2002 GTXDI water control valve question

[jimmyluke]

My ski only reaches 6500 RPM. I had this issue last year and haven’t really worked on it since. I’ve read that the water control valve can have an effect on reaching maximum RPM. Last season even though the water control valve when I took it off the ski seemed to be working properly I bought a new rebuild kit for it. It did not help my RPM issue. Someone mentioned about pulling the line that goes from the water control valve to the tuned pipe off while the ski is backed into the water on the trailer and revving the engine up and as the RPMs increase the water flow should decrease. However my ski the water flow continues to increase with RPM. According to my manual the calibrated fitting under the water control valve should be 4 mm or .156”. Mine measures about .118”. I was considering drilling it out. But thought maybe it is a typo, plus in the manual it warns “ caution: do not change anything on the water flow regulator valve otherwise Serious engine damage can occur”. Keep in mind that this manual was only for a 2002 GTXDI and a GTX 4-tec. But I got looking at the manual for my most recently acquired ski- a 20001 GTXDI which also includes some carbureted models. And the manual states that the calibrated water injection fitting for a carbureted model should be 3 mm or .118” (like mine measures) and 4 mm or .156” for DI models. So I am pretty confident it is not a typo. So should I drill it out to the .156” for my DI? Thank U for your help Jim

 

[mikidymac]

No don’t drill out anything. If it’s not leaking water it is probably working correctly.

 

[jimmyluke]

Dang it- I was hoping you would say to drill it out. No it is not leaking water. I was thinking maybe it isn’t working right because according to the manual that line going from water control valve to the tuned pipe is supposed to decrease water flow with increase of engine RPM. Did you ever use this method of checking the water control valve? (by pulling the line off and watching the water flow) It sounds like a reasonable way to check it. I do have another water box off a 2002 GTX that I bought off of eBay last year. It also has the smaller calibrated fitting on it. Although I don’t know if it was from a DI or not. So if the reason you suggested not to drill out the fitting was because I might ruin the muffler I got that covered.
Thanks Jim.

 

[mikidymac]

Running on the trailer probably won’t get up to the proper rpm or thrust for the valve to work.

 

[jimmyluke]

I just checked my 2001GTXDI and it also has the smaller 3 mm I.D orfice as opposed to the 4 mm that it calls for in the manual. I wonder what gives? Is there somewhere to check that might have updates or changes to the manual?

 

[Rossterman]

To be honest I ‘ve disassembled the valve and if it actually lifts the needle when the diaphram pushes up from water pressure it blocks more of the metered fitting. This would cause more water, not less, to go into the pipe as speed (and rpm) increases since it’s blocking flow to the muffler. I know that’s opposite from what the manual says but physics is physics

 

[jimmyluke]

Maybe yours is different from mine I’m not sure what machine you’re working on but I’ve had mine apart a number of times and checked out the mechanics of it and IF the valve does raise- it definitely decreases the flow to the tuned pipe. Matter of fact if the valve went high enough it would actually completely shut off the flow. But I have no idea under operating conditions how high the valve actually moves. The water is constantly free flowing to the muffler/water box and the valve weather it goes up or down does not close or open Anything going to the waterbox/ muffler. When I did the test to my 2002GTXDI last summer (on the trailer backed into the water) I pulled the line off coming from the water control valve to the tuned pipe and as I revved it up the water flow increased which is opposite of how it should act however I was only testing it at I think it was around 4000 RPMs. Maybe I wasn’t up to enough RPMs to start over-coming this spring? so kind of back to my original train of thought apparently you get more performance at high rpm when there’s less water going to the tuned pipe? And like I had mentioned according to the manual the DI machines should have the 4 mm orfice as opposed to the 3 mm orfice going to the water box/muffler. And both of my DI skis only have the 3 mm orifice and was tempted to drill them out but Micki said not to.

 

[Rossterman]

Here’s how it looked to me. Same valve (96 gtx). Water come in from pump hose to body, Some water goes out the bottom where the valve screws onto the water box. The flow on this is affected by the tapered needle (larger at the end so effectively the flow is blocked into the water box as the needle raises up and the wider area now closes off the clearance around the metal washer that sits in the bottom of the plastic valve assy). As water pressure increases with rpm, the pressure acts agains the diaphram and causes it to expand and lift the needle. My thoughts are as water to the water box is reduced, water pressure increases forcing more water into the hose that goes to the tuned pipe. Although most say it works opposite of that, I can’t see anything in the design that logically supports that. What am I missing?

BTW, reducing waterflow to the pipe at lower RPMs seems like a logical approach. Less heat is produced so less water is required. Probably help with low speed power. As engine reaches max rrpms, more water is added to provide sufficient cooling.

There must be something I’m missing if it works the other way around....

 

[mikidymac]

OMG, I can't believe you are still beating this dead horse.

The water regulator dries out the pipe at high rpm to make the engine think the pipe is larger and give more top end power.

Look at the 1996 Seadoo Racing handbook and it describes the operation and theory of it.

 

[Rossterman]

I'm familiar with the literature in the service manual and such. Just wondering what I’m missing. I’ve studied mechanical engineering, was a rotating equipment machinist and instructor for many years so I know how thing operate. For the life of me, I’m stumped. Maybe the tip of the needle blocks the brass fitting that is mounted in the the waterbox effectively blocking flow down low than raises up under pressure?