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Turbo Guru's - How to work out CFM - Math Guru's also..

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Alright guys,

 

So i was just cruising around reading specs on turbo's, and im wondering whether there was some sort of formula to work out how much air a certain turbo will move at a certain boost.. it's kind of like the maths part of letters and numbers, but im not smart enough to work it out..

 

FOR EXAMPLE:

 

Kinugawa TD06-20G

flows 685cfm at 14.7 psi (1 Bar) Compressor Wheel 52.5 mm / 68 mm (20G) Turbine Wheel 58.8 mm / 67mm

T2 Flange

 

so yeah, using that information, are you able to work out how much air it will flow at say 20 psi, or at 10 psi or whatever?? i know you could just do it basically but im not sure whether air flow works exponentially (not exponentially but you know what i mean) or whether its just normal..

 

Wow, weird thread, i hope that someone understands what im getting at..

 

thanks guys..

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What you need to find is the compressor map, that'll let you know the theoretical air flow and therefore theoretical BHP at a given pressure ratio and efficiency. Compressor flow isn't relative though so by knowing what it flows at 14 psi doesn't help you know what it'll flow at 10 or 20. And in actual fact a turbo will only flow what the head will allow it to flow; so that is why anything you work out on paper will only be theoretical, the more info you have (I.e. flow bench reports) the more accurate you will be but still you will never be 100% accurate.

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To answer your original question (and these are very rough calculations using a lot of assumptions)

 

14.5 ~ 10lb's/min

 

10lb's/min ~ 100 BHP

 

Therefore;

 

685 CFM ~ 472 BHP = 293 rwkw

 

Now if you have a 8cm turbine housing you'd be lucky to get that as the turbine would be too restrictive and therefore would lower the output but it gives you an indication.

I wouldn't run that turbo in a T2 housing it'll be like the T2 GT3071's, they never reach the compressor's potential.

Edited by D_Stirls

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aaah alright, sweet as bro.. i was hoping there was some maths equation or some shit that you could use when looking at turbos to sort out the CFM at certain boost levels..

 

cheers mate ;)

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