Shane Bangerter wrote:
What is the best practice for use of low boost fuel pressure pump for the IV-P TSIO 550 E? Activate on
take off or wait to a certain altitude? I have been flying into Colorado Springs elevation 6,187 with density altitudes over 8,000 this summer and wonder if I should activate the low boost pump while on the ground.
Shane,
I flew my TSIO-550E-equipped IV-P without the boost pump turned on below 14,000’ for the first 3 years/500 hours
or so. About two years ago, I had the engine roll back (my wife’s viewpoint: It quit!!) during climb out of Grand Cayman on a rather hot day. This happened a few more times after refueling out of above ground storage tanks in the summer.
My rationale for not using the boost pump was that I’d set up the engine for WOT/Takeoff Power without the fuel pump, and low boost ran the fuel flow a bit above the recommended 42-44 GPH. Then one particularly hot day, I noted the cylinder temps approaching
420 during WOT climb, so I turned on the low boost. The small amount of extra fuel brought the temps down below 400 almost immediately.
So I started taking off and climbing with the low boost on…and I’ve not had a “roll back” for more than a year…saving my wife from those awful-sounding proclamations to her friends.
So I am now using low boost for takeoff, climb out and cruise above 14,000’. If I’m cruising below 14,000, I
usually turn it off after we’re stabilized in cruise--and cooled down a bit if it’s a particularly warm day.
BTW, I takeoff and climb at WOT to cruise altitude if ATC allows, or when VFR, then run LOP at about 65% power
for cruise. At 1000+ hours, my engine and plugs are always clean; absolutely no carbon buildup, and zero oil consumption.
My thoughts are that when the engine fuel pump and system/seals were all new, it could draw the needed fuel under
all flight conditions, but as the components wore through normal use, small internal leaks allowed the fuel to vaporize within the system, causing the roll backs. I have carefully checked the system for external leaks, both by pressurizing the system, and
by drawing a vacuum on it. No external leaks in two separate tests.
One other thing that might impact. After my kit was nearly complete, Lancair recommended enlarging the fuel tank-to-fuel
selector valve lines from 3/8” to ½”. As my system was already assembled and tested (and a number of
Lancairs had flown for years with the 3/8” lines) I did not make this change.
Bottom line: I’d (now) recommend running with low boost, with the possible exception of low/medium altitude cruise.
The (standard Lancair-provided) pump is rated for several thousand hours of continuous use on low boost. Jeff Edwards always told me it was a good “extra safety item.” I’ve come to accept this philosophy as I’ve gained time and experience in this magic carpet.
My two cents…
Bob