who's tried the fat cat pipe?

i think everyone who's said they've gone over 40mph with a stock kit has tried the "fat cat pipe." ;)
 
does it produce a power band like a dirt bike has? thats what im trying to achieve. it seems the sbp pipe is differently set up, i know nothing about these things but i know its important how long the thing is.
 
That thing will produce an incredibly peaky and narrow powerband, obviously designed by someone who doesnt know 2 stroke theory very well. Dont bother. Your much better off with the SBC ones.
 
1) the chamber is tiny
2) there is basically no headpipe
3)the baffle cone is not steep enough
4)The baffle cone ends in an abrubt wall, then goes to the stinger
5)there is basically no stinger.
 
Foximus said:
1) the chamber is tiny
2) there is basically no headpipe
3)the baffle cone is not steep enough
4)The baffle cone ends in an abrubt wall, then goes to the stinger
5)there is basically no stinger.
Click to expand...

Thanks Foxie. I'm pondering modifying pocket pipes/scratch build vs hitting up SBP again. Your list pretty much sums up the Big Picture. A couple of these occurred to me when I saw the photo.

I'm also wondering how much the smooth curves effect performance vs a simple can which would be easier to construct.
 
curves and turns effect the pipe in absolutely no way. You can have three 180 degree bends in a row, and as long as your not actually crimping the pipe to impede the flow, the sonic resonance will happily follow the path. You can even have angled bends, that go in 20* segments or whatever.

Important things are keeping the cones and chambers cylindrical, and not flattened or ovaled in any way. Thats far more importatnt than placing bends in the pipe.

edit...

if your going to try to make your own pipe, the one piece that is absolutely critical is to make sure you have a straight, clean and smooth entry from the head pipe (which idealy should have a 2-3* taper of its own) into the diffuser cone. So when you weld the head pipe to the diffuser cone, go back with a die grinder and smooth the joint on the inside, make sure its all flush.
 
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Foximus said:
curves and turns effect the pipe in absolutely no way. You can have three 180 degree bends in a row, and as long as your not actually crimping the pipe to impede the flow, the sonic resonance will happily follow the path. You can even have angled bends, that go in 20* segments or whatever.

Important things are keeping the cones and chambers cylindrical, and not flattened or ovaled in any way. Thats far more importatnt than placing bends in the pipe.

edit...

if your going to try to make your own pipe, the one piece that is absolutely critical is to make sure you have a straight, clean and smooth entry from the head pipe (which idealy should have a 2-3* taper of its own) into the diffuser cone. So when you weld the head pipe to the diffuser cone, go back with a die grinder and smooth the joint on the inside, make sure its all flush.
Click to expand...


Actually by curves I was refering to the shape of the chamber and transitions. With limited welding tools I'm wondering just how much performance is sacrificed by making it from stock mufflers parts which are dirt cheap compared to sexy but expensive pocket pipes. In other words very short diffuser exit and entry I guess.

For example would I expect one built this way to be half as effective in boosting torque/WOT compared to the SBP? I know pretty much what the difference is between bone stock and the SBP unit.
 
xlite said:
Actually by curves I was refering to the shape of the chamber and transitions. With limited welding tools I'm wondering just how much performance is sacrificed by making it from stock mufflers parts which are dirt cheap compared to sexy but expensive pocket pipes. In other words very short diffuser exit and entry I guess.

For example would I expect one built this way to be half as effective in boosting torque/WOT compared to the SBP? I know pretty much what the difference is between bone stock and the SBP unit.
Click to expand...

now youve confused me...
 
Mine was from a pocket bike, was cheap ($29 shipped) and was pretty easy to fab up.

14239d1254966944-29-ebay-pipe-hour-welder-moto_0013.jpg


And it does work.
 
hrmm... after re reading more than a few times I think I get what you mean. Are you asking about abrubtly ending the chamber with endcaps and such, as the stock pipe does?


Really you should be aiming for a 6-8* taper for the diffuser cone (7-8 for wider power band, 6-7 for a more peaky max output) and roughly double 12-16* for the baffle cone. Thats what will give you great results.
 
Foximus said:
hrmm... after re reading more than a few times I think I get what you mean. Are you asking about abrubtly ending the chamber with endcaps and such, as the stock pipe does?


Really you should be aiming for a 6-8* taper for the diffuser cone (7-8 for wider power band, 6-7 for a more peaky max output) and roughly double 12-16* for the baffle cone. Thats what will give you great results.
Click to expand...

Well like I say... trying to use parts from stock exhausts which do have a rounded shoulder but nothing close to a real diffuser. I see versions of the Poo Poo pipe that do not appear to have a cone but still get rave reviews. Wondering if these actually perform or, like is common from over-excited hobbyists, just smoke being blown (sorry).

Your info is appreciated in any case and being saved for later reference. I may someday get excited enough to attempt a proper sheet metal construction. For now I'd just depend on SBP for a tried and true design but curious about a "half-fast" version.
 
Kevlarr said:
Mine was from a pocket bike, was cheap ($29 shipped) and was pretty easy to fab up. And it does work.
Click to expand...

Yes. Your project was not only a work of art but I also suspect a real performer. To be honest though, considering how much work you put into it, and $30 plus, it makes more sense for me to just buy another one from Pablo and Jim.


I can get chinese exhausts for less than a saw buck apiece shipped complete with flange etc.. And conduit is almost free at places like Lowes and Home Depot. Soooo... the gears in my head start turning (or is that a stripping sound I hear? :) ).
 
Actually it was one of the easiest mods I've done on the bike, it was more work fixing up the fenders. laff

If there's access to a welder I highly recommend using one. The satisfaction from making making it myself more then makes up for my hour of time. :D
 
Ive got a Fat Cat pipe and I love it, a million time better than stock exaust. It sounds MEAN! And definately makes you go faster. I would like to try an SBP pipe to compare but the fat cat does work and so easy to install
 
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