Part Three: The Transfer Ports

[Wonkydonkey]

I will say

there will be a many more guys to come along and think the strapon Jason gave them was the best... ever
When this happens , just a link or a few of the many fudged saw threads needs to be posted and no more said.

I feel for all you guys that got burnt. No one deserved all his grooming of this forum.

Let’s get back to transfers.

 

[dall]

Great points Dallas, no way to ensure that was really his work, and no debate, he is a Scu* Ba*!!!

Now, if you could only work on expressing yourself and not holding back ...

you dont wanna see that censors dont work that well

 

[MustangMike]

OK, I'll throw out a question …

On saws with a longer stroke (like comparing a 660 to a 460) I generally seem to get better results with a lower Exhaust and Intake ...

But I have not changed transfer heights ... anyone have thoughts on this???

(Specifically, I had a 660 Cross cylinder that ran OK with Ex 100, Tr 120, In 80. I changed the Ex to 97 and the In to 83, but left the transfers alone and it seemed to really wake up. Comments welcome).

 

[MustangMike]

Randy, For example, I've been using your "card trick" to do the Exhaust roof ... so hard to draw or see lines down there! Works great, thanks!

 

[Mastermind]

OK, I'll throw out a question …

On saws with a longer stroke (like comparing a 660 to a 460) I generally seem to get better results with a lower Exhaust and Intake ...

But I have not changed transfer heights ... anyone have thoughts on this???

(Specifically, I had a 660 Cross cylinder that ran OK with Ex 100, Tr 120, In 80. I changed the Ex to 97 and the In to 83, but left the transfers alone and it seemed to really wake up. Comments welcome).

There's no hard and fast rules Mike. What works for one guy might not work well for another. Too many variables. Port shapes, including the radius at the corners, make a huge difference in behavior. I can run the same opening point on an exhaust or intake port, and just change the shapes and make one a turd, and the other a beast.

Now......on a two port engine like a 660.....you can usually get away with less blowdown than you can on a four port engine. I think that's because of the difference in velocity.

 

[srcarr52]

There's no hard and fast rules Mike. What works for one guy might not work well for another. Too many variables. Port shapes, including the radius at the corners, make a huge difference in behavior. I can run the same opening point on an exhaust or intake port, and just change the shapes and make one a turd, and the other a beast.

Now......on a two port engine like a 660.....you can usually get away with less blowdown than you can on a four port engine. I think that's because of the difference in velocity.

I'll confirm these findings, especially the less blowdown on dual port cylinders.

 

[Ketchup]

It seems to me the volume of charge moved is almost more import than case pressure or vaccum generated. The whole point is to get all the spent charge out and replaced by fresh.

The higher the intake, the more displacement volume the piston creates on the downstroke.

As long as the case is fully charged when the intake closes more volume goes upstairs with an earlier intake.

The angle of the uppers is about inhibiting mixing of exhaust and charge. Velocity seems to create a more distinct separation of spent fuel and fresh, especially when the upper transfer ports are well shaped and aimed. Call it case pressure or exhaust vacuum or transfer velocity, it’s important. A higher intake improves velocity as well.

My take away is a wider, higher intake will improved transfer performance both in volume and velocity.

 

[Mastermind]

Harrumph

 

[mdavlee]

Harrumph

View attachment 185014

View attachment 185013

Hmmm. Looks interesting in there[emoji848]

 

[wcorey]

OK, I'll throw out a question …

On saws with a longer stroke (like comparing a 660 to a 460) I generally seem to get better results with a lower Exhaust and Intake ...

But I have not changed transfer heights ... anyone have thoughts on this???

(Specifically, I had a 660 Cross cylinder that ran OK with Ex 100, Tr 120, In 80. I changed the Ex to 97 and the In to 83, but left the transfers alone and it seemed to really wake up. Comments welcome).

But the great dilemma is whether it would improve still more by also bringing the transfers up to follow where you went with the exhaust.
Problem is obviously you can’t always go back if it doesn’t work.

That’s why us hobby porters benefit so much from the experience of the pros who can experiment on multiples of the same model and figure these types of things out.

As much as I get tempted to try things known to be well out of convention, I really don’t want to ruin something tough to replace like an 066 cylinder that took me a year to find a deal on.
Been there done that unfortunately...

 

[huskihl]

Now, if you could only work on expressing yourself and not holding back ...

Said no one.....







.....ever



...

 

[Mastermind]

Hmmm. Looks interesting in there[emoji848]

It's just dust and reflection.

 

[MustangMike]

On that Cross 660 jug, I was not able to make the ports wider, but I did try to improve their shape … a bit flatter and smaller rounded corners … all carefully beveled.

From what I'm hearing here, I guess that may have helped a lot. (I guess I did good!!!)

Now that saw (which also has bridge ports) runs very strong with a Huztl muffler w/unmodified outlets, and a modified baffle (a 1/2" hole and 2 - 1/4" holes above it like mouse ears). Other 660s I have will not run well with a modified baffle muffler like that on it. I hear that may also be related to blow down, but I wish I understood it better!

Right now, I just kinda experiment with mufflers if I don't think it runs as strong as it should.

 

[wcorey]

Now that saw (which also has bridge ports) runs very strong with a Huztl muffler w/unmodified outlets, and a modified baffle (a 1/2" hole and 2 - 1/4" holes above it like mouse ears). Other 660s I have will not run well with a modified baffle muffler like that on it. I hear that may also be related to blow down, but I wish I understood it better!

Generally speaking, a more restricted muffler will coexist better with a longer blowdown.
I have only a fuzzy picture of the dynamics at work there...

Basically, the exhaust needs to exit faster with a shorter blowdown.

So you could look at it that the greatest benefit of raising the exhaust was to increase blowdown to be more in tune with the relatively restricted muffler.
Or not...

 

[mdavlee]

It's just dust and reflection.

View attachment 185052

I thought you might have been trying something out there.

 

[Nutball]

Generally speaking, a more restricted muffler with coexist better with a longer blowdown.
I have only a fuzzy picture of the dynamics at work there...

Basically, the exhaust needs to exit faster with a shorter blowdown.

So you could look at it that the greatest benefit of raising the exhaust was to increase blowdown to be more in tune with the relatively restricted muffler.
Or not...

I'm not sure about that only for the reason of the amount of time it takes the exhaust gasses to cool. When the fuel burns, that fire only lasts for a split second, and that fire is the high pressure you want to run the engine off of. Once the fire goes out, the gasses cool extremely quickly. That high pressure doesn't linger except for what's left of warm gasses and expanded decomposed gasoline.

The muffler restriction depends on how long the power stroke is. I had a 2511t I raised the exhaust on, and one I lowered the exhaust. Both had the same muffler mod, and other mods (compression, intake...) The lower exhaust didn't have worse performance, though it had only a widened and lowered port instead of widened and raised. It was MUCH quieter than the raised exhaust version, and were talking about a roughly .025" height difference. So, draw your own conclusions.

Just my thoughts and experience, not saying I'm right.

 

[MustangMike]

I thought you might have been trying something out there.

Randy has been hanging around Scott for too long, instead of a direct answer … bread crumbs!!!

Granted they are big/obvious bread crumbs, but bread crumbs non the less!

 

[CR888]

Randy has been hanging around Scott for too long, instead of a direct answer … bread crumbs!!!

Granted they are big/obvious bread crumbs, but bread crumbs non the less!

I'm sure Randy would help you Mike (like he's done for many folks), TM the same with THEIR hard earned 'valuable' knowledge. But sadly that small tiny percentage will take advantage of this public sharing and abuse it, copying it and passing it off/selling it as their own work. When these fly-in-fly-out builder's cause havoc with good members, it sends a shiver down their spine making them feel kinda in an odd way responsible cause they put it all out there. Get it. That's what I dislike most about thieves & dodgy operators, it changes the way responsible good people have to do things. Its just they way it sadly is, I don't like locking my car and removing the keys when I go to pay for gas...but I have too. Maybe a saw of JMS did run OK before it seized, but before you give him a plug think of those who's intellectual property he stole, sold to other members and all the people he left in the chit. Its been a while but those members are still touchy, still pissed & wouldn't mind kicking him off a tall cliff.

 

[MustangMike]

I'm sure Randy knows I'm joking with him (did you read my Avatar? I didn't put that there, but I'm proud to have it there!), and I certainly did not mean to give JMS a plug … would not deal with him for anything … but was stating facts from the past.

I have stated in the past, and I still believe, he intentionally booby trapped the saws … there is something wrong with him.

 

[mettee]

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