Hi Paul,
> I don't know if this helps or not, but in 1000 hours of operation I have
> never experienced a vapor lock like Frans has described using Mo Gas. I
> have operated my aircraft on days that are 35c ~ 40c, which have
> included long taxi runs. My experience may not translate because most
> of my take off and landings are at around 1000' MSL. On hot days this
> equates to about 3000' density altitude.
This field was on about 4000' MSL... I took off quite a few times from
this field before, using Mogas. Never had any problems until the last time.
What was/might be different than previous times:
I refueled in the morning but took off in the afternoon.
I had a black carpet on the bagage floor instead of white.
Maybe the fuel itself (although purchased at the same store) might have
had a different formula.
Maybe the fuel filter has a bit more resistance than previous times
(maybe a bit more clogged?).
There are many variables.
Anyway, this event shows that it CAN happen, despite previous positive
experiences, for whatever reason. The engine ran fine after a night
waiting, so even if there is a technical problem (partially clogged
filter) it might wait to show up until a hot and high airfield (which
tend to be the most unforgiving fields for technical problems).
I think with a few minor improvements the fuel system can be made more
mogas proof. See my other posting.
> What I have seen is the engine will not start on a hot day after sitting
> for a while and what I do in this situation is to turn the fuel pumps
> off, start the engine and then turn the pumps on.
I now always switch the fuel pump off during the turbo cool down period,
and let the engine idle until the carbs are drawn empty (this usually
takes about 1 minute). The starting problems are gone, and I think the
carbs will stay cleaner (the fuel inside the bowls will otherwise
vaporize anyway, but then leave some solid residue behind).
Frans
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