Recycle Petrol How?

[Hamish]

Unable to find any answer resulting in this post. Have recently converted a Saito 45,4# and ASP 61, 4# to petrol with Pegasus CDi ignition I am impressed by how easily the engines start and run but at the moment only test bench. The Satio is in an old cub ready for a test flight, weather permitting.

I notice that the petrol remaining in the fuel tank is very discoloured due to the exhaust pressure feed. Obviously the engines run on this fuel but on completion of running I have contained this fuel in a separate container and not recycled.

Can I ask how you petrolheads deal with this? Not considering a separate pump even if available.

[Engine Doctor]

You shouldn't be using exhaust pressure to the tank with petrol ! You are running a serious risk of fire as petrol exhaust is much hotter and pipe from exhaust can be damaged by heat and break down then the fire risk starts! Use a pump as all modern petrol engines do or just use normal carb suction to draw the fuel. 

[Hamish]

I thank you for the advice and suggestion.

From JE

"Plumbing the exhaust into the tank has been a question for many years from way back in the early 70's but I have never heard of an incident wherein a fuel tank exploded. Webra sell a 150 spark engine and it is supplied with muffler pressure so it is not a concern to them. The hot gas would not be a problem but carbon might be however, I would consider the chances in the

million to one odds maybe even better. Besides, methanol is not too slow igniting with a hot glow look at glow plugs and we have been pumping hot gas into methanol for a long time. I would be prepared to say not a problem."

Its how I recycle fuel or just run dry?

[Ultymate]

The only way I can see you not using exhaust pressure is to go to an electric pump like this Pump. I am of course assuming you've tried running your engine without pressure. The above pumps do work as a friend of mine has one on a inline 4 cylinder OS that he converted to petrol. Sadly the carbs fitted to glow engines are little more than dripping taps

[Hamish]

Gave the ASP a run without pressure feed and it appears to be running ok so thanks for that suggestion. Have yet to tweak this engine so further experimenting worth it. I will more than likely take the million to one chance rather than an extra £35+ for a pump on an experimental project. Will drain tank into a separate container and reuse on next fill up rather than contaminate good fuel. Thanks all for advice.

[Bob Cotsford]

If you are using a felt clunk, as is generally advised for petrol, you might be best leaving some petrol in the tank to stop the filter drying out and crumbling.

[Hamish]

Thanks Bob, it is a felt clunk so will take your advice which really answers the whole question of how to recycle fuel.

[Rich too]

I agree, but felt clunk or not, you shouldn’t drain the fuel. Any rubber parts in the system will dry out..