Part 8: The Stratified Chainsaw

[cuinrearview]

Strato saws are gay

Reported.

 

[Woodpecker]

Reported.

 

[P.M.P.]

Reported.

 

[Redfin]

I saw that in the porting artwork thread. Would you mind explaining it a little?
Is that a gutted strato intake with extra volume for Alternative fuel? What fuel is it for? What does the bigger circle hole below the transfers do?

Ever since I laid my hands on a strato 261 I was wanting to use the tunnels for boost ports. This project really had nothing to do with gutting the stratos other than utilizing that real estate. Its on gas right now.

 

[Nutball]

Ever since I laid my hands on a strato 261 I was wanting to use the tunnels for boost ports. This project really had nothing to do with gutting the stratos other than utilizing that real estate. Its on gas right now.View attachment 281762

Cool! What carb are you using now? I must assume a non strato type carb?

 

[Redfin]

Wj69

 

[Mastermind]

Reported.

Ignored.

 

[Flip]

I really like strato saws, much more run time per fill up compared to older saws.

So I've put a 562xp carb/intake on 550xp/545's and a 572xp carb/intake on a 562xp with very good results. Easy bolt on power. The question I can't get my head around is the fresh air charge. You can see in the following pic of a 550xp cylinder with the 562 intake traced out that everything is bigger. I opened up the intake to allow the bigger mixture to flow thru but I left the strato ports unchanged.

I'm thinking that the fresh air charge will need to be same no matter how much bigger the mixture charge is. Is this a concern or does it even matter? The thing I wanted to avoid is fresh air in the combustion chamber.

 

[srcarr52]

I really like strato saws, much more run time per fill up compared to older saws.

So I've put a 562xp carb/intake on 550xp/545's and a 572xp carb/intake on a 562xp with very good results. Easy bolt on power. The question I can't get my head around is the fresh air charge. You can see in the following pic of a 550xp cylinder with the 562 intake traced out that everything is bigger. I opened up the intake to allow the bigger mixture to flow thru but I left the strato ports unchanged.

I'm thinking that the fresh air charge will need to be same no matter how much bigger the mixture charge is. Is this a concern or does it even matter? The thing I wanted to avoid is fresh air in the combustion chamber.

View attachment 284790

It probably wont matter, the strato ports are already much larger than they need to be as the tunnel in the piston is the biggest restriction.

IMO the strato duration vs. intake duration is very critical to achieve power in the RPM range you desire. The intake is filling the crankcase and the strato ports are back filling the long transfers with fresh air, so more strato duration pulls the fresh air further down the transfer port which then delays the actual fuel/air charge. If the fresh air isn't completely wasted out the exhaust then you have poor mixing of the fuel within the trapped volume. But adding intake duration to lessen the strato pull then decreases the crankcase compression which is much needed to provide ample pressure differential for the long transfer tunnels.

For the husky design the strato port timing is when the top of the piston tunnel starts to open the bottom of the transfer port, when this is happing the intake side is already open. So dropping the jug adds intake and strato duration at fairly equal amounts.

 

[Mastermind]

It probably wont matter, the strato ports are already much larger than they need to be as the tunnel in the piston is the biggest restriction.

IMO the strato duration vs. intake duration is very critical to achieve power in the RPM range you desire. The intake is filling the crankcase and the strato ports are back filling the long transfers with fresh air, so more strato duration pulls the fresh air further down the transfer port which then delays the actual fuel/air charge. If the fresh air isn't completely wasted out the exhaust then you have poor mixing of the fuel within the trapped volume. But adding intake duration to lessen the strato pull then decreases the crankcase compression which is much needed to provide ample pressure differential for the long transfer tunnels.

For the husky design the strato port timing is when the top of the piston tunnel starts to open the bottom of the transfer port, when this is happing the intake side is already open. So dropping the jug adds intake and strato duration at fairly equal amounts.

Great post Mr. Carr.

 

[Flip]

IMO the strato duration vs. intake duration is very critical to achieve power in the RPM range you desire. The intake is filling the crankcase and the strato ports are back filling the long transfers with fresh air, so more strato duration pulls the fresh air further down the transfer port which then delays the actual fuel/air charge. If the fresh air isn't completely wasted out the exhaust then you have poor mixing of the fuel within the trapped volume. But adding intake duration to lessen the strato pull then decreases the crankcase compression which is much needed to provide ample pressure differential for the long transfer tunnels.

There's a book of info in this paragraph. I'm gonna have to go to the store and get a suitcase of Natty Light and start thinkin' about it.

I didn't think about the restriction being in the piston tunnels. I always worried about upsetting the case pressure and getting the timing of the fresh air slug off.

 

[Mastermind]

There's a book of info in this paragraph. I'm gonna have to go to the store and get a suitcase of Natty Light and start thinkin' about it.

I didn't think about the restriction being in the piston tunnels. I always worried about upsetting the case pressure and getting the timing of the fresh air slug off.

Unless you are looking for every percentage point you can find, just doing your machine work, and leaving the intake and strato ports unaltered is a sure bet. They will both gain some duration, and though the degrees of crankshaft rotation gained will be different on the degree wheel, it will work surprisingly well. With a lot of these units, you can grind more, and gain less.....

 

[srcarr52]

Unless you are looking for every percentage point you can find, just doing your machine work, and leaving the intake and strato ports unaltered is a sure bet. They will both gain some duration, and though the degrees of crankshaft rotation gained will be different on the degree wheel, it will work surprisingly well. With a lot of these units, you can grind more, and gain less.....

Same, after machine work I don't really add any duration on either, maybe a touch on the strato but not much. I do make sure the stratos match side to side, with differences in the bottom of the transfer port and the tunnel in the piston I've seen as high as 6 deg difference in duration side to side.

The exception to this is the 572, for some reason husky decided to open the stratos first on this saw and it has very low intake duration. I tend to leave the intake alone and add extra intake duration by trimming the piston skirt. Any weight you can remove from those heavy pistons is a plus.

 

[P.M.P.]

Strato saws are gay

 

[Wonkydonkey]

Strato saws are gay

Don't knock it till you’ve'd tried it. Pork chop ....

 

[P.M.P.]

Don't knock it till you’ve'd tried it. Pork chop ....

 

[Mastermind]

Strato saws are gay

Gay saws have feelings too.

 

[Maintenance Chief]

 

[P.M.P.]

View attachment 284863

Hey no fair that gay saw is a non Strato saw. My wife wants one her favorite color. It's saved on her watch list on Amazon haha.Redmax g5000 clone

 

[Brush Ape]

Throw about a 3hp shot of nos at er and see if she sticks. Whats the worst that could happen

1. People start passing out and hit the floor.
2.The light at the end of the tunnel is probably an oncoming train.
3. While you are reading this, something is going wrong but you don’t know it yet.