boost pressure

HI ANDRE

how can i know , how much boost pressure can the turbo give , if i removed the factory turbo , and installed bigger one , like

( FP WHITE ) or ( PRECISION ) , or a twin turbo system was installed , shall i make a run first , check the pressure on the digital gauge , then modify the table , to what pressure it showed ??

If you have access to a compressor map for our new turbo then this will give you a good idea of the sort of pressure ratio the turbo can support, as well as where it is most efficient. Remember that the pressure ratio is the compressor outlet pressure divided by the compressor inlet pressure (which we would normally assume to be ambient air pressure) - Both pressures are expressed as absolute. So for example if you had 200 kPa boost pressure and barometric pressure was 100 kPa, the pressure ratio is 200/100 = 2.0.

When you're actually tuning the engine, you will start at the minimum or wastegate boost pressure and then begin increasing the boost. You will get a sense of when you're at the limit of the turbo's flow as you will start to see the power gains taper off as you continue to increase the boost. Also if you're tuning on pump fuel, normally the knock threshold of the engine will limit the amount of boost you can use. If you get to a situation where you increase boost but need to remove timing to prevent knock, you can find that you actually make no more power. In that case it's sensible to reduce the boost a little bit and place less stress on the engine.