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Octane and powerIt's a common misconception amongst car enthusiasts that higher octane = more power. This is simply not true. The myth arose because of sportier vehicles requiring higher octane fuels. Without understanding why, a certain section of the car subculture decided that this was because higher octane petrol meant higher power.The reality of the situation is a little different. Power is limited by the maximum amount of fuel-air mixture that can be jammed into the combustion chamber. Because high performance engines operate with high compression ratios they are more likely to suffer from detonation and so to compensate, they need a higher octane fuel to control the burn. So yes, sports cars do need high octane fuel, but it's not because the octane rating is somehow giving more power. It's because it's required because the engine develops more power because of its design.There is a direct correlation between the compression ratio of an engine and its fuel octane requirements. The following table is a rough guide to octane values per engine compression ratio for a carburettor engine without engine management. For modern fuel-injected cars with advanced engine management systems, these values are lowered by about 5 to 7 points. Compression ratio Octane 5:1 72 6:1 81 7:1 87 8:1 92 9:1 96 10:1 100 11:1 104 12:1 108 Octane and gas mileageHere's a good question : can octane affect gas mileage. The short answer is absolutely, yes it can, but not for the reasons you might think. The octane value of a fuel itself has nothing to do with how much potential energy the fuel has, or how cleanly or efficiently it burns. All it does is control the burn. However, if you're running with a petrol that isn't the octane rating recommended for your car, you could lose gas mileage. Why? Lets say your manufacturers handbook recommends that you run 87 octane fuel in your car but you fill it with 85 instead, trying to save some money on filling up. Your car will still work just fine because the engine management system will be detecting knock and retarding the ignition timing to compensate. And that's the key. By changing the ignition timing, you could be losing efficiency in the engine, which could translate into worse gas mileage. Again as a practical example, my little tale above about our trip to Vegas on low octane gas. (Whether you want to believe some bloke on the internet or not is up to you). On the low octane gas on the trip down, we could barely get 23.5mpg out of the Subaru. Once I was able to fill it up again with premium at the recommended octane rating, we got 27.9mpg on the way back. A difference of 4.4mpg over 450 miles of driving.Doing the maths, you can figure out that by skimping on the price during fill-up, you may save a little money right there and then, but it costs in the long term because you're going to be filling up more often to do the same mileage. My advice? Do what the handbook tells you. After all it's in the manufacturers better interests that you get the most performance out of your car as you can - they don't want you badmouthing them, and in this day and age of instant internet gratification, you can bad-mouth a large company very quickly and get a lot of publicity. Octane boosters In some extreme cases, the highest octane fuel available might not solve a knocking or detonation problem. That's normally a symptom of a deeper problem in the engine involving carbon deposits on the cylinder heads, bad spark timing, faulty engine management systems or similar. In these cases, some people choose to add octane booster to their petrol. Basically you fill the tank as normal, then put in a measured amount of octane booster and it further raises the octane level in an attempt to stop the detonation. One of the downsides of this is that it can make the engine harder to start from cold, because the octane booster has made the fuel so much less volatile that it's hard to get it to ignite on the first couple of strokes. Products like Klotz and Redex octane boosters are readily available over the counter in most auto parts stores. Octane boosters are typically used by mis-educated motorcyclists who believe the myth (explained above) that high octane = more power.In England, octane boosters are typically also sold as "lead replacements" or "4 star additive". A lot of European cars relied on the lead in 4-star petrol for the increased octane. Lower octane unleaded fuels caused a lot of problems when they first appeared, especially with cars that didn't have engine management systems. Knocking and detonation became evident in a lot of cars and for some reason French and German engines were more susceptible than most. Dumping a shot of octane booster in the tank when filling up solved the problem by raising the RON a few points to make it the equivalent of what old leaded petrol had been. Eventually, by the late 90s, most English and European petrol stations introduced LRP - lead replacement petrol, and the problem went away. Well. Sort of...... Lead Replacement Petrol (LRP) and valve seatsWhilst LRP solved the problem of lower octane unleaded petrol, it introduced a new problem. The lead in leaded petrol also had a secondary function and that was to lubricate the valve seats - the top of the engine block where the valves "park" when not being opened by the cams. With the advent of LRP, detonation went away but the chemicals used to increase octane didn't have any lubricating function. Some older engines started to suffer from increased wear to the valve seats, to the point where the valves could no longer properly close and seal the intake and exhaust ports. There were a couple of high profile cases before I left for America in 2001 but I've never been able to find out the end result. If you have any information on what happened in these cases, drop me a line and I'll include the info here.
Acerca do tipo girlar..Não é sinal de uma boa afinação? tinha a ideia que os fire grilavam quando estão bem afinado..É que o meu grila bastante..
Citar Acerca do tipo girlar..Não é sinal de uma boa afinação? tinha a ideia que os fire grilavam quando estão bem afinado..É que o meu grila bastante.. depende do motor...sinceramente duvido que haja uma unica pessoa com um FIRE bem afinado...a carburador então nem se fala (lol) para mim nada bate a gasolina super que tinhamos...e não uso nem quero usar bp100 por razões muito obvias (e não estou a falar de preços)
Citar Citar Acerca do tipo girlar..Não é sinal de uma boa afinação? tinha a ideia que os fire grilavam quando estão bem afinado..É que o meu grila bastante.. depende do motor...sinceramente duvido que haja uma unica pessoa com um FIRE bem afinado...a carburador então nem se fala (lol) para mim nada bate a gasolina super que tinhamos...e não uso nem quero usar bp100 por razões muito obvias (e não estou a falar de preços) É a coisa mais simples do mundo afinar um FIRE carburado.Havias era de afinar um 33, com dois carburadores duplos, o que dá efectivamente um carburador por cilindro.Isso sim, dá luta...Afinar um FIRE é para meninas!! (lol)
Citar Citar Citar Acerca do tipo girlar..Não é sinal de uma boa afinação? tinha a ideia que os fire grilavam quando estão bem afinado..É que o meu grila bastante.. depende do motor...sinceramente duvido que haja uma unica pessoa com um FIRE bem afinado...a carburador então nem se fala (lol) para mim nada bate a gasolina super que tinhamos...e não uso nem quero usar bp100 por razões muito obvias (e não estou a falar de preços) É a coisa mais simples do mundo afinar um FIRE carburado.Havias era de afinar um 33, com dois carburadores duplos, o que dá efectivamente um carburador por cilindro.Isso sim, dá luta...Afinar um FIRE é para meninas!! (lol) deves andar a gozar...afinar um FIRE não involve mexer no carborador...eu não gosto de afinar carros, só quando os conheço bem e o estado em que estão....é o mesmo com as mulheres....precisas de conhecer bem para saber se está bom ou mau num FIRE a carborador tem mais coisas para afinar que muitos imaginam!! afinar um motor não é rodar parafusos da mistura como certos mecanicos fazem...
No proximo encontro lá estara o uno... Quanto à mudança super => S/C 95 supostamente o meu uno nao precisava de nada...
Citar No proximo encontro lá estara o uno... Quanto à mudança super => S/C 95 supostamente o meu uno nao precisava de nada... O motor antes tinha lá o chumbo a proteger internamente.Quando se passa para sem-chumbo, deveria-se retirar a cabeça fora e rectificar as valvulas e sedes, e descarbonizar por completo o motor.Só que isso sai caro, dá trabalho e ninguêm quer fazer, afinal de contas o motor continua a rodar...
