SonexBuilders.net

.Hi ya'll,

I've seen lots of pro/con posts on the aerocarb. In thinking about my engine options (buying next year?) the aerovee-turbo sounds great and the aerocarb sounds 'mixed'. I'd definitely follow directions carefully and I'm sure that would help but it sounds like most of the issues are folks describing a finicky process for adjusting the needle. Even to the point of describing 1/16 turn adjustments.

Has anyone asked sonex about a possible aerocarb revision so that this portion of the carb isn't so finicky (i.e. make it more repeatable, possibly 4x finer adjustment per turn of the screw)? (I've never looked at one of these carbs in person so I'm not even sure if such a design tweak could be made)

Kevin

Kevin,

The AeroCarb was re-engineered years ago when it became the AeroInjector. Many details were changed including control orientation, overall size, and overall weight. I haven't heard of any more considerations on yet another design update but I suppose anything is possible.

I do know that the factory often gets calls from people who are having difficulty setting up their AeroInjector yet when asked, they never bothered to actually read and follow the directions. This drives our friends at the factory nuts because these same people often get things squared away after completing the tuning procedures called for in the manual. I think most people don't really have much of an issue with the AeroInjector in the long run.

I think it would be a good idea to have a "tips" list for each problem to include real solutions to the problem. One thing I will add is if you are having trouble adjusting your needle, check the play in the ball/socket needle holder. That's a 3/8 X 16 set screw and mine had nearly 1/2 turn (.025) of play. Tighten it up any way you can and eliminate that variable. I had access to an excellent machinist who made me a new holder with a disk and slot instead of a ball and socket, which has zero play. If you are trying to adjust in 1/4 turns with a lot of play you never know where you are. After setting the needle forward initially, a 1/4 turn backward results in zero movement. Plus, does the needle move due to vibration or air movement? Tighten up that needle holder before you start adjusting.

Also the adjusting screw needs to be tighter, a nylon plug threw the screw helps. Onex 58

Mike,

As you so carefully pointed out, the number one reason folks have difficulties with the Aero-Injector is failure to follow the instructions and more importantly, the "sequence" of how to tune the unit. This is meant to be helpful and nothing else. If this helps, great. If not, it didn't cost a thing and I'm not here to debate which carb works better. Simply, if done according to the directions its a great unit, with few moving parts.
I tried on about half a dozen occasions to assist individuals and found one common thread. Seems most were concerned with making the engine idle smoothly on the ground before doing the open throttle exercise. Doing so is a complete waste of time unless you magically hit the sweet spot by accident. The effort needs to be tune for full throttle and manage your mid range and idle through mixture. Sometimes it works out that a person can stay full rich at all three ranges but that's not the norm and only a goal that can be overcome with mixture if it doesn't work out as such. Being full rich for all conditions tells me there is no ability to deal with much of a leaning condition such as flying to a lower elevation airport.
The instructions clearly state the engine needs to hold full power and be able to enrichen the engine and lower the egts by 100 degrees. If not your too lean and need to raise the needle. If one needs to raise the needle more than about 1 1/2 - 2 turns then a larger # needle is warranted. The problem with continuing to raise the needle is it will typically make the mid range and idle way too rich. Better to have a larger needle and have the correct needle height. I know many have modified their taper but thats a whole other story and fly's in the face of the "follow the instructions" theory I presented up front.
In my case, I use the #3 needle at the specified height + or - about a turn. Can't honestly remember. This makes the engine slightly rich at full rich mixture at all three ranges. Full open, mid and idle.
One simply starts the engine full rich and upon startup, I pull the mixture control about and inch and she purred like a kitten.
After run up and taxing into position, one goes full rich for departure.
This setup procedure has been beat to death for many years, but again, I will state that the great majority of individuals I've encountered wanted to fiddle with idle and such first and that's dead wrong. That and the fact that before trying explicitly what the factory recommends, they want to in some way deviate from the factory stated instructions. Both from a tuning aspect and an installation/modification aspect,
I wouldn't leave the proven path until that part of things is done as well as possible. Once the unit is set up within reason, and some practical experience is had, a person can experiment a bit here and there but its important to get the basics well established.
After experimenting with #3 needle I tried another one (2.5 I believe) and never was able to get enough top end, rich mixture and went back to the #3. I had it there and unchanged for over 400 hours of operation from sea level to 10,000'.
My normal field elevation is about 2,300' and at sea level, rather than change the needle height, I could keep the egts in range by bringing about a half inch of throttle out of the equation(less air and same fuel) and the rpm never varied, but, the egts would drop about 100 degrees to the 1250 range.
Once a guy fully understands the operation of the Aero-Injector, only then do you begin to appreciate the benefits of no floats, no more jetting probably ever, no carb heat installation needed. I've been in every combination of humidity, temperature, icing one could imagine and never a hint of carb ice. The level of simplicity and ease of service makes it worth the effort to get it right and then just fly it.

Larry
Waiex121YX, Cammit 3300 almost ready to fire off.

Thanks everyone (I'll happily be using this advice in about a year when I think I'll be starting my engine)

LarryEWaiex121 wrote:Seems most were concerned with making the engine idle smoothly on the ground before doing the open throttle exercise. Doing so is a complete waste of time unless you magically hit the sweet spot by accident.

I agree. I always get comments about my AeroVee idling rough (from people outside the plane); they say it sounds like it's skipping a cylinder. But I assure them it's normal. As the throttle is pushed further forward it runs smoother and smoother. Once I got the right needle (a 2.5 for me) the AeroInjector has been 100% reliable. That's been about 110 flight hours and a year and a half. I do tend to make one small needle adjustment in the winter and one in the spring. Maybe 1/8 turn. I average 4 gph in cruise, and can do less if I need to (but the engine probably likes me better when I don't over do it).

mike.smith wrote:I agree. I always get comments about my AeroVee idling rough (from people outside the plane); they say it sounds like it's skipping a cylinder. But I assure them it's normal. As the throttle is pushed further forward it runs smoother and smoother.

I assume it also runs smoother if you lean the mixture at idle? Does it run smooth at idle in the air full rich?

My experience is that the propeller is able to turn faster at the same throttle setting while flying, so what might be a little too rich on the ground can end up being just right in the air. I think being aware of the need to err on the side of being a little too rich is important especially near idle, since you might discover on final that the engine is turning a few hundred rpm more with the same fuel and runs poorly due to being too lean with no way to adjust richer.

I am one of the lucky ones whose engine seems to run well at full rich on the ground, even at idle. I do lean it out until I notice the slight rise in rpm while taxiing because full rich just seems wrong. I agree that it is absolutely important to tune well for wide open throttle on the ground as explained by Sonex in the instruction manual. Even then, once you get in cruise flight at wide open throttle, if your experience is like mine, you will probably find that since the engine turns faster it will be leaner than expected.

gammaxy wrote:

mike.smith wrote:I agree. I always get comments about my AeroVee idling rough (from people outside the plane); they say it sounds like it's skipping a cylinder. But I assure them it's normal. As the throttle is pushed further forward it runs smoother and smoother.

I assume it also runs smoother if you lean the mixture at idle? Does it run smooth at idle in the air full rich?

Only in the winter. The rest of the year leaning doesn't really change the smoothness of the idle, at least for me. I lean on the ground just to keep from fouling the plugs.

An Aerovee with the Aeroinjector idling rough is not normal. Most likely the needle is faulty.
Get a new needle and after adjusting it, it will run smoothly during idling and high power.
I had lots of problems with the engine not idling properly until I discovered the installed #2 needle diameter was to small (I also tried #2.5 needle what idled perfectly but to rich on high power), because of that during idling when the needle is all the way in the fuel deliver hole extra fuel is leaking passed the needle making it running much to rich.
After I got a new #2 needle with the correct diameter from Sonex (after first trying with a borrowed one) and a few adjustment
it is a different engine. Idling perfectly and running perfectly on high and cruise power.
Flown now for 120hrs and still running very will. During cruise I lean out a bit to get 15l/hr cruising about 97knt
Peter Bakker
Sonex 8464
AeroVee 2.1