Chainsaw Porting Theory

[XP_Slinger]

Sorry about that guys, not trying to back pedal. A lot has gone on since I got alerts for stuff. I see we're on to intake shapes/timing now....keep er' going!

 

[Keith Gandy]

I see that he measured it. I cannot wrap my head around the flow reversal at 250 times a second overcoming inertia.

That is mind boggling. I can see man altering the natural effect quickly with what was occuring from the factory with altering shapes in that intake

 

[drf256]

That is mind boggling. I can see man altering the natural effect quickly with what was occuring from the factory with altering shapes in that intake

I think you're onto something. I really think you are.

 

[Keith Gandy]

I would think size and shape of that intake exit would alter the velocity which in turn would alter that back pressure ? Like altering the venturi in a carb

 

[drf256]

I would think size and shape of that intake exit would alter the velocity which in turn would alter that back pressure ? Like altering the venturi in a carb

Could the Venturi effect be how it overcomes exhaust pressure initially?

 

[Keith Gandy]

Could the Venturi effect be how it overcomes exhaust pressure initially?

Heck if I know! Ill have to ponder awhile.

 

[Keith Gandy]

Could the Venturi effect be how it overcomes exhaust pressure initially?

What is exhaust pressure vs crankcase pressure?

 

[XP_Slinger]

I would think size and shape of that intake exit would alter the velocity which in turn would alter that back pressure ? Like altering the venturi in a carb

I think pressure is gained or lost at intake closing in relation to transfers opening.

 

[Keith Gandy]

If this has been happening in 2 ports already Stihl didnt reinvent the wheel with that Delayed Stratification Scavenging Technology , but only added a big deflector across the exhaust in the muffler to capitalize on what was already occuring and in an attempt to restuff and burn uncombusted fuel? Just ideas fellows! Dont kick me in the nuts toooo hard!!

 

[drf256]

What is exhaust pressure vs crankcase pressure?

Check out that figure above.

 

[drf256]

My next experiment is on exhaust.

The exhaust wave is toroidal, like a smoke ring.

It won't come anywhere near a pipe, and may do absolutely nothing.

I can see a properly placed cone reflecting part of the wave back. I bought stainless sauce cups to weld into a muffler. I'm figuring on cutting the bottom open and facing the V away from the exhaust port.

 

[Keith Gandy]

My next experiment is on exhaust.

The exhaust wave is toroidal, like a smoke ring.

It won't come anywhere near a pipe, and may do absolutely nothing.

I can see a properly placed cone reflecting part of the wave back. I bought stainless sauce cups to weld into a muffler. I'm figuring on cutting the bottom open and facing the V away from the exhaust port.

That will be interesting

 

[Keith Gandy]

The cone at the end will effect that intake negative pressure also. Shoot dirtbike communities have know awhile power valves and tuned pipes offer performance advantages

 

[Mastermind]

In the pipe saw I just ported.....

EX: 85
TR: 120
IN:85

The pipe sends a wave of pressure back into the exhaust port........so the transfers stay closed for 35° after the exhaust opens.

I'm thinking on Al's muffler idea, timing number will need to be different for it to work.

 

[drf256]

In the pipe saw I just ported.....

EX: 85
TR: 120
IN:85

The pipe sends a wave of pressure back into the exhaust port........so the transfers stay closed for 35° after the exhaust opens.

I'm thinking on Al's muffler idea, timing number will need to be different for it to work.

I have no understanding of pipe saws or timing.

I get the basics of it, push back some lost charge and effectively start compression before exhaust closes.

I need to do some reading on this.

That's a seriously high exhaust Randy.

 

[Mastermind]

That's a seriously high exhaust Randy.

Everything has it's place.

Trying that without the correct pipe would make a turd.

 

[Four Paws]

New 550 and 562 with tiny intake ports, wth going on there?

They sure do have a lot of variation.

The 550,562, and 576 all have the tiny intake ports. Not sure why but they do make good power.

What are the durations? What is case volume like In these models?

Perhaps the carburetor has a large main jet and it is fueling heavily. Combined with the strato design the mixture just works out close to stoichiometric equilibrium?

What does a 6100 Dolmar look like? Somebody said they get insanely good fuel mileage.

 

[Mastermind]

What are the durations? What is case volume like In these models?

Perhaps the carburetor has a large main jet and it is fueling heavily. Combined with the strato design the mixture just works out close to stoichiometric equilibrium?

What does a 6100 Dolmar look like? Somebody said they get insanely good fuel mileage.

Normal timing duration, tight case with stuffers.

Very small venturi.......so low pressure signal is very high.

6100 has a larger carb.......and reeds on the strato ports.

 

[jmssaws]

I got a full circle in the works,gonna find out about some cases pressure I hope.

 

[Four Paws]

Normal timing duration, tight case with stuffers.

Very small venturi.......so low pressure signal is very high.

So, one could expect more turbulence in the intake, better mixing, larger ammount of fuel being drawn in?

Perhaps the smaller port area on the 562 is to prevent charge loss out the intake due to the stuffers? Case pressure is going to build faster.

562xp vs. 357xp:
both stuffed, similar displacement.
How do the intake tracts compare...size, shape, duration, carb?
How does bore compare to stroke?

I am asking because I am curious if we can see certain things trend, so we can make a correlation between a certain input and output.

For example...Do we see a small intake time area on a saw with stuffers Time and time again. If so, we could consider it a rule.