This technical report summarizes modifications needed in a gasoline engine to enable it to run on ethanol fuel. It discusses changing the main jet, idle orifice, power valve, accelerator pump, compression ratio, cold weather starting, and thermostat. The report was submitted by Sughosh D. Deshmukh to his professor M. P. Joshi at Shri Ramdeobaba College of Engineering and Management in Nagpur, India to fulfill requirements for a mechanical engineering course.

1. SHRI RAMDEOBABA COLLEGE OF ENGINEERING AND
MANAGEMENT, KATOL ROAD, NAGPUR, INDIA -440013
Department of Mechanical Engineering
2012-2013
Technical Seminar Report
On
“MODIFICATIONS IN GASOLINE ENGINES FOR USE OF
ETHANOL FUEL”
Submitted by
Sughosh D. Deshmukh
Under the guidance of
Prof. M. P. Joshi
1

2. SHRI RAMDEOBABA COLLEGE OF ENGINEERING
AND MANAGEMENT, NAGPUR, INDIA-440013
Department of Mechanical Engineering
CERTIFICATE
This is to certify that Sughosh D. Deshmukh has completed the technical
seminar work on “Modifications in gasoline engines for use of
ethanol fuel” in partial fulfilment of the requirements of fifth semester B.E. in
Mechanical Engineering as prescribed by Rashtrasant Tukdoji Maharaj Nagpur
University at S.R.C.E.M., Nagpur.
Prof. M. P. Joshi Prof. M. M. Gupta
Seminar Guide H.O.D.
Mechanical Engineering Department Mechanical Engineering Department
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3. Acknowledgement
I am thankful to my guide Prof. M. P. Joshi whose personal enrolment in
the technical seminar presentation and report has been a major source of
inspiration for me to be flexible in my approach and thinking for tackling
various issues. He assumes the critical role of ensuring that I am always on the
right track.
I also extend my gratitude to Prof. M. M. Gupta (H.O.D, Mechanical
Dept.) without whose support, co-operation and guidance this paper
presentation would not have been a success.
Last but not the least we would like to say a big thanks to all the staff and
assistants of mechanical department.
Prof. M. P. Joshi Prof. M. M. Gupta
Seminar Guide H.O.D.
3

4. Abstract
The prices of fuels are rising to new heights day after day. Driving for
pleasure has been a thing of past. The need for using some alternatives for
gasoline or diesel fuel is the need of the hour.
Some alternative fuels like CNG, LPG, LNG, Hydrogen gas, Alcohols,
biodiesel etc are thought of after petrol and diesel. One such alternative fuel that
can be used in place of petrol especially is ethanol fuel.
Due to differences in the properties of ethanol fuel and gasoline fuel, the
engine designed for gasoline fuel cannot be used for ethanol fuel directly. There
are some modifications that are needed in the engine for use of ethanol fuel.
This report tries to explain some such modifications which are necessary
in gasoline engine for the use of ethanol fuel.
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5. Index
1. Introduction to ethanol and properties----------------------------------7
2. Comparison between different fuels ------------------------------------8
3. Modifications --------------------------------------------------------------9
3.1. Mainjet changes-------------------------------------------------------10
3.2. Idle orifice changes---------------------------------------------------11
3.3. Power valve changes-------------------------------------------------12
3.4. Accelerator pump changes-------------------------------------------13
3.5. Compression ratio changes------------------------------------------14
3.6. Cold weather starting-------------------------------------------------16
3.7. Thermostat changes---------------------------------------------------17
4. Initial use of alcohol fuel-------------------------------------------------18
5. Fuel injection systems-----------------------------------------------------19
6. Benefits of using ethanol fuel--------------------------------------------20
7. Disadvantages of ethanol fuel--------------------------------------------21
8. Common ethanol fuel mixtures------------------------------------------22
9. Conclusion-----------------------------------------------------------------23
10. References------------------------------------------------------------------24
5

6. List of figures and tables
Fig. 1: Main jet orifice
Fig. 2: Idle orifice jet
Fig. 3: Power valve
Fig. 4: Accelerator pump jets
Fig. 5: High compression piston
Fig. 6: Milled piston
Fig. 7: A turbocharger
Fig. 8: air pre heater schematic
Fig. 9: ethanol percentages.
Table 1: comparison between calorific value of different fuels.
Table 2: modification in parts
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7. Introduction to ethanol
Ethanol is the systematic name defined by the IUPAC nomenclature of
organic chemistry for a molecule with two carbon atoms (prefix "eth-"), having
a single bond between them (suffix "-ane"), and an attached -OH group (suffix
"-ol"). It is a volatile, flammable, and colourless liquid. Best known use
of ethanol is found in alcoholic beverages, it is also used in thermometers, as
a solvent, and as a fuel. In common usage, it is often referred to simply
as alcohol or spirits. The molar mass of ethanol is 46.07 g/mol. The density of
ethanol is 0.785 g/cm3. Heat of vaporization is 840 kJ/kg.
Ethanol has a boiling point of 78.37 oC and melting point of -114 oC The
vapour pressure at 20 oC is 5.95 KPa. Viscosity of the compound at 20 oC is
0.0012 Pa-s.
Ethanol is a versatile solvent, miscible with water and with many organic
solvents,including aceticacid, acetone, benzene, carbontetrachloride, chloroform
, ethylene glycol, glycerol, nitro methane, and toluene. It is also miscible with
light aliphatic hydrocarbons, such as pentane and hexane, and with aliphatic
chlorides such as trichloroethane and tetrachloroethylene.
Ethanol's miscibility with water contrasts with the immiscibility of
longer-chain alcohols (five or more carbon atoms), whose water miscibility
decreases sharply as the number of carbons increases.
Ethanol-water mixtures have less volume than the sum of their individual
components at the given fractions.
Ethanol has a high self ignition temperature of around 326 oC, as
compared to petrol (240-280 oC) or diesel (210 oC).
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8. Comparison between different fuels
The following table gives the properties of various compounds, which
can be used as fuels.
Research
Fuel type MJ/L MJ/kg octane
number
Dry wood (20% moisture) - ~19.5 -
Methanol 17.9 19.9 108.7
Ethanol 21.2 26.8 108.6
E85 25.2 33.2 105
(85% ethanol, 15%
gasoline)
Liquefied natural gas 25.3 ~55 -
Autogas (LPG) 26.8 50 -
(60% propane +
40% butane)
Aviation gasoline 33.5 46.8 100/130 (lean/rich)
(high-octane gasoline, not
jet fuel)
Gasohol 33.7 47.1 93/94
(90% gasoline + 10%
ethanol)
Regular gasoline/petrol 34.8 44.4 min. 91
Premium gasoline/petrol max. 104
Diesel 38.6 45.4 25
Charcoal, extruded 50 23 -
Table 1: Comparison between calorific value of different fuels.
Octane rating is the measure of performance of motor or aviation fuel.
8

9. Modifications
Required for converting gasoline engines for use of ethanol fuel
The engine which is designed for the use of gasoline fuel cannot be used
with ethanol fuel. Ethanol has higher octane rating than petrol. Hence
compression ratio to be achieved while using ethanol is more than that while
using petrol. Also, the calorific value of ethanol is less than petrol; hence more
fuel is needed to be burnt to obtain a certain amount of energy, as compared to
petrol. Ethanol is a cleansing agent. When used in engine, it cleans the dirt and
filth is formed in the engine. This may damage some parts of the engine and
make them useless.
Taking into account all these properties of ethanol, certain modifications
are required in the engine. The modifications vary depending on the maker of
the engine, technologies used, percentage of ethanol to be used as fuel, etc.
Major areas where modifications are necessary are as follows.
9

10. Main jet modifications
The first thing to be altered is the main metering jet in the carburettor. In
most carburettors, this is a threaded brass plug with a specific-sized hole drilled
through the centre of it. This hole is called the main jet orifice, and its diameter
dictates how rich or lean the air/fuel mixture will be when the car is travelling at
cruising speeds. Naturally, the smaller the hole is, the less fuel will blend with
the air and the leaner the mixture will be. As the orifice is enlarged, the mixture
gets richer.
Since alcohol requires a richer air/fuel ratio, it's necessary to bore out the
main jet orifice when using ethanol fuel. In order to operate the engine
successfully on alcohol fuel, it's necessary to enlarge this opening from 20 to
40%.
There are some carburettors that do not use fixed-size jets alone, but also
utilize device known as a "metering rod". This is usually a thin, tapered or
stepped rod that's suspended within the jet orifice, which may or may not be
removable. The fuel, in this case is drawn through the space between the rod
and its housing. Depending on how far the throttle is opened, the metering rod is
lifted out of the hole. Since the rod is thick at its "base" (near the top), and
progressively thinner at its tip (toward the bottom) - the farther it's drawn out of
the hole, the more fuel is allowed to flow between the central rod and the
opening.
The conversion on this type of metering system is basically the same as
the fixed-jet conversion. To enlarge the orifice, either remove the metering rod
and very carefully drill the jet or turn the brass rod slightly. The diameter, if
increased in size, should be increased anywhere from 15 to 35%.
Fig. 1: Main jet orifice
10

11. Idle orifice changes
Most carburettors will require additional idle circuit enlargement in order
for the engine to run at slowest or idle speeds. This is because the circuit which
is fed by the main jet operates fully only when the throttle plate within the
throat of the carburettor is opened past the idle position. When the plate is in the
idle position, the air/fuel mixture is allowed to enter the manifold only through
the idle orifice. If this orifice isn't large enough, it will not provide the needed
amount of air/fuel blend to keep the engine running.
In some engines, it may only be needed to loosen the idle mixture screw
at the base of the carburettor in order to provide the correct amount of fuel. In
some engines, it is possible that the seat itself, into which the tapered screw
extends, must be enlarged in order to accomplish the same thing.
In most cases, if the seat has to be bored out, it can be enlarged up to
50%. This will allow a full range of adjustment with the idle mixture screw,
even if one wants to go back to gasoline fuel.
As a precaution against the idle screw's vibrating loose from its threaded
opening, the idle mixture screw spring can be coupled with a couple of small
lock washers. This will prevent the screw from turning even if it's drawn out
farther from the seat than it normally would be.
Fig. 2: Idle orifice jet
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12. Power valve changes
Most modern auto carburettors have a valve, known as a power valve that
allows extra fuel to blend with the air/fuel mixture when the accelerator is
depressed, in order to enrich the mixture under load conditions. This is a
vacuum-controlled valve, is spring loaded, and shuts off when it isn't needed in
order to conserve fuel.
The power valve used in some of the carburettors is somewhat difficult to
alter and, besides, is sufficient for alcohol use in its normal configuration if it's
working properly. However, there are some carburettors that have easily
replaceable power valves which are available in various sizes. If a power valve
with a 25% increased dimension or so is used, the air/alcohol mixture will be
sufficiently enriched to give engine needs more power when needed.
Fig. 3: Power valve
12

13. Accelerator pump changes
In addition to a power valve, almost all automotive carburettors utilize an
accelerator pump. This is a mechanically activated plunger or diaphragm that
injects a stream of raw fuel directly down the throat of the carburettor when the
accelerator is suddenly depressed.
The reason the accelerator pump is incorporated into modern carburettors
is that as the accelerator is pressed and more air/fuel mixture is drawn into the
cylinders, some of the liquid particles in the blend tend to stick to the walls of
the intake manifold, effectively leaning out the mixture by the time it reaches
the combustion chambers. The extra squirt of fuel that is added by the
accelerator pump makes up for this initial lean condition.
In order to adapt the accelerator pump to use alcohol effectively, the size
of the injection orifice needs to be increased. (anywhere from 10 to 25% is
fine.)
As an alternative to enlarging the hole, simple adjustment of the stroke
length of the pump arm in order to feed more fuel is sufficient. Most
carburettors installed on recent engines already have a provision for seasonal
adjustment, so it's just a matter of putting the pump on its richest setting. Other
carburettors, too, have threaded rods that can be adjusted to accomplish the
same thing.
Fig. 4: Accelerator pump jets
13

14. Compression ratio changes
The ratio is calculated by the following formula:
Where,
b= cylinder bore (diameter)
s= piston stroke length
Vc= clearance volume.
CR is the ratio cylinder volume when piston is at BDC to the cylinder
volume when piston is at TDC.
This modification will do a great deal to improve engine performance and
economy. The compression ratio hike will take advantage of the potential that
ethanol has to offer as a fuel. Optimally, the ratio can be increased to 14- or 15-
to-1. But even a nominal increase to 12-to-1 will result in a vast improvement
over the standard 8- or 8.5-to-1 that most manufacturers incorporate into their
engines today.
The most inexpensive way to increase the compression ratio is to install a
set of high compression pistons. The forged units are designed to pack the
air/fuel charge tightly into the combustion chamber for increased power, and
have special relief notches built into their heads for valve clearance. However,
some engines may not tolerate a 15-to-1 compression ratio with standard
connecting rods and bearings. These components, too, may have to be replaced
with high-strength competition grade parts.
Another way of increasing compression ratio slightly is by "milling'' the
surfaces of the cylinder head and/or block.
A third - and perhaps the most versatile - way of effectively increasing
the compression ratio is by installing a turbocharger. These units, although
range high in price, provide a pressure boost in the combustion chamber
14

15. proportional to the engine's RPM. Hence, compression would not be excessive
during engine start-up as it would be with the other methods.
No problem is encountered with a severe compression ratio increase,
unless switching back to gasoline fuel. To switch back to gasoline, installing a
water injection cooling system that would allow operating the car even on
regular fuel without fear of detonation would be helpful.
Fig. 5: High compression piston Fig. 6: Milled piston Fig. 7: A turbocharger
15

16. Cold weather starting
Since alcohol doesn't vaporize as easily as does gasoline, cold weather
starting can be a problem, especially if the engine itself is cold. To alleviate this
undesirable situation, a combination cold start/dual-fuel system can be used,
which can work with any engine.
The various other remedies to overcome this problem are as follows:
Fuel preheating
In extremely cold climates, it may be necessary to preheat the alcohol
fuel before it enters the carburettor. This can be accomplished easily by
installing a fuel heater.
This can be achieved by passing the fuel through a tube, which passes
over the engine radiator. The hot engine parts will heat the fuel sufficiently. But,
this is not a very effective method, as while starting the cold engine, passing the
fuel over the radiator makes no effect. The engine should be started by some
alternative ways.
Air preheating
Most trucks and autos have air filter housings which are designed to
allow heated air from around the exhaust manifold to channel through a duct
and enter the carburettor when the engine first starts from a cold state. As the
engine warms up, a flap within the air cleaner "snorkel" shuts off this supply of
warm air and allows ambient air from the engine compartment to enter instead.
This flap is usually either thermostatically or vacuum controlled.
External resistance type air pre heaters may also be used for this purpose.
Fig. 8: air pre heater schematic
16

17. Thermostat changes
In order to get maximum efficiency from your engine, the thermostat
within the engine block may need to be changed. A thermostat is designed to
hold the coolant within the cylinder head till it achieves the desired temperature.
Depending on the engine's operating conditions, the thermostat may cycle open
and shut regularly over the span of a few minutes.
The thermostat decides the temperature at which the coolant will enter the
head. As the working temperature of an ethanol fuel engine is less than that of a
petrol engine, the thermostat may need to be changed.
17

18. Initial use of alcohol fuel
An engine altered as per the above modifications will run well on alcohol.
But the alcohol will act as a cleansing agent. And will not only clean out the
tank, fuel lines, and filters, but will also purge engine's internal parts of built-up
carbon, gum, and varnish deposits.
In effect, suddenly a lot of filth will be floating around in fuel. And it
may be enough to clog the fuel filter to the point of not allowing any fuel to
pass. Loosened internal engine deposits can foul the spark plugs badly.
In addition to the fact that alcohol is a cleaning agent, it is also a solvent.
And this means that certain types of plastics used in the fuel system of the
engine may be attacked by it.
In engines that use plastic components, however, there are several areas
of potential deterioration: 1. within the fuel tank, both the float and the strainer
on the fuel intake tube may be plastic. 2. The fuel lines themselves if they are
the clear, flexible type, may also soften. 3. The fuel pump diaphragm may also
be subject to failure. 4. Plastic in-line fuel filters should be replaced with metal
ones. 5. Many modern carburettors use plastic float needles, seals, and floats.
Of course, not all plastics are subject to corrosion, and neither are all
types of rubber. Generally, butyl rubber (like the type used in inner tubes)
should be avoided.
18

19. Fuel injection systems
Since some vehicles are equipped with fuel injection rather than
carburettors, we will briefly touch on the use of alcohol with that system. There
are two important factors in a fuel injection setup: injection timing and control
jet diameter. Fortunately, since many systems now use an electronically
controlled timing sequence, injection timing is not critical in a fuel injected
engine. Neither performance nor economy can be improved substantially by
either advancing or retarding the injection timing process.
Control jet diameter, on the other hand, is an important factor. If the size
of the control jets (which are the equivalent of the metering jets in a carburettor)
is increased, the engine will operate well on alcohol fuel. An increase of 15-
20% is all that's necessary to accomplish the conversion.
An interesting feature of the fuel injection system is that it doesn't require
any gasoline during the cold weather starting process to fire the engine up.
Since the fuel is injected at a pressure of about 250 PSI, the alcohol fuel is
sufficiently vaporized to ignite easily within the combustion chamber.
19

20. Benefits of using ethanol fuel
1. Ethanol is obtained from a number of sources, both natural and
manufactured.
2. It is a high octane fuel with octane number over 100. Engines using high
octane fuels can run more efficiently by using higher compression ratios.
3. It produces less overall emissions compared to gasoline.
4. When ethanol is burned, it forms more moles of exhaust gasses, which
gives higher pressure and more power in expansion stroke.
5. It has high latent heat of vaporization which results in a cooler intake
process. This raises the volumetric efficiency of the engine and reduces
the work input in the compression stroke.
6. Alcohols have low sulphur content and hence help in reducing emissions
and pollutions.
7. Ethanol can be made naturally from crops like sugarcane or by
fermentation of food grains. (It can be made even at home!)
20

21. Disadvantages of ethanol fuel
1. Ethanol has low energy content.
2. More ethanol fuel needs to be burned to obtain same energy as obtained
by petrol.
3. Ethanol has poor ignition characteristics.
4. Ethanol has almost invisible flames, which are dangerous while handling
the fuel.
5. Odour of ethanol is very offensive.
21

22. Common ethanol fuel mixtures
Various types of ethanol fuel mixtures can be used. Ethanol mixtures
usually range from E5 to E100. The numerical representing the percentage of
ethanol in the mix. Commercially available mixtures E85 and E100 need
modifications in the engine, while other mixtures can be used without any
modifications.
Fig. 9: ethanol percentages.
22

23. Conclusion
For use of ethanol in engine, with alcohol percentage above 85%, some
modifications are required. The modifications can be summarised as in the
following table.
Exhaust system
Intake manifold
Ignition system
Fuel pr. Device
Cold start syst.
Ethanol blend
Fuel injection
Carburetor
Fuel pump
Fuel filter
Motor oil
Fuel tank
<=
5% NO NO NO NO NO NO NO NO NO NO NO
E5-
E10 YES NO NO NO NO NO NO NO NO NO NO
E10-
E25 YES YES YES YES YES YES NO NO NO NO NO
E25-
E85 YES YES YES YES YES YES YES YES YES YES NO
E85-
E100 YES YES YES YES YES YES YES YES YES YES YES
Table 2: modification in parts
23

24. References
 Internal Combustion engines- V Ganesan, 4th edition TMH publications.
 "Sustainable bio-fuels: prospects and challenges” Joseph (2007) in The Royal
Society (2008).
 Hydrous ethanol vs. gasoline-ethanol blend: Engine performance and
emissions- Rodrigo C. Costa, José R. Sodré Pontifical Catholic University of Minas
Gerais, Department of Mechanical Engineering, MG, Brazil.
 en.wikipedia.org/wiki/Ethanol
 running_on_alcohol.tripod.com
 Image source: Google.
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