Their ideas make me think of a turbo(in this case a larger carb for more air, not necessarily more fuel). They pump a ton of air into the venturis, they run efficiently and best of all, burn less fuel. If the exhaust(can) on a chainsaw is opened up, the spent gases are exiting much faster that maybe there is a need for less fuel. Those spent gases don't have to travel as far as say if it was piped. I would suspect if it was piped, then you would then have to fatten it up.
Out of curiosity, is there a similar situation for "floating valves" on two-strokes?
Trying not to come off harsh here, but there is not one fully correct statement in this IMHO, well maybe the last one sort of it's a question.
If a large carb flows more air, it must also supply more fuel or else the mixture goes lean and engine overheats.
They pump a ton of air into the venturis, they run efficiently and best of all, burn less fuel
A bigger carb does not run more efficiently, in fact after a certain point air velocity drops so much the fuel break-up is ineffective leading an unevenly and incompleatly mixed charge and poor combustion.
If the exhaust(can) on a chainsaw is opened up, the spent gases are exiting much faster
No, as the volume of gas is more or less the same the bigger the outlet hole the sooner and more compleatly the muffler can empty each cycle, but the velocity of exiting gas will be lower as the same gas volume exits the muffler backed by the same pressure, but through a bigger hole.
the spent gases are exiting much faster that maybe there is a need for less fuel.
No, with a more open exhaust there is more intermixing of clean air drawn in through the muffler and exhaust mixing with new charge. This shows up at low RPM mostly and is why the low speed must be richened to make up for the air ingress from the muffler. This may be an advantage exhaust pipes or tubes have in mufflers over open hole designs.
Those spent gases don't have to travel as far as say if it was piped. I would suspect if it was piped, then you would then have to fatten it up.
A properly tuned pipe will bolt on most times with no adjustment to mixture. I don't see how the distance gas travels has anything to do with mixture, if anything a long outlet will block freash air from getting to the motor from the exhaust side and and actually the motor may run a little rich with a longer exaust path and need leaning if anything.
Out of curiosity, is there a similar situation for "floating valves" on two-strokes?
in a way yes, but rather than valves not fully closing it's more like valves not fully opening. If there is insufficient blowdown time due to high RPM or too much backpressure on the exhaust cylinder pressure is too high when the transfers open and the pressure in the base is insufficient to overcome this residual pressure and move up into the cylinder. This would then be almost like an intake valve on a four stroke that was not opening fully limiting cylinder filling.
Great thread help me out a lot!! Now I understand !!! I think?
