Page 1 of 3 1 2 3 LastLast
Results 1 to 10 of 22
  1. #1
    fxho's Avatar
    Join Date
    Feb 2009
    Location
    MIA 305
    Posts
    168

    Free Flow Exhaust= Slower Speeds???? please help

    I just added a free flow exhaust to my 08fxho cruiser, current mods solas 14/20 impellor, riva velocity stack, riva power filter, pump seal kit, and intake grate and was doing 63.2 ( i know its not as fast as a sho or fzr's but it moves fast enough for me and get me places lol) on gps and i took the ski out today to test it to see if I would have any speed gains and the best I got was 59.9.... Does the free flow exhaust make you lose top end speen??? Because it seemed like it happen to me.

    Did about 6-8 passes and best speed was 59.9

    PLEASE HELP!!!!!

    Thks
    Last edited by fxho; 10-26-2009 at 08:40 PM. Reason: different tittle


  2. #2
    Awamori's Avatar
    Join Date
    Aug 2008
    Location
    Okinawa Japan
    Posts
    275
    +1
    1
    I'm in the same boat and my list of mods is as big as the next guy. If there is one thing I'm learning it's this:

    1. You need before and after RPM's via a on board tach.....if your motor isnt able to get to the go fast RPM's due to being over propped or what have you speed will decrease.

    2. Just adding parts all at once makes it very difficult to find out what is "holding you back". Put the stock prop on would be a start. I'm no expert and others will chime in but if you aint banging the limiter the prop should not change. Just adding exhaust on a two stroke makes huge leaps and bounds but on these four strokes I can't see that kind of speed loss from helping it breath better. Strange!

  3. #3
    Mik72e's Avatar
    Join Date
    Jan 2006
    Location
    Australia (Sydney)
    Posts
    1,472
    +1
    3
    check ur pump shoe and ride plate are sitting higher than the hull and not causing draggggg

  4. #4
    fxho's Avatar
    Join Date
    Feb 2009
    Location
    MIA 305
    Posts
    168
    Does the free flow exhaust make you lose speed at top end??

  5. #5
    Mik72e's Avatar
    Join Date
    Jan 2006
    Location
    Australia (Sydney)
    Posts
    1,472
    +1
    3
    coming more from a 2 stroke back ground the free flow usually loose very little rpms with maybe a spped loss of .5 to 1mph.

    In you case its much bigger speed loss have you try putting back to stock for to see what happens

  6. #6

    Join Date
    Oct 2008
    Location
    Glasgow, U.K.
    Posts
    19
    Assuming that water conditons and the amount of fuel you were carrying were similar on both days, I can't see how fitting a free breathing exhaust could cause your dramatic speed loss.

    Did you notice what your maximum revs were on both days ? If they were the same, then your speed loss must be due to an environmental change.

    With Riva stacks and filter, my 2007 fxho revs out at 10,300 ( I think, because it gets a bit blurry )

  7. #7
    CT Marsh Dredging Crew STItaxi's Avatar
    Join Date
    Jul 2008
    Location
    Madison, CT
    Posts
    975
    I don't think a free-flow would cause a speed loss on a high-revving 4-stroke like that. And even if it did, 3mph is a lot!

    I'd double check the grate, shoe and plate like others have said. Make sure they aren't sagging or crooked. Also make sure there isn't anything stuck in the pump or wrapped around the driveshaft.

    I'm not sure how the rev limit works on the HO motor, but if everything else checks out, maybe you're banging the rev limiter with the FF? You should check your RPMs.

  8. #8
    fxho's Avatar
    Join Date
    Feb 2009
    Location
    MIA 305
    Posts
    168
    Quote Originally Posted by Mik72e View Post
    coming more from a 2 stroke back ground the free flow usually loose very little rpms with maybe a spped loss of .5 to 1mph.

    In you case its much bigger speed loss have you try putting back to stock for to see what happens
    I cant put the stock exhaust back on because when you removeit you have to cut it up and you some of the plastic asa cupling between the connection on the water box and the exhaust exit on the hull.. so no turning back to stock

  9. #9
    fxho's Avatar
    Join Date
    Feb 2009
    Location
    MIA 305
    Posts
    168
    Quote Originally Posted by dudenstumpy View Post
    Assuming that water conditons and the amount of fuel you were carrying were similar on both days, I can't see how fitting a free breathing exhaust could cause your dramatic speed loss.

    Did you notice what your maximum revs were on both days ? If they were the same, then your speed loss must be due to an environmental change.

    With Riva stacks and filter, my 2007 fxho revs out at 10,300 ( I think, because it gets a bit blurry )
    the day i ran 63.2 on gps the water temp was around 70-75 degrees and when I took the ski out this past weekend the tempature was around 90 degrees. As far as the fuel tank, I was running around the same fuel weight. I really didnt focus on the revs that day. Next time I take it out I will pay attention to that, before it was aroun 10,200-10,300.

  10. #10
    fxho's Avatar
    Join Date
    Feb 2009
    Location
    MIA 305
    Posts
    168
    Quote Originally Posted by STItaxi View Post
    I don't think a free-flow would cause a speed loss on a high-revving 4-stroke like that. And even if it did, 3mph is a lot!

    I'd double check the grate, shoe and plate like others have said. Make sure they aren't sagging or crooked. Also make sure there isn't anything stuck in the pump or wrapped around the driveshaft.

    I'm not sure how the rev limit works on the HO motor, but if everything else checks out, maybe you're banging the rev limiter with the FF? You should check your RPMs.
    I will double check all of that. Thanks for the advice. I will check all of that this weekend but I've never had an issue withthe grate, show, nor plate. If the rev limiter is banging, what should I do STITAXI?????

Page 1 of 3 1 2 3 LastLast

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. RXP Stock top speeds?
    By dgmoore in forum 4-Tec Performance
    Replies: 29
    Last Post: 06-15-2016, 05:25 PM
  2. 1995 speedster overheating at slower speeds
    By rahlake in forum Sea Doo Open Discussion
    Replies: 0
    Last Post: 06-01-2012, 04:50 AM
  3. Liquid SPEED Show LAST show of the year..Oh man DONT MISS THIS!!!!
    By PowerShot in forum Race Events and News
    Replies: 0
    Last Post: 12-27-2009, 07:10 PM
  4. Speed Limit on the Chain- oh no!
    By BudLightBunnY in forum Open Discussion
    Replies: 21
    Last Post: 12-18-2007, 09:53 AM
  5. my spx is slower top speed now.....why!!!?
    By levonhelmet in forum 2-Stroke Performance
    Replies: 3
    Last Post: 09-06-2007, 05:59 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •