SonexBuilders.net

Recently, after the descent to landing and just after touchdown, my Aerovee Turbo stops running on the runway. At landing, I reduce the throttle to idle, (which I have set at 1000 rpm because I have not been able to get it to idle reliably at 900). It doesn't seem to matter whether I land lean or full rich.

I use my hot start technique to get it running again but then it seems to give me a hard time during the taxi back to the hangar. It will idle at 1000-1100 and then it drops suddenly to 450-650 and dies. Sometimes, I can save it if I can goose the throttle fast enough. If I am too slow....Hot start technique again.

I just did the 100 hour, oil and filters, new plugs, heads torqued, valves adjusted, timing is correct, etc.
I am in Phoenix and we just started to heat up again but we are only in the 80's to 90's, not yet to 115! I have not adjusted the Aeroinjector. #2 1/2 needle.

I know this is not uncommon to the Aerovee fleet and I am looking for some suggestions from those of you that have solved it. I would rather tap our group's combined knowledge than start from ground zero.

There are threads devoted to vapor lock in the fuel lines from heat etc. I used to have the exact same symptom as you describe - I ran through everything my builder had done to the fuel lines and it was in accordance with the thoughts on keeping fuel lines cool to avoid vapor lock.

My own thought about this is that in addition to the thought on hot fuel lines. After landing and with airflow into the cowl dramatically reduced - the temperature of the air inside the cowl rises dramatically and you can't lean aggressively fast enough to deal with the thinning air. So we need some cold air in there.

I fitted a NACA scoop on the underside of the cowl and arranged for it to point the outside air at the air filter. And the problem WENT AWAY COMPLETELY. Idling at 900 is easily achieved. In fact once the engine is warmed up and with the carb tuned - I can get a reliable idle at 550rpm.

I even got rid of the hard to inspect in-line fuel filter and put back a gascolator.

My fix - colder outside air straight to the airfilter.

YMMV

So, no issues with loss of cylinder head cooling due to pressurizing the lower cowl area anywhere in the flight profile? No "ram-effect" to the Aeroinjector?

I don't use a gascolator, I have all downhill runs to the Aeroinjector, and the entire length of the fuel line is insulated and fire-sleeved from the firewall to the Aeroijector as well.

I do not get the Aeroinjector burble with this application. I reliably got the burble with my last Waiex with 3300 and Aerocarb every time I leveled off from a climb and adjusted for cruise throttle setting.

What size NACA duct did you use and where did you mount it. Any pics?

pappas wrote:What size NACA duct did you use and where did you mount it. Any pics?

No to CHT loss of cooling pressure. Probably because I opened up the bottom slot to the recommended square inches. While the builder got the area correct, he stuffed it full of exhaust pipes, oil and fuel vents and didn't take account of that. So I opened it to the correct square inches CLEAR.

There is no ram air on the Aeroinjector - there is just an introduction of cold air around the area of the filter. Not strongly directed.

Picture - in the morning - I happen to have the cowl in the garage for painting this weekend and can snag you a photo then.

This is a 6" slot. Bought from an automotive race/tuning shop. They use them on body panels for directing airflow for brake cooling. Made of a heavy polythene. I was able to warm is slightly and bend it to conform to the curve in the lower bowl. (Probably ruined all the aerodynamics - but hey - it works!). I then drilled a lot of holes in the flange edge to give it mechanical "tooth" and then epoxied it in place. The brown color coming from the microspheres in the epoxy that give it a slight flexible quality so I didn't create a hard spot on the cowl.

No scat tube - the round opening is just aimed within 6 inches of the air filter hanging off the AeroInjector

I guess the cutout is just below the new side cooling organ pipes?

Gordon

I found some brake cooling ducts online. Yours looks like about a 10-inch long by 6-inch duct. Is that correct? And, the tube would fit what diameter scat? Won't use any scat, but they are available in different sizes.

pappas wrote:I found some brake cooling ducts online. Yours looks like about a 10-inch long by 6-inch duct. Is that correct? And, the tube would fit what diameter scat? Won't use any scat, but they are available in different sizes.

No - 8" long. 6" opening. The OD of the black pipe is 2 1/2"

GordonTurner wrote:I guess the cutout is just below the new side cooling organ pipes?
Gordon

RIP the organ pipes. They were too noisy. Trying the Sonex B slots. Hence the cowl is in the garage this weekend. Some laminating going on! The organ pipe holes are smooth skin again. The B slots are cut. The mold for the internal shape is made and the parts are laminated on it.

Graeme

Are you using the actual Sonex B parts for the cooling exhaust or did you make your own?

Gordon