What a difference a needle makes!

[mike.smith]

Wow, what a difference! After chasing around the mixture and temperatures on the #2 needle, and still running too lean, I finally switched to the #2.5 as Joe Norris suggested. After adjusting the idle screw to idle lower, the engine runs smoother than ever, with an awesome idle (in fact, I need to set the idle screw even further out to get a lower idle). Previously the engine would balk at low RMPs on only the primary ignition. Now it runs with just a little dub, dub, dub on the primary, but pretty smooth. With both ignitions on, it's really, really smooth!

At WOT all my EGTs are now 1250 or less, and even my hot #3 cylinder never got above 370. The other 3 were 350 or so. What a difference! (Previously the EGTs were 1400+, 1, 2 & 4 CHTs were 390, and #3 was 400 and higher.) I flew around yesterday at 75% power and had all my CHTs around 350 or less.

Now I fly WOT with no worries. It's like I installed a new engine!

Mike Smith
Sonex N439M
23 hours on the engine

[MichaelFarley56]

That's great to hear Mike! I'm happy to hear your report and hope you can now really run the crap out of your engine to really break it in!

Your EGT's sound really good; I normally run mine in cruise at around 1150-1200 and my CHT's are normally in the 310-330 range as a result. I'm always happy to put a little bit extra fuel into the engine in order to keep things cool!

Please keep us up to date on how the rest of your Phase 1 goes. It sounds like you're really getting the airplane dialed in!

[Onex107]

I just went to a 2 1/2 needle after 25 hours on a 2. It went so lean it wouldn't run above 2600. The 2 1/2 solved the WOT problem but it's too rich at idle, just like the #2, and I can't reach and adjustment that will give me the 100 degree change from lean to full rich. At 2900 static the mixture is out one inch and at idle, 950-1000, it's out almost to cutoff.
How much do you have to adjust your mixture over the full range of throttle?

[MichaelFarley56]

On my setup (stock unmodified #2 needle) I have it set up so that I push the mixture full rich as I take the runway and then go to full throttle. At 80 mph on a full throttle climb and full rich mixture, I indicate right around 3100 RPM and my hottest EGT is around 1180. This keeps my cylinders nice and cool on the climb. I will leave the mixture full rich unless I'm climbing to a high altitude.

Once I level off in cruise, I set cruise power and lean around 1" of mixture travel (maybe 1/3 of the total mixture travel) for leisurely cruising around the area and low to medium power settings.

As I pull back the power for landing, I find my engine will start to run slightly rough below around 2200 RPM unless I lean a little bit more, so I will lean an extra 1/2" or so.

On the ground for taxi purposes, I also have my mixture pretty lean. Maybe 1.5-2" mixture pulled out, which means I'm probably around 70% leaned out while I taxi. After a while I don't even think about it!

Does that answer your question?

[SonexN76ET]

I recently went from a #2 needle to a #2.5 needle, but it is close to its leanest setting. Mike Farley always gives good advice and insight and he helped me get mine temperatures into an acceptable range. I went to extremes to try to get my #2 needle to work, one time going way too rich. Being excessively rich caused me to loose power on my takeoff as the engine bogged down and I had to abort my takeoff. So I went witht he 2.5 needle and was able to get the engine to run smoothly and the temperatures to stay in the green.

I was never able to get the 100 degree EGT spread between full rich and lean peak spelled out in the manual, however. My CHTs would go into the red before the EGT temperatures stabilized.

I also found that sometimes after I made a mixture adjustment the engine did not respond logically at first. Even though I would lean the needle, the engine would act like it was running rich and vice versa. This happened two or three times out of a dozen or so adjustments. I dont know if the needle carrier turned while I was tightening the set screw or if I pushed too hard when making the adjustment.

Also, if you accidentally forget to lock the throttle in the full open position when you make a mixture adjustment you can kink your throttle cable and or skew the slide thus causing the AeroInjector to run either too rich or too lean. After things get straightened out inside the AeroInjector you will then have to readjust your mixture.

Another item to be alert for is your air filter. Make sure it is clean. I had gotten a little oil on mine and it caused my RPM to be a little lower than normal.

Finally, I had to take off my intake elbows and reseal them. That seemed to help correct a hot right rear cylinder head.

I would like for Sonex to do an AeroInject tuning video. Perhaps some of us at the foundation can put our heads together and create an enhanced AeroInjector tuning guide.

Enjoy your flights and be safe!

[kmacht]

I second that request for an aerocarb tuning video. The tuning instructions that came with the aerovee are adequte if you have been running VW's and the aerocarb for years like the factory has but they aren't quite as clear for those of use just getting started. We could use a video showing what too lean and what too rich look like. Show us exactly how to check for the 90 degree EGT swing. Talk about what it means if the engine stumbles at full throttle or idles rough and what to do about it. A video can show and describe something in just a few seconds that would take pages of writing.

Hey Joe Norris - I know you are reading and montor these forums. Can you help bug someone at the factory to put together a video for us?

Keith
#554
1.2 Hours and Counting

[chuckster]

I'm sorry/amazed/curious that some seem to have trouble tuning the aerocarb as mine ran great right out of the box with only a idle speed adjustment. It's important to remember it is as simple a fuel mixer as you will ever see and it will not be perfect in all areas at all times. It's very simple design is both a blessing and curse. The way I check for proper mix is the old fashion " READ THE PLUGS" . Idle your motor for a minute or two, cool her down and look at them. Then run it up to somewhere close to full power for a minute or so , shut down and read again. Make adjustment as required. Remember good mixture at higher power settings is more important then idle. A good source to see how to read plugs, go to Google and enter " how to read spark plugs "

[mike.smith]

I'm sorry/amazed/curious that some seem to have trouble tuning the aerocarb as mine ran great right out of the box with only a idle speed adjustment. It's important to remember it is as simple a fuel mixer as you will ever see and it will not be perfect in all areas at all times. It's very simple design is both a blessing and curse. The way I check for proper mix is the old fashion " READ THE PLUGS" . Idle your motor for a minute or two, cool her down and look at them. Then run it up to somewhere close to full power for a minute or so , shut down and read again. Make adjustment as required. Remember good mixture at higher power settings is more important then idle. A good source to see how to read plugs, go to Google and enter " how to read spark plugs "

I spent hours on mine before getting it right. It's simple, but its simplicity is sometimes its Achilles heel. See my post "What a difference a needle makes!" Many of us have noted that you many not be able to set the needle with any accuracy unless you are very careful. The set screw, that keeps the needle carrier from moving in or out after setting, is susceptible to extreme movement when the set screw makes contact. Apparently (I have watched it happen looking up into the carb throat) the needle carrier threads can be quite loose in the threads of the carb body. So as you think you are tightening the set screw to keep the needle carrier from moving, you are actually also turning the needle carrier and moving the needle I have observed 1/8" to 1/4" horizontal movement!!!

Keith Macht noted that Sonex suggested he peen the carrier threads lightly with a hammer to cause more friction with the carb body. This apparently worked quite well for Keith and others.

So although it's "simple" there are many gotcha's and tricks of the trade that could be passed onto builders to avoid all these hours of work to track down issues. Now that I have it tuned it's doing quite well, but it took a lot of trial and error to get here.

[MichaelFarley56]

I can't help but agree with everyone on this thread that the AeroInjector, while being dirt simple and having many excellent attributes (no fuel pump, no carb ice, etc.) it does take a while to get the fine tuning accomplished before it's "perfect." I'm running an unmodified #2 needle in mine, and in order to keep the engine running well from idle to full power, I also have mine set fairly rich. I'm to the point that I accomplish fine tuning on my needle in order to set my EGT readings at wide open throttle to be where I want them, which for me is around 1150. This keeps my cylinders cool during a full throttle climb.

The downside is this means my carb is rich at low power settings. I generally have my mixture pulled 2/3 the way out during taxi and runup, 1/3 out during cruise, and pulled back 1/2 way when I reduce the power during landing. It's not a big deal and something easy to get used to, but perhaps slightly different than all of our old "Cessna" experience where you can leave the mixture full rich most of the time.

I've thought about going to a #2.5 needle but at this point, I really don't want to make any changes until I tear into things to install the tubo here in a month (right Sonex?) :mrgreen:

[SonexN76ET]

Just for the record I want to let everyone know that I love my AeroInjector! Once you get it tuned properly it works great! You just need to know what you are doing when you tune it. I think I know mine pretty good now. I flew two trouble free hours this evening and took some great video with my GoPro that I will post later this evening.

So Sonex, please do an AeroInjector tuning video. I think it would be a great help to builders and new owners of already flying Sonex aircraft.