Shave the rave??????

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brock1

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So i went for a little cruise last night and was paying alot of attention on how my 96 xp was running ....It was really running crisp with good response but i couldnt help but notice the very noticable difference of when the raves open up as opposed to when they are not...and in doing this it gave me an idea ....if the point of the rave is to open up and make the port bigger why cant you shorten them up on a stock engine bore and gain more low end power instead of having to wait for them to open up...I would assume it might take a small amount of tuning but i dont see why it cant be done...in my eyes all it would be doing is making the port bigger all the time allowing that extra power then when you hit it it would just open the rest of the way....if im off track please put me back but i just cant help it i love messing with this stuff
 
The RAVEs don't add power. They move it.

Adjustable exhaust can not change how much power the engine makes, it can only change the RPM at which it makes it.

I suggest leaving it alone... they did a fairly good job with it.

opening the port, which actually you are raising it, so it opens sooner as the piston moves down, will lower your low RPM performance.

I find it funny that this forum has a yamahahama ad on it...
 
im sorry i should have worded that differently.....i meant basically what you said ..not add power but change the rate at which the power kicks in i guess i would say......my thoughts are bigger port and more fuel (biggerjets) would make the low end performance beter
 
I may have read it backward... but if they are open all the time... you will loose low end torque, and it will idle like crap.

Without a doubt... the RAVE system gives the 800 a "Dirt Bike" feel... but that's the beauty of the system.

If you want to smooth out the system... then sit, and fine tune the RAVE's and water regulator. If you spend some time with it... you can make it seamless. This is one reason why I suggest making the RAVE adjustment all the way tight. It will give you very nice mid controlability, and torque... but they will still pop open around 5500, and give you that high RPM blast.
 
...my thoughts are bigger port and more fuel (biggerjets) would make the low end performance beter

OK.... that's the confirmation I was looking for.

Bigger ports KILL low end performance. That's why Rotax went to all that time and trouble to build a power-valve engine. On a 2-stroke... more back pressure, and/or "Retarded" port timing will enhance low-end performance. And the opposte holds true... advanced port timing, and low back-pressure gives high RPM performance.


Oh... and bigger jets don't make power. The PROPPER jets make power.
 
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OK.... that's the confirmation I was looking for.

Bigger ports KILL low end performance. That's why Rotax went to all that time and trouble to build a power-valve engine. On a 2-stroke... more back pressure, and/or "Retarded" port timing will enhance low-end performance. And the opposte holds true... advanced port timing, and low back-pressure gives high RPM performance.


Oh... and bigger jets don't make power. The PROPPER jets make power.

ok i thought maybe i was going out on a limb there but i thought it was worth a shot.......i just am not happy with the low end side of this ski....but as the woman says...i will never be happy with it..im a speed and power fanatic so i want it as fast and as powerful as can be......might not matter anymore though i have a guy that wants to trade me a 1997 challenger that needs a top end..(has 130 compression) so i think i may off it for that and ride the other skis i have
 
I wouldn't mind a smoother transition, but that would have been more complex, thus less reliable, and more expensive to accomplish. the selenoid would be a place to start, it's just an on/off, but if you vary it by RPM, ie closed up to 3500, then 1/2 open at 4k then full open at 5k, it might be smoother, but half air pressure doesn't always equal half open raves.

You could electronically control them, like the new snowmobile ones do...
 
The 96 seadoo racing handbook has all the go fast RAVE info your looking for. Basically, screw the red caps all the way in then back out 1 click at a time until you achieve the best performance, you really need to do some radar runs to properly tune the RAVE's. You can also hard jet the water control valve on the water box with a Mikuni carb jet and one in the head pipe. Spim has this done on his ski that I noticed in one of his engine pics. Even that should be tuned with the water temp in mind, you can run too small of jets on get the exhaust too hot. Google for the racing handbook, lots of good info in there for sure! The entire system is very trick even in stock form for sure.
 
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i only clicked this thread because I thought "shave the rave" sounded kinky...

but yes, i noticed improvements with hard jetting the WB, you really just bump down the jets by 5 until you get what you want, but i saw improvements. actually one of the most noticeable differences was water injection when I had the MT version, i had it hooked up to a toggle switch on my dash, and you literally would feel like somebody hit the brakes when you turned it off.

and yes, several runs are necessary when trying to do a "performance tune"
 
WELLLLLLL...........................................


If you want better low end... tighten the RAVE's, and the water regulator. Also... you may want to put in a larger water jet in the pipe. A wet pipe will smooth out the transition. Basically... keep the pipe wet, until the raves open.

Because the way the system works... and because of the nature of our engine (RPM's can hit quick) it's hard to get it perfectly smooth.

On my personal XP... it's a hard hit at about 5500 rpm. I have the RAVE's and water switch at about the same time. My cross-over is like hitting a light switch. But... with that said... I have GREAT low RPM torque. But I run a high pitch swirl impeller, and bored my pump. (so my thrust is in a different range)

On a PWC all adjustments effect everything else. I set up my ski's to rip my arms off, and go fast on rough water. But... I'm sure on flat smooth water... my XP is only running around 52~53 MPH.
 
Oh.... if you want fast and powerfull... go buy a new 260 seadoo ski. Expensive... but crazy fast.
 
WELLLLLLL...........................................


If you want better low end... tighten the RAVE's, and the water regulator. Also... you may want to put in a larger water jet in the pipe. A wet pipe will smooth out the transition. Basically... keep the pipe wet, until the raves open.

Because the way the system works... and because of the nature of our engine (RPM's can hit quick) it's hard to get it perfectly smooth.

On my personal XP... it's a hard hit at about 5500 rpm. I have the RAVE's and water switch at about the same time. My cross-over is like hitting a light switch. But... with that said... I have GREAT low RPM torque. But I run a high pitch swirl impeller, and bored my pump. (so my thrust is in a different range)

On a PWC all adjustments effect everything else. I set up my ski's to rip my arms off, and go fast on rough water. But... I'm sure on flat smooth water... my XP is only running around 52~53 MPH.

thats pretty much what i want...i want it to rip my arms off when i am idleing and mash the throttle i wanna feel that g-force LOL how much did you bore the pump and what pitch swirl are you running
 
I don`t think I`m comparing apples to apples bc ski`s VS heavy boat, but I believe what Doc said about smoothing the transition.
After hearing about a supplement that BRP came out with a few years after the 787 arrived, the info was to have the RAVE`s out 2 turns or flush with the black cap... After repairing a leaking rave, I did just that. Also at the same time I had installed the replacement WCV and also readjusted them to the same spec from what I found when I got the boat which was 3 turns out.
I can say with 100% certainty that it is def smoother, more consistent pull across the rpm range. It still feels strong when the rpm`s get up there, just doesnt quite feel like that "powervalve" hit, a little less agressive, but this is in a boat...

good topic BTW...
 
thats pretty much what i want...i want it to rip my arms off when i am idleing and mash the throttle i wanna feel that g-force LOL how much did you bore the pump and what pitch swirl are you running
hahah one answer, GP1300R with a few mods! for that 2 stroke rush!...lol...
 
oh yeah i wrode the gp1200 last year and it was a blast ...i would love to have one

I had a very nice custom GP1300R, sold it this past spring to buy the boat, call me crazy!:willy_nilly:

off topic pic...:biggrinjester:
 
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Oh.... if you want fast and powerfull... go buy a new 260 seadoo ski. Expensive... but crazy fast.

I did... test drive a RXP-X 260.

Wasn't impressed. like my 02 XP more.

It's a very nice ski, but there's nothing fun about it... way too serious.
 
I did... test drive a RXP-X 260.

Wasn't impressed. like my 02 XP more.

It's a very nice ski, but there's nothing fun about it... way too serious.

to many gadgets on the new ski`s today. riders should build their skills up rather than rely on a BRAKE... the new ski`s took all the fun out... JMHO...

the next thing that will get blamed for an accident, "well the brake didn`t work"... (on the IBR models)
 
You can't go hard brake then hard throttle like you can in a car (yes I know why, and the mechanics of the system).

which, to me, makes it pointless in a race.

They are selling the whole brake thing on safety... it just doesn't add anything for me. i usually put mine into a spin to stop on a dime.
 
My Big Genesis has the 1200cc 3cyl Polaris Domestic engine in it. And it's a hoot to ride. Yes, it's big and stable... but it's still 300 Lbs lighter than a new ski.

Anyway... I'll have to go back and check my impeller... but I bored the pump 2mm. So....... I think the impeller was a 17-24 Swirl that I put in. (I will double check)
 
You can't go hard brake then hard throttle like you can in a car (yes I know why, and the mechanics of the system).

which, to me, makes it pointless in a race.

They are selling the whole brake thing on safety... it just doesn't add anything for me. i usually put mine into a spin to stop on a dime.

yip, when i really wanna stop, i do it basically like I used to do it on snow ski's, throw the back end around, pop the throttle to stop momentum, then let off.
 
I'd say if anything use an adjustable exit nozzle, they can be had new for around $250. You can also get an adjustable pump cone that you can fine tune. Or bump up to a nice 12 Vein setback Magnum pump--If you got some extra coin!:thumbsup:

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