Brian, yeah I've spent some time trying to push a rope up a hill myself. After a while I learned to do a bit more research before commiting myself to a project.
Back in post #71 I mentioned tuning the intake with a piece of hose. That would seem like a worthy project that could yield useful information. The mod would also keep the weight down and retain the handling of the saw.
We've all seen various types of 'tuned' intakes, from long velocity stacks, boost bottles, variable manifold volumes, tunable air boxes and the like. The concept works, so how can we use the concept on a work saw?
I've tuned two-stroke intakes using just a length of clear plastic hose. The 'tuning' is simple (no math involved), you just keep clamping the hose at different lengths to change the resonance in the intake. When you find a spot that gives you the powerband you're looking for, then you cut the hose at that spot and plug it.
I have also made the hose length 'variable'. That is, I put a valve along the length of the hose to allow me to change from one length to another.
On a saw, I could envision two lengths - a shorter length to give high RPM power for limbing type work, then using the valve a longer length to create maximum torque for bucking big wood. An example would be where someone was cutting up a downed tree and started experiencing some bogging with the bar buried in the log, a simple twist of the valve and the saw would then be producing gobs more torque, albeit at a lower RPM.
A tuned intake could stuff another 10-15% into the crankcase. At a lower RPM the time/area of the transfer ports would be capable of moving that extra mixture into the cylinder.
The hose needs to have a fairly large inside diameter, perhaps close to the size of the carb venturi. On a smaller saw, the outside diameter of the hose may allow it to be convienently routed up inside the handle of the saw.
The inside of the hose does get 'wet' from the intake mixture. As long as the hose is elevated above the intake manifold, the hose can continuously drain into the intake and there is no problem. However, if the saw was laid over on its side for an extended backcut, the hose would develop a 'pooling' of fuel in the hose. If the saw was brought back to idle as it was being removed from the backcut, the saw would likely flood and the engine die. It wouldn't take too many such incidents before the operator would start giving the saw a couple of revs as it left the backcut.
I would have already done this on my saw, except it is a strato. The twin intakes essentially halves the amplitude of the wave in each tract. There are further complications on a strato such as one tract pushing the mixture out of the still open other tract and of a change in mixture strength if one tract begins flowing a larger volume. Those problems don't exist on a conventional two-stroke.
This project is likely do-able and does not require much outlay in resources. If successful, the modder would gain much fame and recognition from the chainsaw world, he would be carried aloft on the shoulders of tough men and a laurel wreath placed upon his head - his name would be spoken with reverence.
So, who's it going to be?
