Volume vs pressure

[dubbedup]

This is going to sound dumb as but I have been discussing with a few mates about big turbos... one thing that comes up is volume vs pressure....btw none of us are turbo experts.

For arguements sake I have a vf22 set to 10psi with a ex.wastegate controlling boost, then i upgrade to a t70 with the same setup, still running 10 psi but is the volume larger??

Afterthoughts:

It is my thinking that 10psi is 10psi but if thats the case is there anypoint on putting a bigger turbo unless you need more than 18psi (maxing out the vf22??)

[Guest keltik]

10psi on a 2liter motor at a given rpm will be the same volume of air no matter what you do.

Give this a read, helped me choose a turbo and understand why to choose the one i did: http://www.turbobygarrett.com/turbobygarrett/tech_center/turbo_tech101.html

The idea is that a larger turbo would be more efficient at the volumes you want to pump

[pl0x]

really? the way someone described to me was, 1.5L coke bottle holding 10 psi or 390ml coke bottle holding 10psi

[Koom]

The turbo may be bigger, but the manifold/ports etc is the volume that holds the pressure so that doesn't change (r.e. coke bottle example).

Buuut, bigger/different turbo's will have different efficiencies at the different pressures (effecting temperature) as well as bigger/different turbine housings will effect your backpressure/V.E. at different rpm points which is why a big turbo will often make similar power at say 14psi compared to a smaller one pushing 18psi.

Its all a bunch of complicated comprismises and turbo selection ultimately depends on which comprimises you're willing to make.

[Guest]

or pick a turbo out of a hat and go with it

-smurff

[Guest]

his new snail is already sitting in the garage =) (Dubbedup that is)

[Guest]

ahhh, well, he has already picked from the hat

-smurff

[dubbedup]

the reason behind my confusion...is i have to drive ~350kms on a new (bigger) turbo without a tune on grey injectors....and thought somehow the volume would change but not the psi....

[Guest]

ahhh i see well. . . im gunna stop being a pain in the ass and let people who have a clue talk

-smurff

[dubbedup]

 keltik']

10psi on a 2liter motor at a given rpm will be the same volume of air no matter what you do.

Give this a read, helped me choose a turbo and understand why to choose the one i did: http://www.turbobygarrett.com/turbobygarrett/tech_center/turbo_tech101.html

The idea is that a larger turbo would be more efficient at the volumes you want to pump

thanks - Will read this when i have time

really? the way someone described to me was, 1.5L coke bottle holding 10 psi or 390ml coke bottle holding 10psi

this was my reasoning too....bigger = same pressure more volume

[quote name='Koom said:

The turbo may be bigger, but the manifold/ports etc is the volume that holds the pressure so that doesn't change (r.e. coke bottle example).

Buuut, bigger/different turbo's will have different efficiencies at the different pressures (effecting temperature) as well as bigger/different turbine housings will effect your backpressure/V.E. at different rpm points which is why a big turbo will often make similar power at say 14psi compared to a smaller one pushing 18psi.

Its all a bunch of complicated comprismises and turbo selection ultimately depends on which comprimises you're willing to make.

so i should be sweet with my tune as volume wouldn't change?

[Koom]

I wouldn't say that you will be sweet as but you can most likely drive it if you really, really have to, just keep it off boost. Problems could be caused by necessary timing differences if the V.E. has changed enough at the current setup. I have done a swap recently to a much larger turbo and have been slowly testing bits and pieces and getting sorted for a proper tune. It runs fine but I've kept it to wastegate boost pressure and also taken 4 degrees of timing out through the main load zones. Once I get the car road legal I'll be tuning it properly but haven't had any det as it is currently.

[Swindog]

As koom has said alot of varibles but people have forgotten about flow and where the pressure of the turbo comes in exactly in your rev range. The bigger the turbo the later it will LIKELY be in your range under load.

To say a huge turb o will make your car faster than a smaller turbod car isnt necessarily right, assuming they are both of the same cc.

Thats why most turbos say good for like 450hp or 300hp, if you choose a commonly used setup you wont have probs and youll still make gains. Also depends on if you want top end speed or low end grunt

[dubbedup]

I have bigger injectors going on the setup as well, which i realise i need to get the car tuned for, but to do that i need to get my car to chch, i will just take it very easy and keep it off boost...and let the pro play with it then, thanks all for your help.

[Koom]

You're not going to drive on the new injectors are you?

[dubbedup]

hell no, as these are easily changed once in chch, but everything else is not so easily changed, as i have modified my intake to run both top and side feed injectores. also going to flip intercooler and manifold before i go, sounds like it going to be a quiet drive for my engines sake

[wrx_lou]

definately not sweet bro. I did that and would never do it again.

[dubbedup]

well that makes it a wee bit of a conumdrum(sp) then

 wrx_lou said:

definately not sweet bro. I did that and would never do it again.

[dubbedup]

and all you did was chage turbo or other stuff at same time?

[Koom]

Can't you just get it tuned in Dunedin? Or are you not from there?

[dubbedup]

I can get it tuned in Dunedin just NZefi did a mnt job so keen to give them some repeat buisness...

[Guest boostin]

How easy is it to pull the externals spring out? You won't be boosting it after that!

[dubbedup]

hahaha, if im going to do that i mite as well just take an intercooler hose off and run it N/A styles...

[Guest keltik]

Except for the bit where your turbo overspools and goes bang

[dubbedup]

always a catch....

[pl0x]

 boostin said:

How easy is it to pull the externals spring out? You won't be boosting it after that!

easy as, would just sound like a mass exhaust leak tho?