There is a substantial difference between any “pump” fuel from anywhere in the world and any proper race fuel, especially that used by F1 cars. They are only similar in that they are both used in an ICE and that some of the components may be related. That’s where it ends. The difference comes not only from the fuel profile or fingerprint as determined through gas chromatography (Prior to gas chromatography, a fuel was tested by measurement of its specific gravity), but from the exacting tolerances used in blending the % ratios of the fuel and the extraordinarily specific qualities of the fuels individual constituents.
As said already, any normal “pump” fuel will vary greatly in consistency from batch to batch for varying reasons such as climate, delivery method, storage period, available feed stock, refinery, methodology used to crack and blend fuel, the list is almost endless. The prime example is an E85 fuel, which can vary from under 70% to well over 85% ethanol content due to mixing variations, but primarily due to climate requirements. For improved cold starting, during winter and in colder latitudes the ethanol content is reduced anywhere down to 70%. My own testing on pump E85 in Australia has seen these variations due to season, while commercially available race fuel E85 (Sucrogen and Sunoco) has always been 85% ethanol give or take 0.1% or there about.
Again commercially available race fuels from companies like Elf, Sunoco and Sucrogen (available I MON numbers up to 117+) are manufactured to specific profiles to perform in specific engine types with regard to compression ratio, maximum RPM and forced induction. A fuel that works in a low RPM (under 7,000rpm) and medium compression (12.5:1) will need a very different fuel to a high RPM, high compression or forced induction engine.
Fuel profile is altered through optimisation of the four major attributes of all fuels:1: Octane:
The rating of a fuels’ detonation resistance expressed as a Research Octane Number (RON) or Motor Octane Number (MON)2: Flame Speed
: This determines the speed at which fuel releases its energy. High RPM engines provide a very small “time” window for the fuel to release its energy. Peak cylinder pressure should occur at approximately 20° ATDC. If a fuel is not fully combusted by this time, its energy is not contributing to peak cylinder pressure. 3: Energy component/value:
The potential chemical energy in the fuel, measured in BTUs by mass value (grams, kilograms, pounds etc) not volume. This is critically important as AFR is measured by weight, not volume.4: Fuel vaporization (cooling) quality:
Directly related to the fuels “heat of vaporization”. A higher value provides a larger cooling effect on intake charge. This can show substantial power gains (up to 5%) on a high rpm naturally aspirated engine due to cooler temperatures, increased density and higher levels of atomized (vaporized) fuel in the mixtures. Also a fuel with good vaporization will provide increased sensitivity to throttle inputs.
The general principles Article 19: Fuel of the FIA F1 regulations are “intended to ensure the use of fuels which are predominantly composed of compounds normally found in commercial fuels and to prohibit the use of specific power-boosting chemical compounds.”
Rules 19.7 and 17.8 set down
Before any fuel may be used in an Event, two separate five litre samples, in suitable containers, must be submitted to the FIA for analysis and approval.
Fuel samples taken during an Event will be checked for conformity by using a gas chromatographic technique which will compare the sample taken with an approved fuel. Samples which differ from the approved fuel in a manner consistent with evaporative loss, will be considered to conform. However, the FIA retains the right to subject the fuel sample to further testing at an FIA approved laboratory.
So optimisation of F1 fuels for specific tracks or as a trade off of any or all of the below is possible where you are looking for as an example:
1: improved throttle response where there are low-mid speed cormers
2: power where there are longer straights or the need to run with higher downforce
3: evaporative cooling at warmer tracks
These are all in theory possible while remaining in the fuel profile required by the FIA. Shell, Total and the other fuel suppliers have more than one fuel available for teams to use with optimised qualities based on engine design, requirements of the track and needs/wants of the team decision makers.
Tommy Cookers wrote:Modern Avgas was designed in 1936 to allow a power gain with mixture enrichment around 10 times that of modern pump fuel, yet would meet the F1 spec (apart from the lead).
What is the constant preoccupation with Avgas and early to mid 20th century anecdotal evidence?! As said before, Avgas is generally less dense than the majority of racing and modern pumps fuels, and as a result, tuners must compensate by resorting to richer mixtures when using Avgas.
Avgas also has a very different hydrocarbon profile to a normal pump or race fuel to optimize volatility properties at high altitude, typically through the concentrations of high level of aromatics, which can contribute to poor throttle response when used in engines that require constant throttle variations such as an F1 engine. Aviation engines typically are not required to have constant high speed throttle variations, they generally run at long periods and constant RPM's and as such, throttle response is a secondary concern.
Also Avgas has poor octane quality compared to modern fuels due to the specific requirements for high altitude/lower oxygen use. Low octane quality is one of the quickest ways to destroy an engine. Aluminum piston forgings can be severely eroded or cracked during acceleration events where detonation is present due to the inherent properties of low quality Avgas octane.
Avgas would also fail on:
Lead content: Avgas has various concentrations from 0.125% (0.56g/Lt) to 0.189% 0.85g/Lt) vs.FIA - 0.005%)
Octane number of 99.5 vs. FIA - 87.0
Benzene profile: Avgas has allowable Benzene up to 5.0% v/v (volume concentration) vs. FIA - 1.0%
Tommy Cookers wrote:I think some Ethanol might well show a small power increase in an existing engine on ordinary pump fuel, mostly due to hugely better charge cooling causing a greater massflow of air, fuel, and more power. Ethanol is not a bad fuel, if someone else is paying.
If the Ethanol's oxygen was involved there would be a huge effect,we would have heard about it before. If it can be done with Ethanol, it could be done with water.
Sorry but I am truly bewildered by your logic here in relation to the evaporative cooling aspect or in relation to the substitution of Ethanol for water (unless you’ve cracked the water based internal combustion engine, then I can’t see your logic).
You have argued previously that there was no benefit to using EC from rich fuel mixtures, yet here you are espousing exactly the same from the use of non-energy bearing substances that reduce fuel and oxygen volume in the intake charge to provide the exact same benefit which you said previously does not exist.
So which is it? Does EC is any form, from either water or fuel (ethanol) provide any benefit?
Firstly on your ethanol substitution claim:
While generally having a lower calorific content than the fuel in which it is blended (but typically higher octane), it still contains available chemical energy. Water does not as any potential energy is tied up in the bonds between the two (2) hydrogen and one (1) oxygen atoms that make it up. It’s that simple. You can’t displace a potential chemical energy bearing substance with a non-energy bearing substance and get a similar result.
Secondly in water substitution:
If you are referring to the band-aid, anti-detonation system that is water injection, this only works where you have a serious problem in the first place that you can not fix properly. That is namely excessively high intake charge temperatures or low/poor quality fuel octane issues such as where regulation requires or results in the same.
Absurdly high intake temperatures such as was the case in WRC where water injection re-gained popularity was the domain of such a need due to limitations on fuel octane and the use of a ever reducing turbo inlet restrictor that saw stupidly high low RPM boost levels to produce maximum low RPM torque prior to hitting the super sonic flow limit of the restricting orifice.
So water injection was used by the WRC teams as they were restricted in air flow, had high boost levels with low air flow for intercooler efficiency, limited fuel octane and high compression engines. The perfect, non-perfect scenario where a normally inefficient and temporary solution could work as they had no other options available. Remove one of the regulatory restrictions and the effectiveness of water injection would plummet.
So water injection works on the principal whereby the evaporation of injected water through the process of evaporative cooling reduces the temperature of the engine components and intake charge and then when converted to steam which takes energy from the combustion process, absorbs this energy and slows the speed of the flame front preventing or lessening detonation. It actually takes energy from combustion in the final phase of its use and there is a constant need to ensure proper water ratio's to ensure that you don't loose engine output due to fuel/oxygen displacement, over saturate the intake charge to the stage that combustion is not sustainable or further to result in hydraulic lock. Further what happens when it runs out and the engine that was relying on it can no longer sustain the high temperatures?? Either loose power or loose reliability.
That says nothing of the weight penalty of dragging around 10 to 20 kgs of water plus associated equipment like pumps, filters, lines, tanks etc.
I have seen all from the fool hardy and ill advised use of water injection by those that were told it was a safe and easy system. It is a band-aid fix and potentially very dangerous if not controlled and monitored carefully.
In an engine using proper fuel, proper fuelling for a given compression ratio or boost level and not forced to run overly high inlet or in cylinder BTDC temperatures, water will see a negligible net gain or a power loss due to its displacement of fuel AND oxygen in the form of air leading to incomplete combustion if fuel tables (or jetting in the case of carburetor engines) or reduced fuel/oxygen available in cylinder due to the water present.
Conversely, the use of ethanol for its evaporative cooling (“EC”) properties allows it to be effectively used as a tool when base heat loads such as those under high load conditions materialise and in which base fueling and intake temperature control is insufficient. As such, fuel EC performs a similar function of water injection through the use of fuel to increase net effect of fuel evaporation to control temperatures. Using a fuel for EC however allows that fuel to use all of available oxygen for combustion.
As you are fond of aviation analogies, the Harrier jet used water injection to allow it to hover to stop the Rolls-Royce Pegasus 6 to 11 series engines (UK variant) or Rolls Royce F402-RR-408 (US Marine Corps variant) from overheating and increase take off power as the blade metallurgy problem could not be solved. 30 to 45 seconds constant flow was all it could sustain. Once gone its hover was very limited and the weight of the water severely impacted performance to the point pilots I know that flew them typically went up without a water load. The now defunct US Joint Strike fighter VSTOL had none of these issues as the metallurgy issues had been solved.
What you have said previously is that the addition of extra fuel under load to these high AFR's has no net tangible benefit with relation to in cylinder heat management. If that is the case then water injection should make no difference. If this is the case then OEM and motorsport engine tuners need to go back to school.