AeroInjector Tuning

[sonex1374]

Regardless of the needle# or screw position, I can not get the first trend you describe (rpm/EGT increase) trend you describe. Always get rpm drop and EGT decrease as mixture knob is pulled toward lean. With needle screwed CCW to engine running rough and black smoke I get the same rpm drop/EGT drop trend.

gethomas,

What you are describing suggests there is some fundamental problem somewhere else in your setup. You're going to have to re-look every assumption that you've already made: Is the needle oriented correctly? Is the needle carrier moving while tightening the set screw? Is the fuel flow at the carb inlet sufficient? Is there something inside the carb body that is blocking the fuel orifice? Is the intake getting sufficient airflow into it?

You said that you can adjust the needle such that the engine runs rough and blows black smoke, and that suggests the needle is indeed changing the mixture into the engine. Perhaps there is a problem with the mixture knob, mixture arm position or internally with the mixture arm.

It's also unclear what you mean exactly by the statement:

Always get rpm drop and EGT decrease as mixture knob is pulled toward lean.

Does this mean that the same rpm drop happens at the same point on the knob when pulled out? How much rpm drop and how far out on the knob? I would expect a well-tuned engine to respond to leaning by increasing 10-100 rpm when the knob is pulled out 1/4" to 1", but then as the knob is pulled further out the rpm will start to fall off as the carb gets leaner and leaner, eventually killing the engine all together. How is yours responding?

Without more data to consider, I'm afraid you're not going to get much useful help from others....

Jeff

[gethomas]

Still can't get engine running correctly. With tunning I now have set, engine starts easily, runs smoothly, and takes full throttle without balking. Doing ground runs with cowling on, everything is ok until engine heats up (CHT 250up). Then engine quits when throttle is less than 1/2 open. It restarts but will not continue running a low throttle.

Any ideas on what's going on?

[NWade]

Still can't get engine running correctly. With tunning I now have set, engine starts easily, runs smoothly, and takes full throttle without balking. Doing ground runs with cowling on, everything is ok until engine heats up (CHT 250up). Then engine quits when throttle is less than 1/2 open. It restarts but will not continue running a low throttle.

Any ideas on what's going on?

Have you examined ALL of the items that Jeff went over?

Have you tried running the engine without the cowlings? If so, was there a difference?

What needle are you using? What air filter are you using? What was your fuel flow with the tail down (in takeoff/climb attitude) when you disconnected the aeroinjector and measured fuel flow from the tank to the end of the hose where it screws into the aeroinjector?

—Noel

[gethomas]

Have #2 needle installed. Air filter is the one sold by Sonex. Checked every thing from previous posts. #2, 2.5, 3 needle give same results; EGT DECREASES when going from full rich to lean; at full throttle never get EGT increasing from 1300deg up to 1400deg as mixture control is moved from full rich to lean. These results are static ground tests with cowling off. With cowling on and static, get same results. Fuel flow is about 1gal/min at injector. I can see fuel coming from around needle. Get a fuel stream from injector outlet with needle removed. Engine starts, runs smoothly, and takes full throttle ok. While doing high speed taxi, engine quits when engine heats up (CHT 280up). Can restart ok but requires throttle 1/2 open to run.

[Onex107]

It sounds like the classic example of vapor lock. The "Burps". If you are using car gas it will be worst than 100 LL. You must insulate your fuel line and gascolator if you have one. I eventually removed mine because it was too difficult to insulate. Fire sleeve may not be enough. I have the entire fuel line, from the fire wall to the gascolator, covered with ordinary pipe insulation wrapped with a silver reflective tape which also keeps oil away from the foam. The good thing is you are experiancing this on the ground. It's much more frightening in the air.

[Arjay]

Gethomas. Sounds to me like you are too rich. Try leaning during taxi after warm up, see if that makes a difference
Ron

[pappas]

Do yourself a favor. dump the air filter Sonex sent you. Replace it with the K&Nround filter that most of us use. The K&N flows much more air.

[builderflyer]

You've said the EGTs always drop when you pull out the mixture, not rise........as Jeff Shultz has remarked several messages ago, that means you have started out with a mixture that is too lean. That, combined with your lack of insulation on anything and subsequent vapor lock can explain most everything. The system you have should work for you after addressing these issues. See my other message under "intermittent engine operation"

Art,,,,,,,,,,,,,,,,,Sonex taildragger #95,,,,,,,,,,,,,,,Jabiru 3300 #261