t=91517 talking about an update for the 99 Genesis.

    If i'm not mistaken (and i'll have to read the EMM to verify for sure) I'm running a 99 Genesis EMM and injectors. I'm pretty certain the heads i'm using are 02 TXi spec heads.

    Does anyone know the differences in the heads? I thought it had to do with the water cooling restrictor plates, but they appear to be on the other heads as well. Anyone have any more input on what the update disc does?

    What oversize are you going with your pistons? Anything over .5mm oversize may need the squish area opened up for the bigger pistons. When I assemble a motor, I use the threebond that I use to seal the cases on the head o rings. This keeps the o rings in place the next time you remove the head. No more fighting to get that expanded o ring back in the groove. In your case, it may help with the pitting in the cylinder head too.

  4. #4
    Resident electronics hacker UnityRacing's Avatar
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    Guess I need to figure out what emm I have first and go from there.
    Bryan I went with WSM Platinum .5mm over size. John has everything right now and im confident (hopefully) that he can get my jugs setup properly. Thats the whole reason I sent everything to him vs using a local machine shop.
    I think im going to order another head from ebay. Ive put too much $ in this ski already to risk it all on a pitted head. Im pretty certain the orings shifted during install and got pinched letting water in, and pressure / detonation out. I think this is why that head is pitted. Ill certainly pay better attention this go round on assembly.

  5. #5
    PWC Addict lilman573's Avatar
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    Quote Originally Posted by UnityRacing View Post
    Guess I need to figure out what emm I have first and go from there.
    Bryan I went with WSM Platinum .5mm over size. John has everything right now and im confident (hopefully) that he can get my jugs setup properly. Thats the whole reason I sent everything to him vs using a local machine shop.
    I think im going to order another head from ebay. Ive put too much $ in this ski already to risk it all on a pitted head. Im pretty certain the orings shifted during install and got pinched letting water in, and pressure / detonation out. I think this is why that head is pitted. Ill certainly pay better attention this go round on assembly.
    I've got a set of 800di heads. Are they different? They are the grey ones.

  6. #6
    Resident electronics hacker UnityRacing's Avatar
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    AFAIK yes, they are different.

  7. #7
    Resident electronics hacker UnityRacing's Avatar
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    Keith here is what I could dig up - http://www.greenhulk.net/forums/show...hlight=1261259

    Looks like the 99-2000 exhaust manifold is the same. Looking at the parts diagrams the 99 Genesis had a dual under hull exhaust. I don't remember the donor ski having that, so it must have been a 2000 model. Either way, the logs are the same. Should I be running an 03-04 exhaust manifold, and 02+ heads? Will this conflict or cause issues running a 2000 Genesis EMM? My manifold is fine, but if it needs to be changed i'd rather do it now before I reassemble everything.

  8. #8
    downunder123
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    My PTO was some 5 psi down to the other two when just rebuit (and prior was down by +20psi). The head was pitted inside the dome but looked OK around the O ring area so I gave it a good scrub and decided to go with it again. I was told no machining possible. Are the cylinder heads interchangeable (1 for 1) without any injector mapping?

  9. #9
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by bspanovic View Post
    My PTO was some 5 psi down to the other two when just rebuit (and prior was down by +20psi). The head was pitted inside the dome but looked OK around the O ring area so I gave it a good scrub and decided to go with it again. I was told no machining possible. Are the cylinder heads interchangeable (1 for 1) without any injector mapping?
    What engine/model/year are you asking about?

    In general the Ficht cylinder heads are interchangeable between cylinders on a given engine, while the injectors and EMM are mapped to specific cylinder locations on each engine.

    I may move your question to a separate thread to avoid confusion here.

  10. #10
    Resident electronics hacker UnityRacing's Avatar
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    Pitting inside the dome is usually an indication of pre-detonation.

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