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  1. #1

    Help Me Understand Exhaust Issues

    As a modding n00b, I'm scrambling to learn as much as I can, which involves reading lots of stickies, FAQs, and various threads. In considering my exhaust options (for a 2006 RXP), I'm a bit confused. My boats are 3 hours away at the lake, so I can't just go open them up and peer down inside. I'm hearing words like "mid pipe" and "J pipe" and "water box" and "shorty box" and "08+ setup" and I'm not sure exactly what I should be looking for in a modded setup.

    Here are the mods I've purchased for the boat so far:

    Riva 4" rear air
    Riva catch can
    Riva intake grate w/girdle
    Riva pump wedge and VTS rod
    RE Block Offs
    Solas 15/19 impeller

    Those above mods I'm planning on installing this week. Over the winter, I plan to yank the stock SC and replace it with an X-charger, and put 42lb injectors in. Beyond that, I have no plans to do much else.

    So, exhaust. What are my options, and what should I be considering? Noise isn't a big issue. I don't want STRAIGHT pipes, but I don't mind it sounding loud and mean, either. I don't mind needing to install a thru-hull exhaust kit, but I still don't know in which cases I'd need to do that.

    So please pretend I know nothing about exhausts and help this n000b figure out a direction to go?

    Thanks!


  2. #2
    RIVA CREW's Avatar
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    Your craft is equipped with a 'J' pipe. That'st the silver pipe with a bend between the exhaust manifold and water box (muffler). Going by your comments about noise you definitely want to go with a rear exhaust kit. The RIVA kit for your model is part # RS15050-1.
    Click image for larger version. 

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    Oure Rear Exhaust Kit comes with detailed installation instructions which include a template for properly locating the hole for the outlet. You can preview the instructions online at http://www.rivaracing.com/instructio...5050_1_215.pdf. All of our instructions are available for download in our Online Instruction Library at http://www.rivaracinga.com/instructions.asp

    Keep in mind that you are required to remove the O.P.A.S. in order to install a rear exhaust kit.

  3. #3
    From the instructions, it seems the Rear Exhaust kit replaces the hose and baffle between the water box and the outside of the boat.

    So am I correct in that it goes: Exhaust manifold -> mid pipe (which is a J-pipe in a stock 2006 RXP) -> water box -> outlet pipe?

    I see some people upgrading their setups to "08+." I've talked about that in a previous thread, but does that mean replacing the mid pipe and and water box with 08+ ones?

  4. #4
    RIVA CREW's Avatar
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    That is correct. Our kit includes a block-off for the stock exhaust outlet.

    We haven't experimented with updating to the `08 spec water box. But we do make improved aftermarket water boxes! They flow better which improves performance and they allow you to service your supercharger without removing the water box.
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    For your craft you would order part # RS16082. You won't need our Rear Exhaust Kit, but you will need to order our Billet Exhaust Outlet (paRT# RS15050-ET) and Exhaust Coupler (part# RS16082-ECK) to complete the installation.

  5. #5
    Sayers's Avatar
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    If your going to upgrade to the Riva water box in pre 08 its worth upgrading to the mid pipe and 08+ style box. Ditching the J pipe cleans everything up IMO and the 08+ setup is reported to flow better. The mid pipe is not too pricey new either.

  6. #6
    Quote Originally Posted by Sayers View Post
    If your going to upgrade to the Riva water box in pre 08 its worth upgrading to the mid pipe and 08+ style box. Ditching the J pipe cleans everything up IMO and the 08+ setup is reported to flow better. The mid pipe is not too pricey new either.
    So would that mean I get an 08+ mid pipe (which replaces the J-pipe) and then a stock 08+ style waterbox? Or is there further advantage to getting an aftermarket 08+ style waterbox to go with the different mid pipe?

    Also, would changing to the 08+ style waterbox require a different outlet pipe and/or drilling a new exhaust hole in the hull? Or is the answer different depending on whether the waterbox is stock/aftermarket?

  7. #7
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    Steve, you have several options...Reference my Airflow thread, you can get all your answers there on which way to go....

    You have a few things to choose...money is your only factor, because once you install any of the above mentioned setups, you will SEE GAINS that will be good, and its only until you uncork the intake and intercooler setup will you need to factor in exhaust setups....


    A few things...

    Jpipe is for 02-07 exhaust systems...

    Midpipe replaced the Jpipe in 2008 on most RXP/T-X units, and SOME 215hp units (RXP/RXT/GTX), and was standard in 2009.....But it commonly referred to as the +08 setup.


    The Riva Pipe with exhaust outlet will work on either the current jpipe/waterbox setup you currently have, along with a midpipe/box setup....Because the OEM waterbox outlet location did not change...Going with this setup will get you your sound you are after.

    For added HP gain, you can have your OEM box modified. This modification is usually referred to as "gutted", meaning to take out all the restrictive baffles and increase airflow while decreasing backpressure. Of all the setups that I have flowed over the years, a standard 04-07 water box left full length, with a single 5" hole cut in the baffle wall, and outlet tube trimmed....is the best flowing setup you can have with an OEM box.....The box can be modified by yourself with a few hand tools, and welded back up by a local welder for cheap. its the best cost effective modification you can do...

    If you opt for the +08 setup, you will need to purchase the midpipe, clamp (jpipe is thinner), connecting hose......and most importantly, find a used +08 water box.....This setup will give you more power over the Jpipe setup when swapped without modifying the waterbox.....The +08 waterbox can be modified in the same fashion for the same end result....

    SHORTY boxes, refers to changing the size of the water box. Over the years many people have done this, and the results have been mixed. While some succeeded, many failed because the did not take into account that both exhaust and water flow through the box. Changing the size of the box, location of the exit, etc...will affect the way the box performs. Modifying it incorrectly can cause issues with waterflow, create hotspots, and eventually lead to failure....and IMO, unless you understand all that, don't bother....

    The Riva waterboxes are the next step up. They basically are what people try to achieve when trying to make a SHORTY, but the offer the proper engineering and are built the right way. Either box can be obtained with the Jpipe or Midpipe setup...The major benefit of the waterbox is the ability to remove the SC without touching the entire exhaust system....which needs to be done if you retain the OEM waterbox on either jpipe/midpipe setup......The cost is more, since you also need to purchase the exhaust outlet separate (RIVA should have a combo deal, HINT HINT RIVA CREW)....But the fit and finish is great, and once you remove the SC without having to mess with the exhaust, you just paid for your time you got back...


    So look down the road atleast 2-3 years, see where you WANT the ski to be......and choose wisely

    --Danny

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  9. #8
    Banned User
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    I love the j pipe greenhulk box RIVa thru hull setup. Wouldn't change a thing

  10. #9
    83.0 @ 8400 jhill19's Avatar
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    I preferred the much cleaner look of the 08+ mid pipe with riva waterbox with through hull exhaust.

  11. #10
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    What's the cleaner look? Keep your ski pristine and no issues!

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