Quote:
Originally Posted by ZS Phil
Ah ok, I remember now. Was 2 years ago that now, where does the time go?!
Just got my clutch delivered back from CG today so can pop the engine back in now.
I'm not convinced the orifice size is the problem with the 200 tdis, I have mapped them to give almost a smoke free burn (and very little power). I think the problem is more the position of the holes rather than the size of them.
What I want is the standard spray pattern with a larger orifice. Injection stage pressures can be played with to help with atomization (if needed), I found an interesting paper on this once. But of course that will put more load on the pump.
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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!