07-11-2007, 01:00 PM #1
- Join Date
- Jul 2006
From an old thread but could be revisited.
This was from "vern" in a brainstorming thread last year.
here is another collection of emails that I found very interesting. The first section is from my emails with Rick Pot, and other pertinent forum responses followed from other folks on Riva's site. This was a few years ago, but the ideas are the exact things that are still paying off today in the GPR world. *
Another very interesting update. I talked to Rick from R Pot Design, who was very upfront and helpful. If any of you read about his carbon fiber, clamshell, 1328 cc Don Lamey motored GP1400RC, you may have had a few questions. The answers tie into this thread very well - IF ANY OF YOU HAVE NOT BEEN PAYING ATTENTION, PAY ATTENTION NOW!
The boat has triple pipes, weighs 475 pounds, etc. Sounds rockin', but only went 75 mph on the day of test (0 - 60 in under 4 seconds though). What happened is that Rick had the boat doing 82 mph, loaned out his igniter for a week, then shortened the intake grate blade and narrowed the sides of it in an attempt to get more water in the pump. Then he got the igniter back the same day Watercraft Illustrated came out to do the story. He had no time to test his latest mod (the intake grate reduction grinding), which LOST him 300 rpm and 7 mph, DUE TO OVERFEEDING THE PUMP. After some work on the intake grate, building it back up even thicker than before, he ended up with 84 mph on pump gas, no nitrous. Sorry, don't know which grate he was using, but the effect would be similar to the grates most of us are using.
His opinions on the subject in this thread? 'Fatten up the intake grate bars, or narrow the pump cavity to gain speed'. His boat has over 270 horsepower, yet lost 7 mph due to overstuffing the pump. Think about the impact on our wimpy 155 - 165 hp single pipe boats ... He said at speed, there is literally water backing up at the intake/impeller area, which reduces pump efficiency significantly.
I know we probably won't gain/lose 7 mph, but even 3 mph for carefully filling the intake cavity and/or increasing the intake grate's restrictive impact is worth pursuing. That would put some folks at 74 - 75 mph with single pipes! Also, should free up some rpms for you 14/20 guys. Rick did say 'Do not mess with the back of the grate', the biting edge should not be modified. Keep the work up towards the middle and front of the cavity/grate, as I had guessed earlier. I still favor building up the intake cavity first, allowing the safe slowdown of our grates to still work and keep us on the ski when chopping the throttle.
My take - a square or rectangle is an inefficient shape for an intake. I would fill the 'corners' at the top of the intake first, test, then work down, rounding and smoothing out the front of the intake area, then attack the grate itself. Who knows, we may get close to five mph with an optimal setup. People who have succeeded are not talking ...
vern, if you keep thinking about this, the little light bulb will go on over your head (idea lite.) I figure my adjustable grate would be worth 2-300 rpm, and at least 1.5mph. sounds like I might be able to do better than that. keep up the good work!!
Wet Wolf Tech
Hey Guys ,This is what I have already done to a XL1200ltd, the stator section of the pump is shortened so as to reduce the pump volume by 500cc. 37mm shorter is the tip.
Next is the R&D grate , I have bolted two pieces onto the vertical centre bar in the grate, this narrows the intake area by 16mm.
I GPS today at 64mph in choppy water using a 13/19 concord at 7260 rpms , I have also made a 3 degree up cone for the pump that extends back about 20mm more than a stocker much like the Adjust a Thrust . This thing hooks up incredibly ,it sustains speed that would normally drop off in rough water. We have a 2Hour enduro on this weekend , we a really looking forward to it. I will post the results!
I wondered when one of you was going to mention the pumpstuffer. Inventioneering also make an intake grate for the sea-doos that is essentially a pump stuffer, although this stuffs the middle of the pump. There are a lot of doo guys that swear by it.
Ideally, at low speed, the pump intake needs to be opened up to allow as much water in as possible for the best holeshot and corner to coner performance. As speed increases, the intake needs to be reduced accordingly to prevent overstuffing.
the optimum setup should be self adjusting and self contained. This would also be the simplest setup.
Rich, look at the concordes inlet DUCTS.
I have said enough, probably too much. I hope to have a working prototype by the end of the summer though, I'll keep you posted.
Philip, you may want to try some aluminum Air Conditioning tape that sells at any hardware store. You can cut it easily and it adheres very well
liquid---if you had your ski here within 15 minutes it would be running consistant 74's to 75's that you could see for your own eyes----- for those of you who are still skeptical, and want to do some of your own homework---heres a little hint---there IS speed to be gained from every single component under your hull and even the hull itself-not all of the speed comes from the pump stator veins as some of you mistook that all the speed comes from-you have to look at the whole package-pump,impellor,intake grate,exit nozzle,steering nozzle,rideplate,trim tabs,sponsons,wear ring,hull trueness-- if you "experts" arent seeing the light by now then all hope is lost----hear what i have to say---there is speed to be found in every single part under there!!!!!----just as easily as you lose a mile from bolting up a set of trim tabs--for ex---you dont think for a minute that you couldnt gain a mile from a "custom" set---please
* the last paragraph was from Carl at Island Racing, a speed guru, esp on GPRs
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