"Kyle Boatright" wrote in message
...


I built and now fly a 160 hp carburated RV-6. I always run 100 LL, and
have starting problems I attribute to vapor lock on hot days when I do a
medium length stay on the ground - say 20 to 45 minutes after flying for a
while. I think the starting problem would be much worse using mogas. I've
never had a problem with vapor lock once I got the plane started.

I've read the same thing you have about mogas - it typically has higher
vapor pressure, which is compounded if you happen to get some winter
formulation mogas with higher (winter) vapor pressure during the warm
months. Given my experience and flying patterns (I typically cruise at
10,000' or more during the warm months), I can't see me putting mogas in
my airplane during the summer months. Too many opportunities for trouble.
However, if I lived in a cool climate, or didn't plan on flying high, I
might use it in the winter.

If I was going to use mogas, I would consider a blast tube on the
mechanical fuel pump, plus I'd do everything possible to minimize heat
build up inside the cowling. Additionally, I would follow the EAA mogas
STC's plan of avoiding sharp bends in fuel lines. Beyond that, I might
add a recirc line or purge valve to purge the fuel lines firewall forward
before a hot start.

You should be able to find a pretty good write up on mogas STC's using
google. There is some good information out there, particularly at the EAA
site, IIRC.

You've got a good grasp of the situation.

Rich S.