Vapor Lock
Posted: Sun Mar 06, 2022 12:23 pm
I’ve had vapor lock issues three times now and it always occurred after a flight in hot weather and then shutting down and not starting afterwards. For example, stopping for breakfast in plus 90* temps, or stopping for fuel in plus 90* temps. This is happening to other TSi’s and in particular, one in Las Vegas according to Sling.
The recommendation from Sling is to run AvGas and I hate to do that for the obvious lead issues and it’s debatable if that is a valid fear or not. I’ve decided to run full or partial AvGas in one tank for the three hottest months of the year, and use it for takeoffs, landings and parking. I’ve also rigged up a small 12v battery to a small fan, placed it in the engine compartment after parking, along with a small lithium ion battery, plus use a couple clothes pins to hold the cowling doors open. This makes an enormous difference in the heat in the engine compartment and the engine heat after a stop, but I’m not sure if this will solve the problem. Sling says they don’t know where the vapor lock is happening in the engine compartment.
Last September I was on a long cross country flying to all the lower 48 states. In Virginia I picked up some Decalin fuel additive that I’ve used successfully many times in other Rotax engines. A couple days later I stopped for fuel in Alabama on a hot day and couldn’t get the 915 started again for hours, in spite of only having AvGas in the tanks. I stopped the Decalin and haven’t had another problem while using AvGas.
This brings up another potential issue. Several people on this forum are installing external alternators on their engines. I have no idea if this will increase or decrease the possibility of getting vapor lock. It’s a lot of engine in that compact compartment and another alternator will probably add heat and change the airflow.
https://share.icloud.com/photos/0dcjo7R ... ch_Airport
https://share.icloud.com/photos/048a_yg ... ch_Airport
The recommendation from Sling is to run AvGas and I hate to do that for the obvious lead issues and it’s debatable if that is a valid fear or not. I’ve decided to run full or partial AvGas in one tank for the three hottest months of the year, and use it for takeoffs, landings and parking. I’ve also rigged up a small 12v battery to a small fan, placed it in the engine compartment after parking, along with a small lithium ion battery, plus use a couple clothes pins to hold the cowling doors open. This makes an enormous difference in the heat in the engine compartment and the engine heat after a stop, but I’m not sure if this will solve the problem. Sling says they don’t know where the vapor lock is happening in the engine compartment.
Last September I was on a long cross country flying to all the lower 48 states. In Virginia I picked up some Decalin fuel additive that I’ve used successfully many times in other Rotax engines. A couple days later I stopped for fuel in Alabama on a hot day and couldn’t get the 915 started again for hours, in spite of only having AvGas in the tanks. I stopped the Decalin and haven’t had another problem while using AvGas.
This brings up another potential issue. Several people on this forum are installing external alternators on their engines. I have no idea if this will increase or decrease the possibility of getting vapor lock. It’s a lot of engine in that compact compartment and another alternator will probably add heat and change the airflow.
https://share.icloud.com/photos/0dcjo7R ... ch_Airport
https://share.icloud.com/photos/048a_yg ... ch_Airport