Until recently, the most dynamic domestic cars with a rook on the radiator grill required 93 th gasoline. Nowadays, the most demanded is 95th. But many models, especially supercharged ones, are already asking for the 98th. The trend is simple: the steeper the motor, the greater the octane you give him.
But in nature there are more serious gasolines - with an octane rating of 102, 106 and even 110! You can’t buy them at gas stations - only in specialized companies. Terribly expensive, but suddenly the car will fly?
So the question is: what gives a high octane number? And does it give at least something? And to whom is it useful?
The selection of 102 x gasoline in Russia is small. But our task is not comparative, but analytical. We want to understand where the effect comes from and how significant it is. And for this, two grades of sports gasolines are quite enough.
We got the Russian gasoline TOTEK Tornado C 102 and the French ELF LM S AI 102. Such is the mini-Borodino: ours against the “Frenchman”. And as a reference, we take the known quality AI 98 K5 gasoline.
The results of the analysis of the physicochemical parameters of the fuel samples we have tabulated. Note that for both sports gasolines, the octane number according to the research method (OCI) is slightly less than that stated in the name “102” - approximately 101.6–101.8. The developers also pay attention to this - they say, this is done on purpose, so that in no case go beyond the limit value of the OCH determined by the FIA rules. A similar situation with the octane number according to the motor method (OCHM) is a bit short of normalized 90 units.
In addition, the content of bound oxygen is higher in 102 x gasolines, although in moderation: in TOTEK Tornado gasoline it was found 2.9%, in ELF gasoline - 2.6%. Hydrocarbon analysis showed that there are more aromatic hydrocarbons in TOTEK - this determines its higher calorific value. And in ELF gasoline, traces of nitrogen-containing compounds were found, but in an authorized amount.
In general, we made sure that both gasolines fully comply with the FIA requirements for sports gasolines. And at the same time we found out that the usual 98th also corresponds to them.
There are two main questions. What happens if you use the 102nd in engines that were initially oriented to gasoline with an octane rating of 95–98? And how will the charged versions of these motors react?
For the first "arrival" on the motor stand was installed the usual VAZ sixteen-valve VAZ 21126 with a standard control system. When measuring, we were primarily interested in changing engine power and fuel consumption.
One of the famous horror stories, still common among the people, says that when using too high-octane fuel, the valves can be burned. And the reason for this is the increased temperature of the exhaust gases - due to the supposedly slower burning of fuel with increased detonation resistance. Well, let's control the temperature.
We did not see much difference in engine performance when working on three gasolines. The improvement of all characteristics on sports gasolines does not exceed one and a half to two percent compared to the usual AI 98 - this only slightly crawls out of the measurement error. The change in temperature of the exhaust gases also lies within the error.
In principle, everything is clear. A significantly higher oxygen content in the fuel slightly reduces its calorific value, but a slightly higher aromatic content restores it. In addition, the “internal” oxidizing agent increases the speed and completeness of combustion. The negative is compensated by the positive, and in the end we get an improvement, but not too significant. And the difference between TOTEK gasoline and the "French" ELF is generally invisible. In general, nothing interesting so far.
All the charms of sports fuel appeared when the cycle of comparative tests was repeated on a forced motor, with a modified cylinder head and valves and an increased compression ratio (from 11 to 12). The control program is also adjusted: the fuel supply (time for opening the injectors) and the ignition timing are adjusted specifically for sports fuel.
After such surgery, the charged 98th engine did not like the usual 98th gasoline: with a full throttle, detonation instantly woke up. The knock sensor could no longer cope with it - I had to slow down.
But 102 e came to the court! The result is clearly noticeable: an increase of 12-17% of torque compared to working on base gasoline. The maximum effect was observed in the zone of 3000–4500 rpm. Here’s what’s important: the moment has grown due to the fact that when working on 102 m gasoline, the pedal can be squeezed to the floor, while the pedal still has a power reserve of 98 m, but its further pressing responds with a furious “finger tap”.
Requirements for ordinary gasoline approved for sale in Russia are determined by the Technical Regulation of the Customs Union 013/2011. And in Europe, the requirements of EN 228–2013 apply. In these standards, mainly those parameters that affect the environment are limited: hydrocarbon composition, amount of oxygenates, benzene and sulfur content. Methanol and metal-containing antiknock agents such as lead, iron, manganese are prohibited.Related Materials Additives to gasoline: how to drink gasoline?
For sports varieties, additional restrictions apply. They are formulated in the requirements of the International Automobile Federation (FIA), in Appendix J (paragraph 9) of Articles 252–2009 of the FIA General Regulations. According to them, sports fuel should be commercial, that is, produced at a legal refinery (this cuts off attempts to use all sorts of innovative mixtures that are really not gasoline). That is, the norms of EN 228 for them have not been canceled. And then the principle of “anti-doping justice.” Like people, motors have their own doping, allowing out of the blue to get additional benefits. These are combustion enhancing additives, as well as fuel-related oxidizing agents based on all kinds of nitrogen and hydrogen oxides, the most popular of which is nitrous oxide. Therefore, it is strictly forbidden to use additives that increase power, and any other fuel components that are not classified as hydrocarbons.
In this case, the nitrogen content is additionally limited to not more than 0.5% by weight, as well as some types of oxides - peroxides (for example, hydrogen peroxide) and nitrooxides. But the tolerance for bound oxygen is expanded - up to 3.7% by weight instead of 2.7% in ordinary gasoline.
The maximum permissible value of the saturated vapor pressure is also increased - up to 90 kPa instead of 80 kPa for conventional fuel. This is dictated by the fact that you can’t just get the octane number for a hundred, you need to use a larger number of octane-increasing components, and these are all kinds of alcohols and ethers, that is, oxygenates. Their addition inevitably increases the content of bound oxygen and the pressure of saturated vapors. That is, there is a contradiction between the requirements of TR CU and EN 228 on the one hand and the norms established for sports gasolines, on the other. But it is forced.
The normalized range of changes in the octane numbers of sports gasolines: OCI (octane according to the research method) can lie in the range of 95–102 units, and OCM (octane according to the motor method) should be 85–90 units. That is, ordinary gasoline AI 95 K5 can be positioned as sports. But in these tests, we were interested in just another border of the octane number - the upper one, which climbs over a hundred. We took such gasolines for research.
So, the main conclusion: the increase in traction does not give the engine gasoline. A higher octane number is able to give him no more than a couple or three percent of additional torque. A serious difference is made by tuning the engine according to the ignition timing, valve timing and compression ratio. In this case, the high octane number of gasoline just allows you to squeeze the maximum.
The closer you get to the detonation zone, the greater the effect you will achieve. Therefore, they make sure that with a full throttle the engine "licks" this threshold. Once upon a time, in the era of carburetor machines with a mechanical distributor, experts suggested setting the ignition timing so that with a sharp increase in speed a few clicks of detonation could be heard. The old-fashioned principle is also wired into modern adjustments, but at a different level - according to the signal of the knock sensor and taking into account the requirements, to ensure minimal toxicity of exhaust gases. Therefore, sports gasoline with an octane rating per hundred is not an end in itself, but a means of ensuring the most efficient operation of the engine.
Basic good gasoline AI 98 K5 cost us 42 rubles per liter. Sports TOTEK Tornado C 102 is much more expensive - about 130 rubles per liter (sold in barrels of 45 liters). But the European ELF had to be taken at the "European" price - more than 200 rubles per liter!
Obviously, pouring such gasoline into a regular car is not only stupid, but also expensive. Not for that they created it! Another thing when it comes to a step on a pedestal - for the sake of this, it is not a pity for money if the machine is properly prepared.
As for import substitution, this is a complete order. Our TOTEK Tornado was no worse than the European ELF gasoline, and moreover, it was cheaper. So, according to the price-quality ratio, which is most important for the consumer, the winner in this “battle of Borodino” is obvious.
Andrey Sevastyanov, head and pilot of the B Tuning team
Participants of the RSKG (Russian series of ring races) without fail use high-octane gasoline with an OCV higher than that of the standard AI 98 for forced engines. It is not difficult to purchase them. Lovers of small aircraft use such fuel. As for driving on public roads, on which a powered motor cannot and should not give its maximum, the use of sports gasolines is absolutely unnecessary here. And for serial cars they simply are not needed: not their scope.
Alexander Garmash, organizer of the amateur series RHHCC, manager of RSKG
Do not confuse competition and everyday life. Athletes with an octane rating of 100, 102 and 104 are actively using gasoline, for example, in drag racing competitions, including those of the national level. Such fuel is available for sale, and if desired, it can be purchased - in cans, barrels. Another question is that it is useless on public roads, especially when it comes to a production car designed for the OCI 95 or 98. And do not forget that the price of a liter of "superbenzene" is high.
The standard definition of octane number is known to everyone: this is an indicator characterizing the detonation resistance of fuel for internal combustion engines. The octane number is equal to the content (in percent by volume) of isooctane (2.2.4 trimethylpentane) in its mixture with n heptane, at which this mixture is equivalent in the detonation resistance of the studied fuel under standard test conditions.
It turns out that, since it is a percentage, the octane number of gasoline can not be more than 100? With the usual measurement procedure, yes. But the isooctane, once accepted as the standard, has not the highest octane number! For example, in aniline, the octane number is 320, in monomethylaniline - 280, and in alcohols - from 110 to 156.
Therefore, to determine the octane number in excess of 100, other standards are used - with a calibrated additive of tetraethyl lead (TPP), which allows changing the octane number of the reference mixture in a wide range.
So, the octane number shows how much gasoline can withstand detonation. With proper combustion, the flame front moves along the cylinder from the spark plug at a speed of 30-60 m / s. Everything develops smoothly, calmly, predictably. But if somewhere (usually in the area of the combustion chamber farthest from the candle) explosive self-ignition of the fuel occurs, then a detonation wave rushes towards the normal flame front, the speed of which can significantly exceed the speed of sound. The consequences for engine parts are catastrophic - from burnout of valves to the destruction of pistons and scoring of bearing shells.