046 Intake

[Danger Dan]

Here is something I want to try on a 046. What do you think? :smoking:

 

[Crofter]

Is that Braille or microboost ports?

Edit; looks like nice contours and you didnt make any windows where you dont want them, Lol!

 

[Danger Dan]

Golf Ball Physics

This is a Four Paws jug that I put dimples in. Theoretically they should reduce drag and increase flow velocity. The actual work was very tedious and required specialized high tech tools. :smoking:

 

[joesawer]

Nice looking intake port.
The dimple thing keeps coming up, but most high end four stroke engine builders have given up on it.

 

[Crofter]

It be good copywrite protection!

 

[timberwolf]

Look at the boot, it has already been done closer to the carb.

Also at the point closest to the combustion chamber heat transfer becomes an issue, increasing surface area in the flange is going to allow more heat to be transfered to the incomming charge. The loss of charge density due to heating could well be a far greater factor than any flow improvement gains. If it's not getting enough intake flow why not just make the hole bigger?

 

[Danger Dan]

Yes I noticed the boot, it is where the idea came from.
The point regarding heat xfer is well taken, although as long as the carb is isolated by the boot one would expect the incoming velocity @ wide open throttle to limit such exchange.
The hole has aready been enlarged to match the boot.

 

[timberwolf]

Not sure about that, heat in the carb is certainly a problem, I encountered that with a hot running saw I made a solid aluminium intake for. But no mater what if the charge is heated before or as it gets into the base, it will limit how much will pack into the base before the port closes. Were not talking big potatoes here, but I think the heat vs charge density effect is pretty real and predictable.

 

[timberwolf]

I am thinking the stihl factory is putting those speed bumps in the intake tube more for breaking fuel up and mixing it with the air than for issues of flow improvement. Don't see them on the huskies or any older saws I have looked at, Could it be an EPA measure to help reduce unburnt HC emmissions? Or maybe just something to help low speed operation when the fuel is not being picked up by much air flow?

 

[Crofter]

The manufacturers are all seem to want to limit high rpm one way or the other so you know they are not doing it to enhance high end output.

 

[buck futter]

I think it is funny that he polished the intake piston top and exhaust on a similar saw and now the talk is about roughing the intake.

Leave it alone you are likely fine how it is.

 

[Danger Dan]

Yes, it has been widely acknowledged that there is little benefit in polishing the exhaust port, although it should be smooth to the touch. It is also generally accepted that an intake runner with a uniformly rough surface will flow better than one that is polished, (it's a turbulence / boundary layer issue). With regard to the piston, I've read that the 3120 piston comes polished from the factory. :smoking:

 

[joesawer]

I think the dimples in the boot are mostly to get the fuel off the walls and back into the air. I have noticed that the intake boot is often wet with fuel.

 

[drmiller100]

Yes, it has been widely acknowledged that there is little benefit in polishing the exhaust port, although it should be smooth to the touch. :

i'll differ. the smoother the exhaust, the less the surface area on the exhaust, and the less the heat transfer intothe jug.

 

[timberwolf]

True on the exhaust a smooth polished surface should reduce heating both by minimizing surface area as dr stated, but also by reducing how much radiated heat energy is absorbed. But esp with a two stroke the smooth surface will resist getting carboned up, this helps prevent choking down the exhaust with carbon restricting flow and canceling out any thermal gains of the smooth surface. But if you want to take advantage of the gains the polished surface needs to be kept clean.

 

[drmiller100]

i've never seen a good running 2 stroke carbon up the aluminum exhaust port.

i am truly puzzled what would cause this. too much oil? too low of temps? really crappy header design????

 

[Dennis Cahoon]

i've never seen a good running 2 stroke carbon up the aluminum exhaust port.

i am truly puzzled what would cause this. too much oil? too low of temps? really crappy header design????

My falling saw's would carbon the exhaust port in short amount of time being steadly used. Same with the top of the pistons. The mix oil is the cause IMO. I always ran Husky or Stihl oil @50/1

 

[timberwolf]

I agree Dennis, I saw far more carbon build up running factory oil at 50:1 than 32:1 castor. With more oil the port would stay wet with oil, but not bake on.

 

[Danger Dan]

My falling saw's would carbon the exhaust port in short amount of time being steadly used. Same with the top of the pistons. The mix oil is the cause IMO. I always ran Husky or Stihl oil @50/1

Have you made adjustments to reduce carbon buildup, or do you continue to run said oils @ 50:1?

 

[Dennis Cahoon]

Have you made adjustments to reduce carbon buildup, or do you continue to run said oils @ 50:1?

Still run the oil with no other problems. Just clean the exhaust port and top of the piston every once in awhile.