Freestyle More Bpipe fine tuning questions or is it something else

[Polish jet pilot]

Intro:

Ski:
727cc, ported (cleaned up windows, bored exhaust window 70% of cylinder diameter, EPIC ignition, 12.1 bar compression (pump gas 98-100 octane in Europe), Bpipe Ltd (bored, polished), jetworks valve, cone, cutback -3 mm 2008 oem prop, bored nozzle 84mm, oem carbs (rejetted, no chokes), dual cooling.

I need more hit. I was running my Bpipe like that (before cc increase and porting and EPIC): bottom closed, middle closed, top opened (2 turns or more).

Now I still run bottom closed, middle open 1/4 turn, top opened about 1.5 turns.

The pipe was cool before and is cool now. What is more important: to adjust the bpipe (top, middle, bottom) or to make it sizzle? I think I need to close everything to make it sizzle - if so will this increase the power output? Can somebody give me some advise?
I was told that I can close all teh screws alltogether if riding freestyle only.

Thank you for helping.

 

[Polish jet pilot]

is it the pipe or is it the prop / pump (I still get no cavitation) and that ski is v. fast on top... porting was done specificaly for low end power (not rising windows at all)

 

[Polish jet pilot]

And yes, I did searches and read Fpipe instructions etc. Need more of a personal input on this...

 

[SUPERTUNE]

Your -3mm oem prop is a problem. Use a 12-17 Skat-Trak swirl.
Pipe settings too wet.
Get a aftermarket dual carb intake system to go with the E.P.I.C. cdi.

 

[masterblaster]

to answer you pipe specific ?. Go back to your original settings. A sizzling pipe does squat for low end responce. Ive done alot of testing on this and find that your first settings work best for lowend and response if you dont care about upper midrange and topend,as many of us could care less about that.Experiment with the top screw way out and take it in slowly and see if you get a noticable diff,I found that with the top screw out the perfect amount I got very good lowend responce and power,and with the slight lack of upper midrange power when I occasionally used it ,the motor ran MUCH cooler as well.
the prop chuck mentioned or a 9/15 big hub hooker helps a ton also

 

[ryan]

get rid of the stock carbs.

 

[chriselmore_1]

so far the best results for off idle snap is to have the top and middle screws closed, bottom open .5 turn out and the stinger dry. my buddy set me up like that. since then then ive gone out and tried several other settings and nothing has even came close... just make sure you are using a cut down stock exhaust hose and not that fp silicone thing with the stinger dry.

 

[masterblaster]

thats opposite of what ive found and fp has on tuning for the bpipe,do you know what the porting durations where on that motor?

 

[kevbo]

Nothing he does will help much until his pump load is corrected.

 

[chriselmore_1]

stock cylinder. Stock bore. 180psi. Solas 13/17 nozzle taper bored to 86.5 @ 2.2* with the stock cone.61x/61x with 46sbn. One of toe best 701 setups I have ridden

 

[Polish jet pilot]

Teach me about pump load - I was thinking that since the engine is strong (v.fast on top) I must tune it somehow so it will be putting the right power in the right time to the water - I ve read many good opinions on the oem 2008 prop (as I was told is more of a Hooker type prop with big hub the pitch I think did not change for years and it's still 13/16. Thus my confusion - many ride props that are around 13/.. to begin with - would changing to lower pitch e.g 12/17 swirl (I've installed 4 of those props and never ridden them - thus no chance to compare) solve my problem? Or maybe I should bore the nozzle a bit more - would this give a similar effect (I think 84 mm for that setup is enough)... 12/17 skat swirl or hooker (bigger hub)??

I tested the bpipe a bit yesterday - I opened the top cionsiderably (2 turns) and the response was soft. I will try to close the top and open the bottom... but I think that there is too much water anyways and the pump is not ok...

I just have to use so much strenght to pull anything that I am so sore after each riding .. would like to have the comfort of just hitting the gas and doing the rest in the air..

 

[Polish jet pilot]

Alos, would you recommend a single carb setup? I have a 48mm blackjack on the shelf - it would go nicely with the ATP manifold - this is to tackle the subject of carburation on that boat...

 

[masterblaster]

you cant just open the top more and not close the bottom and mid,like you said if everything is flowing too much water is going to just fill the headpipe everywhere and defeat the purpose. you sure your carbs are tuned right? A single 48 bj would be nice,but not as hard hitting off bottom as dual 46s or 48s obviously. try that 9/15 with a 84 mill nozzle and the top screw open all othersclosed and you will have a smile on your face for pretty cheap

 

[Polish jet pilot]

I am aware of that and I did the testing methodically. The one thing that is really confusing in general is the various contradictions when it comes to tuning the exhaust. E.g. Chuck recommends to close, top, middle and open bottom. This was also told by other people who are in the jetski / 2 stroke business for years. On the other hand, Ive experianced (previously) more bottom end hit with the top open and others closed (opend even 2-3 turns!). Opening bottom gives max rpm, as far as my knowledge goes - which is good as long as we can get those rpm's quickly enought (e.g not to miss the setup wake and use it all the way). I tested with all screws closed as well for a short period of time - no big changes - with top open my throttle respnse got a bit soft but the hit was a bit better.

This would mean I do need a prop with lower pitch to make that engine get to the max revs faster - would this result in this being a "hit"??

Sorry to ask, I just never ridden a full professional big power ski and not sure on may aspects.

 

[masterblaster]

im not sure why chuck or anyone else would recommend turning the bottom screw open for low end unless they are talking about a powervalve motor? they have much lower initial exh duration and Im guessing dont need the sonic wave in the pipe to come back the same as a non pv to hit off bottom. I tried all settings and found my final settings that made the most power by a bunch to match up with what FP the manufacturer says to do with it for a given result.....imagine that

 

[Mouthfulloflake]

I dont know if you saw my Bpipe ordeal thread or not.
I had many issues like you are having, until I added some restrictors into the lines feeding the Bpipe, to get enough pressure to really MIST the water instead of dribble.

that made a world of difference on my boat.

I ended up with bottom and mid screw completely closed, and the top screw just barely cracked open, just enough water to NOT melt the hose to the waterbox, and thats enough water

I couldnt get any bottom at all out of the pipe configured any other way.

 

[masterblaster]

thats what I found to be true also,pressure is crucial,its gotta mist with force to change the sonic flow of the chamber.good post

 

[Dustin Mustangs]

...until I added some restrictors into the lines feeding the Bpipe, to get enough pressure to really MIST the water instead of dribble.

Uh, did you say that backwards? Restricting before the pipe will lower pressure, after will raise it (at the pipe).

 

[Mouthfulloflake]

put your thumb over a waterhose nozzle, what happens?

Uh, did you say that backwards? Restricting before the pipe will lower pressure, after will raise it (at the pipe).

 

[Dustin Mustangs]

put your thumb over a waterhose nozzle, what happens?

The pressure goes up and the velocity drops in the hose. The velocity goes up and the pressure drops in the stream of water outside of the hose. If you want your headpipe to mist better you want pressure, not velocity.