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 604 Posts Member #: 1106 Post Whore Hungerford, Berks |
22nd Nov, 2010 at 01:12:37pm
On 21st Nov, 2010 Paul S said:
I can't answer your questions as I have never tried staged injection. However, I would suggest using the same spray pattern on each of the injectors and setting them the same distance from the valve, even if it means shifting the primaries back a bit. Unfortunately when I started this project, I bought the 63Lbs/hr and 80Lbs/hr Siemens injectors thinking more about the total required fuel than looking into such things as spray pattern. So now I’m trying to utilise what I have without more expense… Probably the wrong way to be looking at this I’m sure. One of the concerns I have with moving the primary injectors back is that with a 26deg spray pattern, the walls of the bosses may impede the spray?? My thinking was that the pencil spray pattern injectors would not suffer the same problems being further back the boss as the 26deg injectors might. Still, your comments have made me think more before I do anything. On 21st Nov, 2010 Paul S said:
I still think that you are using too many variables in your setup to get an understanding of what is going on. Two VE tables and two injection timing tables is four times the chance of getting it wrong. I started out on testing the staging using 2 injection timing tables and 1 Fuel VE table and although I could get fairly good results could not get rid of the lean out on gear change. I thought that it was due to the fact that there was graduation in the transition to staging. (the reset errors that I was getting were due to the fact that I had 2 staging parameters set and did not have staging gradual transition turned on). I then changed to using no injection timing tables but 2 fixed timings and 2 Fuel VE tables. I see your point with too many variables and I will try to minimize these by working on using only one fixed timing value. But not until I work out how to get these staged injectors mounted in the MPI inlet manifold. ’77 Clubman build thread
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604 Posts Member #: 1106 Post Whore Hungerford, Berks |
22nd Nov, 2010 at 01:21:01pm
doh! just read pauls latest post in his inlet manifold design thread:
On 22nd Nov, 2010 Paul S said:
Spray is an issue. The injectors have a 26 degree cone spray pattern. With the above design, there is a slight interference with the spray at the base of the lower boss. However, the same sort of scenario exists in the existing 998Ti manifold and does not seem to cause major problems. I could push the lower injector further in, but I'm trying to minimise major changes to the fuel slug on the transition from single to two injectors per port. ’77 Clubman build thread
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 8604 Posts Member #: 573 Formerly Axel Podland |
22nd Nov, 2010 at 01:36:17pm
The lean out on staging is not an issue just for us. It is normal to have to deal with it on 4 port engines.
Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
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604 Posts Member #: 1106 Post Whore Hungerford, Berks |
22nd Nov, 2010 at 05:23:13pm
On 22nd Nov, 2010 Paul S said:
The lean out on staging is not an issue just for us. It is normal to have to deal with it on 4 port engines. I think that you are looking for a solution to a problem that does not exist if you are trying to get rid of a lean out on a gear change. My concern was that the lean out was on the inner cylinders once the engine conditions passed through the staging parameters. So it's not actually at the gear change, but accelerating directly after. It was enough to make the engine stutter for a split second, which I wanted to get rid of / understand before I install this on the Turbo engine. On 22nd Nov, 2010 Paul S said:
Have you tried staging on MAP? No, to date I have only tried setting with RPM and MAP, not with first staging parameter only. On 22nd Nov, 2010 Paul S said:
I found these datasheets the other day that show the spray patterns in some detail: http://siemensdeka.com/specsheets/FI114992.jpg http://siemensdeka.com/specsheets/FI114961.jpg I think that it is well worth you trying the setup you have with the pencil stream injectors placed slighly further back. That may well just be enough to offset the initial high velocity of the fuel flow stream. I also have the same combination of injectors for the Miglia, but have decided to try something different on that. I have not run with the pencil stream injectors yet. When you say with the setup I currently have, do you mean just run them in the standard MPI bosses or use them as staged injectors in the angled bosses? I have not tried them because I thought they were waaay to big for the 998... ’77 Clubman build thread
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8604 Posts Member #: 573 Formerly Axel Podland |
22nd Nov, 2010 at 05:35:31pm
I meant "use them as staged injectors in the angled bosses" just to try. Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
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