Dom, I think there is a need to post this information for the
many 2 strokers around.
I personally use MOTUL800 2T and strongly recommends MOTUL600($17)
and MOTUL800($22-$25)
Premix ratio calculations (w/o aid of 2T pump)
[Road Use]
Ratio -> 1(2T):50(Fuel)
eg.
10 liters of NEW PETROL is pumped into the tank. (take note that
always top up the premix 2T with the newly added petrol. Previously
treated petrol should not be taken into considerations) Therefore
since...
10litres of fuel = 50units
X litres of 2T = 1unit
10 litres / 50 = 0.2 litres
Therefore 1 unit is 0.2litres. Hence 0.2 litres of premix 2T
MOTUL800 is to be poured into the fuel tank.
For your convenience, the simplified formulae is as follows for
NORMAL MIXING INTO NEW PETROL WHICH IS SAME RATIO AS IN OLD
PETROL
a = petrol quantity (in SI unit as litres)
x = amt of 2T to be added to premix
0.02 = 1/50 = the ROAD ratio
0.0303 = 1/33 = the TRACK ratio
a*0.02 = x
or
a*0.0303 = x
However on special circumstances. ZZZ went decided to attend track.
And he has been using 1:50 premix ratio when he was on the road. So
he will need to re-premix the ratio again so as to attain the
required track ratio which is 1:33 for MOTUL800.
ZZZ is riding a RS250 (full tank 16litres) He read from the pump
meter that he just pumped in 6litres of newly untreated
petrol.
1/33 = 0.0303 (because track ratio = 1:33)
0.0303-0.02 = 0.0103
ZZZ still lacks 0.0103 of premix 2T for his previously road ratio
treated 10 litres of petrol. (10 litres because 16litres full tank
- 6 litres of new petrol = 10 litres left)
therefore... 0.0103*10 = 0.103liters of 2T
Hence an extra 0.103litres of 2T is required to top up for the road
treated 2T.
New petrol to be treated with track ratio
0.0303*6 = 0.1818 litres of 2T
combining the 2 quantities...
0.1818+0.103 = 0.2848litres
Therefore after pumping in the new 6 litres of petrol, ZZZ needs to
pour in 0.2848 litres of new 2T to let his whole fuel tank of fuel
to be filled with 1:33 ratio worth of petrol.
Simplified formulae FOR TRACK RATIO TO BE MIXED INTO OLD PETROL
RUNNING ON ROAD RATIO...
a = amt of fuel already in tank.
b = new quantity of petrol.
0.303 = track ratio
0.0103 = track ratio - road ratio
0.303*b + 0.0103*a = new 2T amt to be pumped in before going to
track.
ZZZ left the track and went to the petrol kiosk to refill his fuel
and realised that he pumped in 7litres of petrol. (Therefore he has
9litres worth of track treated petrol originally) He wants to
change back the ratio of the fuel into road ratio.
0.0303 - 0.02 = 0.0103
0.0103 * 9 litres of petrol = 0.0927 litres of excess 2T
0.02*7 = 0.14litres of 2T to be treated into the new petrol.
However, due to the previously treated track ratio fuel, the excess
2T must be deducted in order to acheive the 1:50 road ratio.
Therefore...
0.14 - 0.0927 = 0.0473 litres of 2T needs to be topped up
only.
Simplified Formulae for ROAD RATIO TO BE MIXED INTO OLD PETROL
RUNNING ON TRACK RATIO...
a = originally inside the fuel tank's petrol amount.
b = amt of new petrol
(0.02*b) - (0.0103*a) = amt of 2T to be poured in.
-> pAISEH... very long. But should be helpful to those who're
potential premix users.
An accurate amt of premixing ratio is required because under mixing
will lead to rapid piston seizure. Over mixing will cause a lot of
white smoke. And as the unburnt 2T staines itself on the combustion
cylinder wall, it will in turn cause piston seizure as well when
the stain becomes too thick.
