Part Three: The Transfer Ports

[Lightning Performance]

Long thread fun stuff. Just curious was any discussion about the angle of the "roof" or top of the transfers , not on the "x y" plane but "z" ? Also differential height transfers on those quad port cylinders with possibly the "exhaust" side leading by a few degrees? I got into a few pages...my short term memory is shot so five pages in I already forgot what was on the first page. Also the impact of grinding the lowers and adding x-section on the intake as in enters the crank case on case volume & intake charge velocity/pulse upstream through the air box. Just curious where everyone ended up.

And while "theory" is behind designs. Always curious on the thoughts on surface finish. AND curious on what folks are thinking about why the new saws love to wrap the transfers around the exhaust port

The wrap around the exhaust port is to atomize fuel and replace or circulate the heat. We are dealing with a heat engine. Adding heat from the exhaust also helps a complete burn of all the gasses.

Kevin grinds transfer entries pretty much like most work saw builder do. He puts them where he thinks the best flow path will be to the port turn. Seems reasonable and pretty standard practice imo. One jug here is getting hogged out on the transfer entry to add case volume in several places.

 

[AlfA01]

A member turned me on to switching styles from the old OEM full circle style on top, to the newer 268xp closed port/open window style on the bottom. This made the 266 more sporty with no other changes. The top one does have more stability in the bore, if that's a consideration at all. The middle one is really a slab sided 268 open port design and I can't say that I have tried it in the 266 to say anything one way or the other, never really thought about it. I do like and build 266's with the full window piston in the bottom picture.

I got a good running Jonny 2171 I built last year with one of those. Fine running saw it is!

 

[kneedeepinsaws]

Was watching tinman on YouTube talking bout the 562 and how it gets hot. He suggested and he wasn’t sure, but increasing the transfer port size to deliver more fuel to cool down the saw.
Is this in theory correct? Would widening the ports and opening up the lower transfers keeping the ratio of size between the two increase fuel delivery to cool it down?

 

[Maintenance Chief]

More fuel is a common theory of cooling from v8s to snowmobiles, a better exhaust usually yeilds better results.

 

[kneedeepinsaws]

More fuel is a common theory of cooling from v8s to snowmobiles, a better exhaust usually yeilds better results.

That didn’t work for me unfortunately

 

[Lightning Performance]

That didn’t work for me unfortunately

If you have a heat problem retard the ignition timing some.

 

[huskyboy]

If you have a heat problem retard the ignition timing some.

Yup everyone is always advancing and even going as far to make movie theater butter flavor popcorn . Maybe sometimes going the other way with the key, or leaving it stock... might be better in some applications?

 

[Lightning Performance]

Yup everyone is always advancing and even going as far to make movie theater butter flavor popcorn . Maybe sometimes going the other way with the key, or leaving it stock... might be better in some applications?

I ported saws sent out that are still in the stock position. 60ish cc pulling a 28ish" bar with a long stroke motor.
I went backwards four degrees from eight advanced on a 361. 16" vs 28" full comp. This saw was not high compression and had no machine work done. 177psi all oem base gasket delete. 0.012 quench. Back it down or risk beating up the motor imo. It pulled a 28" like *s-word but did not overheat buried in fat solid white maple around a 26" log. It needed square chain for a better pull. Was running off the roll lgx72. Only did that test about a decade ago. That is a twelve degree change overall from eight to seven pin rims. The 16" bar runs got hot so we took off three degrees upon moving to a 20" bar. Didn't like the eight pin rim either with 24" or the 28"

Guess I should mention the transfer ports were 125. Not much change need on those as far as shape. Flat quads aimed where they need to be.

 

[Ketchup]

Was watching tinman on YouTube talking bout the 562 and how it gets hot. He suggested and he wasn’t sure, but increasing the transfer port size to deliver more fuel to cool down the saw.
Is this in theory correct? Would widening the ports and opening up the lower transfers keeping the ratio of size between the two increase fuel delivery to cool it down?

I have seen ported 562s with hogged out transfer tunnels that ran well. I don’t think it was for heat, though. An open exhaust and top cover seem to handle most of that. If you’re vapor locking, additional insulation at the fuel line and carb wall seem to help.

 

[kneedeepinsaws]

So with strato engines if you are hogging out transfers near the base of the jug how does that affect the strato ports?

 

[Ketchup]

Hogging out transfers increases case volume which in general will reduce transfer velocity. That’s why most people just blend the edges to make a smooth transition from case to jug. The more material you take away, the more you increase case volume. Aggressive base cuts will reduce case volume slightly but it’s very easy to go beyond that.

The Strato behavior of the transfer happens in conjunction with intake. Both the fuel charge and cold air open at (roughly) the same time and have a similar port area. It’s basically an open loop with fuel charge rushing into the case and up the transfers while cold air rushes across the piston and down the transfers until they collide. I’m just spitballing, but it seems to me that if you increase case volume the cold air will travel farther down the tunnels. Any cold air that comes into the transfers will be the first thing pushed into the combustion chamber. Depending on how much it was increased that could create a lean fuel mix in the combustion chamber.

But like I said, I’ve seen 562s with hogged tunnels and lowers. They run well. We also know that a Husky 365XT is identical to a 372XT except for the more constrictive transfer tunnel. 372 makes more power. Does it do that because it gets more cold air? Slight increases in cold air intake timing do seem to create some power. This seems like another way to achieve that. Maybe it’s harder to achieve a lean condition than I thought.

Here’s what I’m trying to say: In Stratos a slight increase in case volume might draw more cold air and produce more power. Maybe.

But in general, I don’t alter transfers any more than I need to create smooth flow and get the timing right. Sometimes I’ll even leave them aimed higher than I really want because it removes less material. I like tight cases and high velocity transfers. Create too much case volume and any saw will be a turd.

 

[Lightning Performance]

Hogging out transfers increases case volume which in general will reduce transfer velocity. That’s why most people just blend the edges to make a smooth transition from case to jug. The more material you take away, the more you increase case volume. Aggressive base cuts will reduce case volume slightly but it’s very easy to go beyond that.

The Strato behavior of the transfer happens in conjunction with intake. Both the fuel charge and cold air open at (roughly) the same time and have a similar port area. It’s basically an open loop with fuel charge rushing into the case and up the transfers while cold air rushes across the piston and down the transfers until they collide. I’m just spitballing, but it seems to me that if you increase case volume the cold air will travel farther down the tunnels. Any cold air that comes into the transfers will be the first thing pushed into the combustion chamber. Depending on how much it was increased that could create a lean fuel mix in the combustion chamber.

But like I said, I’ve seen 562s with hogged tunnels and lowers. They run well. We also know that a Husky 365XT is identical to a 372XT except for the more constrictive transfer tunnel. 372 makes more power. Does it do that because it gets more cold air? Slight increases in cold air intake timing do seem to create some power. This seems like another way to achieve that. Maybe it’s harder to achieve a lean condition than I thought.

Here’s what I’m trying to say: In Stratos a slight increase in case volume might draw more cold air and produce more power. Maybe.

But in general, I don’t alter transfers any more than I need to create smooth flow and get the timing right. Sometimes I’ll even leave them aimed higher than I really want because it removes less material. I like tight cases and high velocity transfers. Create too much case volume and any saw will be a turd.

Maybe true but increasing case volume on certain saws increases long bar power.

 

[huskyboy]

Maybe true but increasing case volume on certain saws increases long bar power.

I agree.

 

[Lightning Performance]

I agree.

All chainsaw bs and brand bickering about what is inside the case for volume matters far more on these long bars like 40" - 50"
So... it should be good for the 60" one would hope. Surely one way to find out.
I've done some strange things to an about ruined 394 jug that came my way. The ports were already so wide and uneven it was eating rings and ring land pins, no bs. Now the whole thing is so far out of control on the transfer ports it might end up being a long bar monster on a stock case bolted up to it. They are wide and extra long ports now. The jug is getting thin in spots lol. Really was not going to do machine work but wth. Already got too much compression in it. The chamber can be opened up and have two angles vs one. No time for testing. Always fixing broken chit here

 

[Ketchup]

Maybe true but increasing case volume on certain saws increases long bar power.

Yeah I agree. Long bars want a lot of fuel and you can only increase transfer duration so far. Maybe big saw case to displacement ratios are smaller stock or maybe it’s the ratio of transfer tunnel to displacement. There are certainly models that seem less touchy. Hogging out a 660 or 395 can get a lot of grunt. CJS got a 359 to pull 36” by hogging the transfers. Not sure if a strato could do the same.

It’s funny how some saws can utilize more fuel in hard cuts. Just like a saw that idles fat but cleans up in a cut. My 395 does that. It plods along with the 28” but sings with the 42”. A friend has a blue 7910 that actually speeds up in big wood.

 

[Nutball]

Am I wrong in thinking you can compensate for an undesirable case volume by changing the intake timing to get the desired long bar performance?

 

[kneedeepinsaws]

Hogging out transfers increases case volume which in general will reduce transfer velocity. That’s why most people just blend the edges to make a smooth transition from case to jug. The more material you take away, the more you increase case volume. Aggressive base cuts will reduce case volume slightly but it’s very easy to go beyond that.

The Strato behavior of the transfer happens in conjunction with intake. Both the fuel charge and cold air open at (roughly) the same time and have a similar port area. It’s basically an open loop with fuel charge rushing into the case and up the transfers while cold air rushes across the piston and down the transfers until they collide. I’m just spitballing, but it seems to me that if you increase case volume the cold air will travel farther down the tunnels. Any cold air that comes into the transfers will be the first thing pushed into the combustion chamber. Depending on how much it was increased that could create a lean fuel mix in the combustion chamber.

But like I said, I’ve seen 562s with hogged tunnels and lowers. They run well. We also know that a Husky 365XT is identical to a 372XT except for the more constrictive transfer tunnel. 372 makes more power. Does it do that because it gets more cold air? Slight increases in cold air intake timing do seem to create some power. This seems like another way to achieve that. Maybe it’s harder to achieve a lean condition than I thought.

Here’s what I’m trying to say: In Stratos a slight increase in case volume might draw more cold air and produce more power. Maybe.

But in general, I don’t alter transfers any more than I need to create smooth flow and get the timing right. Sometimes I’ll even leave them aimed higher than I really want because it removes less material. I like tight cases and high velocity transfers. Create too much case volume and any saw will be a turd.

now that was very appreciated!!

what about increasing velocity to the transfers.
For example near the bottom of the jug you hog out a little, smooth out edges but you do not increase the port size for the combustion chamber.

This should increase velocity in which fuel flows to the combustion chamber faster than before. you are starting with a wide tunnel and going down in size for the combustion area and thus should increase velocity in the higher rpms? But does that also increase the case volume in what you were saying?

 

[Bjorn]

Was watching tinman on YouTube talking bout the 562 and how it gets hot. He suggested and he wasn’t sure, but increasing the transfer port size to deliver more fuel to cool down the saw.
Is this in theory correct? Would widening the ports and opening up the lower transfers keeping the ratio of size between the two increase fuel delivery to cool it down?

Tinman is the Canadian Iron Horse, dont belive everything he say.

 

[Mastermind]

Are y'all sure you understand what you're talking about here?

LOL

 

[Lightning Performance]

Are y'all sure you understand what you're talking about here?

LOL

No... need you to explain it, please?...