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  1. #1
    keit29's Avatar
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    School me on fuel pressure, injector size, and afr's

    To start, this is my current setup: 2 Rude, 42s, Riva RRFP, Custom water box with through hull, riva rear air, and Inovative wideband.

    I did some tuning yesterday and have the AFR's in check under high rpm. I bought the ski as is and have not tried any other parts yet. I'm sitting at high 14s low 15s AFR until about 5500 when (I'm guessing) the rrfpr kicks in and starts adding fuel (getting down to a solid 11.9 or 12.0ish) My question is, is this ok? Should my AFR's be lower earlier on in the revs? I purchased a set of #50 injectors to try and combat this, but 1. I'm not 100% sure it is bad as is and 2. Will the 50s need more pump? And will the rrfpr allow for low enough pressure to not run rich.


  2. #2
    dnielsen's Avatar
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    I hope those are not Riva 50s! Whats the max RPM and boost you are seeing? 11.9 may still be tad lean depending on RPM and boost. Still too lean at idle, shoot for 13.6 or so. If your happy with the WOT AFRs and still need to add a bit of fuel down low try running the boost reference line from the RRFPR to the oil spray port on the throttle boddy. This will prevent the RRFPR from registering the vacuum that results in fuel being pulled, this should give more fuel down low without affecting the WOT AFRs.

  3. #3
    keit29's Avatar
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    They are riva 50s. whats wrong with them? I'm running riva 42s right now though. I have yet to try the 50s. the rrfpr is tapped at the throttle body.

  4. #4
    Eric Ocman's Avatar
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    Quote Originally Posted by keit29 View Post
    They are riva 50s. whats wrong with them? I'm running riva 42s right now though. I have yet to try the 50s. the rrfpr is tapped at the throttle body.
    Don't think Riva made 42s. You can scrap those rivas. if your afrs look good on to just keep what you got. If you want more injector switch to Bosch 48s. Are you using the reference line? The riva 50s lock up under higher pressure and can burn up/ melt pistons!

  5. #5
    keit29's Avatar
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    I was told they are Riva 42s, I didn't know they didn't make 42's... If i pull them and take a picture could they be identified?

  6. #6
    dnielsen's Avatar
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    Not Riva 42s, likely a set of the OEM 42s that came on the 255 model skis. Save your self some pain and trash the Riva (Delphi) 50s and if you need more fuel do as Eric suggested and get a set of Bosch 48s from the online store. The 48s flow better and will not lock up!

  7. #7
    dnielsen's Avatar
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    Let me save you an engine, read the thread below.

    http://www.greenhulk.net/forums/show...light=Riva+50s

    Now that I saved your engine lets see, a good rebuild is approximately $1,500.00 if you do it your self, $2,500.00 if you have it done. I'll split the cost of the lower build with ya so that comes to about $750.00.

    My PayPal account is [email protected]

  8. #8
    dnielsen's Avatar
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    Here is one less than a week ago! Poor guy......

    http://www.greenhulk.net/forums/showthread.php?t=175247

  9. #9
    keit29's Avatar
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    OK, thanks for the help guys.

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