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  1. #1
    oz_speed's Avatar
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    Piston Blown Advice Needed

    Have a look at the photos below and please offer any advice on possible cause to failure. A small amount of water about an egg cup was also found in catch can. The ski is not mine but belongs to a friend of mine. There was no o2 fitted so I can not tell you the A/F other than the RRFPR was set as per Rive instructions. Only one piston has failed all other are perfect. End off the electrode on the spark plug burnt away too. Head gasket perfect and no sings of blowing or any other faults. I have my own thoughts on the possible cause but would like your input.

    Engine Mods as follow RXP
    Riva ECU
    Riva valve springs and caps
    Riva 50Lb Inj
    Riva XXX Scer
    Riva intercooler
    Riva RRFPR









  2. #2
    Eric Ocman's Avatar
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    IMO Riva injectors..

  3. #3
    Eastside Powersports Slow 91's Avatar
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    hit up Duke or JP. Im pretty sure thats why you need to put CP pistons in any decent modded ski. But it DEF got hot and detonated

  4. #4
    Duke's Avatar
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    Definately need on O2 sensor for that size of a charger.

    Need CP pistons, good injectors and a wideband to tune it just for starters.

  5. #5
    oz_speed's Avatar
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    My thoughts are the Riva injector has gone faulty or stated to lock up causing the one cylinder to run lean. The other two cylinders/pistons are perfect.

  6. #6
    Eric Ocman's Avatar
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    Pretty sure exact same thing happened to dnielsen with Riva injectors. They were specifically made for a certain combo and do not seem to have the flexibility as the Bosch/siemens etc.

  7. #7
    dnielsen's Avatar
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    Just guessing it's the number three cylinder in the block as this is cylinder most report dammaged that have experienced the "LEAN AND BLOW" condition. Exaust side of the piston is melted which would suggest a cylinder that was ran extremely lean. Like the others have already suggested its likely due to the Riva 50s being ran at high psi. A XXX charger ran with the RIVA ECU and Riva 50s would require an enormous amount of fuel to keep the cylinders cool, you likely adjusted the base pressure on the RRFPR (as Riva suggest) to a point in which the injector started sticking at higher boost (WOT or just before). Also if you were running anywhere near 8600 RPM on that ECU it will also start to pull fuel compounding the problem.

    Easy fix, rebuild the engine (CP or Riva pistons, CPs are cheaper), ditch the Riva 50s for the Bosch 48s or 50s, tune for 8550 RPM or lower, and most important is to monitor AFRs always!!!!!!!!!

    Here, you should read this thread also (from start to finish).

    http://www.greenhulk.net/forums/show...ght=afr+tuning

    Oh, and sorry to see this for you........

  8. #8
    oz_speed's Avatar
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    Quote Originally Posted by dnielsen View Post
    Just guessing it's the number three cylinder in the block as this is cylinder most report dammaged that have experienced the "LEAN AND BLOW" condition. Exaust side of the piston is melted which would suggest a cylinder that was ran extremely lean. Like the others have already suggested its likely due to the Riva 50s being ran at high psi. A XXX charger ran with the RIVA ECU and Riva 50s would require an enormous amount of fuel to keep the cylinders cool, you likely adjusted the base pressure on the RRFPR (as Riva suggest) to a point in which the injector started sticking at higher boost (WOT or just before). Also if you were running anywhere near 8600 RPM on that ECU it will also start to pull fuel compounding the problem.

    Easy fix, rebuild the engine (CP or Riva pistons, CPs are cheaper), ditch the Riva 50s for the Bosch 48s or 50s, tune for 8550 RPM or lower, and most important is to monitor AFRs always!!!!!!!!!

    Here, you should read this thread also (from start to finish).

    http://www.greenhulk.net/forums/show...ght=afr+tuning

    Oh, and sorry to see this for you........
    The ski belongs to a bud of mine who as followed the Riva route as a lot of people do. I never liked the idea of no O2 on his set up and he was going to fit one over winter. The piston which as gone is at the front of the engine nearest the bow. I believe the ski was running around 8550-8580 rpm on the smooth before it went.

    I have seen many post on hear about the Riva Inj and people who have had them fail. You would think Riva would do something about it as they must surly know what they are recommending to there customers. By building a kit and selling to the general public as an almost plug and play kit you would think they would really be on the safe side of the A/R and make the kits fool proof.

    He is going to re-build with Riva pistons and fit a set of Bosch 50s. As the ski is now in bits he is going to fit an O2 now.

  9. #9
    dnielsen's Avatar
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    Just remember, even with the O2 sensor and monitoring AFRs he would have spotted high AFR numbers and then added more pressure to compensate (monitoring all three cylinders combined), this would have resulted in adding more fuel pressure and further compounding the problem! The other two cylinders would have then been running a bit rich while the third was locking up even harder and further leaning the cylinder.

  10. #10
    oz_speed's Avatar
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    Thanks for your advice and input. You have all confirmed what we was already thinking but it's alway good to have someone else agree.

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