I have been doing some research and wanted to use this as a point of discussion since our understanding and usage of e85/ eflex fuel is relatively rudimentary at this stage, in my view
For those unaware, e85 or eflex (Caltex Australia's version) is a type of fuel that contains 85 percent ethanol and 15% gasoline (eflex having between 70-85% ethanol and the remaining contet being standard petrol)
Here are some links from our own site for those wishing to do some light reading on the benefits etc:
viewtopic.php?f=56&t=15638
viewtopic.php?f=16&t=21043&start=0
viewtopic.php?f=2&t=11296
As some of you may know, I've been running eflex now in my car for exactly one year (although 4 months of that my car was off the road having work done).
So having some basic understanding of majority ethanol based fuels, I have been exploring the upside potential that the cleaner burning, lower energy combustion of eflex provides.
So far this is what I know :
- ethanol has a lower amount of energy per unit (about 40%less) than normal unleaded petrol (95 Ron).
- because of this, to make the same power at any given point as an engine running on normal fuel, a blend of 85% ethanol to 15% petrol will require approx 25- 30% more fuel to be burnt.
Eg - car A requires 250cc per min to make 100kw at 5000rpm.
Car B with an identical mechanical setup to Car A running eflex will require approx 325cc per minute of fuel to make
100kw at 5000rpm
So generally speaking, your fuel usage will increase and mileage decrease with ethanol fuels all else being equal - which is an important point - ill get to it in my theories/ ramblings below.
- the cooler burn of ethanol fuel allows more ignition timing advance / boost and a general increase in combustion chamber pressures before detonation threshold is reached. These are basic mechanical concepts beyond the scope of this post so if these are unfamiliar to you, some info can be found on google (its great).
- the slower burn characteristics of ethanol fuel allow it to resist pre ignition induced detonation
- turbo / supercharged vehicles love ethanol fuels - they respond much more acutely to it than naturally aspirated vehicles, because typically, a forced induction vehicle's intake charge temperature is alot higher than ambient, and the cooling effect of ethanol (given its high alcohol content) dramatically assists in reducing this charge temp once the fuel is injected into the air stream in the manifold/ plenum runners. Therefore the rate of change that is noticed is alot larger in forced induction vehicles due to this element, in my opinion.
- ethanol is high in alcohol which means it can hold and infact attracts water content readily. In this sense, it can be a cause of oxidisation in certain mechanical parts if water absorption has occurred in the fuel tank or fuel lines etc.
- ethanol (like petrol) is a solvent although in a stronger form. This means in the combustion process, any unburnt or excess fuel (there will be some) can make its way into the lubrication system, and thus reduce the effective lifespan of your engine oil, as it breaks down the esters and oil polymers alot quicker due to its solvent qualities. I reccomend changing oil as soon as every 3500kms or as late as every 5000kms if running ethanol fuel, and ensure your engine oil is API SN compliant for ethanol usage.
So now that we have established some of the above, I want some discussion on some untapped benefits of using ethanol fuels. More specifically, I'm exploring how we can:
1. Generate greater engine efficiency
2. Extract more power from the engine when running ethanol fuels apart from adding boost / timing.
3. Reduce our emissions footprint
Want to get even more granular? I'm talking about avcs.
Avcs is Subaru's variable valve timing system - this allows for continuous adjustment of inlet (and in some cases, exhaust) valve opening, to extract maximum efficiency, torque and emissions control (exhaust gas recirculation of the 21st century)
My theories / questions / ramblings :
- From my research, e85/eflex is a cooler fuel, as established above.
- The alcohol content has a denaturant (so no this wont be an acceptable substitute for vodka)
- because ethanol absorbs / contains more water per unit than petrol, it produces less hydrocarbons in the combustion process ( or my thinking is maybe it dilutes the hydrocarbons in the the exhaust because of the water content???)
- water content of burnt e85 is roughly 28% compared to 11% in petrol. This creates greater moisture in the exhaust. By using avcs overlap, volumetric efficiency can be improved, and instead of just being an egr mechanism, I want to use overlap to cool the intake charge further given the higher water content
This effectively give a cleaner, cooler, denser burn and improve fuel efficiency (the ultimate goal being to get the same fuel efficiency as a petrol car ie reduce fuel consumption by the stoich 20% difference)
Discuss please
Mick