Ethanol & Flex Fuel Tuning: What is Ethanol
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What is Ethanol
07.52
| 00:00 | - Given the impressive dyno figures and massive power gains touted by those who have converted from pump fuel to ethanol, you may be forgiven for thinking that the fuel contains some kind of magic properties. |
| 00:12 | The reality of course is that there is no magic. |
| 00:15 | However if you're considering the switch to ethanol based fuels you need to know what you're getting yourself in for. |
| 00:22 | I'll start by making it very clear that you don't need to be a chemist in order to tune an engine on ethanol fuel. |
| 00:29 | That being said though it's also worth having a basic understanding of the fuel's properties and how these properties can affect what you need to do from a tuning standpoint. |
| 00:40 | Ethanol or ethyl alcohol as it's also known is a renewable energy resource most often derived from fermentation of corn crops. |
| 00:49 | Unlike gasoline, ethanol contains a hydroxyl group which consists of an oxygen and hydrogen atom. |
| 00:56 | This means that unlike gasoline, ethanol contains oxygen and is referred to as an oxygenated fuel. |
| 01:03 | Its chemical formula is represented as C2H5OH. |
| 01:09 | Two of the key benefits of ethanol include the fact that it's a renewable resource as well as its reduction of exhaust emissions, particularly carbon monoxide and oxides of nitrogen. |
| 01:20 | These two points however can be somewhat contentious, as there is also an environmental impact associated with the production of the crops used to manufacture ethanol. |
| 01:32 | We aren't here to debate the environmental benefits of ethanol though, and we'll continue to focus on its advantages in terms of engine performance. |
| 01:41 | 100% pure ethanol is often used as a base for alcoholic beverages. |
| 01:46 | So the ethanol that's used for automotive fuels is referred to as denatured. |
| 01:52 | Denatured ethanol includes additives to make it poisonous for human consumption and this means that ethanol used as a fuel is not subject to beverage alcohol taxation. |
| 02:03 | While it's possible to run an engine on pure ethanol, this can present some issues, particularly when it comes to cold weather performance. |
| 02:12 | For this reason it's much more common to see ethanol used as a blend such as E85, where ethanol is combined in some percentage mix along with unleaded gasoline. |
| 02:24 | It's possible to blend any amount of ethanol with gasoline, however probably the most commonly available blend is E85. |
| 02:32 | When we refer to these ethanol blends, they're defined on the basis of fuel volume, not weight. |
| 02:39 | On the face of it the term E85 is a blend comprising 85% ethanol, with 15% unleaded gasoline. |
| 02:48 | The actual specification for pump E85 however, defines the fuel to have a maximum ethanol content of 85%, while the remaining 15% is to be made up of unleaded gasoline, gasoline blend stocks, natural gasoline, or other hydrocarbons in the gasoline boiling range. |
| 03:07 | We'll discuss what exactly the other 15% of the fuel comprising E85 is a little later in this course. |
| 03:15 | While the specification for pump E85 defines the maximum percentage of ethanol, what many people don't realise is that the minimum ethanol content that can be still classed as E85 is just 51%. |
| 03:31 | The reason for this huge variation in allowable ethanol content, is due to the relatively low volatility of ethanol, which makes cold weather starting problematic on higher percentages of ethanol. |
| 03:44 | For this reason the ethanol content of pump E85 is adjusted based on location and ambient temperatures to ensure that the volatility level is sufficient to provide acceptable cold start performance. |
| 03:58 | If you're confused about the term volatility, don't worry as we will discuss cold starting performance in much more detail further into the course. |
| 04:07 | However this large allowable variation in pump E85's ethanol content, is one of the contributing factors to reliability issues with engines tuned on E85 without the benefit of flex fuel capability and an ethanol content sensor. |
| 04:24 | So if there's no magic associated with ethanol fuels, where does that additional power potential come from? There are really two separate reasons why we can expect more power potential from an ethanol blended fuel. |
| 04:38 | The first is that the fuel simply has a higher octane rating than regular pump gasoline. |
| 04:45 | It's difficult to get an exact answer as to what the octane rating of E85 is. |
| 04:50 | However it's generally accepted to be between 100 and 105 using the research octane number rating. |
| 04:58 | It's worth noting here that there are three common ways of rating a fuel's octane rating. |
| 05:03 | The research method, the motor method, and by averaging the research and motor octane values. |
| 05:11 | In particular this is important when comparing fuels as a fuel with a research octane number of 105, may also have a motor octane number of perhaps 90 which can be misleading if you're not aware of the testing procedure. |
| 05:25 | The average of R plus M, or research plus motor, divided by two technique, as it's name implies takes the average of the research and motor octane numbers. |
| 05:37 | In this case we can add 90 and 105, and divide by two to get the average, which is 97.5 A fuel's octane rating defines its resistance to detonation or knocking. |
| 05:51 | All things being equal a fuel with a higher octane rating will allow more boost pressure, more compression, more ignition advance, or potentially all three. |
| 06:01 | And in an engine that was previously knock limited which being tuned on gasoline, this can provide the potential for large power increases, as we may now be able to achieve MBT timing or also increase the boost or compression ratio while still being able to tune to MBT. |
| 06:19 | The second property that helps ethanol produce power, is its latent heat of evaporation. |
| 06:25 | When we inject fuel into the engine, it's delivered as a finely atomised liquid from the fuel injectors. |
| 06:32 | Once the fuel is injected into the inlet port, or directly into the cylinder, it will absorb energy in the form of heat, as it undergoes a phase change from liquid to vapour. |
| 06:43 | Ethanol has a very high latent heat of evaporation, which is around twice that of gasoline. |
| 06:50 | This means that it absorbs a lot more heat out of the combustion charge as it undergoes this phase change. |
| 06:56 | Or to put it in plain english, it has a much higher cooling effect on the combustion charge. |
| 07:03 | Since heat in the combustion chamber promotes detonation, anything we can do to reduce the combustion charge temperature, will help make the engine less prone to knock. |
| 07:14 | It's the combination of a higher octane rating, coupled with the extremely high latent heat of evaporation, that provides the potential for the power gains that can be realised on ethanol fuel. |
| 07:28 | Now that we have basic understanding of what ethanol and ethanol based fuels are, we can move on with the course. |
| 07:35 | We'll look at the specific characteristics of the fuel a little further into the course though, so that you can understand how the properties of ethanol affect our tuning requirements, and those of the vehicle's fuel system. |
