Normal for an Aeroinjector?

[sonex1374]

Cable routing is the most common reason the slide becomes hard to move. If the cable has tight bends it may become hard to move when the engine is running. What's "tight"? - I'd say a radius of less 3" or so should be considered excessively-tight. I've seen this several times - you look at the cable's bend radius, swear up and down that it's not too tight, then out of desperation you totally re-do the cable routing to make the bed radius nice and large (6"+) and presto - no more sticky cables. That's the place I'd start....

Jeff

[NWade]

Looks like another item on the "fix it before you dare use it" list.

Just a quick FYI: If you bought an AeroInjector in the last couple of years, the factory already slightly peens the adjuster threads before shipping the units out, and the needle carrier is made with tighter tolerances and less slop in the "ball and socket" area. This is on top of changing the needles themselves to be made from tighter-tolerance material over a decade ago. So these are much less of an issue if you are buying newer parts/kits; you just need to pay attention if you buy something used or from an early production batch off a private seller.
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As others have described, my (~2015) AeroInjector had some longitudinal movement of the needle in the carrier and was also susceptible to having the adjuster screw turn when I tightened down the lock screw. Although my engine ran fine on the ground I was concerned about the needle carrier moving over time, as well as being mildly annoyed that tightening the lock screw kept pushing my mixture leaner. So I attempted to deform the socket around the ball by using a punch to deepen the retaining dimples. Unfortunately they had work-hardened when originally manufactured and my fiddling resulted in breaking off a chunk of this material - d'oh!

The good news is that I ordered replacement parts from Sonex and the items that showed up have several small-but-notable improvements. The "ball and socket" fit is improved, and the adjuster threads are peened in a way that resulted in no movement when I engaged the lock-screw.

--Noel

[Area 51%]

Picture a corkscrew roller coaster. That's how my cable is routed. No sharp bend here.

When the engine is off, you can move the throttle lever with harsh language. Near zero friction. It's only when the engine is running that resistance can be felt.

It is an Aeroinjector and not the "carb". It has every bad trait that has ever been posted here. Sloppy needle. One screw turns the other. Sticky slide.

I'm installing an 8in lever in place of the 3in Aeroconversions knob to gain enough leverage to move the slide.

[builderflyer]

It's difficult to visualize why it would be necessary to route a throttle cable in the shape of a "corkscrew roller coaster". In any event, in addition to making the cable radii as large as possible, it is also helpful to fasten the cable to other things along its path, the engine mount, for example, to keep it from moving during throttle usage. With the AeroInjector, if there were any slide stickiness at all (and there shouldn't be anything very noticeable), .it should only be with a throttle reduction, not advancement. You've got something really strange and unexpected going on there.

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

[Area 51%]

The carb (we'll refer to it as a "carb" because Aeroinjector takes too long to write) is oriented with the linkage hook-ups facing the firewall and the fuel inlet forward.

Didn't want two sharp "S" bends in the cables, so, as the cables exit the upper pilot's side firewall near the engine mount attach point, they make a sweeping right hand turn up across the motor mount, then down past the coils, then forward to the carb. Picture a 1ft length of a 20in diameter spring. There are three attach points before they make it to the carb. Four if you want to count the one inside the cabin.

Maximum pressure differential on opposite sides of the slide occurs at an idle. If it's going to stick (excess friction), it should be off an idle. I can duplicate the resistance by pushing up lightly on the slide with my finger while operating the throttle. Engine off of course.

A former Sonex owner/builder stopped by this morning and confirmed the freedom of throttle movement with the engine at rest.

[sonex1374]

...[snip] I can duplicate the resistance by pushing up lightly on the slide with my finger while operating the throttle.

This is a good technique for all new AeroCarb/AeroInjector users to test their setup for excessive friction in the throttle cable or carb slide. Pushing up on the slide through the carb intake/throat simulates the "suction" on the slide produced by the engine's intake stroke. If your throttle control gets hard to move when you apply this finger pressure, you're likely to have problems when the engine is running (and the suction is high).

The AeroVee with it's horizontal slide orientation is more susceptible to this than the Jabiru with it's vertical orientation. This isn't to say that one has problems and the other doesn't - both can work perfectly, and both can have problems if not implemented properly.

Jeff

[Area 51%]

Initial test runs were encouraging with the #2 needle. Aggressive leaning at slow engine speeds was/is the order of the day, but the RPM came up high enough that the brakes wouldn't hold. Thought I was home free.

Tried to take to the skies last Tuesday. Over 2500 RPM, the engine faltered and no amount mixture adjustment made any difference. Only backing the throttle brought the little feller back to life. Smooth as glass below 2500.

Pulled the #2 needle in favor of the 2.5 yesterday. Started instantly and idled smoothly with the mixture knob in my lap. WOT in the chocks got me 3150 on the tach (mixture full in). Aborted a take-off attempt again this morning. The engine would not accept the throttle until I pulled the mixture knob out about an inch.

I can't seem to get two consistent runs out of this thing in any one configuration. Originally, I mentioned the fore and aft movement of the needle in the carrier. Is it even possible the 1/32in of back and forth movement could be responsible for these wild mood swings?

As it stands right now, it's at least rich on both the low and high ends with the 2.5. The plan calls for an adjustment to lean the needle tomorrow. I'm not optimistic.

OK.....now for my question..... Will the mixture needle continue to flow a greater and greater stream of fuel to the throttle slide needle until it unscrews from the injector, or does it have a limit? How many degrees of rotation should there be at the mixture arm? Am I getting a too rich setting because I might have more travel at the arm than I should?

Judges?

[SonexN76ET]

An over rich mixture is an extremely dangerous condition! When I was trying to get my AeroInjector dialed in I also had to abort my takeoff run. Both times I had an over rich setting, I had already become airborne about 100 feet above the runway. Fortunately I had 6000 feet of runway and was able to land straight ahead. My mistake was reading anecdotal accounts of other builders suggesting various AeroInjector settings and their urging to run a rich mixture. What was not said is that it needs to be only very slightly rich. If you follow the AeroInjector manual to the letter you can get the AeroInjector properly tuned on the ground.

Keep in mind that a brand new Aerovee, for instance, will run hot until it is broken in. People who claim they are getting CHT's of 350 or less on their first few flights with an Aerovee are either flying at reduced throttle settings, flying at lower than spec compression ratios, have their CHT probes in the wrong place, or are on the verge of flooding their engines.

Bill Larson offered the best advice to me on the AeroInjector tuning. Unfortunately, I can not locate the instructions he provided me but they just emphasized and clarified what is in the AeroInjector manual. A key point to follow when tuning the AeroInjector is to focus on the stabilized EGT readings at wide open throttle on your ground runs. At full throttle and full rich on the Aerovee the EGT should be around 1300 to 1350 degrees and RPM above 3000. Then if you slightly lean the mixture with your in cockpit mixture lever, the RPM should increase and the EGT should increase to 1400 to 1450 degrees. The AeroInjector manual states the EGT spread should be around 90 degrees from full rich to lean peak.

I know that this is difficult sometimes because while you are waiting for the EGT to stabilize on the ground run you also have to be concerned with not exceeding the redline for the cylinder head temperature.

To cut down on the play on the AeroInjector needle, Patrik on this forum had suggested using a very small O ring between the needle carrier and the area on the needle carrier that you turn when adjusting the mixture on the AeroInjector. I found this works to cut down on the play, but you must be very careful not to damage the O ring while installing and you need to thoroughly inspect the AeroInjector to ensure that the O ring has not torn in order to avoid having any potential fuel blockage from broken O ring pieces.

Please be safe out there and do not take to the sky until you are confident that you have properly adjusted your AeroInjector and that your engine is running to the correct specifications.

Jake

[tx_swordguy]

The arm will only move to closed so far. It will move past full open but it will not "open more". That said the last little movement of the throttle control will open up more fuel without letting anymore air in so in essence it will be a tad rich at that point by just a little bit. This assumes all the adjustments are correct for the engine. To me ( I missed what engine you have) it sounds like it is in the needle adjustment or needle choice. I had to cut a beer can washer to fit between the ball and the square holder for the needle because there was so much slop in it. I also put two ball bearings on top of the needle holder before I put the set screw on. That way it compresses the ball bearings loading up the threads and not turning the needle adjustment when I tighten the set screw. I use a mechanics magnet to pull the bearings out if I need to adjust. I found that a prop that loaded my engine up a little more made a big difference in how my jab 3300 ran and the numbers I was seeing. I went from sensenich to a prince p-tip (both were correct for the engine) but the p-tip I believe loaded the engine slightly more. I would NOT switch props at this time though, just making a statement of my experience. Get it running well before messing with a different prop. One other thing you may take the aeroinjector apart and clean the slide area with carb cleaner. There may be enough junk on the tefflon slide to be grabbing it a little when pressure is put on it. I also flipped mine (tefflon piece)over because of scratches on the one side.. My advice would be to try the #2 and back out .5-1 turn from where you had it. Or use #2.5 and turn in .5-1 turn and see what happens. I assume you are using a vw based engine with those needles.
Mark

[Onex107]

It's a good idea to clean the inside of the intake manifold. Sticky residue can be dissolved by the gasoline and run down on the top of the slide. I didn't do this and yes it happened.