Piped 046 - On A Budget

[CHEVYTOWN13]

Roughed out the ports:

New timing -
Ex = 92 ATDC, (Beyond The Point Of No Return)
Xf = 123 ATDC
In = 79

:hmm3grin2orange:

 

[CHEVYTOWN13]

That vid makes me want to put a pipe on every saw i own. Love it.

L22, how about your Stihl 042?

That wood make a great candidate

 

[Stihlverado]

Sv, yeah, it's the 365 Especial. I believe it is 4 stroking before the cold cut. After that cold cut, it warmed up and this is what it ended up with when I took a reading after the last cut. And the plug looked real good. I'm thinking of going all the way and adding a belly so that I can raise the exhaust roof for a true piped saw at 90º ATDC for some gnarly RPM's. But the Kita 6401 is beckoning for a pipe too

We dont get many kita's or dolmars in our neck of the woods that are played with much, would definitely be interested in seeing a kita piped. The potential and capabilities!!

 

[logging22]

L22, how about your Stihl 042?

That wood make a great candidate

All in good time my brother.

 

[logging22]

We dont get many kita's or dolmars in our neck of the woods that are played with much, would definitely be interested in seeing a kita piped. The potential and capabilities!!

Where ya been??

 

[Stihlverado]

Where ya been??

Horses, ya gotta love 'em or make REALLY big hamburgers!!!

 

[logging22]

Horses, ya gotta love 'em or make REALLY big hamburgers!!!

With cheese??

 

[CHEVYTOWN13]

I'm already dreaming about the Kita 7901

We dont get many kita's or dolmars in our neck of the woods that are played with much, would definitely be interested in seeing a kita piped. The potential and capabilities!!

+1 :drool:

The 6401 might be surprising...

 

[Danger Dan]

Porting revolved around the sonic wave pull / push of the pipe. Therefore, the exhaust port had the highest priority. The main factors include:
- Duration, the increased duration should give the pipe’s reflected sonic wave enough time to stuff the cylinder
- Port Area, according to Jennings the port area, (at the piston) determines the header length
- Shape, the exhaust nozzle is considered part of the header, so they should have the same shape. Also the flatter the the roof of the port the bigger the sonic VA-BOOM !

Again, this is all theory and I have very little experience, so all I know is all I know.

 

[Danger Dan]

Transfer and Intake Porting:

Had to raise the transfers to get the desired blowdown #. Raising them also increases duration, which should give the positive sonic wave of pipe time to pull fresh charge into combustion chamber and pipe.

Not quite sure what to do with intake, the nozzle is asymmetrical and the casting is irregular at best. Thinking asymmetry may be by design and could affect port velocity. so I just cleaned up casting and lowered it a bit. Can always revisit this later.

 

[BigJ]

Roughed out the ports:

New timing -
Ex = 92 ATDC, (Beyond The Point Of No Return)
Xf = 123 ATDC
In = 79

Question: why widen the lower transfer port towards the intake? or is it more of a "creating a better flow path" from all sides as opposed to a "widening"?

 

[kraftzion]

2 stroke tuning

pretty good read if you don't know(i didn't)

http://www.scribd.com/doc/9726341/Two-Stroke-Proformance-Tuning

 

[Danger Dan]

Question: why widen the lower transfer port towards the intake? or is it more of a "creating a better flow path" from all sides as opposed to a "widening"?

A better flow path yes, but from all sides?
I think more of a direct flow path from the intake at full song.

To be honest I read a post from a highly respected builder out of Northern CA who recommended it to another newbie, but he didn't mention why

 

[Danger Dan]

pretty good read if you don't know(i didn't)

http://www.scribd.com/doc/9726341/Two-Stroke-Proformance-Tuning

Yup, there are a few 2 stroke tuning guides out there:
- Gordon Jennings
- Graham Bell
- Blair

Most of it relates to bikes.
There's a section in your link about exhausts, (pipes) and he talks about kart engines, which I think are closer to chainsaws....Thanks

 

[BigJ]

A better flow path yes, but from all sides?
I think more of a direct flow path from the intake at full song.

To be honest I read a post from a highly respected builder out of Northern CA who recommended it to another newbie, but he didn't mention why

I guess I never pictured the flow going from the intake port directly into the transfer. I was picturing the flow coming primarily from the bottom of the transfer.

 

[Danger Dan]

I guess I never pictured the flow going from the intake port directly into the transfer. I was picturing the flow coming primarily from the bottom of the transfer.

I know what you mean...in slow motion. As the piston descends with the transfers and intake closed, static pressure builds in the case. That pressure is equal in all directions. When the transfers open there is flow from high pressure to low. Not sure what the flow pattern looks like @ 14,000 revs. Think of one of those flicker books where you flip the pages to see static drawings become animated.

 

[Danger Dan]

Header

According to Jennings header length should be 6-8 times the diameter of the exhaust port at the piston, which is 1.25 x .625:

The port has semi circles at each end with a square in between, so calculated port diameter is the area of a circle with .625 D plus the area of a .625 square.

- The radius of the circle is half of .625 or .3125
- The area of a circle = pi r squared or 3.14 x (.3125x.3125)=.306
- The area of a square = L x W or .625 x .625 = .391
- Total area = .306+.391 or .697

So 6 x .697=4.182" and 8 x .697=5.576"
The pipe's header is approx. 5.25", so it's in the ball park.

 

[CHEVYTOWN13]

I'm surprised how well Jenning's formulas are still valid.

Actually, I'm not surprised anymore. The pipes I've made using his formula's have run alright.

Good show bro. Keep up the good work.

 

[Danger Dan]

It's back together…going to run a tank or two with the muffler to shake it down and get a baseline. Hasn’t been started since I received it, mixed up some Mobil 2T @ 32:1 and it fired right up.
It appeared the top end had been replaced with a late model; complete with a Walbro and limiter tabs. Followed the rulebook and took a razor to the tabs. Adjusted the carb to a gargle. Also noticed the oiler is working as it should…looks good so far.
The saw came with a 20" Windsor Sprocket tip and Oregon chain. Going to stick with it, but would prefer a 16".

Opened up the muffler and added a second port. Also matched the nozzle, gasket and heat shield. Need to sharpen chain and find some wood!

 

[CHEVYTOWN13]

I tried to post your pictures bro, but they was too big.

Looks good. I'm going to do some muffler and pipe runs with the 365 to see the diff too. Cool beans bro.