Bart D. Hull wrote:
: Just be careful that your plane behaves well with autogas and know its
: limitations. We've had auto conversion Soobs with full return loop EFI's
: get vapor lock being sold "Winter" blend auto gas in the summer months.
: A vapor pressure tester verified this post mortem (Of the airplane, not
: the pilot.) In at least two cases we know of the airplane was wrecked
: due to vapor lock from using auto gas and that definitely didn't save
: them any money. And if you have capacitance probes that were calibrated
: for AV-Gas it doesn't show the correct amount of fuel.

Yes... the usual caveats apply. I bought one of the "vapor pressure testers"
from Peterson when I got the autogas STC for my Cherokee. It's basically a syringe
with a vacuum gauge you can screw onto the end. Pull in 2cc's of fuel, screw on the
gauge, and pull it back to 10cc's on the plunger. The fuel will boil and equilibrate
on a vacuum reading.

It doesn't read RVP directly (many factors affect it like temperature, local
pressure, etc), but it will definately be good for comparison. I test mine once in
awhile (especially in the spring when it's warm and the autogas stations might have a
winter blend). I almost always see 1" difference between 100LL and 93 AKI here (2100'
MSL). "Safe" on the gauge is 6inHG. 100LL will show 8 winter, 7 summer. Cargas will
show 7 winter, 6 summer... on the border of "safe."

-Cory

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* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
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