Hi, and a happy New year from "the tiny Canadian country Version across the pond, Norway" to everyone.
2-stroke Tech is really complicated, and that goes for all that happens in the pipes as well. Just all the Words;
-Waves
-Sonic
-Subsonic
-Initial Pulse
-Residual pulse
-Temperature
and that they are all Connected to each other can make you Dizzy.
The hard part is, that in a stroker (and that goes for pipes as well) is that if you change one thing, you ALWAYS change something else as well.
For example tuned length.
If you make them longer, you also change the volume. If you change the volume, you change the efficiency of the pipes.
Make them Shorter, same thing happens, and you get another motor characteristics.
And off course, if you play With tuned length, you also play With same motor characteristics.
And then you got all the section length and tapers. And every aspect of shape influence all other aspects of shapes. (ehh......am I on the correct English line here now?
? :-D )
What I found when playing With different pipes on my bike, same dyno same day, is that pipes is definately THE MOST Critical part regarding Power. It is just unvelivable what influence them make for Power.
My best peak Power Chambers performed an outstanding 20 more rwhp than the baddest, and made a whopping 32 more rwhp than the Stock pipes. Thats just amazing, but I also has to say the H2 was jetted to suit the Jollymoto's. But we adjusted the Power jets based on the hunch, when trying the different pipes. So yes, the Stock pipes went leaner off course, than the best Chambers.
On pretty big cylinders as seen on the 500's and the 750's in particular, we just cannot make the best pipes possible..........because we have no room for them regarding ground clearance.
The most effective ancient 125cc/cylinder gp pipes has a larger belly diameter than Our 167 or even 250 cc cylinders pipes.
Triples dragraceres therefor has a lot bigger pipe Dimensions than we can use, because more volume makes more efficient suction, in to a certain limit off course. More suction gives more air/fuel to the combustion Chamber, more in the headers for the returning wave created by the exhaust pulse reflected by the baffle cone to push back into the cylinders thus more Power.
My Jollymoto pipes are considered as quite large for a triple, but still has only 108mm belly diameter. A H2 requires AT LEAST 120mm belly diameter to be the most efficient as possible I believe. Maybe more, depending on the tuned lenght thus volume, and also that if you make the diameter bigger, you also has to change the taper dataes for the headers and first cone, or the lenght of them, or both.
At least I found, that the more volume, the more effective the pipes became. The jollymoto pipes produced same peak powwer as the TNT and Figarolies, but at a 1000 rpm or so, lower peak Power rpm. That means, they produced a lot more torque, AS THE SIMPLE RULE FOR TORQUE AND HP IS: HP=TORQUE X RPM.
Interesting thread this is, and hopefully more comments will be made, also when modified wirges are tried in real life.
They are good, but make sure you fabricate silencers that starts With a taper, so that they perfectly matces the end of the baffle cone. That modification is maybe essential to make them work almost identical as the dencoes I think.
And yes, silencers can be used as a stinger. But it is unecessary. A better solution is making a venturi just after the baffle cone that takes care of the pressure release for the engine. It is the id of this venturi that play the large role here, not the stinger lenght.
And if you do it this way, you can make the silencers tube id for example 2mm larger than the venturi. That means, you do not get more pressure in pipes (making the engine goes hotter) due to clogging in silencers.
At least this is what I did when my jollymotoes were modified, and it worked well. Used a 25mm venturi, 20mm long. Then a 28mm perforated silencer tube.
Hopefully, someone can come up With 120mm pipes for Our triples, and still make good cornering without pipes touching the pipes. That definately means more efficient motor, or in other Words, more torque.
Gotta love the 2-strokes :-)
Jørgen