Other bpipe pressure relative to amount to open the top water screw for best spray patterns

[masterblaster]

swapmeet..yes in essence that is what makes the most diff in tuning a ski to make more power,Ive seen so many people do it half ass fig Id post our results with many many hours of tuning.I find that setting up your bpipe correct you stand to gain more "usable"power for what most of us do than any other mod,more power can be found here than,any one of,bigger carbs,tl ign,lite weight fw,porting,mag pumps,high comp heads,big intakes,carbon reeds,basically what ever you throw at a ski,wont make as big a diff than a properly tuned bpipe.
Powervalve motors and very large CC motors being the only exception,even then only a slight diff in water settings need to be changed to achieve the same result

 

[RMBC Freeride]

Here are some pictures of the bottom screw spray pattern at various openings.

Definitely want to thank masterblaster for bringing up this topic. There's alot of good info here.

I had neglected my bpipe screw settings for a long time because my previous engine setup was pretty well dialed in. However, this spring/summer I started messing with a new engine and needed to address the water in the bpipe. It turns out that my middle screw was leaking a ton of water even though it felt like it was closed all the way. I broke it open while water was flowing thru it and then re-closed it and stopped all water flow. Turns out I had way to much water entering my pipe. Bottom was 1/2 turn open and the middle was leaking and I am now feeding the engine and pipe via (2) 1/2" water lines from a mag pump. I have very high water pressure to the pipe.

So after figuring that out, I messed with the spray pattern as described by Torr. Here are the results. I only wish I had a pressure gauge on my garden hose to know how much pressure was going into my pipe. (I did this using the bottom screw just for reference, it is hard to see and photograph the spray pattern of the top screw.)

Barely Cracked open (approx 1/16th turn)

1/8th turn open

1/4 turn open

3/8 turn open

1/2 turn

5/8 turn open

My bad, I didn't photo it at 3/4 turn or above.

Sent from my XT907 using Tapatalk 2

 

[Crab]

Good post Neil, we got the freak flatwater flipping today plate to plate, video is on FB under "Jeff Smith (crab)".

Water tuning is critical with the little 735cc...

 

[swapmeet]

Thanks MB! I missed your post.


So, which one of those is best? The photo with the 1/8th of a turn looks like a nice fine spray. :dunno:

 

[Skirunner24]

Great post and pics. I too had no idea such fine adjustments could make such a large difference in spray pattern till I hooked up my headpipe to a gardenhose to check it out.

 

[lanmine657]

Awesome experiment Neil!!! Where you been brother

 

[masterblaster]

rmbc,in 99% of skis especially with 1/2 line the 1/4 turn setting you have illustrated would be your best bet,if you can get the top screw to spray just like that..its a little harder to see and photograph though. a little cheater tip Ive come up with is using a ultra fine dremel wheel and cutting a tiny X in the tip of the screw.I find I can get a finer wider spread pattern with the water opening the screw less. Its diff for every pipe though you have to use this process to verify it.

 

[Freakrider]

My top adjuster is completely sealed off with carbon, prolly from being closed so long. Thinking about experimenting and taking head pipe off and clearing it out. Might see if it improves low end response, I keep wondering why one engine builder insists that top screw open brings moisture into topend. What kind of evidence has he seen over the years to reach this conclusion ? Rust on cylinder cross hatch ?

Edit: masterblaster, reading your response again today in post # 5 and the engine builder's thoughts were that the engine while running draws moisture back into the topend if top screw is open any.

 

[Freakrider]

Took head pipe off and top adjuster was not clogged, hooked it up to the hose and checked spray patterns. Gonna try top open only 1/2 turn, middle n bottom closed since the top screw is for low end hit. Also have seen msd water injection just at the top and the hit was amazing. What do you guys think of this setting ?

 

[masterblaster]

I would guess this builder was talking about moisture dripping outa the head pipe top screw after the motor shuts off and sits.With exhaulst flow going out while the motor is running,no water is going down the mani into cylinder. even if it wasnt runnin,hold the pipe upside down at the angle it bolts up and run it on the hose and youll see what I mean.
Ive seen msd water injection put right in the first inch of the headpipe where it bolts to the mani and still no issue.
Its always a good idea to fog your motor if its going to sit a bit,if your really nervous or its gonna sit long term,you can always pull the top hose on the head pipe and blow the headpipe dry with a compressor

 

[Freakrider]

I would guess this builder was talking about moisture dripping outa the head pipe top screw after the motor shuts off and sits.With exhaulst flow going out while the motor is running,no water is going down the mani into cylinder. even if it wasnt runnin,hold the pipe upside down at the angle it bolts up and run it on the hose and youll see what I mean.
Ive seen msd water injection put right in the first inch of the headpipe where it bolts to the mani and still no issue.
Its always a good idea to fog your motor if its going to sit a bit,if your really nervous or its gonna sit long term,you can always pull the top hose on the head pipe and blow the headpipe dry with a compressor

Engine builder was referring to sonic wave with the expansion chamber. See this link regarding transfer cycle.

http://en.m.wikipedia.org/wiki/Expansion_chamber

 

[Freakrider]

Yesterday I ran just the top screw open little over one turn and it had more response low end compared to just the middle adjuster open. Anyone think that's too much water flow at over one turn ?

 

[swapmeet]

Bumping this up, finally getting around to doing this. My bottom screw is really dumping water, and the screw is seized *surprise face*.

 

[masterblaster]

freakrider..old post but where did you end up on the top screw,did ya ever take it off and get a visual on its pattern?

swap...seen that more than a few times, put some waterweld in the hole and sand it flat.

 

[Freakrider]

freakrider..old post but where did you end up on the top screw,did ya ever take it off and get a visual on its pattern?

swap...seen that more than a few times, put some waterweld in the hole and sand it flat.

Top screw open 3/4 turn the others closed...did not check spray pattern but bottom end hit improved a little from previous setting of only middle screw open.

 

[swapmeet]

freakrider..old post but where did you end up on the top screw,did ya ever take it off and get a visual on its pattern?

swap...seen that more than a few times, put some waterweld in the hole and sand it flat.

I forgot to update. I played with this idea for a few hours on Friday. Got the other two holes sealed up with new BK twisters.

I tried to get a spray pattern and definitely struggled. I sanded, filed, and cut on the screw trying different methods.
The shapes I tried were a point, point with grooves cut (dremel disk) Offset point or basically an angle, and the OEM end with a X cut into it.
All of these options never yielded consistent patterns. If they were cranked, or maybe a 1/4 turn open, they had a bit of a spray, anything beyond that it was just a stream of water.

What I have has a good spray pattern, but its still dependent on the water pressure.

As mentioned before, If I don't know how much pressure is at the head pipe, in conjunction with my flow control and by-pass restrictions, it's almost a shot in the dark.

If the qty of water i'm currently injecting will keep the exhaust cool enough, then I should be able to maintain a good pattern.
BUT, If I back the screw out, the pattern immediately becomes a stream because of the shape of the hole in the head pipe.
But its worth a try. I'm excited to try it out.

If anyone has a suggestion on a better way to achieve more of a spray pattern please chime in.

 

[LegDragger64]

No matter what the spray pattern looks like with pipe off on a garden hose , it's gonna be a lot different with 7,000 rpm exhaust gas blowing through it.

 

[swapmeet]

Good point.

 

[masterblaster]

freakrider,its really worth a few min to take it off and check the other holes are really sealing and try and get a decent flow pattern on the top hole. So much of the port timing and flow porting of a given motor setup depends on response from the pipe in where you want the power curve to begin.

swapmeet...if you have large cooling lines with no restrictions between the pump and the pipe you should be able to get close to the same pattern with the pump as the garden hose. Its prolly over kill but i have 2 skis,i took the head pipe off each and hooked them to the other ski cooling input while running it against the bulk head in the water for brief wot blasts with the flow control valve disconnected on the output side and directed overboard for minimal adjustments. while the patterns may have been slightly diff with more pressure,you couldnt visually see that they were.
some bpipes have to large a hole to give a good spray flow pattern,try filling it and re-drilling it smaller. you will likly get plenty of water through it as is though for our kind of riding. One screw only slightly open is almost always enough to keep the pipe plenty cool enough not to melt couplers.only question is will it be enough water to get the pipe to hit in the lower rpm band.
while im sure it looks better with high rpm exhaust pushing on it, a wide misting pattern will effect the sound wave in the pipe much more than a needle point stream hammering the other side of the pipe.ever seen the spray pattern a msd water injection tip produces? they dont use a straight water jet for good reason.

 

[Raddog]

I just went out to the garage to look at my head pipe after reading through this thread twice and both top and bottom holes were plugged with carbon(middle is stripped and permently shut) ran a tiny drill bit through and cleaned them out, will have to put the garden hose on it tomorrow. How this didn't melt a coupler is beyond me.
Cheers Ray