MVVS 26 IFS User Manual
Page 2
11)
Small objects must be kept at a safe distance from the engine when it is running. Never throw any
objects towards the spinning propeller.
12)
Be careful in choosing the location where you wish to start the engine. Avoid dusty or sandy areas.
13)
Start the engine in well-ventilated areas only. Never start the engine indoors.
14)
When starting the engine make sure that bystanders, especially children, are at a safe distance of at
least 10 meters.
15)
The engine power output makes it possible to fly big models. Mal-operation of such models may
cause serious damage. Start using the MVVS 26 in model planes only after you have mastered
operating smaller models.
16)
Periodically check that the engine is firmly fixed to the engine mounts. Never start a loose engine!
17)
Always use a balanced propeller! Always replace the propeller when damaged!
18)
Make sure that no part of your body intersects the plane of the spinning propeller.
19)
Always wear close-fitting, well-fastened clothes when starting or operating the running engine.
Never wear loosely hanging clothes (ties, scarf, etc.).
20)
Never try to stop the engine by any part of your body.
21)
Always stop the engine either by turning off the ignition switch or by completely closing the
carburetor throttle valve.
Selecting a suitable propeller
It is usually the case that propellers of the same dimensions coming from different manufacturers are not
the same. Oftentimes not even propellers of the same dimensions produced by a same manufacturer are
not the same. The engine power is best utilized when the propeller dynamics curve and engine power
curve (revolutions / power output) intersect in the area of the engine top power output. Unfortunately, no
propeller manufacturer provides this information. Engine power output is also a variable quality. It
depends above all on the silencer used and can considerably vary. The situation is further complicated by
environmental parameters (temperature and atmospheric pressure in particular): low temperature and high
pressure increase propellers’ input requirements by 20% in comparison with input at hot weather.
MVVS 26 has been designed to generate maximum power at 8500 RpM, according to the type of exhaust
used. If you wish to utilize the maximum power output, choose a propeller which allows the engine to
reach these revolutions, or slightly lower revolutions (given the unloading of the propeller depending on
the speed of flight) on the ground.
We do not recommend using propellers with which the engine reaches more than 9000 RpM. on the
ground.
Suggested propeller dimensions: 16x8, 16x10, 16x11, 16x12, 17x8, 17x10, 17x 12, 18x8
Fuel
Always use unleaded 95-octane petrol mixed in the proportion 40 volume units of petrol to 1 unit of
Mobil Racing 2T oil. If necessary, quality brand-name synthetic oil intended for racing two-stroke
engines can be used too. Mix it in the proportion 30:1.
Never use inexpensive oil developed for garden appliances or synthetic oils intended for the operation of
methanol model engines. The manufacturer declines all responsibility for all engine damages arising from
the use of low-quality fuel.
Store fuel in containers designed for this purpose. Do not use mixed fuel older than 90 days.
Assembly
Since air is used to cool the engine, sufficient air circulation under the cowl must be ensured. Never
forget about a hot air outlet – which must be bigger than the intake. Gas engines heat up to a much greater
degree than methanol ones!
Do not forget that the engine needs oxygen from the air to be able to operate. Therefore ensure access of
air to the engine intake as well. Caution: intake of warm air from beneath the cowl may cut the engine
power output.
Caution! When mounting the engine in the model use seals to protect all openings and prevent the
pollution of the engine’s inside with sawdust, residual abrasives etc.
Exhaust
Use only factory-made exhausts pipes designed for this type of engine, preferably brand-name MVVS
engines with which you also get the power output guaranteed.
The manufacturer declines all responsibility for all engine damages arising from the use of improper
exhaust systems.
When mounting the exhaust follow the manufacturer’s instructions. Make sure to secure sufficient
cooling of the exhaust.
3270
compact, medium level of power output
3266
tuned pipe, with adaptor 3265 provides the highest power output, with the flat torque curve,
useful for the model planes
3266
3270 3265
Carburetor adjustment
Basic setting:
adjusting needle ( L ) for low RpM range 1 turn and 50 minutes
adjusting needle ( H ) for high RpM range 1 turn and 35 minutes
for WT 793
(Minutes refer to hands of a clock)
Walbro WT 793
The new engine comes adjusted to the basic setting.
After the engine has been run in, adjust it following the instructions below:
- start the engine and warm it up
- let the engine run at idle speed for approx. 5 seconds
Step I
Accelerate to 2/3 of the throttle range within approx. 1 sec (faster acceleration). Repeat three
times – if the engine accelerates quickly and without a hiccup go to Step III. If acceleration is not smooth
go on to Step II.
Choke
H needle adjusting screw
L needle adjusting screw
Lever - throttle
Pressure pulse inlet