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  1. #1
    formerly Gold06RXP Turbo Nick's Avatar
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    Turbo cylinder wall to piston clearance?

    So ive got my blown turbo eng. apart and noticed on the two good cylinders that they where a little tight at the top of the bore. Some minor scuffing at the top was noticed. I have the Riva pistons and there spec is .0025-.003 clearance. I had mine set at .0027-.0028. Im building a new engine now and want to make it a hair looser. Where should i have them set it at? .003-.0032? Any suggestions appreicated


  2. #2
    TURBOGTX's Avatar
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    with my ski I'm using stock pistons with the boost set to 16psi, but on the race cars I use .0035" to .004" when running 30+ pounds of boost and over 600HP

  3. #3
    formerly Gold06RXP Turbo Nick's Avatar
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    Hmm? Ok so you think i should make them about .003-.0035? Is there any disadvantage to running them looser? Any noise or anything like that? I think my finale boost #s gonna be 20-21 PSI

    Thanks!!

  4. #4
    blackvr's Avatar
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    on a race engine with no knock sensors its fine to run them loose. i would stay around the .003 that you had. if you loosen em to much the motor will be much noisier and will drive the knock sensor nuts. its happen to me before on previous engines. if your noticing scuff marks on the pistons or the walls its more then likely from heat, (either engine running to hot or egt got hot at one point). doesnt take much to scratch a piston or wall when running 93 octane gas. and also with the meth injection you have to be careful because its not spraying all cylinders evenly. so when you lean out the fuel from the injectors and rely on a single jet to provide even fueling, its not a accurate way to supply fuel. best bet is to run a direct port.

  5. #5
    formerly Gold06RXP Turbo Nick's Avatar
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    Thanks Black!! Ill just go with .003 and call it a day. It was very minor scuffing. This is my first turbo engine of any sort so i dident know what to expect. As for the meth injection it seems to be doing its job very good. Eng looked beautiful on inside other than that grenaded cylinder!! Thanks for advice
    Quote Originally Posted by blackvr View Post
    on a race engine with no knock sensors its fine to run them loose. i would stay around the .003 that you had. if you loosen em to much the motor will be much noisier and will drive the knock sensor nuts. its happen to me before on previous engines. if your noticing scuff marks on the pistons or the walls its more then likely from heat, (either engine running to hot or egt got hot at one point). doesnt take much to scratch a piston or wall when running 93 octane gas. and also with the meth injection you have to be careful because its not spraying all cylinders evenly. so when you lean out the fuel from the injectors and rely on a single jet to provide even fueling, its not a accurate way to supply fuel. best bet is to run a direct port.

  6. #6
    blackvr's Avatar
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    cool yea dont worry bout the minor scuffs. on rec skis like ours its hard to keep em perfect. u just gotta get a 9200 ecu. u have no idea the diff in acceleration. it was night and day when i switched from a 8650

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