ilovecars

iTrader: (4)

ok here is my question. i wanted to know if psi is psi for example 12psi will always be 12psi like if i put a smaller turbo and it makes 12 psi on an engine but then i take a big turbo and limit it to 12 psi will it be the same?

thanks, phill

mike25

no it will be different. 12 psi on a big ass turbine will flow more cfm then 12 psi on a smaller lower flowing turbine

ilovecars

iTrader: (4)

why is that?

zay52790

psi just means pressure, the important thing is airflow or cfm, and i bigger turbo will move more air at the same psi

ilovecars

iTrader: (4)

to me that makes no sense cuz wouldent you have to flow a certain amount of air to make the psi in the tubes? so i dont understand why it would be different.

mike25

hhmm let me explain it like this.

take a 50 gallon sprayer for instance. you have a 1 inch sprayer head on it and a 2 inch sprayer head. naturally, which is going to spray the 50 gallons faster?

the 2 inch head is going to spray it faster because its got a bigger "housing" so to speak.

like wise a turbo housing at .63 is naturally larger than a turbo housing set at .48 sizing simply because it has more size(volume), so therefore it will push more cfm than a smaller housing will

ilovecars

iTrader: (4)

i understand that. so im incorrect at where psi is measured? is it not measured in the like overall tube? i dont see why 12 psi out of a smaller housing wouldent be the same as 12 psi out of a large housing.

mike25

psi is simply a set pressure. it determines when a bov decides to open. naturally you would think that psi would dictate power, but as said its simply a pressure level. cfm is how fast you flow something. you can flow air a 50 cubic feet per minute(distance/speed it travels) at a set 12psi(pressure) and have it be totally different than a faster flowing 60 cubic feet per minute setup running at 12psi(once again a dictator of pressure)

ilovecars

iTrader: (4)

ok i think im understanding this more. so 12 psi either way will be 12 psi but how fast the 12psi is moving is different?

slowswap

These guys speak the truth.

mike25

exactly youve got it. take a piece of pipe for instance. you can put enough pressure on it to equal 12psi. now take cfm. cfm ishow fast that 12 psi pocket of air is traveling(as well as how large it is)

BLAZIN07SS

iTrader: (7)

yep these guys are right.

ilovecars

iTrader: (4)

awesome. then why dose the speed affect it? is it because the fast the 12psi is moving the more of it can get shoved into the cylinder?

mike25

well the psi isnt moving more of it, the cfm is. but your onto it. a bigger turbine will spool more air pushing more into the cylinder per combustion cycle as opposed to a smaller turbine.

BLAZIN07SS

iTrader: (7)

cfm=cubic feet per minute. if you can push more air, you can increase volumetric efficiency into the cylinder

mike25

i believe the psi is more indicative of the pressure at which air is packed into the cylinder. 50cubic feet of air packed into a soda can at 12psi is different than 40 cubic feet packed in a can at 12psi

ilovecars

iTrader: (4)

ok i think im getting it. excuse my awkward wording but is it sorta like a bigger turbo will push more of the 12psi into the cylinder?

mike25

in a sense, yes. basically exactly the concept

ilovecars

iTrader: (4)

yea i get the ve part im trying to understand i guess the physics of it all.

ahhhhhhhhhhhhhhhhhhhhhhhhhh perfect!! lol totaly werid but i totaly get it now.

mike25

hehe its pretty simple. always helps to understand the basic physical concepts of how it works.

SSBLKBTY

A bigger turbo will have a greater lag time, due to the greater energy required to get the spool going to produce the additional psi

ilovecars

iTrader: (4)

yes indeed. so to compensate a little would the lease amount of charge piping possible for the smaller turbo help at all? or is that a totaly differnt thing

BLAZIN07SS

iTrader: (7)

but properly sizing a turbo for your application and needs is the most important.

ic piping diameter has something to do with it. but remember turbo's operate off of exhaust volume. learn how to read compressor maps. they will be your friend. lol

ilovecars

iTrader: (4)

:P the sizing is fine i dont need a huge turbo im doing it mainly for a nice boost in power and then reliability. and to make all my ignorant ******* friends jaw drop.

BLAZIN07SS

iTrader: (7)

give me a minute so i can calculate the essential "perfect" turbo for your set-up. whats you power goal?