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

[audioman81]

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

[87witmoreboost]

Sounds like you took from school what you needed. Turn a wrench and you'll be two steps ahead of most 2-dimensional engineering graduates.




I dropped out of engineering school, if that counts!

I do consider myself a hobbyist engineer though...

--billyM

[ModularTurbo]

BillyM is completely right I say amen brother.

Also I would like to point out that boost is merely a restriction to flow and is really pointless and unused in any performance calculations that matter. You can not use boost to figure anything out because it is an answer to an equation not a variable to be plugged in in order to solve one.

[Big Rob]

I don't think anyone who has claimed volume is proportional to boost has ever looked at a compressor map. If they had they would notice that for a specific mass flow there are a huge spread of available pressure ratio's.
Its all about MASS of air, MASS of fuel forget about volume.

[figgie]

I don't think anyone who has claimed volume is proportional to boost has ever looked at a compressor map. If they had they would notice that for a specific mass flow there are a huge spread of available pressure ratio's.
Its all about MASS of air, MASS of fuel forget about volume.


huh?

MASS of air is only PART of the overall equation.

DENSITY which is related to Temprature is also needed.

[GrimJack]

huh?

MASS of air is only PART of the overall equation.

DENSITY which is related to Temprature is also needed.Err... you feeling ok today, dude? You've got it backwards, which is odd for you. Temp is used to calculate density, and density is used to calculate mass. Unless my memory deceives me...

[BillyM]

Mass is the final number, presure x density = how many molecules...

Figgie wrong, Grim right...

--billyM

[figgie]

Mass is the final number, presure x density = how many molecules...

Figgie wrong, Grim right...

--billyM


Say what?

What physics/chemistry class where you paying attention to?

Mass does not change. Mass is constant for a given element/chemical (come on this is basics physics!). 1mole of N2 (28.012 Mass Units) + O2 (31.998 Mass Units) is the same wether it is measured here, on planet earth, the moon, jupiter or deep space. Come on! this is one of the first things physics teaches. Mass does not change! Weight does!

As for Pressure?

You ALMOST got it right.

The equation is Mass, Volume Density = Mass(kg or moles) x VOLUME which is no where near the same as pressure. We are not dealing with static gas here!

mass is only calculated for an unknown gas or unless you feel like finding out why the answer is the way it is ;)

Grim

the atmosphere we breath is well known Mass wise (N2 + O2 + traces of the rest). 1.229kg/m^3. There is zero need to calculate mass volume density unless you want to take it down at the mole level.

[GrimJack]

Agreed on the mass not changing bit. However, the volume and pressure do change, by quite a bit, depending on location.

Air at sea level isn't even vaguely close to what is in my intake manifold at 20 pounds of boost.

I currently run MAP, which uses a temperature sensor and a pressure sensor to calculate the mass of the air entering the engine and the ECU adjusts fuel injection to match. I'd have to go look up the ideal gas law as I haven't been in school for 20+ years, but I'd suspect that it'll tell me I can derive mass from pressure and temperature.

[87witmoreboost]

Agreed on the mass not changing bit. However, the volume and pressure do change, by quite a bit, depending on location.

Air at sea level isn't even vaguely close to what is in my intake manifold at 20 pounds of boost.

I currently run MAP, which uses a temperature sensor and a pressure sensor to calculate the mass of the air entering the engine and the ECU adjusts fuel injection to match. I'd have to go look up the ideal gas law as I haven't been in school for 20+ years, but I'd suspect that it'll tell me I can derive mass from pressure and temperature.

Grim,

PV=mRT --> (m/v) = [P/(R*T)] = density

R is constant. You car knows the pressure and temperature, which gives the density. Engine speed determines the rate at which air leaves the manifold, giving a volume. Multiply by that ECU-calculated volume, and there you have mass.

[figgie]

Grim

Actually, the only thing that really has changed at sea level v. the 1+ atmosphere inside of your manifold is absolute pressure.

Barometric compensation - compensates for the density due to altitude if you use it that is. If you do use it, it helps in adjusting for changing exhaust velocity due to the lack of atmosphere hindering the exhaust on it's way out.

Hence why turbo props can go to 20k+ feet and still remain running.

300kpa inside of your manifold stays the same if it is 300kpa @ sea level or 300kpa @ 30k feet. :)

[annoyingrob]

300kpa inside of your manifold stays the same if it is 300kpa @ sea level or 300kpa @ 30k feet. :)
It won't be the same, higher up, you will be running a greater pressure ratio to achieve the same manifold pressure. By going from sea level to somewhere way above sea level, you will likely be running at a reduced efficiency, as you start pushing higher up on the compressor map. ;)

I always calculate using 13.5psi (instead of 14.7) base atmospheric pressure to compensate for my altitude when doing flow calculations..

[figgie]

It won't be the same, higher up, you will be running a greater pressure ratio to achieve the same manifold pressure. By going from sea level to somewhere way above sea level, you will likely be running at a reduced efficiency, as you start pushing higher up on the compressor map. ;)

I always calculate using 13.5psi (instead of 14.7) base atmospheric pressure to compensate for my altitude when doing flow calculations..


Incorrect!

It WILL be the same.

The pressure ratio is irrelevant to achieving said 300kpa. Now your example shows only that it will take more WORK to achieve said 300kpa but in the end. If it take .5 times the work or 1000x the work. As long as it is 300kpa inside of the manifold. 300kpa will be measured anywhere inside of the manifold, if is a Death valley or if it is 75 miles above this planet's surface. ;)

so since you did bring it up.

Show through equation why 300kpa inside of the intake manifold be the same regardless of altitude (I am even going to make it easy for you. sea level and 30k feet is fine).

and just so we are on the same page.

kpa = kilopascals ABSOLUTE

[87witmoreboost]

Incorrect!

It WILL be the same.

The pressure ratio is irrelevant to achieving said 300kpa. Now your example shows only that it will take more WORK to achieve said 300kpa but in the end. If it take .5 times the work or 1000x the work. As long as it is 300kpa inside of the manifold. 300kpa will be measured anywhere inside of the manifold, if is a Death valley or if it is 75 miles above this planet's surface. ;)

so since you did bring it up.

Show through equation why 300kpa inside of the intake manifold be the same regardless of altitude (I am even going to make it easy for you. sea level and 30k feet is fine).

and just so we are on the same page.

kpa = kilopascals ABSOLUTE

Figgie, PLEASE give up on this thread. The point was made many posts back by BillyM.

annoyingrob is right about the pressure ratio, as were most of the other posts that you argued over their theory.

This thread had great info and it's getting tailed with banter. People like to search and find answers without having to read a ton of info that doesn't matter. Mods should delete everything after BillyM's post.

/thread.

[figgie]

Figgie, PLEASE give up on this thread. The point was made many posts back by BillyM.

annoyingrob is right about the pressure ratio, as were most of the other posts that you argued over their theory.

This thread had great info and it's getting tailed with banter. People like to search and find answers without having to read a ton of info that doesn't matter. Mods should delete everything after BillyM's post.

/thread.

I don't think so.

I deal with facts and in this case Physics along with Thermodynamics.

last I checked.

Ideal gas laws, though used incorrectly in this post as we are not dealing with a perfectly static gas is a law not a "theory".

Same with Avograda and Boyle's law which all can be used here though incorrectly.

So seeing as that information that you and annoyingrob posted is infact incorrect. My job is to correct you.

So as I posted to annoyingrob and now you.

Show us through equation why 300kpa inside the manifold @ what altitude X is not the same ( != ) as 300 kpa inside the intake manifold @ altitude Y. How it gets there is at this point irrelevant. Once you figure that out. Then you can put in can turbo X get there efficently, same with Turbo y and turbo z. ;)


and if that is to much work.

How much work does turbo x need to do to flow y cfm @ alt a, @ alt b. (that is assuming that it can flow efficent enough to even get there).


Actually we don't even have to use turbos.

How does an airplane calculate air speed at altitude (the old fashion way of pitot static tubes). How about altitude? Angle of attack?

Btw this is really just a setup question for you two to understand what is actually happening inside of the "system" (which happens to be an engine in this case).



Pressure * density is not only wrong it is INCOMPLETE. You can ask for a delete but it is not happening when the information provided by you two is just flat out incomplete hence why I am asking for an equation solution with real numbers and not typing ;)

also keep in mind.

this is the Turbocharge SME sub-forum not the Turbocharger speculation or best guess sub-forum.


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

I can!

You should come over the EFI101 forums where it is constant.

BillyM got it right on post #7.

Lastly: Repeat after me, Temperature, Volume, Pressure, Density. Learn the terms!


Then he does not heed his own words in post #26

Mass is the final number, presure x density = how many molecules...

Figgie wrong, Grim right...
--billyM

Contradictory since temprature is nowhere to be found..... odd though as he did mention it prior.

Oh well.

You should see when the topic, Barometric Compensation: Needed on a standalone or not comes about. I have "discussed" this subject with Jason S (AEM now doing the Pro_EFI) and he never backdown from the BACP not being needed. Talk about fun discussion!

[87witmoreboost]

I don't think so.

I deal with facts and in this case Physics along with Thermodynamics.

last I checked.

Ideal gas laws, though used incorrectly in this post as we are not dealing with a perfectly static gas is a law not a "theory".

Same with Avograda and Boyle's law which all can be used here though incorrectly.

So seeing as that information that you and annoyingrob posted is infact incorrect. My job is to correct you.

So as I posted to annoyingrob and now you.

Show us through equation why 300kpa inside the manifold @ what altitude X is not the same ( != ) as 300 kpa inside the intake manifold @ altitude Y. How it gets there is at this point irrelevant. Once you figure that out. Then you can put in can turbo X get there efficently, same with Turbo y and turbo z. ;)


and if that is to much work.

How much work does turbo x need to do to flow y cfm @ alt a, @ alt b. (that is assuming that it can flow efficent enough to even get there).


Actually we don't even have to use turbos.

How does an airplane calculate air speed at altitude (the old fashion way of pitot static tubes). How about altitude? Angle of attack?

Btw this is really just a setup question for you two to understand what is actually happening inside of the "system" (which happens to be an engine in this case).



Pressure * density is not only wrong it is INCOMPLETE. You can ask for a delete but it is not happening when the information provided by you two is just flat out incomplete hence why I am asking for an equation solution with real numbers and not typing ;)

also keep in mind.

this is the Turbocharge SME sub-forum not the Turbocharger speculation or best guess sub-forum.




I can!

You should come over the EFI101 forums where it is constant.

BillyM got it right on post #7.




Then he does not heed his own words in post #26



Contradictory since temprature is nowhere to be found..... odd though as he did mention it prior.

Oh well.

You should see when the topic, Barometric Compensation: Needed on a standalone or not comes about. I have "discussed" this subject with Jason S (AEM now doing the Pro_EFI) and he never backdown from the BACP not being needed. Talk about fun discussion!

You ARE correct about pressure not changing at different altitudes, assuming constant temp.

It is tiring to read your posts because you bounce all over the place with your theory. Point being, your rants arguing everyone about their technical engineering theory is unnecessary and at times, incorrect.

This was sweet thread up to the end of page 2. I hate to knock on you as you seem to have a good technical understanding of things, but it's just old now. Let this thread die so that when people search for information about pressure in larger turbo's, they can read all that they need in two pages. I am equally adding to the rant here, but it's an attempt to preserve this information.

Nothing personal, let it end.

[IJ.]

87wit: No it's not going to be deleted.

Accept it that Figgie has taken the time to provide a complete answer and move on.

I'm quite happy to be corrected if I'm wrong about something and look at it as furthering my knowledge and will thank someone for educating me.

[BillyM]

BillyM got it right on post #7.

Then he does not heed his own words in post #26

"pressure x density"

Contradictory since temprature is nowhere to be found..... odd though as he did mention it prior.

Oh well.


Typo on my part, I meant to say Volume x Density ...doesn't make you right though.

Mass is the final result. Volume x Density.
Density is a factor of Pressure & Temperature. <--there is where temperature went, it wasn't missing

...and the next person who says pressure-ratio doesn't matter, all that matters is total MAP, I add to my ignore list. Try sizing a turbo for a motor at sea level and then size one at 10,000ft. Pressure ratio is absolutely important. ...that is how you derrive the efficiency of the turbo, and thusly temperature. <--important

Figgie, you realize this whole arguement was started by symantecs, right? Big Rob wasn't saying "mass" as in the specific mass of air, he was saying total mass of the air in the cylinder, and he's 100% right in that. Mass is the final number. Yes, "the mass of air" is not the final answer, but the "mass of the air in the cylinder" is.

--billyM

[Big Rob]

Mass of air in cylinder + mass of fuel in cylinder with spark equals bangs ;).

[annoyingrob]

So seeing as that information that you and annoyingrob posted is infact incorrect. My job is to correct you.

So as I posted to annoyingrob and now you.

Show us through equation why 300kpa inside the manifold @ what altitude X is not the same ( != ) as 300 kpa inside the intake manifold @ altitude Y. How it gets there is at this point irrelevant.


Argue with you? OK!

With all else being equal, 300kpa is 300kpa is 300kpa. You are entirely corect with this, nobody is arguing that. What I AM arguing about is that not everything else is equal. Air temperature will be different within the manifolds.

Lets say at location A, air pressure is 100kpa. You want 200kpa in your manifold. That's a 2:1 pressure ratio your turbo needs to run at. At location B, air pressure is 60kpa. To achieve 200kpa in the manifold, the turbocharger is now running at a 3.3:1 pressure ratio.

http://www.turbobygarrett.com/turbobygarrett/images/catalog/Turbochargers/gt40_images/GT4088_703457_2_comp_e.gif

Here's a compressor map of a Garrett GT40-88.

To create that 200kpa at location A, the turbocharger is running at 74% efficiency. To create 200kpa at lcoation B, the turbocharger is only running at 72% efficiency. The reduced efficiency of the compressor means that it's pumping more heat into your air charge. That means the air in your intake manifold, while still being the same 200kpa, is hotter.

And with your seemingly massive knowledge of thermodynamics, you understand that while at the same pressure, the hotter gas will have less density.

So there, my point is proven. It's not the same, it's less efficient. 300kpa at sea level will be a denser charge than 300kpa up in the sky, running the same motor and turbo, which you told me was wrong.

[Doward]

Guys, I seriously have a tear in my eye right now, reading all this (I'm so proud of the discussion!) I've got to go pick up a laptop, then I'll be back to straighten this out.

You guys all seem to be forgetting a very basic thing - these are equations, and they can be worked both ways.

In a given turbo system, volume WILL be static. If you increase mass of air, you MUST increase the density. Works the other way around - increase the density, you increase the mass.

Doesn't matter if it's by pressurization or temperature. The fact is, if you can make a CT26 and a PTE67 make 20psi of boost, you are not getting the same amount of power due to difference in temperature. If you have a PTE67 making 15psi and 20psi, you get differing power levels not so much according to temperature, but more due to the pressurization delta.

300kPa is 300kPa. I don't care if you make it here, or on the Moon. What IS different, however, is how much work it took to make that 300kPa (figgie hit this one) - if you are attempting to make 300kPa from a 100kPa atmospheric pressure, that takes a certain amount of work.

Making 300kPa from a 50kPa atmospheric pressure, takes much more work. This is reflected, as Ian pointed out, in the Adiabatic Tables. You can also calculate Adiabatic Efficiency with the flow map - map out your Pressure Ratio (which will take into consideration the atmospheric pressure you start with) and figure out your mass flow of air. X/Y coordinates that point right at your AE, provided other variables are held constant (you can look up and see what temperature points are used, but invariably, we can figure everything out if we know the atmospheric temperature and pressure at any given moment)

[BillyM]

I'll one up Rob's map, and I'll map out the pressure ratios on a t04e 60trim, that a 5m turbo will consume at ~350hp. The first map is at sea level, the second is at ~14k feet, or .6 atmospheres, as Rob has has used in his explaination. Temperatures are static, and I've not compensated for the effect of reduced pressure at the tailpipe on spool speed.

Actually, the only thing that really has changed at sea level v. the 1+ atmosphere inside of your manifold is absolute pressure.

Barometric compensation - compensates for the density due to altitude if you use it that is. If you do use it, it helps in adjusting for changing exhaust velocity due to the lack of atmosphere hindering the exhaust on it's way out.

Hence why turbo props can go to 20k+ feet and still remain running.

300kpa inside of your manifold stays the same if it is 300kpa @ sea level or 300kpa @ 30k feet. :)

Your "holy-crap-batman-surging" 60-trim at 14k feet says otherewise...
HAC also compensates for turbo efficiency, don't forget it.
Enjoy,

--billyM

[figgie]

I'll one up Rob's map, and I'll map out the pressure ratios on a t04e 60trim, that a 5m turbo will consume at ~350hp. The first map is at sea level, the second is at ~14k feet, or .6 atmospheres, as Rob has has used in his explaination. Temperatures are static, and I've not compensated for the effect of reduced pressure at the tailpipe on spool speed.



Your "holy-crap-batman-surging" 60-trim at 14k feet says otherewise...
HAC also compensates for turbo efficiency, don't forget it.
Enjoy,

--billyM

and you are not telling me anything I don't know. ;)


BTW

you forgot one thing on that nice graph. That is only HALF of the turbo equation. That particular half is the compressor section but where is the turbine section along with the associated A/R? Also you are making a terrible assumption that the pressure ratio inside of the system (which in this case is the motor) is open to atmosphere where it is not.


again, 300 kpa @ 40k = 300 kpa @ 0 feet. How you GET THERE is what changes but the end number is the SAME. Be it by TurboA or undersize TurboB, Turbine, Auxilary power units doing the work, Compressor driven on 3 phase 440v airplane electrical system.

CAPISCE?

***I am feeling generous today.

http://www.turbobygarrett.com/turbobygarrett/tech_center/turbo_tech103.html
Now with all that information, let see equations.

btw no cheating in using google, I myself do not need "graphs", equations only please. and BillyM that graph is nice and all, but like my professor used to tell me, show the work and add the exhaust turbine section that you missed. I "do not know" how you arrived at your conclusion and I can not read your mind to see how you derived your answer. ;)***

[BillyM]

...you sound like a chump, fresh out of a entry-level college chemistry or physics class. Infact, you're probably the asshole who argues with the teacher on, wait for it, symantecs as he's using non-standard methodology to help the class understand a difficult subject. So you have a solid grasp on the physics behind it *claps* (you might not be the only one), now figure out how to help people with it, instead of slinging it around trying to impress others.

You can throw around the "rules" all day long, and it's still not going to help 90% of the people on this forum. I put my information into visible graphs, helpful simulations, and easy to understand "what if" methods for the benefit of the greater majority.

-It is important that people understand that different turbos put different ammounts of air in the motor at the same pressures. This is due to efficiency-related temeperature's effect on the density of air in the cylinder.

-It is important that people understand different elevations cause change in a BIG way of how capable a turbo is in any certain running circumstance. Telling people that 14psia is the same at sea level and 30k feet is "correct" but the way that the general populous perceives that is "my car is turbo, it will make the same power at sea level and 30k feet".

I'm done in this thread, don't worry, figgie will help make this clear as mud for you who are trying to learn something...

--billyM

[figgie]

Too much crying because he does not know equations

--billyM

Ahh someone's feeling are hurt!

Shame too as this was a nice thread too!

FYI

Incase you missed it, this is the technical section where you either post facts and items to support facts and not hyperboles & answers or you just mosey right along to other less technical parts of this forum. Crying, throwing tantrums when cornered does not do anything save create noise as with your last post.

Myself, I could care less what you think, assume, guess at who I am or what I do. In the end, it does not affect me in any way, shape or form.

general populous perceives that is "my car is turbo, it will make the same power at sea level and 30k feet".

and then at that point we would correct the "general supramania populous". The "General Populace" could care less how it works.

[BillyM]

87witmoreboost was right on the money on the last page... Your incessant ranting over theory, while correct (noone else is incorrect), is tiring. Consider me tired.

People aren't going to get anything out of your method of "help" in this thread, and I won't waste my time playing your game of "ego stroke" because I'm plenty secure in my grasp and knowledge of how this all works and I just flat don't have the time. If you need that kind of attention, you might want to go back to class and argue with the instructor. Atleast he's paid to put up with your kind of personality.

The first person who tells you you're a donkey, you can tell him he's wrong.
The second person who tells you you're a donkey, you can explain why you're not.
The third person who tells you you're a donkey, you might just be an donkey.

--billyM

[figgie]

87witmoreboost was right on the money on the last page... Your incessant ranting over theory is tiring. Consider me tired.

The first person who tells you you're a donkey, you can tell him he's wrong.
The second person who tells you you're a donkey, you can explain why you're not.
The third person who tells you you're a donkey, you might just be an donkey.

People aren't going to get anything out of your method of "help" in this thread, and I won't waste my time playing your game of "ego stroke" because I'm plenty secure in my grasp and knowledge of how this all works. If you need that kind of attention, you might want to go back to class and argue with the instructor. Atleast he's paid to put up with your kind of personality.

--billyM

my my. Someone ate a sour bowl or two of stale cheerios today.


I suggest you look my previous history up. I have no ego. I have and will call incomplete statements, ignorant statements etc. Symantecs, no such thing. Typing leaves zero room for interpretation so when I come in and post, is because there was lots of room for interpretation.

Anyway. I don't feel like derailing this thread anymore than what you already did... so exit stage right I go.

[Doward]

...you sound like a chump, fresh out of a entry-level college chemistry or physics class. Infact, you're probably the asshole who argues with the teacher on....

You just lost any respect in this discussion you may have had. Resorting to name calling ends your side of the argument rather effectively, in my opinion.

The 'technical engineering theory' as it was called by someone previously, holds completely true. The fact of the matter is there are too many variables (has anyone here even considered the airflow velocity changes in the curves on the IC system? Or pressure drop from the IC? Pressure drop from the filter? Exactly.)

Don't get pissed because someone mentioned there is more to something than an oversimplification presents. I do it all the time, taking the technical and 'dumbing it down' so the average Joe can understand it. Many times I get called on it, that there is 'more than meets the eye' to the subject I'm trying to explain. Those people generally fall into the same category I do - there is RIGHT and there is WRONG. Period. I don't mind breaking out of that mold to help someone else understand a complex subject, however.

That said, this is a TECHNICAL forum. There will be TECHNICAL THINGS PRESENTED. No big deal - PM someone if you don't understand something. I enjoy explaining things in layman's terms :)

[87witmoreboost]

I love/hate this thread.

[GrimJack]

Guys, keep it civil. The debate in here was going rather nicely until you had to start taking shots at each other instead of the subject.

[Snotcycle]

ok, so its really late but im going to take a stab at explaining this in words everyone can understand.

The next time you go into starbucks to get a fattening pastry and bad coffee, go over to where they keep the milk and sugar. Carefully take a big straw(white wrapper with black on the ends), and a little straw(white wrapper with green on the ends). first blow through the little straw with significant force, then blow through the big straw. to achieve the same given (manifold) pressure--or resistance--with both straws require very different volumetric flows. IE you must blow ALOT more air through the big straw than the small one.

Anyone who does this experiment and does not come to a similar conclusion is either a bumbling idiot and should never have been allowed near a computer. or they are kin of the divine, and i will buy them coffee so they can show me.

/endthread
AMIRITE?

[zambini]

never understood th8is relationship until this thread.. so psi is a measure of VOLUME, and the density OF that volume, depending on temerature, allows more or less MASS into a space!

word.

thank you.

[Nick M]

Interesting thread.

[figgie]

Minus well put this thread to rest.

http://www.supramania.com/forums/showpost.php?p=1142019&postcount=1

That spreadsheeet was created by me to help a couple of the techie folks in this great forum out.

It is configurable for lots of things.

Atmospheric pressure, VE of engine, Engine displacement etc.

play around with it and see the relationship between turbo volume v. power, plenum pressure v. displacement, Turbo sizing v. efficency points. These are rough guesses but can get you really close.

Those turbos in that spreadsheet are the Garrett GT series ball bearing turbos with one inclusion of the HKS T04z replica made by ATP Turbo.

[Nick M]

I do it all the time, taking the technical and 'dumbing it down' so the average Joe can understand it.

I don't see a problem as long as it is accurate.