Intake swirl?

[cowboyvet]

I'm learning and reading a mountain of books and threads on porting. In doing so I think of an old trick I was shown on old carb 4 strokes. I was shown by a very good head man years ago a trick he used in his porting. It was tested and he showed me smoke flow and volume flow testing. More importantly his heads dominated the race tracks locally. What he did was make the intake ports look like a swirl you see on an "easy out". He cut ridges and valleys in a gentle curve around the runners. He would sometimes build it up with material if needed to make the cuts but he had more flow by the time the valleys were cut. The effect was better atomization of the fuel air mix. That is one of the reasons fuel injection produces more power because of the better atomization. Attempting this would be way over my head at this time but I was just curious if anybody had tried anything like this. I keep seeing how everybody wants to leave the intake a little "rough" to help with atomization. I can't help but think about what this old timer showed me on 4 strokes and wonder what smooth with swirls would produce. Like I said this is way over my head to even think of attempting. Anybody heard of anything like this? Would it be better in theory?

 

[Meadow Beaver]

I think the swirls or channels in the intake aren't needed. A rough intake will allow the fuel to oxygenate giving the saw more power. A smooth intake will cause the fuel to bead on the intake, which I know doesn't work too good.

Sorry if this isn't completely understandable, I've been sick all week and can't think too clearly.

 

[cowboyvet]

I understand what your saying. I leave my intake rough and polish the exhaust. I was just thinking on a far more advanced level than I'm capable of actually doing any time soon. The old timer explained it to me as rough causes backwards turbulance which do help atomize the air/fuel but hurts velocity. The gentle swirls also mixed it up but kept the turbulance moving in the correct direction of flow which in turn increases efficiency. This all might be a moog point in a two stroke though with the extreme turbulances caused by the crankshaft spinning around. I do know his headwork on small blocks was absolutly amazing in performance so he knew what he was talking about. 4 strokes and 2 strokes are two different animals to some degree but both have to breath and I know the better you atomize the fuel the better it burns. I was just throwing it up there because there are some pretty resourcefull guys on here who do alot of experimenting. Has anybody tried anything like this? Would the crankshaft just void any benifit of it or would it help get more into the crankcase faster? Just some thinking plugging up my brain.....

 

[cowboyvet]

I guess it is also like another point I keep reading. Everybody keeps saying to keep the throats straight from the outside to the inside. A slight curve in the surface would form a venturi which would help move more air also. I can see in my future I will need to build another flow bench to fit chainsaws and sit down with some junk cyl. to do some playing. The swirls take a mill, lathe, and a tig setup which I don't have but still would like thoughts or experiences on the theory of it.

 

[trappermike]

"Swirl" intake ports are generally a 4-stroke thing to help atomization of the air-fuel mix,remember it's a short trip down the intake port and into the combustion chamber on a 4-stroke.
However on 2-strokes the fuel has a much longer path and is "churned" around in the crankcase also. As many good people tell here,a fine "brushed" finish on the intake port is best.