Turbo Size psi/volume

[FlikRacing]

I have been doing research for awhile now, and I am trying to figure out if a ct-26 pushing 6.8 stock psi is the same as a 60 trim turbo pushing 6.8 psi? What is the difference.

I know that the cylinder are not bored out and the inter cooler piping stays the same, so there is no room for more volume through those pipes including the throttle body. SO the same volume is allowed through it's path, but now we have a different size turbos.

it may be a dumb question, but I am trying to figure this out.

 

[Doward]

it depends.

Turbos are not characterized by 'pressure' - they are characterized by 'flow potential'

Also, trim means absolutely shit.

That said, a CT26 feeding a 3.0L motor @ 5000rpm @ 6.8psi is vastly different from T4 60-1 wheel doing the same.

 

[IJ.]

Valve opens the CT @ 6psi can get xx volume into the cylinder valve closes

60 trim can get more volume of air in during the valve open time add the correct % of fuel to this light it off and you get the bigger BOOM and more power.

Boost is everything the turbo can flow in excess of the motor's displacement.

A ct @ 20 Psi is going to deadhead (run out of flow) heat the intake charge above what is useful.

A 60 trim still has some overhead left before it reaches this condition.

This is a gross oversimplification but I hope it helps you understand the relationship of boost/volume.

 

[gofastgeorge]

Pressure is pressure........
6 psi will flow the same amount of air through
a given hole size, in a given amount of time.
It doesn't matter if its being pushed with a CT27,
or a GReddy T88-34D.

The only way you can get more air through a given hole size & time,
is by increasing the pressure.

Simple gas flow dynamics.

There is more potential for greater flow
(if the pressure is increased)
with the larger turbo.

There is also more potential for increased pressure
with the larger turbo.

But if they are both regulated (with the waste gate)
to the same pressure,
they will both move the same amount of air.

 

[IJ.]

So you're saying a ct26 and a GT45 will flow the same volume/power at 10 psi on a 7M?

 

[bmoss85]

a t88 will flow a larger volume of air at 6psi than a ct26. its the volume of air you get into the engine that counts.

if it were true that a t88 and ct26 flowed the same, no one would need to upgrade their turbo.

thats like saying a truck tire and a bike tire hold the came amount of air because they both can hold 60psi of air.
its the same amount of pressure, just a different volume of air.

 

[BillyM]

Pressure is pressure........
6 psi will flow the same amount of air through
a given hole size, in a given amount of time.
It doesn't matter if its being pushed with a CT27,
or a GReddy T88-34D.

The only way you can get more air through a given hole size & time,
is by increasing the pressure.

Simple gas flow dynamics.

There is more potential for greater flow
(if the pressure is increased)
with the larger turbo.

There is also more potential for increased pressure
with the larger turbo.

But if they are both regulated (with the waste gate)
to the same pressure,
they will both move the same amount of air.

NO THEY DO NOT! They may share the same volume, but if you could count the molecules in that cylinder, you'd come up with some different numbers, I promise you...

The only way to get more air is to increase pressure? ...well ideal gas laws be damned!
"Temperature, you go sit in the corner! ...there is no room for your stupid influence in George's reality."

If gas flow is so "simple" why did you do it wrong?

------------------------------------------------------------------------------------------------------------------

Firstly: Volume is static. ...the volume of air in the cylinder does not change from 6psi out of a t88 or 6psi out of a hair-dryer.

Second: Volume is not density. ...don't get them confused, you'll only confuse others.

Thirdly: Temperature affects everything. ...guess what those silly numbered islands are on a compressor map, Temperature indications!

Lastly: Repeat after me, Temperature, Volume, Pressure, Density. Learn the terms!
-------------------------------------------------------------------------------------------------
For the original poster, to answer your question:

Look at the compressor maps of each for 1.5 pressure ratio between 10 and 30lb/min at 3000-6500rpm and see what the efficiency is like.

A 60-trim will be within 70% eff. from 3000rpm to redline and above 74% eff. through all shiftpoints if shifted at redline.

The stocker, (estimated between t3-60 and t04b-"S"trim by compressor specs), is also at 70% eff. at 3000rpm, but it falls off to 60% at redline.

...now lets look at this at 12psi, say you got a little shimy shim in the wg, ~15lbs/min at 3000rpm, ~35lb/min at redline...

60-trim, we're looking at ~70% eff. at 3k, ~74% eff. at redline at 85krpm turbo speed, averaging over 75% eff. while in boost from 3k to redline.

Stocker, you're seeing ~65% eff. at 3k, ~50% eff. at redline, at over 120krpm turbo speed, averaging less than 65% eff. while in boost from 3k to redline.


...now it stays about the same eff. for the 60-trim all the way up through 18-20 psi or so...

...and the stocker drops off REAL fast.

Eff. affects temperature, and that affects density. Volume is the same, pressure is the same, but if temperature is higher, the density, or ammount of air molecules in there, is lower. ...higher eff, higher density, higher power.

Short answer: upgraded turbo will make more power

--billyM

 

[Sparkynutz]

a t88 will flow a larger volume of air at 6psi than a ct26. its the volume of air you get into the engine that counts.

if it were true that a t88 and ct26 flowed the same, no one would need to upgrade their turbo.

thats like saying a truck tire and a bike tire hold the came amount of air because they both can hold 60psi of air.
its the same amount of pressure, just a different volume of air.

If you are using the same piping same motor and only thing different is the turbo then the only difference in volume would be the turbo housing..... hardly the difference between a bike tire and a truck tire to me.

wouldnt the only real difference be the rate at which the 6psi is acheived and % of total potention of said turbo?

 

[1992supraman]

I asked a fellow member about this yesterday and this is what he said.
"It gets really complicated, but the fact is that the 57 trim flows more air and cooler air at 8 psi than the stocker does. Turbos are pretty cool in that they produce both volume flow and pressure independent from each other (not completely independent, but with an old school supercharger, boost came strictly from flow). A T-78 flowing 10 psi into a 7m could easily make 400 hp, whereas a stock ct-26 couldn't make 400 at 20 psi.

 

[GrimJack]

OMG. I can't believe we are having this debate.

 

[IJ.]

LMAO I did mention my post was the dumbed down Gumby version

Funny how people get caught up with a theory and don't see the reality.

Billy: Nice non Gumby post thanks!

 

[IwantMKIII]

edit: just delete the stupid posts in this thread.....(even this one after the others are dealt with lol)

 

[rumptis]

I consider myself a petty smart person...not as in I know everything but that I can learn things and understand things with some studying and time to ponder it.

However this has never made sense to me.

Like someone said if all things are equal other then the turbo I don't see how the same PSI can push anymore volume of air past the same valve or restriction.

Can someone give us some more technical info or point me in the right direction?

I do now doubt what IJ, Doward and others are saying because they know a lot more then I will never know but I can't put my mind around this.

 

[Scot]

Thanks to a couple of posts on this thread I think I can finally explain why a larger "more efficient" turbo "can" make more POWER than a smaller "less efficient" turbo at the same psi. Hot air bad, cold air good.

 

[GrimJack]

Here's a hint that should point you in the right direction.

Say that turbo #1 compresses 100 pounds of air to 30 psi very efficiently, so that the temperature of said air in the intake manifold is 50F.

Say that turbo #2 compresses 100 pounds of air to 30 psi less efficiently, so that the temperature of said air in the intake manifold is 75F.

Because air is denser as it gets colder, the first turbo can squeeze more mass into the same volume.

Keep in mind that this is just one variable in a *very* complicated equation.

 

[rumptis]

So it's all about temperature, I figured with all the discussion on this there had to be more to it then just temperature but thats all I could figure out myself.

I was wondering how much a difference in density there is at different pressures and temperatures and came across this.

http://www.engineeringtoolbox.com/air-temperature-pressure-density-d_771.html

Does anybody have any true intake temperature readings with different turbos?

 

[GrimJack]

Anyone with a MAFT Pro can log intake temps. Mine sit at around 70 at cruise. Not sure what they jump up to at WOT, I don't have attention to spare when I'm trying to stay on the road.

I'm sure most of the guys with standalone systems could log this too.

 

[IJ.]

Do some reading on "Adiabatic Tables" I used to sit for hours doing Calculations and end up with pages of data to do Turbo/IC sizing.

These days since BB turbo's and Chinese IC's it's much easier now it's a case of "1 BIG Turbo and 1 IC that fits the hole" = BIG bangs and lots of power and smiles from IJ!

 

[87witmoreboost]

NO THEY DO NOT! They may share the same volume, but if you could count the molecules in that cylinder, you'd come up with some different numbers, I promise you...

The only way to get more air is to increase pressure? ...well ideal gas laws be damned!
"Temperature, you go sit in the corner! ...there is no room for your stupid influence in George's reality."

If gas flow is so "simple" why did you do it wrong?

------------------------------------------------------------------------------------------------------------------

Firstly: Volume is static. ...the volume of air in the cylinder does not change from 6psi out of a t88 or 6psi out of a hair-dryer.

Second: Volume is not density. ...don't get them confused, you'll only confuse others.

Thirdly: Temperature affects everything. ...guess what those silly numbered islands are on a compressor map, Temperature indications!

Lastly: Repeat after me, Temperature, Volume, Pressure, Density. Learn the terms!
-------------------------------------------------------------------------------------------------
For the original poster, to answer your question:

Look at the compressor maps of each for 1.5 pressure ratio between 10 and 30lb/min at 3000-6500rpm and see what the efficiency is like.

A 60-trim will be within 70% eff. from 3000rpm to redline and above 74% eff. through all shiftpoints if shifted at redline.

The stocker, (estimated between t3-60 and t04b-"S"trim by compressor specs), is also at 70% eff. at 3000rpm, but it falls off to 60% at redline.

...now lets look at this at 12psi, say you got a little shimy shim in the wg, ~15lbs/min at 3000rpm, ~35lb/min at redline...

60-trim, we're looking at ~70% eff. at 3k, ~74% eff. at redline at 85krpm turbo speed, averaging over 75% eff. while in boost from 3k to redline.

Stocker, you're seeing ~65% eff. at 3k, ~50% eff. at redline, at over 120krpm turbo speed, averaging less than 65% eff. while in boost from 3k to redline.


...now it stays about the same eff. for the 60-trim all the way up through 18-20 psi or so...

...and the stocker drops off REAL fast.

Eff. affects temperature, and that affects density. Volume is the same, pressure is the same, but if temperature is higher, the density, or ammount of air molecules in there, is lower. ...higher eff, higher density, higher power.

Short answer: upgraded turbo will make more power

--billyM

I am totally bummed I missed this thread when it was fresh.

Billy, beautiful delivery.

You sound like fellow mechanical engineer.

 

[BillyM]

I dropped out of engineering school, if that counts!

I do consider myself a hobbyist engineer though...

--billyM