Flowing the Nozzles

If you really really want an efficient smooth running injected engine,  then you must flow the nozzles. What's that? Its when you do some flight testing to try and get each cylinder to peak at the same time. It allows you to run lean of peak, way lean of peak, and still have a smooth engine. Frankly with my set up its cheating. I have the very cool AF2500 engine monitor which makes data logging a snap. This is the cats meow in engine monitors as far as I am concerned. I don't even have to take out a pen like rocketboy had to do on his flow matching. The AF2500 monitor will log everything for you and all you have to do is get out your laptop and d/l it. Once all that data is on your box, then sky is the limit. You can graph and do all kinds of tricks with Excel or other data manipulation software. Here is a copy of the actual raw text file that come out of the unit. You Can see it captures every damn thing, EXCEPT air data. It would be very nice to correlate the engine to air data. That way you could see the effects of speed on various fuel flows and egt's. This stuff can get complicated quick. There is sooooo much data. I cant imagine what it was like before this techno stuff.

So I start out by calling Don at AFP and asking him what the procedure should be for data logging. He said:

1. Fly the plane to a cruise setting

2. Keep MP under 24" to prevent detonation

3. Start the setup .5gph above peak. Try and get around 15gph. (remember I have a 6cyl). Expect this to be 10 on a 4 banger. High flow rates keep the spider from becoming a factor. Don't ask me why, that's just what he said.

4. Pull .2gph and log. Keep doing that until you get a miss.

On the first run I actually had to write the data down since I forgot my engine monitor book and could not change the sample rate while air born in the unit with out it. This is my first run. Injectors Nozzles are .028 stock. You will note that in the stock config there is .9gph spread between the cylinders. We want to get around .3 or so. 

I sent this data to Don in an e-mail and his response was: "It looks like from your data that cyl 5&6 are a little lean and cyl 1,3 and 4 are a little rich.  To start with I would put a .028 +5% restrictor in cyl 5&6 and a .027 restrictor in 1,3 and 4.  Special size restrictors are $25.00 each."  Argh. 25$ a pop. I asked about swapping them out and he does not do that. So each one of these puppies that I experiment with is a throw away if it does not work. ARGH! I was disappointed to find this out since my whole system is his.

So that's what I did. Here are the results with the following Injectors. This is data straight from the engine monitor. You can see that I am now w/i 4gph. Yipee! Real close. I sent this to Don and his reply was  "put the .028 back into 5&6 and see what you get."

So I put the .028's back in. I have not done a Data capture yet but you get the jist by now.  When I do Ill put this data in below.

And finally this data. Now w/i .1gph. Now we are talking matched

Back to Super 8