Well, I’m just a hack that ports on the weekends. I don’t have the hundreds of saws under my belt that many here do. What I’m doing is baby steps for paying customers, so I’m timid. As always, the particulars of the model change what I do. And I make plenty of mistakes.
I have two split approaches: Gut or Finesse.
If I gut the strato I typically:
-cut Base minimally to set squish
-Dramatically widen exhaust, only raise for RPM (Often no raising to hold torque), pollish
-eliminate boot dividers (but keep carb dividers) -*just this sometimes
-sometimes widen or link intake ports
-Blend lower transfers
-Set squish at .018” (wider for higher rpm, .022”ish, some small saws I’ll go down to .015”)
-Start with blowdown at 16 degrees and work up to 22 degrees
-keep intake as high as possible, epoxy as needed
-timing advance, really depends on the saw how much.
-large muffler opening, no screen
-delimit carb (if possible)
These saws puke fuel. I don’t like doing it. The power band is annoying. It’s a lot more work. But there is a certain raw power.
Finesse Style:
-cut base to set a low exhaust. .030” or greater usually. Still watching intake floor.
-Set squish at .018”. wider for more rpm, tighter on some small saws
-Lower transfer blending, but trying to keep case volume low.
-Widen and raise exhaust somewhere near stock. Every saw is different here. I usually err towards lower than stock by 3-5 degrees, but some saws need more duration
-Set blowdown at 20 degrees. Raise to 17 as needed. Again, duration (and upper port Area) may dictate here.
-set piston windows for clean air so timing is 2-4 degrees ahead of mixed intake. Sometimes only match timing. I lower cold air ports and raise windows to the primary upper transfer.
-Widen mixed intake port. On most saws there isn’t much room here. I want a lot of intake Port Time Area, but not by sacrificing case pressure.
-Open muffler to 80% exhaust port area. I want a little back pressure. I may even keep a screen. This one varies widely by model.
-Delimit Carb
-Timing advance as needed after tests.
I wanted this thread because I don’t feel like what I’m doing is good enough and may have fundamental errors, so feel free to pick it apart. That’s what I’m here to do.
I agree. The quality of many of these saws is very impressive. That’s a major reason I don’t want to give up on them.
I like that you’re talking about a specific model. The reality is that strato saws vary as widely in there design as other saws, so to nail down good strategies we have to get specific. Terry Syd did that and his threads are very helpful.
What you’re saying about compensating the cold air to keep up with changes to mixed air is probably the BIG fundamental of strato porting. I think it also opens opportunities for changes we wouldn’t make on a single track 2stroke.
Some of the things I want to explore here are:
How much more air can we put in these saws?
How much more fuel Can we put in with that air?
How much In-transfer mixing is happening?
How much mixing happens in the combustion chamber?
How do we take advantage of that?
Is exhaust back pressure more of a factor in Stratos?
@Cooper264 mentioned Nitrous. The cylinders have more port volume and more ports. Can we use that for race fuel saws?
I feel like there’s a lot of potential here.
