Quote:
Originally Posted by p_b82
The problem we have is that as soon as you change the flow rate, you will change the flow pattern away from "standard"
I think I un-earthed the same paper, or you linked me it, as I spent a good while trying to understand the very complex nature of atomisation VS burning characteristics - especially under a compression ignition system.
What could not be denied was that the finer the mist, the better the combustion.
The longer time ignition has - the cleaner the burn too; the combustion becomes more complete as it has longer to use the available oxygen.
It isn't just a single simple factor as droplet size, but I do think that for our engines, with the limitations of the head and the flow characteristics we have, 200's just aren't the way to go; if they were easily tamed then it would have been done by now IMO.
From what I've read, more smaller holes should burn cleaner, if we're still top end limited by the pump, then so be it; but what I didn't want is to build something that coked the vanes up and needed a turbo rebuild after only a few K miles. That seems to be the net result of any-one with a VNT that tried to use 200's.
Hopefully I'll know in the not too distant future, and can feedback any findings... Not that many people here will go down the route I am!
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That's pretty much my understanding of the matter too but as with everything it is a compromise, all very well having optimal atomization but if you can only get 40mg/stroke of fuel in the it defeats the point, May be better to have slightly less than optimal atomization (but still got enough for minimal smoke) but ultimately allow more useable fuel in per stroke than SDIs allow for.
Just doing some quick maths looking at combined orifice area looks like this:
Sdi (5 x 0.22) total area is 0.190
At a guess your proposed nozzles (assuming the part number ends 882) (6 x 0.205) total area is 0.198
Sdi modified (5 x 0.23) total area is 0.210
200 tdi (5 x 0.24) total area is 0.225
My concern would be at what angle do those 6 hole injectors enter the head in the engine for which they were designed? Is there an offset bowl in the piston? What is the clamp angle in the original engine? It is these factors which I believe makes the burn so rubbish with the 200 tdis.
There is so little info about those 6 hole nozzles and even less about the engine for which they are designed so finding the answers to the above questions is very difficult by simply looking online. Either pull a scrap engine to bits and get the measuring tape out or as Kris said, get them fitted and suck it and see. The letter being the much easier option I imagine.