750sx pipe selection question.
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  1. #1
    I dream skis sportsfreak29's Avatar
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    750sx pipe selection question.

    I'm building a 300sx/750 conversion ski that will have one of the first Rhaas pump kits and am trying to decide which pipe to run.

    Ski specs:
    1992 750sx small pin motor with a #20 cylinder ported for freestyle and a re-machined 27cc stock head.
    Dual sxr carbs.
    Advent ignition.
    Lightened 750 flywheel.
    Hooker 9/15 or 10/16 impeller.
    Might get a pump stuffer kit but on the fence about it.

    I have a Factory Pipe exhaust manifold, 2 new 650sx Factory Pipes from the Factorypipedeal.com, Mod and a Limited, and a PJS 750 pipe that was modded to fit into a JS hull.
    KIMG0299.JPG

    I've always been a 550/650 ski and Factory Pipe fan.

    This will be my first exploit into the 750 realm and need some input here. Thanks.
    Last edited by sportsfreak29; 02-22-2018 at 11:39 AM.
    If you're not crashing, then you're not trying!!!

    Ski situation in limbo!

    Special thanks to Chris Newmiller, and Mitchell at M&M Marine!

  2. #2

    Re: 750sx pipe selection question.

    FP 750 SXI Limited pipe makes tons of power. Has that light switch feeling though. Is the 300sx much more narrow than the sxi?

  3. #3
    Top Dog bandit88's Avatar
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    Re: 750sx pipe selection question.

    That PJS pipe will be a higher rpm pipe. Ive rode a 300sx once and am not too familiar with the dimensions and exhaust routing, but I think you may run into issues with both of those if you plan on running the stock fuel tank. Might be better off with a 750 pipe that routes back to the under side of the exhaust since that is what it looks like the 300 does. The factory 750 limited is likely too long to fit. R&D snail pipe might be a good choice, but again, a higher rpm pipe. Not saying that a higher rpm pipe is bad, I'd run one, but everyone has a hard on for max bottom end.
    -95 750SXI
    -86 440 with PJS800 conversion - http://www.pwctoday.com/showthread.php?t=466927
    -90 TS650
    -91 300SX

  4. #4
    I dream skis sportsfreak29's Avatar
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    Re: 750sx pipe selection question.

    I'm going to be removing the oil tank, cutting out the oil tank recess, glassing it over, installing an aluminum rear exhaust pipe out of a 650sx and putting the Waterbox up front.
    If you're not crashing, then you're not trying!!!

    Ski situation in limbo!

    Special thanks to Chris Newmiller, and Mitchell at M&M Marine!

  5. #5
    Top Dog bandit88's Avatar
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    Re: 750sx pipe selection question.

    Oddly enough, Im joining the club and picking up a 300sx tonight. Not sure what I will be doing with it, stock, 550 swap, or a 650. Whatever happens im going to try to keep it basic. I dont have a crazy build in me right now lol.
    -95 750SXI
    -86 440 with PJS800 conversion - http://www.pwctoday.com/showthread.php?t=466927
    -90 TS650
    -91 300SX

  6. #6
    PWCToday.com Is My Home Away From Home theVetteman3's Avatar
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    Re: 750sx pipe selection question.

    Your weight and a couple other factors will dictate if you should run a 9/15 or 10/16. Usually we run 9/15s on 750 engine skis which are bigger and/ or have bigger guys riding them. Like X2s. On my dual carb 550/750 the 10/16 was perfect, and the 9/15 would have been too low. Hookers and the Rhaas pump swap does an excellent job of not cavitating a ski in a traditional way, but it slows down your power delivery. So if you under pitch you might have less low end. I ran into this big time when I switched to a ported 800 on my same ski. I dropped a pitch impeller and then decreased the nozzle size by 4mm and got a huge increase in low end each time.

    Anyway, regarding pipes, my recommendation is to try and ride a ski locally that has the pipe. Each feel different and our tastes are all different. Anyway here's my thoughts based on the ones I have tried. I build good engines, my preference is to have pipes that get me good usable power and I'm not concerned about every last RPM. Rankings are all out of 10, 10 being the best. Overall is not an average, more of my overall worth or preference in using.

    Factory Pipe Limited 650 pipe
    low end - 6
    high end - 8
    power curve - 5
    peak power - 7.5
    overall - 7.5
    This feels like a baby 750 limited pipe. A bit less power and way less of a hole before the power hits. I believe this is a better designed pipe than the limited because the pipe diameter is close to the optimum size, where as the 750 limited pipe exceeds it. Basically the 750 limited is like a big turbo with more lag but perhaps a bit more peak power.

    Factory Pipe Limited 750 pipe
    low end - 5 (more like a 1 then 8 when pipe hits)
    high end - 8
    power curve - 2 (low end feels high because power dips so much before pipe hits)
    peak power - 8
    overall - 7
    Good overall pipe but the power drops before the pipe hits way too much for my taste. Makes cruising more difficult and sometimes I just have a hole when I want more power. These thoughts are on stock 750s and ported 800 btw.

    PJS EX6250 "big 650/750 pipe". (same specs as 750 wrap around per Bill)
    low end - 6 (predictable usable power)
    high end - 7
    power curve - 9 (very linear, useful power all over)
    peak power - 7
    overall - 7
    Excellent pipe for linear power. Will make less peak than factory pipe perhaps, and will not have the "hit", so most will feel like it makes less power. I have found good results using this on ported engines, such as on my 550/800. For rec riding, wake jumping, and basic tricks I always have power when I need it.

    Coffmans big 650/750 pipe
    low end - 7
    high end - 6
    power curve - 8 (very linear, useful power all over)
    peak power - 6
    overall - 7
    This pipe has a more linear power delivery than the 750 limited pipe. It might make less power but it has solid low end and the linear delivery makes it more useful. I had one of these on my 650/750 dual carb and loved it. Excellent performance for the price too. More low end than the PJS. Perhaps slightly less high end, but then again I believe I have modded my PJS pipe for less water/ better high end.

    Nynja C4 / TNT Superstock
    low end - 6 (honestly this may be higher, it has been a while)
    high end - 9
    power curve - 9 (very linear, useful power all over)
    peak power - 8
    overall - 8
    Less off pipe hole than 750 limited. Feels like a better set up, more advanced design. Power band is at least 200 rpm more than an equivalent 750 limited. I have heard bottom end can hit just as hard or harder with plenty of tweaking. Very limited power band, feels almost dry pipe like.


    For comparison:

    SXR dry pipe, now ECWI
    low end - 4
    high end - 10
    power curve - 7
    peak power - 10
    overall - 6
    I do not like this pipe without ECWI. Power comes on too late which means at normal rec riding speeds you are always in the hole of power pre-pipe hit. When set up properly with ECWI this is very good and a different story. One of the best pipe designs out there. I'd still prefer a Nynja.

    PJS XIR Side Draft Wet Pipe
    low end - 8
    high end - 10
    power curve - 10 (very linear, useful power all over)
    peak power - 9
    overall - 10
    This pipe feels just as strong on a 800 as a sxr dry pipe, but without the useless off power hole. Very linear and strong power. Power band that feels more like a dry pipe. On a rec ported 800 this was an amazing combo in my xir. Probably my favorite pipe and my benchmark. I think only a sxr dry with ECWI can get close to touching this.


    I have also done the dried out OEM 650 pipe. I would not use that at all on a 750 engine, especially dual carb.
    Last edited by theVetteman3; 02-23-2018 at 08:56 AM.
    1985 JS550/800 "Pretty Red": Newmiller 800, Rhaas 750 pump conv. [56.3mph gps]
    2009 1100 SJ:
    Kawi 1100 build in progress
    2009 SJ MINT:
    KP steering adaptor, Worx 228 intake [45.8mph gps]
    1987 WJ650:
    6M6, JD Intake Grate, 17/20, cheater pipe [47.8mph gps]
    1994 XiR: 830cc Superstock, PJS side draft, 13/18 swirl [53.7mph gps]
    1998 SXI PRO:
    3DR hull mods [TBD]



  7. #7
    I dream skis sportsfreak29's Avatar
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    Re: 750sx pipe selection question.

    I'm 5' 10" and will be down to about 205 lbs by April.
    If you're not crashing, then you're not trying!!!

    Ski situation in limbo!

    Special thanks to Chris Newmiller, and Mitchell at M&M Marine!

  8. #8
    Frequent Poster lonczakd's Avatar
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    Re: 750sx pipe selection question.

    Here's some ideas for fitment. I don't remember who's these were but I had the pictures saved on my pc.attachment.php.jpgP1020597.jpg

  9. #9
    PWCToday.com Is My Home Away From Home wmazz's Avatar
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    Re: 750sx pipe selection question.

    Quote Originally Posted by theVetteman3 View Post

    For comparison:

    SXR dry pipe, now ECWI
    low end - 4
    high end - 10
    power curve - 7
    peak power - 10
    overall - 6
    I do not like this pipe without ECWI. Power comes on too late which means at normal rec riding speeds you are always in the hole of power pre-pipe hit.
    When set up properly with ECWI this is very good and a different story. One of the best pipe designs out there. I'd still prefer a Nynja.
    This pipe is an example of a design with a steep angled head-pipe immediately
    after the exhaust manifold. Ex manifold diameter at the collector may also be
    too big.

    Judging Peak power on hard hitting pipes is deceptive. Because the hit is caused
    by a steep acceleration curve, that is caused by a significant drop in HP preceding
    the acceleration hit.

    Exhaust port shape can make a hard hitting pipe worse!

    The harder the hit, the more HP that was lost!

    Large diameters and steep angles, and hard hitting power do not guarantee higher HP
    when compared to a smaller diameter pipe. It is possible that two designs can have
    nearly the same peak HP, but have different or misleading acceleration curves.

    For free-style and fun riding, an exhaust manifold with stock diameter exhaust
    tracts, and collector (like stock SX-i-r 750/800 exh manifold) combined with a
    head-pipe that have small diameters and angles. Long shallow angled head pipes
    make more peak HP, and have more throttle feel.



    Bill M.
    Last edited by wmazz; 02-24-2018 at 05:27 AM.
    Horsepower == Speed, RPM != Speed



  10. #10
    PWCToday.com Is My Home Away From Home theVetteman3's Avatar
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    Re: 750sx pipe selection question.

    Good info Bill.

    Also I meant no ECWI not now. I haven't tried a sxr dry with ECWI but I have experience with the HX 720 factory pipe with ECWI, and a couple other skis. On a good pipe that's a big improvement.
    Last edited by theVetteman3; 02-26-2018 at 08:09 AM.
    1985 JS550/800 "Pretty Red": Newmiller 800, Rhaas 750 pump conv. [56.3mph gps]
    2009 1100 SJ:
    Kawi 1100 build in progress
    2009 SJ MINT:
    KP steering adaptor, Worx 228 intake [45.8mph gps]
    1987 WJ650:
    6M6, JD Intake Grate, 17/20, cheater pipe [47.8mph gps]
    1994 XiR: 830cc Superstock, PJS side draft, 13/18 swirl [53.7mph gps]
    1998 SXI PRO:
    3DR hull mods [TBD]



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