MS 880 meets DCHotsaws

[Mastermind]

No, I didn't feel we needed the unlimited coil. I did pull the limiter tabs on the low and high speed needles, and touched up the velcity stack with the sanding wheel. Haven't done anything to the carb as of yet, may not. I actually would like to try a HT1 on it.
Basically, added a port to the muffler, set the squish, ported the cylinder by opening up the bottom transfers, cleaning and matching the top transfers, widened the exhaust, widened the intake and lowered it a few degrees, and then added boost ports, coming from the top of the bottom transfer. Should be sucking plenty of fuel, which makes it pull hard for a "still tight" engine. That video was only the 3rd cut that saws ever made.

Boost ported work saw huh? Fingers or true boost ports??????

Yep! you gotta watch those builders from Ohio and TN.........I'm sure glad you didn't put me in that group!......Hahahahahahaha!

:msp_ohmy:

 

[logging22]

Are you talking about Ricky Hennessy?

I met and raced that guy here a couple years ago. He did beat me, but not by much. And i have only been doing it for a few years. Not 30. He was nice enough to talk too i guess.

 

[Dennis Cahoon]

Boost ported work saw huh? Fingers or true boost ports?????? :msp_ohmy:

Yes Fingers........but look more like 2 opposed bent thumbs.:hmm3grin2orange:

 

[Mastermind]

Yes Fingers........but look more like 2 opposed bent thumbs.:hmm3grin2orange:

I've done a few saws with fingers......still working out the correct height in relation to the transfers though. A few degrees higher would be best.....right?

 

[Dennis Cahoon]

I've done a few saws with fingers......still working out the correct height in relation to the transfers though. A few degrees higher would be best.....right?

Yes, higher IMO......Why not add alittle cheap transfer timing.

I've ran a few with fingered boosts over the years, and my son has a 660 with boosts he's running now. They will suck more gas, but stump well!

 

[GBD]

Yes, higher IMO......Why not add alittle cheap transfer timing.

I've ran a few with fingered boosts over the years, and my son has a 660 with he's running now. They will suck more gas, but stump well!

This confuses me a little. If main transfer opening is set correctly, cylinder pressure just blows down to be lower than cc pressure when transfer open. If boosters open earlier, spent gasses will start backflow down them. If blowdown period is more than adeqvat, isn`t it easier just to raise the main transfers to gain transfer time/area?:msp_confused:

 

[Dennis Cahoon]

This confuses me a little. If main transfer opening is set correctly, cylinder pressure just blows down to be lower than cc pressure when transfer open. If boosters open earlier, spent gasses will start backflow down them. If blowdown period is more than adeqvat, isn`t it easier just to raise the main transfers to gain transfer time/area?:msp_confused:

Rule of thumb........If you raise transfers you gain RPM and take away torque.

More area with a very slight bit of transfer timing out of the boosts, without raising the main transfers is what I was wanting. Your question is a little confusing itself.

 

[GBD]

Rule of thumb........If you raise transfers you gain RPM and take away torque.

More area with a very slight bit of transfer timing out of the boosts, without raising the main transfers is what I was wanting. Your question is a little confusing itself.

Yes, raising transfers will reduce exhaust blowdown time/area keeping the total exhaust time/area the same, and thereby reducing max torque and moving it up the rpm scale. My question is, will not added boosters opening earlier do the same thing?

 

[Mastermind]

Yes, raising transfers will reduce exhaust blowdown time/area keeping the total exhaust time/area the same, and thereby reducing max torque and moving it up the rpm scale. My question is, will not added boosters opening earlier do the same thing?

I think what DC is saying is that the height of the boost ports raises usable rpm without loss of torque.

This confuses me a little. If main transfer opening is set correctly, cylinder pressure just blows down to be lower than cc pressure when transfer open. If boosters open earlier, spent gasses will start backflow down them. If blowdown period is more than adeqvat, isn`t it easier just to raise the main transfers to gain transfer time/area?

Wouldn't those back flowing spent gasses increase crankcase pressure and boost the incoming main transfer flow??????

 

[GBD]

I think what DC is saying is that the height of the boost ports raises usable rpm without loss of torque.

That is not what he wrote.


Wouldn't those back flowing spent gasses increase crankcase pressure and boost the incoming main transfer flow??????

It would be very interesting if it worked that way.:msp_biggrin: Modern high performance two strokes open all the transfers at the same time, though.

 

[Dennis Cahoon]

It would be very interesting if it worked that way.:msp_biggrin: Modern high performance two strokes open all the transfers at the same time, though.

Some stock chainsaw cylinders have angled upper transfers, giving it gradual transfer opening times.

 

[Mastermind]

Some stock chainsaw cylinders have angled upper transfers, giving it gradual transfer opening times.

I hadn't thought to throw that in there Dennis. The MS461 has the transfers angled in the strangest way I've seen.......they are lowest in the center.....and angle upward away from each other.

 

[parrisw]

Are you guys talking about the roof of the uppers being angled?

 

[Mastermind]

Are you guys talking about the roof of the uppers being angled?

The angled height Will. On some newer Stihls like the MS261 they are out of level to the tune of ten degrees or so.

 

[parrisw]

The angled height Will. On some newer Stihls like the MS261 they are out of level to the tune of ten degrees or so.

Wow, that's allot.

 

[Dennis Cahoon]

The angled height Will. On some newer Stihls like the MS261 they are out of level to the tune of ten degrees or so.

It must work if Stihl's doing it EH!

 

[srcarr52]

The angled height Will. On some newer Stihls like the MS261 they are out of level to the tune of ten degrees or so.

The most I've seen is 6 deg stagger in duration, 10 is absurd. I guess they are just leaving you room to work.

 

[Mastermind]

It must work if Stihl's doing it EH!

Well Big D........I must admit to leveling them up.

 

[Mastermind]

The most I've seen is 6 deg stagger in duration, 10 is absurd. I guess they are just leaving you room to work.

They are a quad port design and the slope steadily runs from high at intake side to lowest at exhaust.

 

[srcarr52]

They are a quad port design and the slope steadily runs from high at intake side to lowest at exhaust.

They must be really trying to wedge the exhaust out for emissions and not just push it out with a little extra a/f charge like we are doing in ported saws. I bet they have a long blowdown as well? I'm sure you're bringing those down to normal 2-4 degree duration stagger?