Rough running...hot gasoline? Vapor lock?

[bvolcko38]

I'm using the number 2 needle

[bvolcko38]

After much trial, I have found that the aerocarb is getting hot...160F hot. I am experimenting with a scat tube from the rear baffle down to the aerocarb.

[Onex107]

At one time I did have a scat tube cooling the AeroInjector to try to prevent the "burps". They were devastating and almost shot me down a couple of times. It was ineffective and I had to wrap the exhaust pipes and insulate the fuel line to stop the problem. Right now in this hot weather I have a rough engine after flying when it's hot soaked. The engine lopes at idle. Between 950 and 1100 rpm. My research says it's probably a vacuum leak. But i haven't been able to find it. I'll return the scat tube cooler to see if a cooler carb changes anything.

[bvolcko38]

This cured all!

[Tnhelm]

I wonder if this inlet disturbs the negative pressure area for engine cooling. If not I assume your engine CHT’s have remained unchanged.
Is the vent directed to the aero injector With scat tubing or just ventilating the area?
I’m very interested because I’m building OneX 137, getting close to cowling work, and very concerned about fuel delivery.

[Onex107]

My fuel system is designed to be downhill all the way from the tank shutoff to the AeroInjector so that any vapor bubbles that form, and they shouldn't form due to the insulation, will tend to go back up to the tank. That solved my "burp" problem and the engine runs great. But, after flying for an hour and landing with a heat soaked engine it wouldn't idle smoothly. It surged from 1000 to 1200. After reading about the 160 degree temp on the AeroInjector, I added a scat tube from the front of the baffle, in front of the dip stick, directly to the AeroInjector above the the air filter. A simple alum duct on the end directs it. Taa Daa. Smooth idle. In spite of all my care in insulating the fuel line the hot AeroInjector was vaporizing the fuel as it entered the mixture valve and needle orifice. Always learning from others.

[WesRagle]

Hi Guys,

Question: Why is the carb getting so hot?

Is it radiated heat from the exhaust? From what I have read the under cowl temperature is about 130 deg F.

Years ago I had the very humbling experience of dragging my new airplane (O-360 engine) down the taxiway of Meacham International Airport on a hot summer day due to vapor lock while taxiing. Turns out the well known fix was to add a heat shield on the exhaust pipe where it passed near a 90 Deg. fitting that fed fuel to the carb. I applied that fix and never had the problem again.

Wes

[bvolcko38]

There was no cool air for the carb. None,zero, nada. The only air available had been through the head/cylinder fins and oil cooler. On top of that the carb sits inches away from and between two very hot exhaust pipes. Perhaps if I had the bottom mount oil cooler and the "smile"opening in the cowl below the prop, things might have been a little cooler, but the plans said the"smile"was not necessary with the top mount cooler. I did eventually close of the NACA duct by 60% or so but still have very good numbers.