FUEL

דלק
יחסי חומרים בדלק 2 פעימות
Mixing 2-stroke Nitromethane Fuel
Formula for 2-Stroke, Non-FSR engines, makes one gallon (128 ounces)
כמות ל1 גלון

All measurements by volume:
10% Nitromethane (12.8 oz)-ניתרומטאן
12% Synthetic Oil (15 oz)-שמן סינטטי
4% Castor Oil (5 oz)-שמן קיק
Balance Methanol (95 oz) -מתנול(כהל מתילי)

For high performance engines, increase Nitromethane accordingly. For use in very hot temperatures, use a combination of 8% Synthetic and 8% Castor oils for better lubrication. While this formula is used successfully by our local flyers, use at your own risk. Your mileage may vary.
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Fuel

Specific Gravity

Air/Fuel ratio
for maximum power

Heat Energy (Btu/lb)

Latent heat of evaporation (Btu/lb)

Max C/R
(conservative)

Use

  
Acetone .791 9.5 - 10.5:1 12500 225
(23.7)		 17:1
(approx)		 ACETONE has all the basic requirements as a fuel being midway between petrol and methanol with an anti-knock rating approaching methanol. As an additive to methanol it reduces pre-ignition sensitivity and promotes easier starting under low temperature conditions (up to 10% for these purposes).
In small percentages (about 3%) it also reduces methanol's hygroscopic properties. 		1316
(.60)
Benzole .879 11 - 11.5:1 17300 169
(15.4)		 15:1 BENZOLE is often blended with methanol to give a greater energy per unit volume with reduction in the latent heat of vapourisation, this being a compromise to gain increased range (lower fuel consumption). 1573
(.71)
Ethanol .796 6.5 - 7.5:1 12500 410
(63.1)		 ? ? 1923
(.87)
Ether .714 9.8:1 15000 153
(15.6)		 1:1 ETHER has a very low knock rating but this makes it an essential ingredient for model diesel fuels. In other fuels its volatile nature and low flash point make it useful as an additive (up to 5%) to improve starting and give a rapid throttle response. 1531
(.69)
Methanol .796 4.5 - 6.5:1 9970 472
(104.9)		 17:1 METHANOL permits the use of very high compression ratios when unsupercharged or high boost pressures when supercharged. The large cooling effect increases volumetric efficiency and is of particular use in supercharged engines reducing charge temperatures after compression. A tendency to pre- ignition is most noticeable at weak mixture levels. 2216
(1)
Nitro Methane 1.13 .5 - 2.5:1
(can be even richer)		 5000 258
(516)

(103.2 at leanest mixture)

 6.5:1
(10:1 with rich mixture)		 NITRO enables considerable power increases to be obtained (70% minimum with proper use). Most often blended with methanol, in various proportions, to provide power increases consistent with engine strength etc.
A tendency to detonation is reduced by an increase in mixture strength, reduction in engine temperature or reduction in compression ratio.		 10000
(4.51)

at the leanest ratio
2000
(.9)
Petrol .743 12.5 - 13.5:1 19000 135
(10.8)		 10:1 PETROL is sometimes added to methanol in moderate proportions for increased economy (as with Benzol).
However, like Benzol, it should be understood that the fuel will not have as great a cooling effect and also, because of the reduced fuel flow, less oil will pass through the engine so consideration should be given to increasing the percentage of oil in the fuel.		 1520
(.69)
Propylene Oxide .83 9.6:1 14000 220
(22.9)		 ? PROPYLENE is used as an ignition accelerator particularly with nitro (up to 20% by volume with pure nitro) where noticeable increases in power are possible. Also promotes easier starting and smoother running when blended with methanol (up to 5%). 1458
(.66)

FUEL RATINGS
by Brian Hampton

To determine a fuel's rating, two things must be taken into consideration.
The first is heat content (Btu's/lb). The higher the figure the more heat will be produced by combustion to produce power. With just this consideration it would appear that Methanol (near enough 10000 Btu/lb) is twice as good a fuel as Nitro (5000).

However, we know this can't be right.

Now look at their respective Air/Fuel ratios. Methanol, at its richest figure, is 4.5:1 whereas Nitro is .5:1. This indicates that 9 times as much mass of Nitro is needed for the correct A/F ratio than Methanol. So, theoretically, Nitro could provide 4.5 times as much power as Methanol at the expense of horrific fuel consumption. This is why the needle valve must be opened more as Nitro content increases and also why the needle is less sensitive.

In the column headed "Fuel Rating" I have divided each fuel's Btu content by its richest A/F ratio to get a comparative figure. This shows that (other than Nitro) Methanol is the best fuel.

With this in mind I have rated Methanol as 1 and then compared all other fuels to get the figure in brackets which gives a clearer indication of how each fuel rates against Methanol.

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Flash Point
(deg C)		 Boiling Point
(deg C)		 Freezing Point
(deg C)		 Specific Gravity General Description
16 64 -97 .796 Methanol (Methyl Alcohol) CH3OH
is a volatile, highly flammable, water-clear liquid with a mildly spirituous odour.
Miscible with water or nitro methane in all proportions and almost all with petrol.
43 101 -29 1.13 Nitro Methane CH3NO2
is a highly flammable water-clear liquid with a mild odour, containing approximately 53% by weight of oxygen.
Water will mix with nitro to the extent of only 2.5% by volume.
-18 56 -94 .791 Acetone (Dimethyl Ketone) CH3COCH3
is a highly volatile, highly flammable, water-clear liquid with a strong, sharp, characteristic odour.
Miscible with all the chemicals listed here and water.
-40 35 -116 .714 Ether (Diethyl Ether) C2H5OC2H5
is an extremely volatile, highly flammable, water-clear liquid with a strong, lingering characteristic odour.
Miscible with all the chemicals listed here but not with water.
-11 80 5 .879 Benzole (Benzene) C6H6
is a flammable, water-clear liquid with a dull, sweet odour.
Miscible in most proportions with all the chemicals listed here but not with water.
88 211 5 1.2 Nitro Benzene C6H5NO2
is a flammable, yellow, oily liquid with a strong odour of almonds.
Miscible in most proportions with all the chemicals listed here but not with water.
0 34 -104 .83 Propylene Oxide (1:2, Epoxypropane) CH3-CH- CH2
is an extremely volatile, very reactive, highly flammable, water-clear liquid with a light gaseous odour.
Miscible with all the chemicals listed here but only partially with water.

FUEL COOLING ABILITY
by Brian Hampton

The number in the column titled "Latent Heat of Evaporation" indicates the fuel's ability to absorb heat from both the air and from the engine as it vapourises. The higher the number the more effective it is.

A quick glance down the column seems to show that Methanol is the best at internally cooling an engine. But, as with Fuel Ratings, there is more to it than meets the eye. We have to take into account the Air/Fuel ratio to get the full picture.

To have a true indication we must divide the Btu/lb figure by the A/F ratio. For instance, with Methanol having a Latent Heat of Evaporation of 472 Btu/lb and an A/F ratio of 4.5 this gives a figure of 104.9 (the number in brackets in the Fuel Characteristics chart).

Using the figures for petrol we get 10.8 which shows that Methanol (104.9) is almost 10 times more efficient at removing heat. For this reason a petrol fuelled engine is much more reliant on cylinder and head fins to radiate heat, a point of concern when converting a glow engine to spark ignition.

Now consider the figures for Nitro Methane. Even at the leanest A/F ratio it is almost as good as Methanol (103.2) but at its richest setting it has 5 times the cooling effect of Methanol (516). This helps explain why an engine using nitro can not only develop more power but may also run a little cooler.

 
 
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