Smash:
There's a few issues involved with tuning. primary air/fuel ratio and ignition advance. The ideal (stoichiometric) A/F ratio is 14.7:1. This will make the most power with the least ammount of fuel burnt. It also burns very hot. If you add extra gasoline to the mixture and make it "richer", like 12.5:1, it makes less power and burns more fuel, but the added fuel provides a controlled burn so when oxygen levels drop, the flame goes out and cools the cylinder temperatures (quench effect). A stock sports car will run around 12.5:1 to make good power and keep gas mileage up. When you add boost, you use more fuel, make more power and therefore more heat. Aftermarket tuners will richen the mixture as low as 11.0:1. This keeps temperatures down to prevent melted pistons. It knocks a few hp off your total and also kills your gas mileage, but adds safety to your high rpm, full throttle adventures. Also, the added 50% hp over stock from boost more than outweighs the 2-3% you lose from the rich mixture. The next component is ignition timing. If the spark plug fires too early, you get engine "pinging" or "knock" . This is hard on pistons, wrist pins and connecting rods and can cause catastrophic engine failure. You get more engine knock from using a low octane gas or having a high compression ratio. High octane gas burns slower than low octane. High compression ratio makes the air/fuel charge hotter and the flame front travels faster on ignition. The solution is to retard the timing. Adding boost is like increasing the compression ratio, so the ignition needs to be retarded under boost. The more boost you have, the more retard you need. On the other hand, ignition timing retard kills power output for the emmount of fuel used because the spark occurs later and the gas is still burning when the exhaust valve opens and power is wasted by burning the gas in your exhaust manifold rather than in your cylinder. So... you need progressive ignition retard based on increasing boost levels. Your stock ECU wasn't programemd to run boost and won't retard the timing.
In summary, adding boost without at least doing some dyno tuning with a knowledgeable tuner will result in too lean of aur/fuel ratio and too much ignition advance, which will then slowly destroy your engine.....or quickly depending on how much boost you have and how long you run at high rpm/full throttle conditions.
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