441 porting questions

[Mastermind]

Then we should need less blowdown? We want to overscavenge intentionally?

Exactly. The 562XP has about 10° BD stock.

 

[paragonbuilder]

So you are pushing more of the fresh air and some of the fuel charge out of the cylinder with the longer duration.
My question is if the carb is compensating for the proper ratio anyway, what is being accomplished?

 

[Mastermind]

So you are pushing more of the fresh air and some of the fuel charge out of the cylinder with the longer duration.
My question is if the carb is compensating for the proper ratio anyway, what is being accomplished?

You're assuming that the fresh and mixed layers are mixing in the combustion chamber. According to everything I've studied on these engines the fresh layer is just to push out spent gasses. I'm sure some mixing does happen though.

 

[paragonbuilder]

You're assuming that the fresh and mixed layers are mixing in the combustion chamber. According to everything I've studied on these engines the fresh layer is just to push out spent gasses. I'm sure some mixing does happen though.

Yes I suppose I was...
For the saw to tune right, I would "think" it would have to...
However if the saw runs better, your theory that it may not sounds plausible. Either that or the extra fuel charge passing through the chamber could be helping cool the piston and cylinder more, thereby allowing more charge to get stuffed on each stroke.
Thoughts?

 

[Mastermind]

Yes I suppose I was...
For the saw to tune right, I would "think" it would have to...
However if the saw runs better, your theory that it may not sounds plausible. Either that or the extra fuel charge passing through the chamber could be helping cool the piston and cylinder more, thereby allowing more charge to get stuffed on each stroke.
Thoughts?

I sure won't pretend to understand these engines completely.....because I really don't.

When you can, look at the piston sides on a strato saw. The fresh air passes across the cut outs in the piston, so it has to cool it I think.

 

[paragonbuilder]

I sure won't pretend to understand these engines completely.....because I really don't.

When you can, look at the piston sides on a strato saw. The fresh air passes across the cut outs in the piston, so it has to cool it I think.

Yeah I remember that from the 201t I did. That's true. That would help. [emoji848]
But I believe the evaporative quality of gas is what does the most cooling, which is why even a little lean on the tune can cook the saws.
If I remember correctly the optimal fuel ratio for the most output, is too lean to run in an internal combustion engine, it will burn up.

I wonder if stratos tend to run hotter than conventional saws?

 

[Mastermind]

I see more strato saws with fried crankshafts than regular saws.

 

[paragonbuilder]

I see more strato saws with fried crankshafts than regular saws.

I know you have ported while keeping the stratos, and gutting them. Do you see an advantage either way?

 

[Mastermind]

I know you have ported while keeping the stratos, and gutting them. Do you see an advantage either way?

Not normally. But the MS241 really gains from gutting them.

I try to find ways to make sure the spitback mixes on all of them. That makes a bit of difference too.

 

[paragonbuilder]

Not normally. But the MS241 really gains from gutting them.

I try to find ways to make sure the spitback mixes on all of them. That makes a bit of difference too.

Hmm. I'll need to remember this when I rip my 261 down!

 

[Mastermind]

Enough about saws. Lets talk about farming now dot dot dot

 

[paragonbuilder]

Enough about saws. Lets talk about farming now dot dot dot

How's the herd?

 

[Crzybowhntr]

That's a real log you're cutting on there. Fine saw!!

 

[Mastermind]

How's the herd?

Very well. Should start calving in April.

 

[Mastermind]

That's a real log you're cutting on there. Fine saw!!

That was one of the first 441s I did......

 

[Crzybowhntr]

That was one of the first 441s I did......

Safe to assume they got stronger as you did more?

 

[Redfin]

Ive been studying a 261 jug recently. One thing I have found curious is the strato charge is not under compression from the downward stroke of the piston and the charge is only directed toward the secondary tranfers. Look at the piston, the strato charge is contained to the cutouts and pin area.

 

[Mastermind]

Safe to assume they got stronger as you did more?

Not really. I got this one nailed down pretty quick.

 

[Mastermind]

Ive been studying a 261 jug recently. One thing I have found curious is the strato charge is not under compression from the downward stroke of the piston and the charge is only directed toward the secondary tranfers. Look at the piston, the strato charge is contained to the cutouts and pin area.View attachment 58297

It's the upward piston movement that fills the case with intake charge, and that same low pressure fills the upper part of the transfers with fresh air thru the strato inlet. They sorta meet in the middle if that makes sense.

 

[Redfin]

It does.