Explain to me G60 boost pressures

[flusted 0]

Ok so from what i understand and correct me if im wrong, boost pressure builds up when theres a restriction ie no valve overlap and both valves shut?

When you have flow work done the restrictions are less so the boost flows in and out the engine easier showing less pressure?

(I know i havent worded that very well but someones more than welcome to write that in a more understandable way)

 

So, if say a 68mm pulley makes 15psi but due to flow work your boost gauge only see's 11psi, what will the ecu see and set fuel to? :shrug:

[dirtytorque 0]

Ok so from what i understand and correct me if im wrong, boost pressure builds up when theres a restriction ie no valve overlap and both valves shut?

When you have flow work done the restrictions are less so the boost flows in and out the engine easier showing less pressure?

(I know i havent worded that very well but someones more than welcome to write that in a more understandable way)

 

So, if say a 68mm pulley makes 15psi but due to flow work your boost gauge only see's 11psi, what will the ecu see and set fuel to? :shrug:

You are basically right in what you are saying however boost pressure is not the only factor.

You need a re-map because you engines volumetric efficiency(VE) has changed.

Your car will under fuel because it thinks less air drawn into the engine but in reality more air is being drawn in(especially at mid to high rpm) its just that less of the air is lingering in the manifold due to the better breathing of the 16v head.

A new fuel map would take the engines improved VE into consideration when doing its fuel calculations.

 

You need a re-map.

[flusted 0]

i wasnt discussing it as in my engine, i just wanted to understand the thoery in general. Im on the case for a new chip as we speak for mine 8)

[dirtytorque 0]

i wasnt discussing it as in my engine, i just wanted to understand the thoery in general. Im on the case for a new chip as we speak for mine 8)

cool. 8)

[Yandards 0]

i wasnt discussing it as in my engine, i just wanted to understand the thoery in general. Im on the case for a new chip as we speak for mine 8)

 

Your original post sums it up really, a better flowing head, intake manifold, TB and intercooler will result in a more efficient system hence less boost pressure.

 

Boost pressure is misleading really, what you really want is more CFM - that is what generates power and is basically a figure of the engine systems (head, intake etc) ability to 'move' air through itself. Higher CFM will always make more power.

 

Yes an increase in boost pressure will force more air into the cylinders but if you make them capable of flowing more air in the first place then you will see the same results.

 

You only have to look at the peak performance you can squeeze out of the 8v system - even with a CNC big valve head, to see that a stock 16v head will produce similar power on the same size pulley.