Do not use a tank that is too big if you plan to use muffler pressure because there will be a significant difference between mixture values at the beginning and end of the tank. The sizes below are about right and provide a fair bit of reserve. Somewhat smaller sizes can also be used if you are careful by not running too rich and/or limiting flight times, and/or not flying continually with full throttle. The best tank sizes therefore depend somewhat on personal tastes.
- Saito 30, 40 6-8 oz
- Saito 50, 56 8-12 oz
- Saito 65, 72, 80, 82a, 91,100 14-18 oz
- Saito 120, 150 18-20 oz
- Saito 180 20 - 24oz
- Saito 220 24 - 30 oz
At full throttle the Saito-180 uses a little under 2 oz per minute of fuel. Assuming one needs about 15 minutes of running time per flight, a 24 oz tank provides plenty of reserve because the engine is probably
not normally operated continually at full throttle. However, most people don’t fly with continuous full throttle, so you can get by with a smaller tank say 18-20oz
Another factor is the needle setting. A richer mixture, will naturally use more fuel.
The Graupner tanks (sold by Hobby Lobby) are excellent but only available in larger sizes. However, in my opinion, the tubing and clunk hole diameter are a little too thin for the Saito-180
If you are paranoid about leaking tanks, you should consider coating the exterior stopper area with Goop. However don’t do this unless you are sure you will no
t need to ever disassemble the tank.
A Tank Tip:
Sometimes an engine will just not run right. In many cases the problem is the fuel system, viz tank, kinked fuel lines, clunk hole too small, junk in tank etc. To
determine if you have an engine problem or fuel tank problem try this. Get another tank that you know is good and temporarily tape it to the side of the fuselage just behind the engine with the
height of the carb level with the mid-level of the tank. Try using masking tape to attach the temporary tank. Now disconnect the old tank and connect up the temporary tank. Start the engine and
see if your problem goes away. The larger engines like the 150 and 180 are best with 1/8 ID fuel tubing; use a large diameter clunk hole and tubing on your test tank if you are checking a
150 or 180 engine.
(...so what do you say about that idea ? ...... “tanks a lot”)
TANK POSITION: Keep the center-line of the tank close to the level of the carb spray-bar (or a little
lower), and also keep it as close as possible to the rear of the engine. With a properly located tank the
engine will run fine with muffler pressure. If you use an appropriate fuel pump, or the Cline regulator, the tank position is not so important.
FUEL TUBING: “Normal” or “Standard” size fuel tubing has 3/32 inside diameter; it will work OK
for all Saito engines provided you have a conventional tank setup; ie the tank is just behind the engine.
However, if you are using a larger engine (150 size or bigger) with a long length of fuel tubing (eg the
tank back over the CG) make sure there is no restriction on fuel flow and I prefer “Large” size (1/8” ID)
tubing for those larger engines when using longer fuel lines. Also when using the larger engines make
sure the hole in the clunk is not too small (ie it should be about 1/8 ID), and if you use a fuel filler valve it
is better to use a large size one such as the large Dubro model. If you are using the Cline pressure pump system the tank pressure is quite large and the thin 3/32 ID tubing is adequate.
The symptom of insufficient fuel flow is evident at full throttle if you are unable to get a rich setting by
fully opening the needle valve. There might be a number of reasons for constrictions so don’t assume it is only the tubing.
Sullivan filters are very good. The larger one is well-suited for 120,150,180 engines.