Why lower compression for a turbo.

[M3turbog16]

please explain why you need to lower the compression ration when adding a turbo to can car..My dad and are arguing over this I tell him you need to he says why..you dont need to..can someone please explain why this has to be done?

[///MCubed]

Lowering the compression ratio is not required for low boost settings. It is lengthy as to why some aftermarket turbos do this, but I am not going to explain it and I will point you to a book by Corky Bell called "Maximum Boost". This is a good stepping block to understanding this. Main reason to do it is to prevent pinging.

[Joey325i]

well if you lower the compression, theoretically so you can boost more without blowing the motor, although it may sound good, but you
will have more lag if you lower the compression

[Konstruktion]

Lowering the compression ratio allows (like Joey said) you to increase the boost. Lowering compression lowers combustion pressure, prevents pinging, detonation, knocking, etc. That is why intercoolers are used in most turbo applications to cool the air once it is compressed. By lowering the compression ratio, lowering the charge temperature, reducing the ignition advance, and using higher octane fuel, higher boost pressures can be run. Retarding the ignition and reducing the CR can also reduce power and engine efficiency/gas mileage, so there is a trade off.