firewall is almost like his panel... a blank canvas for you to create and
organize on. No two firewalls will be the same.
(click on a pic to see a larger version)
||The scene behind the
firewall with the baggage floor removed. Note the different method of routing the low
pressure brake lines. I didn't like the way the plans call for them
to loop aft of the bulkhead. This would also have interfered with
the parking brake valve I installed.
UPDATE: check the Ideas
& Products page for a better way of supplying brake fluid...
all those chronically leaking low pressure tubes have now been
||Work in progress. Note the
Van's transducer manifold in the upper right. Hoses below it are
just taped in position for now.
manifold installation. Oil pressure is on the left, manifold
pressure in the center, and fuel pressure on the right. The unused
tap on the fuel pressure partition will be used as a source of fuel
for the electric primer circuit when I get to it.
|Big picture from the
right & left sides.
The electric fuel primer circuit is still not installed yet but will be visible
on the left side.
Preparatory to starting the cowl I have taken a
preliminary step that I want to recommend. I got this
tip from Scott McDaniels at Van's. He says that with all the new small
alternators (mine's a B&C) you can cut the bracket off by over an inch
at the inboard end, re-drill the hole, and use a shorter belt. This will
keep the alternator in tighter to the engine and eliminate any
interference with the cowl as the engine moves around. My Sam James cowl
is quite a bit tighter in this area than the stock cowl so I needed a
small blister anyway. Look at how far down most
alternators hang and then look at this pic. BTW, finding a shorter belt was no
problem - the local auto parts store has Goodyear Gatorback belts in .5"
increments. I cut my bracket off 1.5" and note where I am in the
adjustment slot. I'm using a 35.5" belt
||Detail of the four blast
tubes exiting the top rear of the cooling plenum. They go the
left/right mags, fuel pump, and gascolator.
||Quick drain in action at
the first oil change. Note the oil breather adjacent to the left
exhaust pipe and the new style Vetterman exhaust mount system.
||Oil cooler installation.
This is the "Stewart Warner style" cooler sold by Van's
that is actually made by Niagara. On hot ambient temperature days my
oil temps are a bit hotter than I'd like so I continued to
experiment with different oil coolers, see below.
cooler swap: Niagara vs. Stewart Warner
cooler on left, Stewart Warner on right)
Since flying my RV-8 (four months ago) my oil temps were a bit higher than I'd like
on days where the ambient temp is 80 or above. When it is above 90
they were definitely too high (like 218 at low altitude low power
cruise). On one 90+ degree day in Central Oregon departing from a
5,000 elevation airport with the engine already hot, and while
following another plane's climb profile, I saw 245... yikes! Since
then I've learned to manage oil temps and have never seen over 230
regardless of the ambient temp. Still, I did not feel like I had
Several RV List
contributors had spoken with Pacific Oil Coolers lately and been
advised that Stewart Warner coolers were the most efficient, so I
called them also to see if a swap with my Niagara would lower my
temps. They told me "absolutely" and that I "could
possibly see a 20% reduction". Of course they wouldn't guarantee
anything. Frankly I simply didn't believe the 20%, but I'd be happy
with 10-15 degrees (5-8%).
When doing my final FWF
installation I had originally bought a Posi Tech. Solely on the
experience of several RV-Listers I sold it and bought a Niagara from
Van's. At that time I thought the Niagara was the identical product
to a SW... ignorance is bliss. Again, the Niagara has worked well
for 120 hours for all but very high ambient conditions, which is
only a problem here in the Great Northwest for 2-3 months a year. If
you lived in Arizona or Florida it wouldn't have been unacceptable.
Curiosity got the better
of me so I ordered one and swapped the SW for the Niagara while
doing an oil change. The flanges and bolt hole dimensions are
identical, but the core is recessed about 1/4" deeper than
Niagara. This required a very minor modification on my mount... no
problem. I ground ran it as usual when doing an oil change to look
for leaks, none noted, and buttoned it up to be flown the next
morning. I have now flown 7.5 hours over the last two days in
ambient conditions of around 80 degrees on the ground. The
comparisons I made are not good scientific method, rather my own
feel for what temps would have been before versus what I was seeing
now. After flying the plane 120 hours in the last four months though
I feel like I have a good handle on what was normal for a given
flight condition. Sorry, proper data would have been tough to get
(identical ambient conditions combined with identical climb/power
profiles) and way too much work.
here's what I found: when doing an extended climb before at 120-130
mph on days like this I would see peaks of around 220-225. This
weekend I saw peaks of 205-215. Cruise at 7,500-8,500 feet, with the
power settings I typically run, before would typically be 189-202,
this weekend they were 182-185. During long high-speed descents temp
would never drop below 180 with either cooler so the vernatherm must
be working. When assessing this information it should be noted that
my plane is non-standard and may make the oil cooler's job a bit
tougher. I have a Sam James closed cooling plenum. This forces you
to mount the oil cooler lower behind cylinder #4 than with Van's
standard baffles, hence half the cooler inlet is cylinder fins. This
probably impedes airflow and also may pre-warm the air, not good for
Hmm, what conclusions can
we draw from this? My own sense is that the SW does indeed cool
*just a bit* more effectively than the Niagara. In fact my own
belief is that I'm seeing an 8-10 degree reduction. The Niagara is
$241 from Van's, the SW was $397 outright from Pacific Oil Coolers.
Was the swap worth it? In the long run, probably. Was it dramatic?
No. Will I keep the SW installed? Yes, that 8-10 degrees is
important on those hot days. So there you have it, as close a
comparison as I can give you.
|Unlike some finished planes
I've seen, I want to be able to drain my gascolator before every
flight. This required some special engineering, and mostly some
quality time in the machine shop. Buddy and fellow builder
Randy Griffin made this work of art, and even had it anodized blue
for me. It allowed us to locate the gascolator in the perfect
position to be accessed for draining via a 1" hole in the
bottom of the cowl. Note the reinforcements it's mounted to. These
are riveted to the firewall angles, and there is also an .063"
plate on the back... don't want that sucker vibratin!
builder's have asked if Randy Griffin would make more of these for
sale. Randy says that it's just not economically feasible. He has
however provided the part drawing as a .dxf file. You could take
this file to your local machine shop, and with CAD equipment they
should be able to reproduce it.
(right click to download)
|There are many versions of
the basic Marvel Schebler carburetor, and mine had a 1/4" NPT
outlet on the inlet boss... perfect as a take-off for my fuel
pressure gauge. That way I'll know exactly what pressure is being
delivered to my carburetor. If you mount it further upstream you
could get a clog and the gauge would not reflect it. The aluminum
AN822 fittings you see here were subsequently changed to steel. After hearing stories of
aluminum AN fittings failing when used on the engine I decided to
use STEEL AN fittings whenever anything went into the engine. I've
still used aluminum everywhere else. These darned Lycomings vibrate
like crazy, and I just didn't want a failure here — hot fuel
spilling on your hot exhaust is not good.
||Details of my FAB (filtered
air box) and carb
heat cable installation. I elevated the cable clamp to provide the correct
angle of operation, and I also drilled holes closer to the pivot on
the arm to provide for less cable travel. The hole being used seems
to provide a good compromise between enough leverage and reasonable
cable travel in the cockpit.
Flow Sender Trials & Tribulations
||I first fit the fuel flow sensor you see here into a line up
front... wouldn't go. The fittings on the Aeroquip line, combined
with the AN fittings on the sensor, made it too long. There have
been reports of fuel flow gauges displaying inaccurate
readings caused by the pulses generated by the Facet auxiliary pump
when mounted too close like this. I am using an Electronics
International FP-5 fuel analyzer and the E.I. folks tell me that it
has circuitry built in to filter these pulses out. It will be simple
to tell - watch the fuel flow and then turn on the aux pump... we'll
Turns out the E.I. FP-5
fuel flow gauge does NOT properly filter out the pulses from the aux
fuel pump — once flying I was getting erroneously high flow
readings with the aux pump on. I was concerned because this would in
turn lead to incorrect "fuel consumed" readings. E.I.
admitted I was given bad information on that issue originally, and
the source of this information is no longer with the company. Both
in their installation manual and on the phone they insist that the
flow sender needs to be AFTER all fuel pumps to avoid a vacuum on
the sender at any time.
There's only two ways to do this, at
least in a carburetor installation. One, mount it inline between the
engine driven fuel pump and the carb, or two, mount it on the
firewall and run long lengths of flex line from the fuel pump to the
sender, then from the sender to the carb. While at a local aircraft
part store I found
a special AN fitting allowing me to hard-mount the sender to the
carb. This installation yields even larger errors. At the same
K-factor setting the flow readings are probably 40% too high. Then
when I turn on the aux pump they actually go down. Go figure.
After flying with it this
way for a couple of weeks I felt it was more accurate in the
original configuration. I next relocated it back behind the
firewall, but used my special hard coupling to mount it directly to
the back side of the firewall thereby leaving an even longer
straight tube from the Facet pump to the flow sensor. I've flown
many tanks of fuel since then and even though the flow does indeed
jump up 2-3 gph when the aux pump is on, the accuracy is impressive.
After a few tanks to get the k-factor adjusted properly the
all-important actual "fuel remaining" calculation now
yields an error of .2-.5 gallons when I fill up... good enough for
me. Frankly I don't understand how it can be so accurate when the
boost pump throws it off so much, but there is no denying the
accuracy. If you spent a whole tank in the pattern with the pump on
I suspect it would throw it off, but for normal RV flying I have
come to trust this computation as the true reflection of how much
fuel I have left. The regular fuel gauge works pretty well also, but
of course is completely inaccurate when the plane is on the ground
in the three-point attitude. If I want to know how much fuel is in
it I just flip on the master and the FP-5 defaults to the "fuel
remaining" screen... voila, I know instantly how much fuel is
left and can plan accordingly.
Additional factoids: E.I.
uses a Floscan 201 flow transducer which seems to be the standard of
the industry. I understand Vision Microsystems uses the same sensor
as does Matronics and JPI. The 201 is for low wing aircraft and has
a smaller orifice for the fuel to flow through, but it has greater
resolution in that it breaks a gallon of fuel into something like
8,500 pulses. They also offer another sensor with a larger orifice
(205?), but it has lower resolution and may be slightly less
accurate. The reason all of these instrument manufacturers instruct
you to mount the sensor downstream of ALL pumps is to avoid a vacuum
condition. Apparently it is possible for avgas to be separated into
a "benzene state", and they want to avoid that under all
conditions. Frankly, I think that in the low pressure carburetor
installations this is just about impossible. Anyway, these
instructions come from Floscan and I'm sure are driven a bit by
To the their credit, Dave
Campbell at E.I. has been very helpful and attentive through this
process. I continue to have confidence in both my E.I. instruments
and the company.