To find out characterics about the turbo.

Best flow rates.

Ideal BHP level if possible

etc etc

 

you plot your pressure ratio against the folw of the engine and see what efficiency band it drops into,,,, you can then work out how much extra heat is being put into your intercooler intake

 

you need to know the flow rate of the engine too get this use

L x rpm x VE x pr
--------------------- = CFM
5660

to convert from cfm too lb/min (which most compressor maps are in multiply by 0.07)

L = engine capacity in liters
rpm = i hope you know that one
VE + volumtric efficiency
PR pressure ratio


boost +atmospheric pressure
------------------------------------ = pressure ratio,
atmospheric pressure

 

From memory. Pressure ratio on the y axis, air flow on the x axis. You then have the lines representing turbo rpm and the 'island' regions relating to efficiency. If you have an idea of the bhp required and boost you want to run you can start looking at Maps. You can then see for the pressure and air flow where the turbo is operating. If it operating far from the central island you will need to change the turbo spec. There will also be a surge line.

This could mean a completely different turbo or modifications to trim, exh housing ect.

This is how I understand it, and welcome any corrections.

 

saving me typing it all.. as above really

 

I think between us Gareth we could write a book.

'Internet tuning for beginers, by beginers'. Guest editorial by Phil

 

 

here you go Ryan. If you re-read the above does it make sense???

the % figures are the efficiency.

 

what is the pressure ratio scale in? P2C/P1C

 

the PR scale is a ratio

so work it out like i first showed

so if you was running 20 psi boost it would be

20+14.7
----------- = Pr = 2.36 pr
14.7

 

Got so many titles for that book it's hurting my head!

 

Its a ratio, therefore doesn't have a unit. It's as Gareth pointed out above. As long as the units are the same top and bottom of the equation, i.e psi or bar. Either way you will end up with the ratio. This is what is known as a dimensionless number

So at 2.00, the pressure coming out of the compressor is double that of what is going in.

i.e runnning 14psi will be

14psi boost + 14psi atmospheric pressure(roughly)
------------------------------------------------------------- = 2.00
14 psi atmospheric pressure

The variable is the boost. Stick different no's in and the ratio will change

 

i know VE can be worked out by a fuction of HP/torque, rpm and volume,,, but my fooking head is blank,, i know ive done it before aswel,,,, dohhhhhhhhh

 

Calculating VE

A brief explanation in simpler terms:

Also:

How to read turbo flow maps