The E20 Conundrum - A Technical Critique

 

A question boggling our minds in recent times is whether the E20 Petrol is harmful to our car and scooter engines. Whereas the mainstream media is surprisingly quiet and is merely repeating the press-briefings of the government or proceedings of some hurriedly called conferences of experts, it is the social media that is critical of a forced migration of nearly twenty-five crore engines to the 20% Ethanol-blend universally dispensed at petrol pumps. I felt there was a need to present a purely technical critique of the E20 movement, free from political rhetoric and perceived gains or losses. Here it is.

What is the immediate impact of E20 on us in entirety, not limited to our petrol vehicles.

1.  Lower Power from our engines:

Ethanol has far lower calorific value than pure petrol. That is because of the chemistry and can’t be dismissed by arguments.

Combustion energy of both fuels and the impact on E20 is given below:

Petrol                 43.0 MJ/Kg

Ethanol              26.8 MJ/Kg

E20                     39.6 MJ/Kg

Net Loss             7.9%

It is clear that there is a reduction of 7.9% in the combustion heat in the cylinders. A recent public statement of Anurag Saraogi, the ED of Biofuels Division of BPCL confirms that there is significant drop in mileage with Ethanol. Fortunately, modern car engines can partially compensate it with some automatic tweaking, such as injection timing, mixture control etc. but only to the extent of 2-3%. So, ideally speaking cars will suffer a loss of power of about 5-6%, though a controlled trial can establish the real figure. The same can’t be said of motorcycles, which are build with much less sophistication. And motorcycles and scooters are the mainstay of the masses. Users, of cars and scooters both, have reported upto 15% loss in mileage. That means that one has to use 15% extra fuel for travelling the same distance. That is a minimum 15% hit to your wallet. Besides, if one uses 15% extra of E20, of which 12% (80% of the mix) would be petrol, the saving on fossil fuel would be marginal at best.

2.  Impact on Rubber and Plastic Parts:

Ethanol is an organic solvent and attacks rubber gaskets, seals, and pipelines. This early decay of rubber parts may lead to leakages of fuel, lubricants, air and compressed gases from the cylinders. Replacing them with suitable plastics or alloys will overcome this problem even in older cars, but at significant cost and downtime. The problem with this decay is that once it sets in it will accelerate quickly.

3.  Corrosion of Metal Parts of the Engine:

Ethanol is soluble in, or dissolves in itself, both petrol and water. The hydroxyl group end of the Ethanol molecule mixes well with water and the ethyl group at the other end with petrol. While ethanol dissolves perfectly into petrol, introducing water changes the equation entirely. If an ethanol-petrol blend absorbs too much water, the ethanol's chemical affinity for the water will overpower its bond with the petrol.

There is some minuscule amount of water (permitted by law) even in pure petrol. That water is not miscible with petrol and settles down in the fuel tank. This water accumulates over time and is a cause of corrosion in the sheet metal of the fuel tank. But this corrosion was largely limited to the tank. If you run your car till the tank is nearly empty, some water from the bottom would be sucked by the fuel pump and circulated all around. Scooter and Motorcycle engines draw their fuel by gravity from the bottom of the fuel tank, which means that they are always drawing some water. They also run until their tanks are near empty (a matter of habit) further aggravating the problem.

Ethanol and water make a good solution. It is then circulated all around the engine. Some water would then settle down in the engine sump, where the lube oil lives, over time. This water in circulation causes severe corrosion of engine parts – liners, pistons, connecting-rods, crankshaft and camshaft, rocker arms and pins, gears and many more. This corrosion is devastating and will demand costly repairs.

Besides Ethanol itself is hygroscopic, meaning it naturally attracts and absorbs moisture from the surrounding environment. Because water and petrol do not mix, the heavier water-ethanol mixture will drop out of the petrol suspension and sink to the bottom of the fuel tank. This phase separation can severely damage an engine if the fuel pump draws from the watery layer at the bottom of the tank.

Solution

While the government has not yet conclusively clarified that controlled trials were conducted on petrol engines of cars and scooters, it is not relenting on E20 and pushing ahead with plans for higher blends. There is some loose talk of E20 compliant vehicles. Let’s examine the technical options.

a)  E20 Compliant Engines – Official claims of there being no damage to engines is amply countered by users in the social media. Engines are opened up and blackened engine parts, rubber components, sludge in the engine are shown as proofs of the extensive damage that E20 has done to their vehicles. Such extensive damage is not possible in a few months, or even a year or two, of usage and, in my opinion, many of those are simply result of poor maintenance. Loss of mileage, on the other hand, is a fact established by Chemistry and Thermodynamics.

Government’s claims that there is no damage to the engine yet asking that vehicles become E20 compliant are contradictory. Both can’t be true.

The quick route to E20 compliance is change of rubber and plastic parts to ethanol resistant designs. This would mean replacing all seals, gaskets, fuel-pipelines at significant cost. Repair and/or replacement will also be needed to fuel-pump, the fuel tank will need to be coated with polymer or special paints. There will, therefore, be many days of vehicle downtime.

b)  Engine Optimised for E20 – In the long run an IC engine can be optimised to not only overcome these problems but also exploit the benefits of Ethanol. Some of the modifications would be as under. They are so large and costly that only new vehicles will have them. Only a few are discussed here.

 (i)  ECU calibration

There will be need of a software upgrade since Ethanol burns differently. Modification will be required in:

    ·       Injection duration

    ·       Ignition timing

    ·       Cold-start enrichment

    ·        Knock detection

(ii)   Compression ratio (Optimization) – Engine Geometry

This is where the real gains will happen as offered by Ethanol.

Petrol engines typically have compression ratio of 10:1. This can easily go up to 12:1 or even 13:1 since Ethanol offers high Octane number chemically. This change in engine design alone will not only offset the loss in mileage felt at present but take the fuel efficiency near that of diesel engines.

(iii) Changes/Improvements in Materials – The problem of water in the fuel and resultant corrosion, sludge in the lubricating oil etc. can only be solved by better materials. Ethanol is hygroscopic as well as a good solvent and needs to be addressed with such changes, if smooth and fault-free engine operations is needed for years. Apart from the changes needed in an E20 compliant engine, following will be needed among others: 

    ·       Stainless steel or coated fuel lines

    ·       Ethanol-compatible fuel pump

    ·       Compatible injector materials

    ·       Modified fuel tank coatings

(iv) Ignition Timing – Ignition timing, along with changes in engine geometry, can be a game changer since Ethanol tolerates more spark advance before knocking. Whereas a compatible engine advances timing only slightly, an E20 optimized engine can take it to the mechanical limits of the engine. This extracts more pressure, and hence work, during the power stroke.

(v)  Combustion Chamber Redesign - An E20 optimized engine, as opposed to an E20 compliant one will also require modifications to the Piston crown shape, Squish areas, Swirl and tumble, Injector spray pattern, Valve timing etc.

Why Ethanol is the Future?

Ethanol blend, if done well, not only saves fossil fuels and foreign exchange, it also actually improves the performance of the engine. It permits a higher compression ratio due to its high Octane number. A higher compression ratio improves the thermodynamic efficiency of the Otto Cycle.

Ethanol has a higher latent heat of evaporation. The charge-air is therefore cooler and more of it, in weight, can be admitted into the combustion chamber thus improving not only combustion efficiency but also the power since more fuel can now be burnt.

The turbo charger can be redesigned to create higher charge air pressure for the new engine.

Are We Ready for an Ethanol Future

It is clear from the above that optimised E20 engines will need huge investments in Research and Design, changes in production processes, new supply chains, new approvals etc. An E20 compliant vehicle will be totally new beast and may even cost much higher than the existing models.

Are we ready for it? Maybe, we are. But if the goal posts keep moving to E30, E40 and E100, the technology remains in a flux, and the Indian car and scooter owner is doomed.

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