This is why forged pistons, rods, and cranks are popular in the aftermarket. If you want to go crazy with boost, you need to make sure the internal components can handle the added stress. By adding stress, you reduce engine longevity. By adding pressure and heat, you’re adding stress. Simple and effective, so what’s the drawback? By adding power, you’re increasing the pressure and heat in the cylinders. With more fuel burned, you can’t help but show your teeth from ear to ear. By adding air, you can now add more fuel.
By increasing boost, you’re increasing the amount of air packed into the cylinder. If a car comes with a factory turbo, often it’s tuned to keep boost levels reliable and efficient. Adding boost is one of the most simple ways of adding power to a forced induction engine. More Boost!Īdmit it, boost makes you smile. Fuel economy may be significantly sacrificed in these situations, with power and reliability taking priority. For example, with turbocharged applications, AFR well under 12.5:1 are often used in order to reduce combustion chamber temperatures, in order to have a system which runs much more reliably. It’s important to understand that there are certainly other factors which need to be taken into consideration for AFR tuning. This means a compromise must be made, so power is sacrificed in the name of better efficiency and fuel economy. Although manufacturers want to generate maximum horsepower so the engine is fun and responsive for the driver, they also need to make sure the engine is efficient and meets government emissions regulations. Now it’s obvious why tuning AFR is going to mean more power. According to SAE, maximum power is generated at an AFR of about 12.5:1, while maximum thermal efficiency is achieved at an AFR of about 16:1 (of course these numbers vary based on many engine parameters). This ratio is by mass, meaning for every gram of fuel you burn, you will need 14.7 grams of air. Gasoline composed entirely of octane has a stoichiometric air/fuel ratio of 14.7:1. Related article: High vs Low Octane Petrol 2. By tuning the timing, especially in the case of using higher octane fuels or water/meth injection, you can unlock a lot of untapped potential. That said, manufacturers will still attempt to keep ignition timing within a safe range.
Some cars will come with the capability to advance timing significantly, and they will often recommend premium octane fuels as these are less likely to generate knock. Knock, if not properly addressed, can easily ruin an engine. By advancing the timing (igniting the spark earlier) the probability of generating knock increases. Although efficiency is obviously a priority for manufacturers, so is reliability. If you fire too late, you’re wasting energy, as you want to make sure that peak pressure occurs when the piston is very close to top dead centre, so that as much of the pressure generated is turned into useful work. If you fire too soon, you’re creating a force counter to what the engine is trying to achieve, since the piston is attempting to compress a mixture, and the combustion is supplying pressure to force it down. When this spark fires is critically important. The cylinder is filled with an air fuel mixture, and your spark plug is awaiting the signal from the ECM to fire away. Think about a piston on its compression stroke. The idea behind ignition timing is simple.