Contributed by: Fly RC Magazine | Published: October 2004 | Views: 88252 |  Email this Article
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This
review appears courtesy of Fly
RC Magazine.
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Article
by:
Andrew Coholic
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SuperTigre,
a respected name in model engines, has been churning
out engines for more than 50 yearsand until
now the engine has always been manufactured in Italy.
After a brief hiatus, these popular sport engines
are back in hobby shops. All production and tooling
have moved to a plant in China to become more competitive
in the world market. The GS40 R/C is a .40 cubic
inch displacement, ringed piston engine with the
large ST quiet muffler. The new engines appear to
be essentially identical to the previous Italian-made
versions I have owned.
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| SPECIFICATIONS
ENGINE:
SuperTigre GS40 R/C
MANUFACTURER:
SuperTigre
DISTRIBUTOR:
Great Planes Model Distributors
Displacement:
.40 ci
Weight:
18.30 oz.
Type:
Schneurle ported, single conventional ringed aluminum
piston running in a hardened steel sleeve, with
ball bearing supported crankshaft
Prop
range: 9x6 - 11x6
Recommended
prop: 10x5 - 10x6 for sport use
Price:
$75
SUMMARY
This is a well constructed, quality-made sport engine
that should be very long lasting. This type of engine
(ringed) is more tolerant of ingesting small amounts
of dirt than a ringless lapped engine. It has a
minor tendency to load up in a prolonged idle while
on the ground, so youll want to adjust your
transmitter idle setting accordingly. Overall, I
rate the machine work and appearance as excellent.
The instructions, written for the newcomer pilot,
are exceptionally good. At $75, its a good
value for your dollar.
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INITIAL
IMPRESSIONS
I first noticed the excellent packaging. The large
box was brightly colored with the ST emblem, and
the model number clearly stated - while on the inside,
the engine, muffler, carburetor and miscellaneous
screws and nuts were neatly packaged in separate
sealed bags, and nested in foam padding. Also included
was a glow plug (not always included today) the
instruction booklet, an exploded view of the engine
and carburetor, the warranty card and a nice set
of peel and stick decals. The stated weight including
the muffler is 19.08 ounces. Measuring the engine
complete with all screws, glow plug and muffler,
on my digital scale gave a reading of 18.30 ounces.
Its always nice to be under the claimed weight
rather than over!
RUNNING THE ENGINE
The operating instructions are excellent, and are
targeted towards the beginner. To break in the engine,
I used an APC 10x5 prop and the supplied glow plug.
SuperTigre recommends a fuel with 18 to 20% oil
for break in. I used fuel with 5% nitro and an 18%
30/70 castor/synthetic oil blend, as castor offers
excellent protection to the newly machined parts
while they are running in.
During break-in, I measured the engine rpm, the
exhaust gas temperature and the cylinder head temperature
with the RCATS ground based data gathering unit.
This system displays the data monitored on my laptop
computer, and is really handy for tracking the engines
performance. I did the test runs outdoors, and it
was quite cool (53 degrees F).
The first run was five minutes long, at an rpm of
8,500 to 9,000 (with the carb opened fully). At
this very rich setting, the cylinder temperature
and exhaust temperature were only 120 F. A good
amount of oil was coming out the muffler exhaust,
telling me that the engine components were receiving
adequate lubrication (unlike an ABC, this type of
engine can safely be broken in on the rich side).
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After
the initial run of five minutes, and a short cooling
off period, I ran the engine in five minute intervals,
slightly leaning the high speed needle after each
minute of run time. The engine was allowed to cool
between runs (every five minutes or so). By the
end of the second 10 ounce tank of fuel, I had run
the engine between 15 and 20 minutes total, and
the 10x5 prop was running a steady 13,100 rpm without
sagging, while the cylinder head temperature and
the exhaust gas temps were up to 275 F.
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INITIAL
RUN
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Propeller
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Max
RPM
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EGT
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CHT
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Idle
RPM
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9x7
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13,400
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297
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292
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3,400
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10x5
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13,100
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252
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262
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3,200
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10x6
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12,150
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263
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265
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2,950
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10x7
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11,600
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238
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228
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2,950
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11x4
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12,100
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242
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226
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2,800
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11x5
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11,100
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245
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243
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2,400
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11x6
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9,800
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264
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256
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2,400
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Without
disturbing the factory set low speed needle, I recorded
an idle rpm of 3,600fairly steady but there
was a tendency for the engine to load up (incomplete
combustion accompanied by reduced rpm) after more
than 20 to 30 seconds. The transition from low to
mid range was rough, but the engine would keep running.
Hot and cold starts were immediate when using the
electric starterhand starts were possible with
a healthy prime and a strong flip.
At this point, I felt the engine was sufficiently
broken in to try experimenting with some different
size propellers. Using the supplied glow plug and
the same 5% fuel, I ran the ST GS40 on seven different
props, from 9x7 through to an 11x6. The following
chart shows the results: |
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each of the test props, I let the engine warm up,
reset the high speed needle and allowed the temps
to stabilize. To check the idle I tried to get as
low an rpm reading that would still allow the engine
to run steadily, without quitting. In all cases the
transitions were quite good, considering I had not
yet adjusted the low speed needle, and the engine
was far from being completely broken in. Starts were
again immediate when bumping the spinner with the
electric starter. Hand starts were somewhat difficult,
yet possible hot or cold. I preferred to use the starter. |
For
the next series of runs, I changed to a 15% nitro
fuel with 18% synthetic oil. I was careful to make
sure and richen up the high speed needle before each
prop charge/run, and re-tune for just off peak rpm.
I still used the supplied glow plug, which, by the
way, held up great throughout the test runs. The results:
As
you can see, the rpm across the entire range of propellers
was slightly higher. The temperature readings, both
exhaust gas temp (EGT) and cylinder head temp (CHT)
were very close, and to be honest I couldnt
see much of a performance between this fuel and the
fuel used for initial break in. The transition with
the 15% seemed a bit better, and I had at this point
also begun to adjust (lean) the low speed needle somewhat.
I found the factory set position to be very close
to the proper position. I ended up turning the idle
needle in about 1/3 of a turn, to lean it a bit to
prevent loading up. More than that and it was too
lean on the bottom end.
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FINAL
BENCH TEST
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Propeller
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Max
RPM
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EGT
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CHT
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Idle
RPM
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9x7
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14,030
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280 |
290 |
3,400
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10x5
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13,200
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272 |
273 |
3,400 |
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10x6
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12,450 |
266 |
249
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3,200
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10x7
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11,700 |
251 |
229 |
2,950
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11x4
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12,700 |
267 |
278 |
2,400 |
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11x5
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11,850 |
232 |
248
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2,400
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11x6
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10,450 |
235
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246 |
2,400 |
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GLOW
PLUG TIPS
The last test I performed on the bench, was to try
a few different glow plugs, other than the supplied
one. I did a series of runs with a K&B 1L, and
also with one of the Tower Hobbies plugs that closely
resembles an O.S #8. Surprisingly, using both of these
other plugs gave a 200 rpm increase, and also the
transition and idle was noticeably better than with
the supplied
ST plug. I imagine the plug that was provided is a
bit on the cold side for this engine and the fuel
I am running, especially in the cooler temperatures
the day I was testing. For my test flights I chose
to use the Tower Hobbies plug, which I thought performed
the best on the
test stand.
TEST
FLYING THE ST GS40
I installed the engine into a SIG Four Star 40 ARF.
This is a sport aerobatic plane weighing five pounds
and one ounce. How did it fly? Very well! I performed
all test flights with 15% and an APC 10x6 prop. I
had the idle set so the plane would sit stationary
on the grass strip. The throttle had to be advanced
slowly in order for it to clean itself out
after a prolonged idle, but it was acceptable for
an engine with relatively low run time, and a bit
of tweaking left on the low speed needle valve.
The Tigre ran like a champ - from slow speed to high,
transitioning up and down, the engine never hesitated,
nor did it hiccup or sputter. I put the plane through
many aerobatic maneuvers such as inside and outside
snaps. Extended vertical climbs (during which the
engine again ran steady, without any signs of trouble)
took the five pound plane up many hundreds of feet
easily.
Try as I might to find a fault, the engine ran great
during all attitudes and maneuvers. Throttling back
to land, it dropped down into a steady idle and remained
there until I landed and taxied back to the pit area.
Other than having to remember not to advance the throttle
too quickly from idle (only on the runway while waiting
to take off - in the air the engine didnt seem
to have the tendency to load up) this engine outperformed
my expectations.
WISH
LIST
The soft compression makes hand starting
somewhat difficultthis will improve with more
run time. There is also a tendency for the muffler
to stick to the exhaust manifold after
a while. Not unique to the SuperTigre engine, tightening
down the cast aluminum muffler onto the aluminum
manifold tends to cause it to gall or adhere. When
this happens, you need to ease the muffler off,
not muscle it off, whenever you remove the muffler.
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The
engine differs slightly from the previous model manufactured
in Italy. The engine now has made in China
cast into the backplate and crankcase castings. The
screws holding the back cover and head on as well
as the single muffler clamp screw are now Allen head
cap screws instead of the traditional slot head screws.
Allen head screws are much easier to remove and torque
down without damaging either the engine or the screws.
The engine and muffler appear to have a glass-bead
blasted finish. It gives the engine a shiny and nicely
finished look. |
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Disassembly
of the engine revealed a quality die cast crankcase,
nicely machined inside and out. The back cover is
also a die casting, and has a groove and rubber
O-ring that provides a leak-free seal without the
need for a paper gasket. The connecting rod is machined
from bar stock aluminum alloy, and has been bronze
bushed at both the lower and upper end, always a
nice touch. Two lubrication holes are drilled into
the bottom end of the rod to allow a good supply
of oil to lubricate the crank pin. The die cast
piston appears to have been honed to finished size,
and has a cross hatched surface texture. The single
expansion type ring is pinned to prevent rotation
and eliminate the chance of catching a port.
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The
wrist pin is blind bored, and held in the piston with
C-clips at either end. The piston has a small area
relieved to allow you to get at the edge of the C-clip,
again, a nice feature when it is time to overhaul
the engine. The crankshaft is a single-piece steel
machined unit, ground to finished size, and is supported
in the crankcase by two ball bearings. The thread
is the standard American 1/4-28, although the crankshaft
diameter immediately in front of the die cast drive
washer (which is held on by a split collet) is slightly
larger at 7mm, and may require the spinner backplate
or propeller to be reamed to fit. |
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HEAT
TREATED STEEL SLEEVEThe un-plated, heat
treated steel sleeve is quite robust, with a wall
thickness of 60 thousandths of an inch. The sleeve
has been honed to a straight cylinder, without any
taper. The sleeve is a tight press-fit into the
crank case, and in order to remove and reinstall
it, the case had to be warmed up, expanding it enough
to loosen up the fit. This type of close fit will
make heat transfer from the cylinder liner to the
crankcase fins more efficient, and although working
on the engine is a little more difficult, it makes
for better cooling.
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HEAD
AND CARBThe head again is a die casting,
with an integral brass insert cast into the center
where the glow plug threads in. Always a plus, it
prevents the plug seizing in the head, especially
after a hot run. The head shape consists of a wide
squish band (0.165 in. wide) with a bowl shaped combustion
chamber. |
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The
carburetor is of the two needle type, and is held
to the case with a draw bar and nut. The carb barrel
is sealed to the carb body with a rubber boot, and
the high speed needle also has an O-ring to seal
it. There is also an O-ring seal between the carb
neck and the crank case. Little chance of air leakage
anywhere! The carb felt smooth and without play.
I have always liked the Super Tigre carbs, sometimes
even fitting them to other manufacturers engines.
CLEARANCESI
measured the parts while disassembled with a digital
vernier caliper, and found all parts to have textbook
fits and clearances. However, the lower end of the
connecting rod was fit with a 0.0025 in. clearance,
with a little noticeable play, although still within
accepted limits. I like to see this fit with a little
less clearance on a 40-size sport engine because
a slightly tighter clearance can be associated with
better wearing characteristics. This is a personal
opinion and is not something that would stop me
from buying this engine.
The muffler is also a casting, and appears to have
some sort of baffling inside. It cannot be taken
apart, so I couldnt see exactly what was done.
The manifold is also a casting, and the arrangement
allows the muffler to be swung around to any angle
required for your specific installation.
Overall, I rate the machine work and appearance
as excellent.
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CONCLUSION
The SuperTigre GS40 is targeted towards the flyer
looking for a durable, dependable and strong running
engine that will provide years of use. It is a
well made sport engine that is very easy to tune
and handle. The ringed piston design will be more
tolerant of dirt ingestion than the many non-ringed
ABC/ABN designs that are so prominent today. The
three year warranty is as good as any other in
the industry. The supplied muffler is very quiet,
and the ability to rotate the exhaust to suit
the installation is a big plus. It can be hand-started
but this was not the easiest thing to do, so I
relied mainly on my electric starter.
During bench testing I ran about half a gallon
of fuel through the engine, and have consumed
a similar amount in flight testing. A ringed engine
such as the GS40 will require a longer break-in
than a non-ringed (e.g., ABC) engine in most cases.
This engine shows good performance and will most
likely continue to show performance increases
over the next few gallons of fuel as the break-in
process continues. The quality and good running
of the Tigre lives on!
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This
article appears courtesy of Fly RC.
Fly
RC Magazine is published by Maplegate Media.
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The comments, observations and conclusions made in this review are solely with respect to the particular item the editor reviewed and may not apply generally to similar products by the manufacturer. We cannot be responsible for any manufacturer defects in workmanship or other deficiencies in products like the one featured in the review. |
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