turbo question

Sorry if this sounds stupid but its really been bothering me.
Why would 10 psi from a tiny turbo give you less power then 10 psi from a bigger turbo? isnt 10 psi 10 psi? can somone explain this

 

easy, the amount of airflow, from a tiny turbo won't be as much as a larger turbo at same psi, this is where manufactuer flow charts come in handy.

 

thats what i was thinking but it still kind of seems confusing to me

 

doesnt the smaller turbo have issues when pipe size and other factors increase?

so the smaller turbo can flow 10psi, but the CFM is lower becuase it will need smaller pipe diameters to reach 10 psi?

 

i dont get it

 

my tiny turbo is gonna school all of you, you are all going down! :lol:

 

stop going off topic and answer my question

 

alot of the older factory turboed cars that used small turbos actually ran pretty high boost, but the don't gain that much more power. for example on my car the stock turbo tdo4 at 12lbs compared to my vf28 at 12lbs there is a very noticable difference in power just because of how much more cfm the vf28 pushes compared to the td04

 

ok, thats kinda what i was thinkin. since the turbo is bigger it can flow more air @ the same pressure as a smaller turbo.

so even though they fwo the same PSI the larger turbo will push more air into the motor, becuase it has a a higher CFM rating.

 

exactly

 

<--- Gold Star!

 

kk thanks, now im off to prove my friend wrong

 

think about it.....

blow through a hose... it is only so big and only enough air flows through...

get a frain pipe or 3in pipe and a mouth like mivk jagger and you could mover more air through it... yes it may be only 10 psi each but the 10 psi in a garden hose compared to a 3in piping is a huge amount of air movement difference.. hence more power... hope that kinda explains it... not the most technological but practical if you ask me

 

But isn't the pressure isn't measured within the turbo...?

If your post turbo piping is a constant size, how would the size of the turbo change to amount of air at certain PSI is? If you put 10psi of air in a box, it's 10psi, whether your or Mick jager put it there.....Mick would just have to work less.

 

lol

 

its like he said, the bigger the piping, the more air it takes to create the same amount of pressure. a bigger turbo has a bigger volume and will hold/push more air compare to a smaller turbo.

 

Remember that the turbo itself is considered part of that pipe that Mick is blowing on so if it's a small turbo it will have a smaller inlet and outlet and therefore a lower cfm rate at the same pressure. Think of the straw and the rain gutter, twist them into a crazy straw and that's the turbo. The diameter of the straw and the drain pipe don't change when you make a crazy straw out of them.

Stupid analogy concluded, now I'm gonna go drink beer through my crazy straw...cause I can.

 

Think of it terms of water. Which pipe is gonna allow it to flow quicker? Its kinda like a water wheel on a river if you really wanna get crazy. If you set up two pipes into a water wheel the one with the larger diamter will move it quicker because more water is hitting it. If you changed the water wheel to a turbine and the water to air the same thing occurs. The larger the piping the quicker it will flow because of less restrictions. Does that make any sense to anyone besides me?

 

But the intake manifold is always the same size...

Ok so how about this...

You have a 10 foot tall turbo, blowing into a 3 inch tube
You also have a 2 foot tall turbo, blowing into an identical 3 inch tube

you measure the pressure in each tube.

Are we saying that if you spin the turbos so that both gauges read the same PSI, that the one for the bigger turbo will somehow be pushing more air? would it not just be more efficient (spining slower)?

 

Think of pressure (psi) independently of volume. If you had the equipment to do so, you could seal up the Metrodome and pressurize the entire volume of air inside it to 10 psi. Or you could pressurize the volume of air inside a soup can to 10 psi. The pressure of both would be identical, the volume, and hence MASS of air inside each would be drastically different. Now think of those volumes of air entering an engine, getting matched with appropriate amounts of fuel and having a spark applied.

One of those volumes/masses of air will give you eleventy squillion horsepower. The other would get owned from a dig by a Segway.

 

I think I’ve got my problem. I’m thinking of it as the turbo pushing air into an enclosed space to increase the pressure, instead of the turbo itself compressing the air.

So the bigger turbo can compress more air to Xpsi than smaller turbo in the same amount of time.

 

but the 10' turbo would not have to spin as much to keep the same pressure as the 2' turbolol this is turnign into a huge mess, and did blubaru06 say e was gonna drink beer through his turbo?

 

I still don't see an acceptable explanation here.
Whatever size your turbo is, they all push air through the same restriction; the throttle body. And if the pressure is measured at the intake manifold, then 10PSI is 10PSI and that is the end of it. The reason why there is boost in the first place is because you have more airflow than the engine can ingest, so air backs up and pressure builds. It should not matter if your turbo can flow a million CFM, because if your engine only consumes 100 and boost is set for 10PSI, then the turbo can not be flowing one million CFM, ever.
I've pondered this question numerous times and have yet to find an acceptable explanation.

 

Go ride in an STI that has a TD-04 turbo, boost limited to 10 psi. Then swap out the TD-04 for an FP Green or something, limit boost to 10 psi again, take a ride.

Come back and see if you still say "10PSI is 10PSI and that is the end of it"

 

This thread is relevant:

http://forums.nasioc.com/forums/showthread.php?t=739466

Obviously there are a lot of factors at work here. The size of your motor, the relative size of two turbos being compared, how efficient each turbo is at the desired boost level, how hot/cool of an intake charge each turbo can produce, etc etc.

But this guy tried putting a stock WRX turbo on a built 2.4L motor. Result? He couldn't make power with it (surprise surprise). The motor can take in vastly more air than this turbo can supply, it was sucked completely dry and couldn't produce more than 9 lbs of boost. Now if you put a turbo on that motor that is properly matched to the displacement and flow characteristics of the engine, CLEARLY you are going to be able to make more power even at only 9 lbs of boost.

 

:?: