Husqvarna 350 comparison video with cut times!

[blsnelling]

what program did you use for that?

how is that interpolated?

I used Excel. Without having the actual data, I created it manually by looking at your original graphs and working to smooth it out.

 

[blsnelling]

What you're seeing is that the saw with the lowest RPM peak HP is the slowest saw. By the same token, the saw that makes it's peak HP at the highest RPM will cut the fastest, given it's not a super peaky powerband.

After a little more inspection, it would appear that perhaps the Kafar kit makes it's peak at a little higher RPM than the Hyway, with both having similar peak HP. However, the Hyway has a much broader powerband. Is that an accurate interpretation? I might have expected the OEM and UK kits to be a little faster than the other two as well. No?

 

[Mattyo]

my original hypothesis is that if I port the cylinders to similar specs, I'll get a similar result. ...there really *should* be minimal difference between saws IF the porting is exactly the same. in which case, it wouldn't matter what cylinder you buy, just that you port it to good spec.

if you want, I can put DATPLOT to work and get 2 saws at a time rather than all 7 at the same time....


also, the kafar kit was a TURD at NY gtg.... I significantly opened the muffler and now it seems to be in the running...

the hyway kit still is running a screen, though the muffler is somewhat opened underneith it, still not opened as much as yours was Brad...

 

[Mattyo]

 

[Mattyo]

If you go by the polynomial trendlines, Hyway makes 4.8 peak at 9krpm. Kafar 10k rpm 4.6 hp.... or therabouts. Its entirely possible, that these curves really don't match the powerband at all.... there may actually be a double hump on the band, maybe a real plateau, I don't know. I'm not a mathematician, or an expert on 2 cycle dyno curves.

 

[blsnelling]

They key to making these saw run will be for you to get the transfers up. You don't want more than 15°-16° of blowdown. I think that's the biggest difference. Don't take your exhaust any higher than 105°. Even 107° is good. Contrary to popular conception, raising the exhaust isn't going to make more RPMs with these. I found the opposite to be true. If you port these like a 372 with the exhaust at 98°-100° they'll actually be slower.

 

[blsnelling]

View attachment 502751

When you look at the usable RPMs above 9000 RPMs, there's not a whole lot of difference in those two graphs.

 

[Mattyo]

I think the hyway has 18-19 degrees of blowdown w/ a 105 exhaust. just dunno how far to push blowdown ...

did you grind the bearing cap, or the base of the cylinder? forgot to ask

 

[blsnelling]

I think the hyway has 18-19 degrees of blowdown w/ a 105 exhaust. just dunno how far to push blowdown ...

did you grind the bearing cap, or the base of the cylinder? forgot to ask

The cylinder base. I don't have a mill to do the bearing cup.

Good numbers are 107/122/80, no higher than 105/120/80.

 

[Mattyo]

put the bearing cap in the 4 jaw.... simple

 

[blsnelling]

I didn't thunk of that, lol.

 

[Mattyo]

if at all possible, I really don't like the idea of machining the bases of cylinders, gotta keep the thickness up on those ears.... makes more sense to me to machine the bearing cap....BUT, consider going to M6 bolts to hold the cylinder down, because the m5's bottom, and you won't necessarily have many usable threads to grab the bearing cap to properly seal

 

[Paragon Builder]

Matt I really think your saws need to breath better to take advantage of your porting. Look how much better the kafar kit did from Ny to CT by opening the muffler. Did you try my muffler on your hyway saw? Bet it wakes it up!!!


Sent from my iPhone using Tapatalk

 

[Mattyo]

I know I know... i'll work on it one day. I really want to retain spark screens in my saws if possible, so i'll have to come up with something that works....

 

[blsnelling]

I usually leave the spark screen in mine. Just open up the whole area under the deflector. If desired, you can always use a larger mesh screen.

 

[blsnelling]

if at all possible, I really don't like the idea of machining the bases of cylinders, gotta keep the thickness up on those ears.... makes more sense to me to machine the bearing cap....BUT, consider going to M6 bolts to hold the cylinder down, because the m5's bottom, and you won't necessarily have many usable threads to grab the bearing cap to properly seal

The general rule of thumb is to leave at least .250". I've had to go a little thinner before and never had an issue. Besides, you have no other reasonable option on the 353/346.

 

[Mattyo]

I mill the chassis on cases all the time, I don't see why the 346xp would be any different

 

[blsnelling]

I've seen no historically documented reason to go to those efforts. Do you do this with the crank still installed?

 

[Mattyo]

yup! Its easier when its not there, but its simple enough to use plumbers putty around the crank to prevent chips from getting down in the crankcase area

the putty is sticky so it holds onto chips well

 

[Mattyo]

once the case is indicated its really easy to make such a cut. and I retain all the thickness on the cylinder ears. AND, theoretically the next jug would still fit with minimal effort, assuming I'm not using a popup. I've probably milled more than 20 cases, I think I've done 1 popup. that said, because I'm just milling the case, not doing a popup OR cutting squishband, I don't get the significant boost in compression necessarily.