but I run lower timing than most.
Elaborate some more on this, I totally forgot to ask you on this earlier as well as which diesel you run too.
Kawi, here is the thing, if our fuel is adhering to the crown surface regardless of being a gasser or diesel, we aren't making heat from it until its vaporized and has been consumed by the flame front or if you like, the reaction front. The distillation temperature has a hand in our point of vaporrization in the chamber as well does timing because our pre-injection heat buildup due to mechanical compression is what gets us as close to if not on that distillation point providing a short and sweet delay angle, in turn swirl will hopefully distribute the fuel vapor next to the oxygen for the power stroke to begin. Remember swirl is not just created by port design, but by squish action in the quench regions (if used) of the chamber (quench region - fixed position w/ the head/ Squish - caused by the piston crown area directly under the head approaching TDC). Sir Harry Ricardo specialized in rapid combustion process, he was the person who had come up with the 'Swirl chamber' that is used in some head designs.If you think about changing the timing always keep in mind the fuel's characteristics.
Speaking of swirl in terms of assisting cylinder evacuation, I see it can be one of a few variables on relieving the cylinder to allow the next clean charge to come in. However, if our intake valve or valves are not designed properly to work in fashion with our converging and diverging sides of the valve throat area, swirl strength could most likely be lost due to disruption in flow, once you look there we proceed to the bore, and piston crown. How will the flow twist and turn into the chamber without causing a reversion type of situation and fill the cylinder the quickest? The valve is our roadblock, if its a big road block, our new charge mass could be lacking in density (pounds of air) therefore combustion will suffer and power will as a result. Once you have burned whats possible, we proceed to the exhausting phase. As far as swirl being a chief factor, I don't think it is in the beginning, our cylinder pressure has more say because of the blowdown phase, once our valve has lifted enough off the seat for flow to begin, thats our initial greatest flow velocity situation. At valve crack, nothing has happened yet. Going back to the convergent/divergent comment, this time we have to flow around a valve face instead of next to a valve curtain everything on this end is needed close attention too for efficiency. Once again, if we have enough turbulence to cause a choke or reversion occurrance, our new charge will be dilluted even if the turbo is spinning, flow can only go as fast as our runner allows and that begins at the valve head and seat area up to the turbocharger. Don't forget about the valve pockets in the head.
The swirl itself, can navigate around the valves coming off the bowl or bore wall and into the exhaust port, but, the only thing with a swirling mass of air is your swirl action in this sense. Exhaust or intake is creating a LONG path for evacuation. For the most part IMO, swirl is used to satisfy our flame front.
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