Thread: I gained 250 rpms!
08-06-2007, 10:16 AM #1
I gained 250 rpms!
This one surprised me ... I found that my BOV blockoff was leaking some boost, so I had that welded shut ... fixed that POS. I have two superchargers, both new clutches, metal washers, and shimmed to 105 in lbs slip, etc, etc. Funny thing is that I have been down rpms, running 7700-7750 most of this season no matter what I do. I did some upgrades this winter, including switching to a Riva rear air intake ...
Anyway I put the upgraded IC tubing back in, cleaned all the silicone couplers, and expected to see 8000+ rpm (finally) ... and did not. Ski still only run 7750 rpm, as has been the case all month.
I finally pulled the cowl and seat off and brought them into the cottage, and looked the rear air intake area around the rear seat/grab handle. I had never opened up the grab handle at all, and it looked like a pretty small area to suck air into the rear air intake. I took a cutoff wheel and opened the seat release opening so that the opening goes all the way across to the handle area, basically cutting off a couple square inches on each side. Stuck things back on the ski and blasted off - BAM! 8000 rpm!! And it pulled 8000 rpm all day ...
Soooo ... if you too have a rear air intake and your rpms seem low, pull the seat off, see if your rpms go up, if so, do some work on the seat/grab handle to open up that area a bit and let more air in. I am curious if others have found similar results ... I was shocked to instantly (within 15 minutes, no other changes) gain 250 rpms.
08-06-2007, 10:19 AM #2
I just HAD to do it to You Vern!
You were begging for it!!!
08-06-2007, 10:23 AM #3
- Join Date
- Dec 2006
- Crest Hill, IL
08-06-2007, 10:28 AM #4
Sorry Mark, I know ... I shoulda snapped some pics ... I was just so excited that I had my dang rpms back, I just jumped on and screamed off to have fun ... My friend Dan confirmed that opening up this area really helps rpms on rear air intake skis, but I wanted to let people know, and also ask if others found the same thing ...
08-06-2007, 10:33 AM #5
Good Job Vern. Just yankin your chain, buddy.
08-06-2007, 11:13 AM #6
I'll try this and let you know what my results are Vern. I just went to the rear intake and was a bit disappointed at the results (or lack of). I wonder why Riva would not recommend opening up the handle if this is the case.
I thought about drilling 2 more flow rites in it... what I did do was open up the water drain holes to about 1/2" (+ added 2 more) to allow quicker draining.
One other thing I wasn't too happy about- after riding the other day I took my seat off and found a bunch of crap sitting on top of the intake's pre-filter; dirt and small pieces of tree debris... I was thinking that I should maybe have left the big filter up front inside the hull...
08-06-2007, 12:07 PM #7
You HAVE to cut holes in the grab bar. with or without flow rites. I suggest no flowrites unless you are jumping waves/surf riding etc...
Last edited by The Bandit; 08-06-2007 at 01:57 PM.
08-06-2007, 12:13 PM #8
I almost cut my seat bottom too ... but did not. But the seat bottom really kind of protudes down quite a ways and is pretty close to the intake too. I would kind of like to cut the bottom of part of the seat there too ... would allow much more airflow in it looks like, but I did not want foam or water possibly getting sucked by the intake.
08-06-2007, 12:25 PM #9
Cutting into the grab handle is all you need. It will get all the air it needs.
96 air 90 water humid as hell and I was still getting 8600 all day yesterday.(rpm's are too high, I know)
08-06-2007, 12:33 PM #10
Thanks Steve, good to hear. Did you just cut in holes basically the size of two 2.5" Flo-Rites?
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