04-14-2012, 05:11 PM #1
Less is more... new best of 85.3!
I have to admit - I was a bit confused when I did the Vtech flash to 8360 and found I'd lost speed. I only beat my previous best of 78.3 by a paltry .5mph. The ski felt MUCH stronger with the tune, but I was disappointed that I didn't see a bigger gain up top and it seemed like I was banging on the rev limiter.
I'd placed an order with Erik @ SFR this week to tweak a couple 15/22R props I'd had. Both to 13/23.5, one cutback. He'd emailed yesterday to let me know they'd shipped; I paid the man (same day turnaround - love it) and he emailed this morning to confirm payment, said to let him know what I thought.
I told him I couldn't wait to try the new impellers and hopefully they'd help with me hitting the rev limit so quick. His reply: "even though you bumped your rev limit up 200 rpm and your hitting the rev limiter you will not pick up any speed because of the fact you are hitting the rev limiter. one thing you can do is to ride the ski at WOT and slowwly back off the throttle lever until you can hold a steady rpm just under or without hitting the rev limiter."
After knocking out my spring chores this afternoon (powerwashing the deck), I threw my vest on and went out for a run to try it. Ambient temp 68 degrees, water is low 60s, less than 10' above sea level - mild wind, a little chop in the open areas. First loop of the lake got an 80.9mph! Holy crap - he was right!
Decided to try again - stayed into it... hit the 8360, then back down till I see 20rpm less and try to keep it right about there (ends up being 3/4 throttle). Finish the loop - look down at the GPS speedo app, and it's showing a top speed of 85.3! Did an export of the data - consistently above 80mph, multiple readings on the lap as I played with the throttle at or above 83mph.
Lessen learned. Any monkey can just pin it... just like we tell the guys on their bikes at the track when we coach them... throttle control.
Psyched to get some more work done this week (Riva valve train upgrade, new props, etc)... can't wait to see what it does after those! Thanks to Jerry for all the advice and parts, Bill @ WMF Watercraft - I've known him since we were kids and I swear he's having as much fun with this as I am, and Erik at SpeedFreeks Racing... that quick reply on a Saturday made my weekend.
04-14-2012, 06:56 PM #2
- Join Date
- Feb 2011
04-14-2012, 07:14 PM #3
Congrats, what app are you using? What are your mods?
04-14-2012, 07:35 PM #4
04-14-2012, 08:00 PM #5
App is the paid version of "SpeedBox" from Hans Schneider. Logs the last 3 hours of data as well - tested it last year versus a GPS-based lap timer from my race bike and the speed was consistent. I think the tailwind helped push to 85+, but I'll take it...
Mods are as follows:
2008 RXP-X (bought off REID2168 a couple years ago)
Filled Ride Plate Holes
R&D Intake Grate
Riva 4" Front Air
Riva IC Relocation Kit
Riva RRFPR w/ Walbro Pump (set to 60psi)
Riva Adj Exit Nozzle w/83mm Ring
JD1 Pump Pressure Relief Kit
Riva XX Charger Upgrade + Viton Seal
HKS SSQ Blowoff
Solas 15/22R (untouched)
2* Wedge + VTS Rod
Reverse Bucket Trimmed
Riva Pro Series Sponsons (middle position)
Riva Pro-Series OPAS Blockoffs
Riva Waterbox + Thru Hull Exhaust
Riva Catch Can
Intake Flame Arrestor Removed
Vtech Flash @ 8350 RPM
It's coming out of the water this week for some more work:
Riva valve train upgrade (to go to Vtech flash for 8600)
Innovate MTX-L for AFR monitoring/logging
Riva Rear Air (will test back to back)
Next weekend, I'll have the tools on the dock/lift to play with the following:
Trying two SFR tweaked props - 13/23.5 and 13/23.5 cutback
R&D Anti-Cavitation Cone + Spacers
Erik says the cutback prop will have more cavitation on the holeshot but pull better midrange. As much as I'm playing with top #s right now, most of my actual riding is on a course we have on the lake, so the midrange is good. I'll try the cut prop first, see how the cavitation is, then put in the r&d cone and see how they feel.
The ski feels great - it'll catch and walk away from my wife's ~74mph Stage 1+ RXTX... shot some video of it the other night, it's wild.
04-14-2012, 09:37 PM #6
very nice speeds.... id love getting my rxp at those kind of speeds... but is doubtful to see 85
04-14-2012, 10:04 PM #7
ryan, your ski sounds like it's going to be a runner when you get the prop dialed in!!!!!!!!! what kind of ride plate are you running?
in my testing i have found the R&D cone to lose rpm and speed in the rxp-X
04-14-2012, 10:17 PM #8
Good info on the cone. The perk to a lot of this is I can move stuff over to the RXTX.
Thinking about pressure relief now. It's got the JD1 kit in it now - don't know if I should do more. No signs of stuffing so far...
04-14-2012, 10:36 PM #9
Was just wondering what the results of the added squeeze of the venturi with the cone and spacers will be. Be careful as this may result in added pressure in the tunnel causing the ski to stuff sooner even with the PRV. Mine tried to stuff at 78 with the Worx grate and 1 JD PRV. Be on your toes for sure if you know what I mean....
04-14-2012, 10:44 PM #10
if it's the ride plate that was on reids ski it should be one that i did for him now i understand why your ski is running so good!!! i would not add any more press relief than you have now. i have run an rxp-x with no pressure relief's @ 86+mph with just an R&D intake grate, 83mm nozzle and my rideplate all day long..... as well as a few 84mph ski's.
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