Sent: Sunday, December 28, 2003 1:45
AM
Subject: [FlyRotary] Fuel Coolers
Hi
Guy's;
I'm looking for a small, compact fuel cooler of some sort. I tried Google, but
get a ton of listings for ******partstore.com, but none of them actually lead
to any fuel coolers. I did find one other but it was for a fairly large cooler
(12"x3"). I was hoping for something closer to 3"x4". I've been monitoring the
firewall temp at the location of my fuel pumps and filters (on the cool side
of the engine) and it is consistently around 60C, while doing touch &
goes. I'm considering putting a tee in my return line to install a temp sensor
to measure fuel temp before it returns to the header tank as I suspect that it
is considerably warmer than this, due to heat from the turbo charger, which is
in fairly close proximity to the injection rail.
During extended touch and goes, the turbocharger is producing full power every
few minutes and I've began to use both boost pumps while in the circuit. this
combination seems to contribute to a build up of vapour in the header
tank. I also keep the boost pump on to keep the header tank pressurized
to 7psi to help counter the vapour issue.
A few days ago, after an hour of touch and goes, the vapour press apparently
built to 7psi and during my pre-landing checks while on downwind for runway
33, I found that one of the FI pumps had just begun to cavitate indicating
vapour-lock. I immediately switched on both boost pumps, but the second boost
pump began to cavitate also, followed shortly after by that eerie silence that
we all hate. I immediately began to vent the pressure off the header tank
while continuing to pump to it, and set-up for a dead-stick landing onto 24.
Landing was uneventful and restart was easy as soon as the excess vapour
pressure was vented from the header tank.
I understand the conditions that contributed to this, and it can be overcome
by venting build-up pressure on a timed basis, but I prefer to keep the header
tank as a closed system while in-flight. I realize the Ed is the only one who
is flying with a similar system using a header tank. Ed, if IRCC you had
similar problems with vapour lock before you switched to Avgas?
Now many of you will suggest that I just switch to Avgas, but that is not an
affordable option for me. The price difference here is so horrendous as to
make the difference between whether I can afford to fly or not. Of course I'm
not willing to risk continued vapour problems to save money either, but rather
try to find an affordable solution that will safely solve the
problem.
My current plan is to shroud the fuel pumps and filter to isolate them from
the cowl heat and duct a 2" hose from a NACA duct like the ones used for
ventilation on an RV (and probably many others) to this shroud, but have the
air pass through a small fuel cooler located at the air inlet to the shroud.
Exit air from the shroud would have its own exit out the bottom of the
cowl.
So my question for the list is does anybody know of a source for an
off-the-shelf compact fuel cooler? Any other suggestions would also be
appreciated. While I've considered the option of doing away with the header
tank, at this point I'd like to try to keep it as it does have advantages for
managing 6 fuel tanks.
Ps....
This really isn't as bad as it sounds... really :-)
S. Todd Bartrim
Turbo 13B RV-9Endurance
C-FSTB
http://www3.telus.net/haywire/RV-9/C-FSTB.htm
Hi
Todd,
Glad to hear your incident did
nothing more than re-arrange your seat cushion. I have never had a
situation of impending vapor lock (such as caviation of the EFI pumps) that
turning on the boost pump did not resolve. I do however, have my fuel
pumps and header tank shielded with a fiberglass box covered with aluminum
foil. I also have an NACA duct funneling outside air to the box.
So I think your plans would certainly help the situation. Plus, you may
have a bit more heat under you cowl what with the turbocharger. Other
than my header pipe which do a 90 deg bend and out from the cowl
- nothing much of a heat producer, also I do have louvers on both sides
as well as a rather large opening on the bottom.
I had considered a fuel
line cooler (which they do make), but unless you are funneling cool outside
air to it (and no inside hot air) then it could make the problem worst by
picking up more heat from the hotter under the cowl air. In any case, I
have not tried a fuel line cooler, but would think that provided with cooling
air, its couldn't hurt.
But, Yes, I have found auto
gas to be more conducive to percolation than Av Gas.
Ed Anderson