Part Three: The Transfer Ports

[huskyboy]

If two worksaws cut the same speed, but one is torquier that’s the stronger saw. For many reasons imo.

 

[MustangMike]

Well my cylinder is gonna be here soon, I have an idea what I'm going to do but we shall see once it's in hand.

I'm torn between:

1. Peak power
2. Wider power band
3. Semi-peak power with some of the wider power band

As Mason knows I love torque, a saw you can really lean on. But my thoughts on porting have changed.

What saw is the cylinder for, and how would you port it differently for each of the above?

 

[Mastermind]

I thought you might have been trying something out there.

Been there on the 661. Made a popping noise that I couldn't stand. Didn't run any stronger either.

 

[mdavlee]

Been there on the 661. Made a popping noise that I couldn't stand. Didn't run any stronger either.

That popping is annoying on some of them.

 

[00wyk]

Stump, interesting post, but I hope you don't mind if I play Devils Advocate!

First, I have nothing but distain for JMS, his shoddy procedures and how he cheated folks, but I also remember some of the 064/660 saws he sent to the CT GTG and I will tell you they were VG runners, so he knew something. Perhaps they were just his "I got lucky" saws that he saved to send to us, I don't know, but they ran.

Secondly, I have had this intake debate with other builders, and my thoughts are that is it similar to why the lowers are larger than the uppers, which don't even fully open.

1) The intake goes into the crankcase, not directly into the combustion chamber, so IMO volume is more important than velocity. If the upward piston movement generates 5 psi of vacuum, the more area that exists when it first opens the more air/fuel mix will be sucked in.

2) For the upper transfers, direction and velocity are important, and if the lowers have more area for the pressure, this will increase the velocity of the uppers. It is like a garden hose, the larger the diameter of the hose, and the smaller the spray jet, the more velocity you will have.

Those are my thoughts on these issues, for whatever they are/or are not worth! Opposing comments are always welcome!

It's a complicated field you're touching on, fluid dynamics. In a chainsaw you see a lot of different forces placed on the fluids. Once a fluid starts to become turbulent, it behaves in a very different manner than laminar flows as well. Like Randy says, it's a good idea to picture what the engineer was trying to do, and why, before you start grinding away.

https://www.khanacademy.org/science/physics/fluids/fluid-dynamics/a/what-is-bernoullis-equation
https://en.wikipedia.org/wiki/Fluid_dynamics
https://en.wikipedia.org/wiki/Bernoulli's_principle

 

[mettee]

As Mason knows I love torque, a saw you can really lean on. But my thoughts on porting have changed.

What saw is the cylinder for, and how would you port it differently for each of the above?

7910

Where it sits I can move stuff around a bit to get the exhaust and intake where they need to be.

As far as the transfers, I suppose there is a couple options. mdavlee said flat, staggered 2 degrees for all out power. My guess is that more taper/stagger widens the power band. And I suppose that would be done bar partially doing them flat with one of the upper transfers tapered/staggered.

Squish is .021

I did my lower transfers like below, which I tend to think is the all out power method, but I could be wrong because it looks like its gonna flow.

 

[MustangMike]

Yep, I understand it is complicated, which is why we just have to go with what works.

Can't open the first one (w/Int Exp), but the 3rd one shows exactly what I was trying to say … the larger diameter exerted more pressure. When that piston opens the intake, IMO you want as much volume as possible. The PSI will be the same, the more area the greater the flow.

Conversely, going into the combustion chamber, velocity, direction and turbulence are very important.

 

[mettee]

Not sure I understand you, but I wanna ....

Can you make it for dummies?

 

[stinkbait]

if you are a jms fan you should go to ass site and not come here
as far as digging through cylinders because you want to max out a work saw is pure stupidity ( id word it different but i wont )

Wow. I wasnt putting in a plug for jms and never stated that I supported him in any way. I have read all the threads, and know all info that people were willing to share. That being said, saws are a hobby for me. I've never ported saws for money. The main reason is that I just dont have time. I've learned a lot about porting from threads on here and as over the years and appreciate every bit of the info. I only mentioned him because there was a short period where he shared photos of his work and numbers and I just wanted to know everyone's input on that approach to transfers. He's not the first piece of *s-word to be on a forum and will definitely not be the last.

Sent from my SM-G930V using Tapatalk

 

[Time's Standing Stihl]

That popping is annoying on some of them.

@leadfarmer

 

[p61 western]

@leadfarmer

Lmao rub it in.

 

[huskihl]

 

[Stihlbro]

View attachment 185199

What you did there.......that speaks volume. I liked it.

 

[huskyboy]

Wasn’t just the 661 that popped, he advanced the timing way too much on most his saws he did. I’m talkin .050 or more off the key on a 394 .

 

[mettee]

I try not to give the turds any more attention than they deserve, in this case it's zero.

Let's talk transfer ports... Yeah!

 

[Wonkydonkey]

Yeh, ++++++1

 

[Ketchup]

Pulled a saw apart once that had notches cut into the crank weights. The notches were tapered and aimed at the transfer lowers.

Anybody else seen this? Could it help transfer velocity? Is it worth the extra resistance?

 

[MustangMike]

View attachment 185199

We were just playing with one of them this morning … my wife bought it at the used toy store for $4.50, like new! It is a big hit with the Granddaughter (1+1/2)!

 

[Redfin]

What you did there.......that speaks volume. I liked it.

You should see the rest of the vid.

 

[mettee]

Pulled a saw apart once that had notches cut into the crank weights. The notches were tapered and aimed at the transfer lowers.

Anybody else seen this? Could it help transfer velocity? Is it worth the extra resistance?

I would love to see what that crank mod looks like