working on other builders saws

[danimal]

Meh.......we're all grown ups here.

We are all grown ups? Right?

Dude! At 5'4" n over 60...i dont think i'll ever grow up at this rate.

 

[Lightning Performance]

pretty close, the reality is that the area of the port window should be the same as the area of the throttle shutter, but if the boot is bigger I go with that instead.

Well said! I go to the boot to. Guilty as charged.

*s-word... There was another train wreck and I missed it, *s-word *s-word and *s-word. Carry on

 

[tree monkey]

Aren't most intake openings at the wall already at least as big as the boot?

you have to work with what you are given.

if ya want to be a good saw porter, ya have to study the right thing. reading books based on bikes, quads, sleds, boats, cars, plains, rockets, is useless info.

 

[huskihl]

you have to work with what you are given.

if ya want to be a good saw porter, ya have to study the right thing. reading books based on bikes, quads, sleds, boats, cars, plains, rockets, is useless info.

I mostly study here lol

 

[wcorey]

...When the velocity is gone it's gone and fuel falls out and clumps up.
...Swimming pools of fuel is what that will create.

So then with a properly proportioned intake tract, what happens to the air/fuel mix a millisecond later when it clears the port and dumps into the crankcase...?
Same thing I'd guess. What's the difference?

pretty close, the reality is that the area of the port window should be the same as the area of the throttle shutter, but if the boot is bigger I go with that instead.

So then time/area (beyond that threshold) isn't a primary concern on the intake?
Sounds like the port outlet shape on most should end up almost square with a bit of radius on top/bottom...

 

[Czed]

you have to work with what you are given.

if ya want to be a good saw porter, ya have to study the right thing. reading books based on bikes, quads, sleds, boats, cars, plains, rockets, is useless info.

Nice thread what saw model is this sorry if i missed it.

 

[tree monkey]

I mostly study here lol

not all the info you get hear is good.
I may not share everything I know, but I won't mislead anyone either

 

[tree monkey]

So then with a properly proportioned intake tract, what happens to the air/fuel mix a millisecond later when it clears the port and dumps into the crankcase...?
Same thing I'd guess. What's the difference?

at higher rpm's it's not a big deal. if the port timing/duration is ideal for lets say 10,000 rpm, the velocity of the fresh charge is still pushing/stuffing the case as the port closes. if the port is bell shaped, bell mouthed, larger at the port window then the carb, then the charge slows down and has less push. this results in less charge it the case. longer intake tracks do the same thing because of it's volume.

this is a bigger problem at idle when velocity is much lower, this is when it pools in the boot and port.

 

[tree monkey]

So then time/area (beyond that threshold) isn't a primary concern on the intake?
Sounds like the port outlet shape on most should end up almost square with a bit of radius on top/bottom...

time area can be changed without changing the area of the port. simply move the entire port up or down in the cylinder. why bell mouth it if you don't have too. epoxy is your friend here

a round intake track from the carb through the port window would flow the most, but a round window doesn't work as a port window. port timing would suffer. so flatten it out to an oval till you get the port duration needed.

 

[tree monkey]

Nice thread what saw model is this sorry if i missed it.

372 ne with oe top end

 

[tree monkey]

Dude! At 5'4" n over 60...i dont think i'll ever grow up at this rate.

yeah but ya might grow "out" of it.

 

[drf256]

Glad we are back on the rails here.

Good stuff.

Scott, you envision the entire intake port flowing as one, or asymmetrical with more flow on the floor?

My ports have started getting smaller as my grinding continues. Especially intakes and upper transfers.

I still see the port window needing to be slightly larger than the throttle butterfly or boot cross section myself. Poiselles law of laminar flow and such. I certainly can be wrong.

 

[Czed]

372 ne with oe top end

I've worked on a couple of overly enthusiastically ported 372s over the years it was easier just to change cylinders and start over wish i had pics you guys would have enjoyed them.

 

[Czed]

That was when oem was pricey now they are reasonable.

 

[mdavlee]

One of those Dominant pistons is wide enough it would probably cover that intake port. The skirts are 41mm wide if I remember right.

 

[Keith Gandy]

I mostly study here lol

Thats why I ask so many questions here too

 

[T.Roller]

Here to learn

 

[Mastermind]

Great thread.

 

[Deets066]

Great thread.

Lol

 

[thomas1]

Great thread.

You're welcome.