Hx-40wii safe boost on stock compression

[buddy]

boost is a measure of restriction at the engine, not a measure of flow from the compressor. Different chargers most certainly will flow different amounts of air at the same pressure ratios.

Post the compressor maps.

Flow different amounts of air mass, based on their efficiency. At the same intake air temp, the compressor will flow the exact same air mass and volume at the same boost. The amount of boost and demand (restriction which is the RPM of the fixed displacement air pump) does determine how much of each flows through the compressor. Thats why you get a turbo that has more efficiency at the pressure ratio you want to operate. Which might be a differnt turbo based on intended use and goals.

 

[littleboy]

Me thinks you need to go refigure ... stock ata coolers are in the 6-900 cfm range. The basic upgraded ones are 1200 - 1500 cfm.

 

[btfarm]

Higher available volume = faster response. With the added advantage of additional flow reserve for elevated momentum of flow.

 

[THEFERMANATOR]

First dang post of the topic, now who is confused? Go learn yourself to read better.

You are quite frankly. You CLEARLY state the CFM is the same at the same boost pressure, and then say the mass air flow is different. CFM= cubic feet per minute. If the intake air temp is higher, than there is less CFM of air per a given volume of air. Take an 80 cu ft scuba tank(industry standard), it holds 80 cubic feet of air max. At about 90 degrees it is at roughly 1800-2000 PSI of pressure, but at 125 or so it will be up around 2200-2400. The cubic feet of air is exactly the same, but the pressure is different. This is my point that you are confusing "mass air flow" for CFM and your point is being muddied up. CFM IS how much air is moving and IS the measure of the air mass. This is where the confusion is coming into play and why we are pointing out your contradictions in terminology.

 

[Dylly]

At one point this was frustrating me, but now its just ammusing. For myself and Buddy's sake, please familiarize yourself with a couple concepts:

Volume: is the quantity of three-dimensional space enclosed by some closed boundary.... AKA 6.5L of displacement of an engine.

Ideal gas law:
pV=mRT
Rearrange
m=(pV)/(RT)
where,
m= Mass
p= pressure
V= Volume
R= Gas constant

So, (disregarding units)
V= constant (6.5L)
R= Regnault constant

Pressure and Temperature are the only variables here.

As you decrease the temperature at a given pressure, mass increases - which has been stated by Buddy.
As you increase pressure, at a given temperature, mass increases - which has also been stated by Buddy.

Depending on the turbo, a decrease in pressure can create a larger decrease in temperature which overcomes the pressure loss and makes up for it in mass gains.

Thats what you experienced THEFERMANATOR, which can, and will happen when operating a larger turbo in a more efficient range than that of the prior smaller turbo.

 

[THEFERMANATOR]

At one point this was frustrating me, but now its just ammusing. For myself and Buddy's sake, please familiarize yourself with a couple concepts:

Volume: is the quantity of three-dimensional space enclosed by some closed boundary.... AKA 6.5L of displacement of an engine.

Ideal gas law:
pV=mRT
Rearrange
m=(pV)/(RT)
where,
m= Mass
p= pressure
V= Volume
R= Gas constant

So, (disregarding units)
V= constant (6.5L)
R= Regnault constant

Pressure and Temperature are the only variables here.

As you decrease the temperature at a given pressure, mass increases - which has been stated by Buddy.
As you increase pressure, at a given temperature, mass increases - which has also been stated by Buddy.

Depending on the turbo, a decrease in pressure can create a larger decrease in temperature which overcomes the pressure loss and makes up for it in mass gains.

Thats what you experienced THEFERMANATOR, which can, and will happen when operating a larger turbo in a more efficient range than that of the prior smaller turbo.

I FULLY grasp the concept, but the terms are being confused. CFM IS the volume of air moving, plain and simple.

 

[littleboy]

I FULLY grasp the concept, but the terms are being confused. CFM IS the volume of air moving, plain and simple.

x-2 This is why porting heads and bigger turbos make more power. More cfm being pushed through the engine.

 

[ak diesel driver]

2007)


Actual cubic feet per minute (ACFM) is a unit of volumetric capacity. It is commonly used by manufacturers of blowers and compressors. This is the actual gas delivery with reference to inlet conditions, whereas cubic foot per minute (CFM) is an unqualified term and should only be used in general and never accepted as a specific definition without explanation. Since the volumetric capacity refers to the volume of air or other gas at the inlet to the unit, it is often referred to as "inlet cubic feet per minute" (ICFM).

Actual cubic feet per minute is the volume of gas flowing anywhere in a system independent of its density. If the system were moving air at exactly the "standard" condition, then ACFM would equal SCFM. However, this usually is not the case as the most important change between these two definitions is the pressure. To move air, either a positive pressure or a vacuum must be created. When positive pressure is applied to a standard cubic foot of air or other gas, it gets smaller. When a vacuum is applied to a standard cubic foot of gas, it expands. The volume of gas after it is pressurized or rarefied is referred to as its "actual" volume.

The term cubic feet per minute (CFM) is ambiguous when it comes to the mass of gas that passes through a certain point because gas is compressible. If the pressure is doubled, then, for an ideal gas, the mass of the gas that passes by will also be double for the same rate of flow in cubic feet per minute. For instance, a centrifugal fan is a constant CFM device or a constant volume device, meaning that, at a constant fan speed, a centrifugal fan will pump a constant volume of air rather than a constant mass. This means that the air velocity in a system is fixed even though mass flow rate through the fan is not.






Density of air



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The density of air, ρ (Greek: rho) (air density), is the mass per unit volume of Earth's atmosphere, and is a useful value in aeronautics and other sciences. Air density decreases with increasing altitude, as does air pressure. It also changes with variances in temperature or humidity. At sea level and at 15°C according to ISA (International Standard Atmosphere), air has a density of approximately 1.225 kg/m3 (0.0023769 slugs/ft3).





Contents
[hide] 1 Temperature and pressure 1.1 Water vapor
1.2 Altitude

2 See also
3 References
4 External links


[edit] Temperature and pressure

The density of dry air can be calculated using the ideal gas law, expressed as a function of temperature and pressure:

where ρ is the air density, p is absolute pressure, Rspecific is the specific gas constant for dry air, and T is absolute temperature.

The specific gas constant for dry air is 287.058 J/(kg·K) in SI units, and 53.35 (ft·lbf)/(lbm·R) in United States customary and Imperial units.

Therefore:
At IUPAC standard temperature and pressure (0 °C and 100 kPa), dry air has a density of 1.2754 kg/m3.
At 20 °C and 101.325 kPa, dry air has a density of 1.2041 kg/m3.
At 70 °F and 14.696 psi, dry air has a density of 0.074887 lbm/ft3.

The following table illustrates the air density - temperature relationship at 1 atm or 101.325 kPa:

Effect of temperature



Temperature

Speed of sound

Density of air

Acoustic impedance



in °C

c in m·s−1

ρ in kg·m−3

Z in N·s·m−3



+35

351.88

1.1455

403.2



+30

349.02

1.1644

406.5



+25

346.13

1.1839

409.4



+20

343.21

1.2041

413.3



+15

340.27

1.2250

416.9



+10

337.31

1.2466

420.5



+5

334.32

1.2690

424.3



±0

331.30

1.2922

428.0



-5

328.25

1.3163

432.1



-10

325.18

1.3413

436.1



-15

322.07

1.3673

440.3



-20

318.94

1.3943

444.6



-25

315.77

1.4224

449.1

 

[Dylly]

You are quite frankly. You CLEARLY state the CFM is the same at the same boost pressure, and then say the mass air flow is different. CFM= cubic feet per minute. If the intake air temp is higher, than there is less CFM of air per a given volume of air. Take an 80 cu ft scuba tank(industry standard), it holds 80 cubic feet of air max. At about 90 degrees it is at roughly 1800-2000 PSI of pressure, but at 125 or so it will be up around 2200-2400. The cubic feet of air is exactly the same, but the pressure is different. This is my point that you are confusing "mass air flow" for CFM and your point is being muddied up. CFM IS how much air is moving and IS the measure of the air mass. This is where the confusion is coming into play and why we are pointing out your contradictions in terminology.

Yes/ No... Careful about contradicting yourself. CFM is the same at the same boost pressure, infact for an engine, the CFM is the same regardless of pressure, as your scuba example explains.

The above hilighted in Red, is a horrendous attempt at chemistry/ physics. "CFM IS how much air is moving and IS the measure of the air mass. " - you're kidding me right? DEFINITIONS!!! It has been a while since you've done any chemistry or physics, obviously.

An engine demands a certain amount of CFM at a certain RPM... the higher the RPM the more CFM it demands. Now, at 2000 RPM it will demand the exact same CFM regardless of pressure... Keep in mind the CFM increases on the suction side of the turbo with increase in boost pressure BUT the CFM that the engine experiences is EXACTLY the same.

So, CFM is NOT a measure of mass, the Ideal Gas Law works out the Mass based on temperature and pressure.

 

[littleboy]

So... as horsepower goes up cfm requirement goes up. Why??????

 

[buddy]

CFM= cubic feet per minute. If the intake air temp is higher, than there is less CFM of air per a given volume of air. This is where the confusion is coming into play and why we are pointing out your contradictions in terminology.

That is not correct. If the intake temp is higher, there is less mass in a given volume of air, its still a given volume. You could take a cubic foot of air, and heat it up, and it will expand into more volume, like in a baloon or increase the pressure in a fixed volume, or cool it off and it will contract. This much is true, and plays a big part in the system.

Cubic Feet per minute is a volume flow, takes no temperature or mass into consideration. 1 cubic foot is 1 cubic foot is 1 cubic foot. That 1 cubic foot could have 0.07 lbs of mass, or it could have 0.05 lbs of mass depending on its temp, and that is the differecnce between mass and volume flow.

The oxygen tank is compressed air that is referenced at a specific temperature, to give you the exact amount of oxygen particles for an exact amount of breathing time for a given persons demand, and its repeatable. If you fill it with higher temp air, they will have to cram in more than 80cuft to make sure you have the same amount of oxygen. While the air is in the tank, if it heats up, it wants to expand so pressure goes up. This is exactly why there is less mass flow with higher IATs, and also lower CFM through the turbo. If the turbo heats up the air, then that air expands, so its a lot easier to make more boost. But its somewhat pointless because the mass of that volume is lower. If the air remains colder in the intake, then its not expanded as much and it takes the tubro moving more ambiant air to fill the intake and supply the engine demand. So at lower IAT, the turbo and air filter have more CFM demand. This is why a good compressor map is done by air mass and not air volume flow. A good map will be in lbs/hr versus CFM.

Imagine now, you took that 80 cubic feet of air and you evacuate the bottle over 60 seconds, how much CFM did it have? You let 0.39 cubic foot of volume out over 1 minute. That is 0.39 cubic feet per minute. But wait, what the hell, you were told that was 80 cubic feet, so why isnt it 80 cubic feet per minute? When you compress something you are shrinking the volume and increasing the mass, so your bottle has 80 cuft worth of ambiant air in it that is only 0.39 cuft any way you slice it. Just like the fixed volume of the engine.

I am not confused, because I understand all of the principles involved, whereas many people do not.

A DMax has a demand for 600CFM at 5000rpm, but if you are pushing 30psi, that would essentially be 1800CFM. So an 800CFM intercooler is about right and BTfarm explained how an upgrade can help.

The horsepower increase is from torque and RPM. As RPM goes up, so does CFM demand and horsepower. But if you increase the horsepower with more fuel, it really just needs more air mass, and the way you get that is by compressing more air into the same volume or making it colder. So technically, it is a CFM increase at the turbo inlet, but just a mass change to the engine. So its more technically accurate to explain it in terms of air to fuel mass ratios. When you say stoichiometry that is in terms of mass, so if you want a 40:1 air to fuel ratio you need to calculate the fuel mass and then the air mass you will need.

 

[Dylly]

I FULLY grasp the concept, but the terms are being confused. CFM IS the volume of air moving, plain and simple.

I understand what you are saying here only because I now realize that you are talking about at the inlet of the turbo. At the outlet, the CFM is the same regardless of pressure... you can only fill 6.5L to 6.5L no matter if it is 5psi or 100psi... there is just more MASS at 100psi (of identical air) NOT more volume.

Since you fully grasp the gas law concepts, then you must agree that if you have more CFM going through your air filter/ at the inlet of the turbo, the ONLY way you can have a case where pressure is lower but yet flowing more CFM is if the temperature of the air on the engine side is lower... I hope we can agree on that.

 

[THEFERMANATOR]

I understand what you are saying here only because I now realize that you are talking about at the inlet of the turbo. At the outlet, the CFM is the same regardless of pressure... you can only fill 6.5L to 6.5L no matter if it is 5psi or 100psi... there is just more MASS at 100psi (of identical air) NOT more volume.

Since you fully grasp the gas law concepts, then you must agree that if you have more CFM going through your air filter/ at the inlet of the turbo, the ONLY way you can have a case where pressure is lower but yet flowing more CFM is if the temperature of the air on the engine side is lower... I hope we can agree on that.

Yes if you have a colder air mass coming out of the turbo you will be moving more airflow pre-turbo at the same boost level. My pont is I am referencing atmospheric pressure or total flow going into the engine. I could care less how much volume it is moving at pressure so long as it is moving more air into the turbo at the same boost pressure. I grasp your concept of you can only put 6.5L of air into the engine, and to get more you have to increase the pressure of it or decrease it's density to maintain the same boost pressure with more flow. Your thinking CFM after the turbo, and I am figuring CFM for the entire engine.

 

[buddy]

Yet you have to understand the differences in CFM of the engine versus the compressor to design the whole solution. The general use of CFM has caused more confusion than that if everyone understood mass flow. And CFM is not the measure of air mass, its part of the equation, but not enough info to determine accurate air to fuel ratio.

 

[THEFERMANATOR]

Yet you have to understand the differences in CFM of the engine versus the compressor to design the whole solution. The general use of CFM has caused more confusion than that if everyone understood mass flow. And CFM is not the measure of air mass, its part of the equation, but not enough info to determine accurate air to fuel ratio.

I concern myself primarily with TOTAL airflow into the engine, and that was the measurement I referenced in my posts. I reference pre-turbo as it is the most consistent since it is at atmospheric and tells you what EVERYTHING is doing together as a whole versus just what the turbo is doing. I like to use the KISS method, but look at the whole picture.

 

[buddy]

I concern myself primarily with TOTAL airflow into the engine, and that was the measurement I referenced in my posts. I reference pre-turbo as it is the most consistent since it is at atmospheric and tells you what EVERYTHING is doing together as a whole versus just what the turbo is doing. I like to use the KISS method, but look at the whole picture.

Yet, you somehow felt I didnt know what I was talking about and I contradicted myself with the information post turbo. Unless you have a pre-turbo MAF to do engine management its not very useful. Understanding your IATs and boost level, compared to RPM and displacement is how we must determine an appropriate air to fuel ratio, and determine a proper turbo sizing (mass flow), intercooler sizing (engine CFM) and air filter rating (turbo CFM).

And pre-turbo CFM still does not tell you the mass flow, but combined with ambiant air temp sensor it can control the fueling system for desired air to fuel ratio.

 

[THEFERMANATOR]

Yet, you somehow felt I didnt know what I was talking about and I contradicted myself with the information post turbo. Unless you have a pre-turbo MAF to do engine management its not very useful. Understanding your IATs and boost level, compared to RPM and displacement is how we must determine an appropriate air to fuel ratio, and determine a proper turbo sizing (mass flow), intercooler sizing (engine CFM) and air filter rating (turbo CFM).

And pre-turbo CFM still does not tell you the mass flow, but combined with ambiant air temp sensor it can control the fueling system for desired air to fuel ratio.

Explain to me how a pre-turbo mass air flow sensor that measures ALL of the air going into the turbo does not tell you the mass flow? And yo uare overcomplicating the airflow equation. Look at total airflow, boost, and intake air temps. But if 2 turbos are pushing teh same amount of boost, but one is moving more air then it is doing it more efficiently. You don't have to do fancy post turbo airflow calculations and then figure in intake air temp to get air density to achieve it unless you are trying to bring confusion to a situation. Look at airflow into the turbo and boost amount as it makes it a simplified equation.

 

[buddy]

You are now contradicting yourself several times in the this thread. Either a MAF is only a volume sensor or its not. You use CFM and mass flow interchangably.

You dont get it, its simple, and I am not overcomplicating anything, these are basics that so many people dont understand. Air volume flow, CFM, does not tell you anything about mass. It is volume. Maybe this will help, 1000CFM of 40F air is like 80 lbs/min, but 1000CFM of 120F air is only 68 lbs/min. You might not care about the differnce, and make general comparisons, but when youre talking needing 2000CFM pre-turbo or more on some engines it really stacks up against you. And it is critical understanding on gas engines, diesels spoil people for Air to Fuel ratio tolerance.

So to get actual Air Mass Flow you need a temperature sensor, and CFM is not mass flow, its volume.

You maybe never have to care about this because the vehicle manufacturer designs the system to account for these things. Except a lot of people dont have the feedback and control on their engine.

 

[THEFERMANATOR]

You are now contradicting yourself several times in the this thread. Either a MAF is only a volume sensor or its not. You use CFM and mass flow interchangably.

You dont get it, its simple, and I am not overcomplicating anything, these are basics that so many people dont understand. Air volume flow, CFM, does not tell you anything about mass. It is volume. Maybe this will help, 1000CFM of 40F air is like 80 lbs/min, but 1000CFM of 120F air is only 68 lbs/min. You might not care about the differnce, and make general comparisons, but when youre talking needing 2000CFM pre-turbo or more on some engines it really stacks up against you. And it is critical understanding on gas engines, diesels spoil people for Air to Fuel ratio tolerance.

So to get actual Air Mass Flow you need a temperature sensor, and CFM is not mass flow, its volume.

You maybe never have to care about this because the vehicle manufacturer designs the system to account for these things. Except a lot of people dont have the feedback and control on their engine.

You know I had a whole post typed out in response, but I have realized that there is no reasoning with you and your view in this matter. So why should I bother? You have your view on it, and I have mine. I was simply trying to bring a KISS view to this theory, and make it so that others could understand why different turbos react differently. And how running at a given boost level on one turbo can flow differently than another turbo at the same boost level by "keeping it super simple".

 

[WarWagon]

The rule of thumb has been 14 PSI for the factory turbo's because they simply heat the air up more than the extra boost number is worth. Other turbo's are worth more PSI before IAT's get stupid high.

It would be a better question to ask what is your injector pop pressure set at and what is combustion pressure at 20 PSI of boost?

You got more to worry about than prone to fail TTY head bolts as the bottom end is known to crack out on high mile 6.2/6.5 engines. head gaskets blow because these TTY bolts give it up. Or the heads got hot... I have blown other things than head gaskets pushing these engines to the limit. Cooling system, high ECT, has more damage potential than high boost. High IAT, ECT, and boost sustained is hard to say what will give it up first.

I'll I would suggest is take it easy if you are worried about the engine lasting. Being as you are planning an engine replacement - you might as well enjoy it. Myself being cheap, I still don't run anything but head studs. However my first 6.5 was pushed Hard with TTY bolts and they held. The piston scuffed and burned through before the gaskets could blow.