The big AeroCarb/AeroInjector thread

[nwawingman]

I have been very happy with the performance of my AeroInjector. I will admit it took some time to get it adjusted correctly, but once it was dialed in, I have not had to mess with it. Starts good and runs the same every time I go fly. I have it configure to where it is on the rich side if my mixture is pushed in all the way. I normally take off with it pulled out about 1/4 of an inch or so. I normally taxi with it pulled out about an inch to help keep the plugs from the possibility of foiling. The best advice I could give for making the adjustment is to follow the instructions in the manual, take your time, and expect that you will be making multiple adjustment before you will get it right. There was times I thought I was never going to get right. Sometimes the best thing to do was just call it a night and try again tomorrow. I have had to adjust my AeroInjector twice now. Once when it was first installed and a second time when I replaced my solid throttle cable to the new heavier stranded cable Sonex now offers. Both time it took some time. There is a very small window of adjustment you have to hit so small adjustments are key. You know you are really close when it will idle at 1200 rpm and take throttle smoothly. If it won't take throttle smoothly and you can't seem to get it just start over by setting the needle back at the starting point like described in the manual. This seemed to help me the most. My AeroVee was started the first time without any adjustment being made to the AeroInjector right out of the box. It ran well enough for the first start surprisingly. Then the fun of getting dialed in began. Just take patience. Also, I would also like to recommend that you do full power run with the cowling on and the tail down and also at level attitude before you fly to verify your mixture settings.

[fastj22]

Mike Neidenthal is almost ready for first flight. We have been adjusting his first generation Aerocarb for the last few weeks. At first we found the original owner had installed the needle 90 degrees off. After fixing that, we still couldn't get the engine to run through the entire throttle range. Installing the #3 needle helped. Jeff Schultz helped us a lot, he really knows the Aerocarb!. We had trouble keeping the engine running mid range to idle unless we aggressively leaned. Today, Mike did a simple ¼ turn lean on the needle, and the engine worked great. Ran full rich through the throttle range, and even better when leaned to the specific throttle setting. A couple of high speed taxies confirmed the engine is ready for first flight. The groove is narrow and sometimes difficult to find, but when you find it, the Aerocarb works very well. Even the older style.

[XenosN42]

Would like to throw my 2-cents in. Today I test ran my AeroVee/AeroCarb powered OneX engine for the first time. I have some experience since I also have an AeroVee in my current XENOS and a few months ago I helped a local builder tune his AeroCarb. Therefore, my experience today may not be typical.

The engine and AeroCarb ran PERFECTLY the first time! All I did was to follow the AeroCarb manual to the letter when I set it up. The engine took throttle smoothly, developed 3050 static RPM, and ran with no change in RPM when I turned off the primary & secondary ignition systems. It even idled fairly well around 900 RPM. Beyond the numbers the engine just sounds good. In some ways I think it ran better than my XENOS AeroVee.

Just my one off experience so take it for what it's worth. However, word to the wise: Read, re-read and follow the manual. :idea:

-- Michael
N42XE; XENOS flying 4 years
N169XE; OneX first flight soon

[sx1094]

What damage does all this ground running at WOT due to a new engine that is not broke in to get this AeroCarb adjusted? Sad this thing is so difficult. Because of the different results by different builders, the quality control of this unit must be lacking.

[mike.smith]

What damage does all this ground running at WOT due to a new engine that is not broke in to get this AeroCarb adjusted? Sad this thing is so difficult. Because of the different results by different builders, the quality control of this unit must be lacking.

It's not difficult, but you can't get it adjusted running on the ground. You've got to be in the air looking at all the numbers, and looking at fuel burn. You should not make a habit of running the plane WOT on the ground. Yes, you need to get it to idle properly and to do the initial WOT run-ups (tied down) to make sure it's safe to fly, but beyond that you aren't going to get it dialed in on the ground. My experience has been that engine temps and fuel burn are going to give you the information you need. For the AeroVee, if fuel burn is below 4gph you are way too lean. Much over 5gph and you are too rich. EGTs are good for trends, but don't have much to do with engine health at any given moment. It's the CHTs you need to manage, and you need to be in the air to see what's going on there. IMHO you should not be comfortable with 400 F CHTs even during break in. Too hot. If you have to run rich during break in to keep temps down, then do it. You can always dial it back later for better fuel burn. I currently average 4.4 gph and CHTs run 290 (#2) to 340 or 350 most of the time. Climb out on a hot day, #3 cylinder may hit 390 for a brief time. If it starts to climb past that I push the nose down and even throttle back a bit if I need to. 400 F CHTs are not acceptable to me.

[SonexN76ET]

I will pick this up where Mike left off and add my two cents to the ground running portion of the adjustments. Except for adjusting the timing based on performance in the air I had to do most of my other adjustments based on ground runs. My AeroInjector mixture had a very narrow range of where it would run well. A couple of times after a test flight test I would try an adjustment of perhaps 1/16th of a turn on the needle. I would ground run to test that to ensure it was safe to fly.

You do have to do a significant amount of carefulground running to ensure the settings are safe to take the plane up in the air. I scarred the hell out of myself trying to take off with a too rich mixture and had the engine start coughing, sputtering and loosing power and had to abort my takeoff while 50 feet in the air. Another time I set my mixture too lean and had to land immediately due to high EGT and CHT temps and the engine starting to missfire. This is not a reflection on the AeroInjector but rather on me not knowing exactly what I was doing. Tuning your engine is not something to take lightly. This is one area where you need to exercise caution.

For ground tests and adjustments you need to make sure you do not overheat your engine. You can maybe only get three relatively short runs in before you need to let the engine cool down completely.

Make sure you tie down the tail and block the wheels. Sweep the area in front of, below, and around the propeller to remove stones, gravel, and other FOD from tearing up your propeller.

You need to idle the engine to let it warm up to operating temperature.

Follow the Sonex instructions on tuning

Make sure at full rich your EGTs do not exceed 1300. Better not to have them exceed 1250. This is in steady full throttle ground runs. Pulling back the mixture to lean peak should raise the EGT by the spread recommend by Sonex. If I recall correctly this should be an increase of 90 degrees. Check your manual for the correct number.

On a new engine your CHT will rise quickly during ground runs. Do not exceed the redline of 450 degrees. As soon as your CHT goes above 400 pull the throttle back, let the engine cool down a bit then shut her down and let her cool off while you systematically make your adjustments in very small increments.

Above all else, carefully follow the ArroInjector and Aerovee manuals and be safe. Make sure you read and understand the manual and pay attention to every single detail!!!

There are many interrelated items in the tuning process besides mixture and idle. Your timing needs to be spot on. Your valves need to be properly adjusted with the correct gap. Your valve timing also needs to have been done correctly when you assembled the engine. Your fuel flow needs to be tested to ensure it is sufficient. Your air filter needs to be clean and uncontaminated by engine oil.

Have a systematic plan for each engine ground run. Record your EGT and CHT readings. Keep the ground runs in the green temp range. Be safe. Follow the AeroInjector manual.

These same items for the most part apply as well to the Rotec TBI and most other fuel delivery systems.

Good luck!

Jake

[sx1094]

Has anybody tried to use a lubricant on the slider inside the AeroCarb to help prevent sticking? Thanks

[Fastcapy]

-Removed-

[mike.smith]

Has anybody tried to use a lubricant on the slider inside the AeroCarb to help prevent sticking? Thanks

That would not be advisable. Any lubricant will only pick up grit and make things worse. When my AI was sticking it was 100% because of the routing of my cables. The route had two bends that were very shallow, but that was at least one bend too many. Once I ran the cables in a single arc to the AI it was as smooth as glass. Here is my Kitlog page:

http://www.mykitlog.com/users/display_l ... 250&row=18
http://www.mykitlog.com/users/display_l ... 251&row=17
The center photo here is the money shot:
http://www.mykitlog.com/users/display_l ... 253&row=16

[142YX]

I voted for the last option because it was the only choice for someone who isn’t running the Aeroinjector after trying it.. but I don’t like the wording and wish there were one more option. I would describe my opinion as:

“The AeroCarb/AeroInjector is not the right choice for my mission and have chosen to go a different rout.”

I don’t hate the AeroInjector and think the wording of that option is just too strong.. but I have decided not to go with it.

I flew Waiex #142 with an AeroInjector twice; on my first two flights. To keep a long story short, I had two issues with my setup:
1-I could not develop full power
2-I did notice burps and power hesitations

For that reason I am converting over to a Rotec TBI MKII, with a pressurized fuel system. If my mission was different; say only local flights in part of the country where the seasonal weather changes were not that significant and I wasn’t interested in tweaking performance, the AeroInjector may be the carb for me. But the reality of my mission is that I need the TBI to perform reliably at sea level and 8000 DA elevations on a regular basis - on the same day, I live in one of the hottest, most miserable climate areas of the country, and yet hangar the airplane where it snows during the winter, and I don’t particularly find the adjustments to the AeroInjector to an easy nor a pleasant job and don’t want to do it multiple times per year.


For the more detailed version of the story:

I really like the simplicity of the AeroInjector, and had high hopes that I would get it to run my Jabiru 3300 well. The initial setup during ground runs prior to first flight seemed too easy – I just threw the #3 needle in there and followed the instructions in the manual, and the engine lit up and came to life without issue on the first try. It would idle quite well, and I had no indication that the engine wanted to do anything other than continue running between 700-1000 rpm. I was able to achieve the specified ground static RPM (I got somewhere between 2900 and 3000 RPM on the ground), and response to the fastest throttle inputs I could give it seemed smooth and hesitation free. “Hard idle” throws after full throttle runs seemed smooth as well. This was all on the initial setting! The one gripe I had during this phase was that I was not able to get it set to hold a good idle RPM tolerance with the idle screw.. when I thought I had it set perfectly to about 800-850, it would tend to fluctuate by about 150 RPM or so despite my best efforts, but this didn’t seem that bad. I did note that the stated procedure in the manual to “set so that full rich produces 90-100 F lower than peak EGT temps at full throttle” was an impossible task to do on the ground, as the Jabiru would hit its max ground running CHT temp limit within about 15 seconds of full power application.. and the EGT’s had not settled out by that point – so I could never really perform this test. I tried it twice to no avail, and also tried a build up approach of trying to get something out of half throttle, ¾ throttle etc; but then got too worried about damaging something and thought it best to just see how it ran in the air and get the data point then. It was running, and refused to quit no matter what I did to it, so I thought it was time to go fly.

On first flight, my initial climb rate was much less than I thought it should have been, only about 800 fpm. I quickly realized that the source of that issue was from the lack of RPM that I was developing, only about 2800 or so and definitely less than I had been able to achieve statically on the ground only a few days prior which I found odd. I elected to continue the flight, as the engine was still running smooth and again, didn’t feel like it was about to die at all. Once I got to altitude after my first climb out I tried the mixture knob, and sure enough as I pulled it back the RPM did increase, but EGT temps went screaming up through the roof so I stopped and pushed it back in. I continued the rest of the flight like that and everything went fine, temps stayed in the green, had no indication that the engine was about to quit (even on final when I pulled hard idle), but I never did get to full power.

I killed one weekend after that flight trying to adjust the AeroInjector. It was apparent from the rise in EGT, fuel flow numbers (compared to the “typical” values in the Jab manual), and lack of power that on first flight that I was running much too rich. As soon as I tried to adjust for a leaner setting, the engine simply wouldn’t run. I tried these adjustments several times, and for the most part got very consistent results: 1/8 of a turn appeared to make no change, and after ¼ of a turn (lean) the engine would not start at idle like it used to. I could start it at, say 1/3rd ish throttle but it would immediately die when brought back to idle. It was disconcerting to me that the adjustment was this sensitive, because of the slop (free-play) in the needle setting is easily 1/8th of a turn’s worth (if not more). It is possible that I was not as precise as I thought with my adjustments during tightening, however I consider myself to be reasonably mechanically inclined and tried my best not to have it drift while tightening. After 10 hours of work, I ended up with a setting almost where I originally was to begin with. I tried to be a tad on the lean side (somewhere between 1/16th and 1/8th leaner, maybe). The thought I had walking away from this exercise was that if it truly was this sensitive and finicky, maybe I would get lucky and nail it – but I certainly didn’t want to have to do this on a regular basis. I was also a bit disgruntled because I had just put 15-20 or so startup cycles on my brand new, not broken in $19k engine in an attempt to get something that would let me develop full power.. which I needed to break in the engine!


All of the fuel flow data from the first flight. The black line being to the left of the red line indicates that my fuel flow was higher than what Jabiru defines as "typical".

On flight two I saw largely no improvement in the amount of power that I could develop. Temps were still in the green, but as soon as I tried to lean out the mixture EGT’s again went soaring above the limits almost immediately, the engine began to run rough, and I wasn't close to the RPM that I was hoping for. On this flight I also experienced my first “Burps”, which seemed to happen randomly on several occasions. In addition there was at least one time where I advanced the throttle in flight and got a very sluggish response (first time I had experienced that). It was a good deal warmer (at least 20 F) on the day of flight 2 compared to flight 1 which probably contributed to vapor bubbles forming.. but I have a high quality, very insulated, continuously up-sloping, short-as-possible fuel line running directly from the gascolator to the AeroInjector, so the only thing I could probably do to make it any better would be to blast tube or remove the gascolator. The burps weren’t bad, didn’t feel like the engine was about to die.. but it did put thoughts in my head like “well at least I am right over the field right now”. I also live in a mountainous area (Mojave, CA) and will frequently find myself out of glide range to an airport and don’t want to put myself in the situation where those thoughts come into my head – if I can avoid it.


Shown here is the leaning out experiment that I performed on flight #2. As the data shows, EGT's increase by approximately 200F, go over limits, without much gain in RPM (only about ~75). The large RPM drop is what I attribute to roughness, well before the engine developed full power.

Somewhat unrelated to all of this is the fact that I also haven’t passed a fuel-flow test on the ground yet. The Jab needs 10 GPH and the thumb rule states 1.5 times the max burn rate of the engine is what you should have. I can only get 12 GPH at about half fuel, and it drops off to about 9.5 GPH on the last gallon or so. My fuel system is: TANK - BALL VALVE - RED CUBE - 3/8” HARD LINE – GASCOLATOR - 3/8” FLEX LINE – AEROINJECTOR. Pretty simple. I could remove the red cube fuel flow transducer and maybe the flow under gravity feed alone would improve enough to pass this test – but I am not willing to do that because I nerd out on flight test data and I like the situational feedback that a fuel flow indication provides me in flight. In order to mitigate the burps, and provide the fuel flow the Jab needs for full power in any situation, my only options are to nix the gascolator AND red cube (and hope for the best), or to add a fuel pump. I don’t want to see what happens when I feed the AeroInjector with an unregulated fuel pump.. and by the time I add a regulator? Why not just go with the Rotec? By that point I have destroyed the AeroInjector’s main advantage of being the “simplest” solution.

I have read almost unanimous reports from everyone who has run both that allude to the Rotec TBI bringing high EGT’s under control. Best theory I have right now would be do the inarguably better fuel atomization that the Rotec gives over the AeroInjector providing a more efficient charge for the engine to burn quickly in the cylinders, and not as it is leaving the exhaust valve and passing the EGT probes. But who knows. If it works, I'll be happy.

Right now I feel painted into a 4 dimensional corner of being not able to lean the needle due to inconsistent running at the low end, therefor being quite rich at the high end and not being able to lean out due to EGT concerns and/or rough running, seeing evidence of vapor form in the fuel lines and not being willing to remove the only “unnecessary” restriction in my flow path to get the gravity feed to work. Add to this the concern of screwing up my brand new engine for not breaking it in properly as I am two flights deep and have not been able to develop full power yet. Each one of these concerns points me in the direction of a different fuel system setup, for which I am now one week into the modification process.

The new fuel system will be:
TANK – BALL VALVE – 40 MICRON FILTER – 3/8” HARD LINE – GASCOLATOR – 3/8” FLEX LINE – ELECTRIC PUMP - 3/8” FLEX LINE – ENGINE PUMP - 3/8” FLEX LINE – RED CUBE – ROTEC TBI MKII

My optimism is high, but I will report back with the results good or bad.