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Fuel Characteristics.
The technical side
Extracted from "Performance Tuning in Theory & Practice; Two Strokes
by Graham Bell"
And Brian Hampton
(I hope I quote correctly, as these tables are widely in use)
To have a true indication for Latent Heat of Evaporation, we must divide the
Btu/lb figure by the A/F ratio. (the number in brackets in the Fuel
Characteristics chart).
In Fuel Rating, each fuel's Btu content is divided by its richest A/F ratio to
get a comparative figure
| Fuel |
Specific Gravity |
Air/Fuel ratio
for maximum power |
Heat Energy (Btu/lb) |
Latent heat of evaporation (Btu/lb) |
Max C/R
(conservative) |
Use |
Fuel Rating
(methanol
=1) |
| 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) |
Description of the liquids
Flash Point
(deg C) |
Boiling Point
(deg C) |
Freezing Point
(deg C) |
Specific Gravity |
General Description |
|
| 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. |
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