When you guys mention turbo lag, what is actually happing to the car? Does it lag when you drive it, or slow down after ther turbo kicks in? Also ther turbo just happens automatically... so what do you guy mean to boost your psi to get more out of ya turbo? Im a lil confused in this department.

 

Perhaps a better understanding of what a turbo does is in order. Essentially, the turbocharger is a turbine -powered compressor whereas exhaust gasses leaving the engine are forced through a turbine, spinning up the turbocharger's compressor. That compressor is compressing the intake air for the engine, to get more air in the engine for more power.

Turbo lag is the delay between hitting the gas and getting the power to kick in. As it's based on the flow of exhaust gasses, an idling turbocharged engine isn't actually compressing the air going in - it's essentially a normal engine at this point. Slam the gas and the exhaust gasses will start spinning the turbine, or spooling up the turbo, and eventually, the turbo will start compressing. The amount of lag here depends very much on the size of the turbo - bigger turbos take longer to spool as a general rule, but are capable of more compression.

The other thing you asked about was boosting PSI. The PSI is pounds/square inch. It's a measure of air pressure. Since the turbo is compressing air into the engine, the more air the better. By adjusting the boost, you're adjusting the amount of compression the turbo will put into the engine. Too much boost and you're going to blow your engine, if it can't handle the extra power.

Clear?
-N

 

^^^ thank you, that explains everything.

 

Good explanation!

The only thing I would add to that is that is that the limit to the amount of boost an engine can take is limited mostly to engine design. The limit of course being detonation. Exhaust/intake restrictions, fuel supply/quality and timing all play a small but crucial rolls in raising the limit, but the design of the combustion chamber is by far the most influential factor in how much boost the engine can take before hitting detonation.

So one can't simply turn up the boost and get gobs of power. There is a balance to achieve so as not to destroy the engine. Most modifications to turbo cars are conducive to this end; that is, the mods do more to offset detonation than anything else.

This is one case where the Evo is a little different than most turbo cars. Most mods make power in and of themselves, without significantly decreasing the likely hood of detonation.