Late Summer Onex Flight

[Stogie6]

*

[gammaxy]

Thanks for sharing. I noticed the stammers during the takeoff roll and a rough idle before takeoff. From your other posts, it sounds like you've redone your fuel system since then? Are you satisfied the issue has been resolved?

[Stogie6]

Thanks for sharing. I noticed the stammers during the takeoff roll and a rough idle before takeoff. From your other posts, it sounds like you've redone your fuel system since then? Are you satisfied the issue has been resolved?

Short answer...no. My fuel system is an in-line fuel filter to the aeroinjector. I need to figure out how to install a fuel strainer somewhere between the firewall and filter. There are comments as to the need or not to install such a device. Water may be the culprit to the stammer. But works its way thru the system. Not a great feeling when you are flying to hear the chuga-chuga! No gascolator. I have also gone back to factory setting on the needle. Just finished my first condition inspection and changed out filters and magnetron spark plug wires as they got on the exhaust pipe and burned thru. My next step is to wrap the exhaust and install insulation around the fuel filter and adjust the needle accordingly. My last flight prior to the annual was absolutely perfect. 45 minutes orbiting the field at 1800 plus feet (125 mph indicated). No issues encountered. Wish I had my GoPro for that flight.
More as Phase I continues.

[kmacht]

My fuel system is similar. Inside the cockpit I have a tank finger strainer, fuel shutoff valve and an inline filter with a clear housing that can be checked for contamination before every flight. It then goes through the firewall and straight to the aero carb. The carb is the lowest point in my fuel system. At the inlet to the carb I have a T with a 90 degree fitting going to the fuel line, the center part of the T going to the carb inlet and the bottom of the T has a Curtis drain valve installed. If I suspect water I can drain and take a sample from that valve. Insulating the fuel line is always a good idea. I used fire sleeve along the whole length of the line from the firewall to the carb. The fuel line just gets too close to the exhaust for me to be comfortable without it.

Whatever you do, please do not continue flying until you figure out exactly what the problem is. A stumbling or hesitating engine on takeoff is a serious issue that needs to be addressed. There are far too many accidents where a sonex has lost power on takeoff, many with not so great outcomes.

Keith
#554

[radfordc]

Sounds like a classic case of Aeroinjector "burps". Search the threads for tons of info on why and how to fix.

Watching the video caused me to think about "decision making". On the initial powerup you can hear the engine stumble a bit. With several thousand feet of runway ahead the takeoff could have been aborted but wasn't. Climbing out and turning crosswind the engine continues to stumble and you set up for a precautionary downwind landing, but again you decided that flying was a better choice than landing. I retrospect would you have made different choices?

[Fastcapy]

I had the burps frequently with the 2 aerocarbs I had. 2 or 3 of every 5 flights would have engine stumble on takeoff where I would have to abort the takeoff.

After months of messing with rerouting fuel lines, changing filter location, redoing vent lines, and all other kinds of things. Nothing I did stopped the issue until I finally dumped the aerocarb and put the Rotec TBI on it. Well over 100 takeoffs on the TBI an NOT A SINGLE BURP!

[petep]

Been thru this issue several times before. The AeroCarb / AeroInjector does not have a vent to port off fuel vapors as does a traditional carb that has a float bowl with a vent to the atmosphere. Depending on the design of the fuel lines some aircraft make vapors worst that others because of the heat in the cowl. The best answer is to carefully look at the fuel lines design to keep a constant down hill slope to the Aeroinjector to encourage any vapor bubbles to escape back to the tank and not be ingested into the engine. Avoid getting the fuel lines any closer to the exhaust that can be avoided. Wrapping the exhaust will help to some degree but is not a total answer. Several builders has installed burp lines and achieved positive results, search burp in the Aerovee forum. Of course going to a different carb might be another option but that move can be expensive and time consuming not to mention the unintended consequences that it may introduce. If you have the burps they will not go away until you take positive actions to resolve them.

[Onex107]

I went through a long period of changes to fix the "burps". They are a serious problem. In the beginning they happened during taxi out and always during taxi back after flying. A big burp every 5 or 10 seconds during cruise is scary. The engine continues to run and you can maintain altitude but. We have another problem with car gas here in the Midwest where they have winter gas and summer gas. The winter gas has a higher vapor pressure and doesn't change over until the weather is warmer. The Aeroinjector is not the problem. So called Vapor Lock can still occur with a standard carburetor effecting fuel flow under the worst conditions The short answer is insulate. Fire sleeve was not good enough by itself. I ended up removing the gascolater because it was too difficult to insulate. My exhaust pipes are wrapped and my entire fuel line, even the end of the Aeroinjector, is covered with two layers of foam pipe insulation. I know, it's not fire proof, but, in twenty five years of flying fire has never been a problem like the burps. Maybe you could fire sleeve the foam insulation. Problem solved, never reoccurred again, even in 90 degree temps.

[SonexN76ET]

David,

Here is what I would do to address your engine stumbling and hesitation:

1. Make sure your fuel system is running downhill all the way to the AeroInjector. Any high spots will collect air and fuel vapors and lead to burps.

2. Try this inline filter https://www.amazon.com/dp/B0002M8XUK?ref=yo_pop_ma_swf

Or this one http://www.jegs.com/i/JEGS-Performance-Products/555/15031/10002/-1

3. The Earl’s filter will need this coupler to get it as close to your firewall as possible by attaching directly to the bulkhead fitting http://www.jegs.com/i/Russell/799/640000/10002/-1

The Jeg’s filter may work better on a Onex because it attaches directly to the bulkhead fitting without the need for a coupler fitting.

You will have to judge where the best place is to fit your filter as you have to allow enough flex in your fuel lines to handle engine vibration and engine movements to avoid cracking a fuel fitting or overstressing a fuel line.

4. Use this fitting on your AeroInjector to keep the fuel line closer to the AerInector and away from the exhaust https://www.amazon.com/dp/B0002M9NPO/ref=cm_sw_r_cp_api_i_BXh7AbRBC8Z73

5. Turn up your idle RPM. I recommend setting your idle to 950 to 1000 rpm on a new engine. On a new engine for some reason with the AerInjector it does not like to loaf at idle below 950 rpm and then go to full throttle. I know people will scoff at me but try it. It helps.

6. Make sure your spark plug wires are securely fastened away from the exhaust and other engine hot spots.

7. Insulate your fuel lines and filter as others have suggested.

8. Make sure you have tuned your AeroInjector EXACTLY as the manual prescribes. PAY ATTENTION TO EVERY DETAIL.

9. Verify proper operation through short ground runs without overheating your engine before you attempt flight again.

10. Make sure your engine cooling air outlet is sufficiently sized to allow proper cooling and airflow.

I am not bragging, but my engine now runs flawlessly and is very smooth. I know your’s can too.

Sonex has said any water in your fuel will drain out of the AerInjector before the engine fires up because the AerInjector is the lowest point in the fuel system and there is nowhere in the AerInjector for the water to collect as there is in a carburetor with a float bowl.

Please keep us updated on your efforts.

Thanks,

Jake

[EdW]

This brings up a question... you show flared fittings. Aviation flares are different from automotive. Are you mixing hoses/fittings?

Ed