Custom/Hybrid Planning a PFP waterbox build...cause I'm cheap

[Cannibal]

Ok, so I purchased a used PFP with resonator, and I hate loud skis, so I'm out to build myself a waterbox. Sure you say "why don't you just buy one, they are $225 +shipping"....and the answer to that would be; I'm cheap and believe I can build one for MUCH less, like ~$75.

Here's my parts list so far:

5' - .125" x 4" 6061 flat bar - $12.00
2 - 8.75 x 6.75 x .125 sheet - $18.90
2 - 2" schedule 40 ~ 6" each - I have this
Brazing rods (I will have left overs) $26.79 (includes shipping)
Metal Shipping - $18.33
Total: $76.02

The brazing rods I will order are HTS-2000 rods, and melt between 717 and 737*. The box shouldn't see nearly those temps, so I should be good.

Here's a Sketch Up that I drew that creates a couple pockets to prevent water back-flow and the three baffles should help dampen noise.

The top inlet might change to straight, it depends on where the pipe sits when I mock it up.

Any critique or criticism?

 

[Matt_E]

They look pretty simple. Go for it.

 

[2ride]

Nice...

 

[Cannibal]

Ya they do. I know they claim that theirs "was designed to maintain correct back pressure in the exhaust chamber to obtain maximum performance" but what do I really have to lose? Maybe a few ponies?

 

[swapmeet]

Love this kind of stuff. I'm all about making my own parts. Can you post a pic of those rods?

 

[Cannibal]

Love this kind of stuff. I'm all about making my own parts. Can you post a pic of those rods?

Me too!

Check those rods out here: http://www.aluminumrepair.com/

You have to buy a lb at the minimum, but I found smaller quantities on ebay. I've brazed other metals, but never aluminum, so I'll need some practice pieces.

I figure I'll completely braze the baffles to one side of the box, then install the other side and spot braze through some drilled holes.

 

[swapmeet]

Ah, I have some of those. I use mapp gas and it takes forever to get hot enough on the stuff I've tried to bond. Oxy Acetelyne (sp) is too dirty.

Maybe with the thinner material you'll have more luck.

 

[Cannibal]

They say oxy/acetylene works fine with a neural flame (not too much acetylene), but propane up to .25" also works according to their website, then Mapp for thicker, then oxy/acetylene for heavier jobs. A rose bud works best, all you are doing is heating the metal up, you don't even need to heat directly where you will braze if acetylene soot is an issue, which it really shouldn't be with a clean tip and flame set correctly.

I'll have to play with it. I might end up just using propane or Mapp, but oxy/acetylene was my go to for this.

 

[keith t]

but what do I really have to lose?

too much backpressure or incorrect design could lead to higher exhaust temperatures - and melted piston crowns ?

subscribed anyways because what you are doing looks good

 

[Kawastyler]

I build a box with 3 baffles years ago and it dosnt work. To much flow resistance. For my Bunpipe replica i have a box with a baffle i middle half high off box, in/outtubes 4cm over ground off bottom. Tested with b-pipe and works good. Louder then stock SJ/SXR but no compare to PF with resonator.But its a problem from our carbonchamber too.......back to back tested they are louder then FP-chamber:-((((((

 

[CARBONX2]

Use the silencer design software on this page, it does work on bigger engines
http://www.mh-aerotools.de/airfoils/javapipe_en.htm

 

[JetManiac]

You will probably spend more time and money in materials and R&D and then end buying the PF waterbox in the end.

However, maybe you will come up with something good. Why the angles on the inlet/outlet?

 

[WILKEY]

Haha trying to reinvent the wheel it looks like to me. Good luck dude!

 

[lazyt747]

Post up some progress pics.

 

[Cannibal]

too much backpressure or incorrect design could lead to higher exhaust temperatures - and melted piston crowns ?

subscribed anyways because what you are doing looks good

Good point.

I build a box with 3 baffles years ago and it dosnt work. To much flow resistance. For my Bunpipe replica i have a box with a baffle i middle half high off box, in/outtubes 4cm over ground off bottom. Tested with b-pipe and works good. Louder then stock SJ/SXR but no compare to PF with resonator.But its a problem from our carbonchamber too.......back to back tested they are louder then FP-chamber:-((((((

Thanks for the input. Maybe I'll simplify it by making it a 2 baffle vertical setup.

Use the silencer design software on this page, it does work on bigger engines
http://www.mh-aerotools.de/airfoils/javapipe_en.htm

I'll play with that when I have a bit more time on my hands. Thanks.

You will probably spend more time and money in materials and R&D and then end buying the PF waterbox in the end.

However, maybe you will come up with something good. Why the angles on the inlet/outlet?

Very typical for many things I do.

The angled outlet is so I could make the outlet one piece without any miters, and still scavenge the water out of the box. The angled inlet was actually left over from an earlier design that was taller than the chamber outlet. As it's drawn, I believe the inlet will need to be straight, but that will be determined when the system actually arrives and I mock it up in my hull.




Here's v2. The 2 baffle design.

 

[lazyt747]

V2 looks way less restrictive. I like where you are going with this.


How exactly does a waterbox get rid of the water that flows back in to it? Is it basically cooked out of there with the exhaust fumes/heat or is it just pushed out?

 

[Cannibal]

The water that is in there creates mass and dampens the noise, in general, the larger the box, the quieter the ski (dependent upon design of course). Your exhaust system is adding water to cool the exhaust and dampen noise. With these PFP systems, they lay mostly horizontal, not nearly as much rise and fall that stock or Factory systems have. Without a waterbox, you risk having water flow all the way back into the engine when it's not running.

The way most boxes are designed (and if you look at my outlet, the lower one), they have the outlet so it either angles into the box, or goes in the box and bends and terminates near the bottom of the box. This way, when you give enough throttle, the force pushes the water that is in the box up and out that tube.

Using a Jetworks flow control valve, you can tune when water is injected into your exhaust stinger that then fills your box. You are not creating a lot of heat when operating at lower RPMs, so we usually set them up to not inject water at that time, freeing up the restriction in the waterbox so when you grap a handful of throttle, it's ready. Higher pump RPMs create more pressure so then it starts injecting water.

If you look at the bottom of the second baffle, I added a 1/2" hole. This will allow the water that is trapped there to pass into the second chamber when the waterbox is drying out at lower RPMs and also for blowing the ski out at the end of a ride.

 

[lazyt747]

I see what you mean now. It took me until I finished installing my Factory B-pipe this past weekend to grasp how it fully works. Thanks for the explanation.

How is it coming along?

 

[#ZERO]

Interesting project but those HTS-2000 brazing rods were made for small repair jobs and not a structural part that will see a lot of vibration and exhaust pressure. Those rods are made basically from aluminum and a zinc mixture. More zinc is added than with any conventional aluminum alloy to lower the melting point to less than that of aluminum so that the brazing rod will flow long before the aluminum gets hot enough to melt. If you want the part to last you'll need to use a 4043 filler alloy and TIG or MIG weld it IMO.

 

[Cannibal]

Just got my system yesterday and mocked it up. I tell ya, that resonator fits in my hull so well, I'm half tempted to just run it for now and worry about building a box later.

If I do build it, I will have to build my adapter to go from my Kawi cyl to the PFP (no Rad Dudes, I don't want to buy yours) first so I get the spacing correct.

I'll update this when I get to that point.