Hx-40wii safe boost on stock compression

[sathackr]

Ok. Buddy and Dylly are correct.

I'm not a turbo expert but I do understand the basic laws of physics and the principals of fluids under pressure, the work required to move them, and what happens to them when you perform work on them.

Take 2 tanks of an equal volume...say 0.5 cubic ft (scuba tank).

Fill one to 20psi using a small compressor.
Fill the other to 20psi with a big compressor.

Q. Which compressor moved more air?

A. Neither. Both tanks have the same volume of air at 20psi. (Ok, maybe the one filled with the small compressor has a tiny amount more air as it took longer to fill and had time to cool, but the difference is negligable)

At a given pressure, your engine's cylinder(essentially an air tank), at the bottom of it's intake stroke, will hold a given amount of air(.8125 liters to be exact).

It doesn't matter if you used a leaf blower or Hurricane Katrina to push that air in there. If they are both at 20psi then they both hold .8125 liters of air at that 20psi.

Now...all turbos create backpressure. Anyone who says a turbo is free energy is not correct. That 30psi of backpressure the GM-4 turbo generates to make 15psi of boost...What do you think created that? A compressor...your piston to be exact. And guess what it took to compress that air? Energy. Where did that energy come from? Your crankshaft. Energy used to compress air going out the exhaust valve is energy that doesn't make it to your rear wheels.

If you install a more efficient turbo that can create an equivalent level of boost at a lower backpressure, you just saved yourself that energy that was initially needed to drive your inefficient turbo at 30psi. I think the ATT dropped the backpressure by something like 20psi. Less energy to drive the turbo = more energy to drive the wheels.

And we got another nice effect...ever felt an air compressor when it's running? Yep it's hot. As anyone that's ever looked at the IAT under boost knows, when you compress air, it gets hot. But wait...we're compressing the exhaust gas less. It used to be at 40psi, now it's at 20psi with our new, efficient turbo. Guess what that means? Lower exhaust temperatures. Probably significantly lower. Ever seen your IAT under 20psi of boost with no intercooler? Probably somewhere around 400 degrees...a 300 degree increase in temperature for that 20psi. Since our exhaust is cooler guess what we can do? Make more power!

So...that nice performance increase you saw didn't come because the turbo has magic pixie dust that flows more air at the same psi. For a given temperature, volume, and pressure, the mass of the air must remain constant, at least in this dimension. The performance increase came from the more efficient wheels that create the same level of boost at a reduced backpressure.

Horsepower requires fuel. Fuel requires air. The more fuel molecules and air molecules you can pack into your cylinder, the more horsepower you can make till it goes boom. The less of those horsepowers you use to make that horsepower, the more you have going to the wheels.

 

[buddy]

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".

Except you were spreading false logic, that helps no one learn the truth in design. You cannot oversimplify CFM vs mass flow, otherwise you would never be able to read a compressor map accurately.

 

[THEFERMANATOR]

Except you were spreading false logic, that helps no one learn the truth in design. You cannot oversimplify CFM vs mass flow, otherwise you would never be able to read a compressor map accurately.

Let me lay it out for you in a way that even a kindergartner could understand. Take 2 80 cu foot tanks, both at 2000 PSI. Make one of them 100 degrees and the other at 130 degrees. Which one will have more volume of air in it? Obviously the tank thats 100 degrees will have more air in it at the same pressure due to the difference in the density of the air in it. Using your logic both would have the same mass in them, yet I guarantee you the cooler tank will have more mass in it by weight and by cubic feet of air in it. I may be confusing the terminology that an engineer would use with those that a "common sense" educated person would use by using your logic. I understand what your trying to say, but obviously others here do not. And it is the way you are conveying it that is the problem. ANYTHING can be simplified. This discussiuon reminds me of when I used to deal with engineers when I was a line tech. They would always go into these big in depth explanations that would confuse the hell out of anybody other than an engineer, and in the end they wouldn't be able to find a solution to the issue at hand. Apply some "common sense" thinking and the KISS method, and I would find the solutions to problems they couldn't. So I was not spreading "false logic" as you accuse me of, I was simply breaking it down to try and make it "easier" to understand that it IS possible to get more air at the same boost. Your wording is like reading a lawyers contract for something with fine print.

 

[buddy]

OMG, you are kidding me. Just because you cannot comprehend the written English language does not mean you should jump into a thread to discredit the truth of how things are ENGINEERED. This is not complicated, and if you are going to come to a thread about turbochargers you better be prepared to back up your claims. So far you have actually made several false staements and now trying to reconcile them. The simpified view is not the truth, and cannot be trusted when making design choices.

How many times do I have to say colder air has more mass, I have said it every step of the way and you have ignored it, I explained why you air tank has difference pressures based on mass. Maybe you havent figured it out, but just because it says 80cuft on it, doesnt mean someone put 80cuft of air in it, they put the required amount of volume in it, to get the right mass, and so it doesnt explode from overpressure if it heats up after filling. That might be 60cuft, it could be 90cuft of ambiant air based on the temperature when filling. The reason I harp on this is because people keep preaching CFM, which is volume, not mass. I showed you that the same volume could have less mass when it was hotter. What more do I have to say so you understand it? If youre going to talk turbo tech, you have to speak in terms of both CFM and mass flow. That is if you want to be correct.

I tried to explain this a few years ago, and it was painfully obvious no one wanted to understand it then. So I will leave you to understand it how you would like to.....unsubscribed

 

[buddy]

Where is the unsubscribe, used to be in usercp that there is no link for anymore!

To make the link easier, the air tank, is like post turbo, so if trying to look at this preturbo, you have to look at pre-air compressor machine. If you put 80cuft in, depending on the temperature, the mass will vary greatly. Its not the same mass necessarily if you just put in 80cuft, unless you use a controlled temperature value. What I am assuming is they fill the bottle to a particular pressure based on the ambiant air temperature. However, once in the bottle, if it heats up, its no longer 80cuft of air. If you release it, it could be 100cuft of air, each cuft having less mass. So after compression you cannot think in terms of precompression volume, and you cannot guarantee that because you pumped 80cuft of air in there that it has the same oxygen content as another 80cuft of air.

 

[Dylly]

Let me lay it out for you in a way that even a kindergartner could understand. Take 2 80 cu foot tanks, both at 2000 PSI. Make one of them 100 degrees and the other at 130 degrees. Which one will have more volume of air in it? Obviously the tank thats 100 degrees will have more air in it at the same pressure due to the difference in the density of the air in it. Using your logic both would have the same mass in them, yet I guarantee you the cooler tank will have more mass in it by weight and by cubic feet of air in it. I may be confusing the terminology that an engineer would use with those that a "common sense" educated person would use by using your logic. I understand what your trying to say, but obviously others here do not. And it is the way you are conveying it that is the problem. ANYTHING can be simplified. This discussiuon reminds me of when I used to deal with engineers when I was a line tech. They would always go into these big in depth explanations that would confuse the hell out of anybody other than an engineer, and in the end they wouldn't be able to find a solution to the issue at hand. Apply some "common sense" thinking and the KISS method, and I would find the solutions to problems they couldn't. So I was not spreading "false logic" as you accuse me of, I was simply breaking it down to try and make it "easier" to understand that it IS possible to get more air at the same boost. Your wording is like reading a lawyers contract for something with fine print.

I was going to explain all the holes in your example but I think Buddy did a good job.. This isn't rocket science, but you should be refunded whatever you paid for your "common sense education". There is a fine line between bull$hit and lies, and well.. I see through the bull$hit.

Now the only thing that you said that was the truth is that you can run more CFM of ambient air (Pre turbo) at a lower engine pressure (post turbo) with a larger turbo.... This means you are flowing more mass but ONLY if the selected turbo causes the AIT temperature to be lower. There is no other way it can happen. The only variables are pressure, mass, and temperature since the volume of the engine is fixed. So, if both engines sitting side by side, at the same elevation, are set to the same psi but running different turbos, pressure is now a constant, not a variable. The only two variables left are mass(pre or post turbo, no difference) and temperature(post turbo only/ IAT). Now, if you know the temperature of the air going into the turbo and the CFM going into the turbo you can figure out the mass of the air... but the MAF sensor would figure that out for you.

So, if you are seeing different numbers from your MAF sensor at the same psi, the temperature post turbo has to be different. The one showing a higher MAF number will be at a lower Air Intake Temperature.

You can flow more CFM pre turbo which essentially means more mass AND show the same pressure inside the engine ONLY if the temperature of the pressurized gas is lower.

 

[littleboy]

I was going to explain all the holes in your example but I think Buddy did a good job.. This isn't rocket science, but you should be refunded whatever you paid for your "common sense education". There is a fine line between bull$hit and lies, and well.. I see through the bull$hit.

Now the only thing that you said that was the truth is that you can run more CFM of ambient air (Pre turbo) at a lower engine pressure (post turbo) with a larger turbo.... This means you are flowing more mass but ONLY if the selected turbo causes the AIT temperature to be lower. There is no other way it can happen. The only variables are pressure, mass, and temperature since the volume of the engine is fixed. So, if both engines sitting side by side, at the same elevation, are set to the same psi but running different turbos, pressure is now a constant, not a variable. The only two variables left are mass(pre or post turbo, no difference) and temperature(post turbo only/ IAT). Now, if you know the temperature of the air going into the turbo and the CFM going into the turbo you can figure out the mass of the air... but the MAF sensor would figure that out for you.

So, if you are seeing different numbers from your MAF sensor at the same psi, the temperature post turbo has to be different. The one showing a higher MAF number will be at a lower Air Intake Temperature.

You can flow more CFM pre turbo which essentially means more mass AND show the same pressure inside the engine ONLY if the temperature of the pressurized gas is lower.

You post such an educated post yet you ask the question that started this thread.... :rolleyes5: Seems you should be able to figure out what you need to know from all that edjumucation.....:hello:

 

[Slim Shady]

Is the volume of the engine fixed from the cylinder volume only, or the intake and cylinder volume. Since the valve is closed and the cylinder volume only becomes available when the valve opens and only for a short period of time. Would this set up a pressure pulse in the intake of which the compressor woudl have to work against?

Then would we need to figure in leakage past the compressor wheel since we are not using a positive displacement pump.

Just some questions? I may be stupid as well and just not know it so I am asking.

 

[Dylly]

You post such an educated post yet you ask the question that started this thread.... :rolleyes5: Seems you should be able to figure out what you need to know from all that edjumucation.....:hello:

Haha its funny because i recieved my answer on the first page: 20 psi.

Unfortunately i know very little about back pressure which is why i started this thread.

 

[Slim Shady]

Is the intake manifold in its entirety and the cylinder considered the fixed volume, maybe we could think of the intake as the accumilator in the pressure system. If we go to higher and high pressure would the pressure wave from the valve closing create a pressure spike which would cause a negative effect on the compressor causing the flow to stop or (stall) for a specific period of time or would the air continue to compress causing the air to heat up building more heat and pressure, then would the mass of the charge in the cylinder be less, becuase of the compression pulse heating? Or am I full of it ? Doesn't all this play a certian part in the equation or is it just that simple to plug in numbers and get the correct answers the first time. I guess then we would not need product testing if everything was just simple enough to plug in ALL (key word) the numbers. JUSt asking cause I am not an engineer or an engineering student, of course I can pay someone (family) to do that for me so I don't have to know, I can be just plain stupid in engineering and be semi smart in other things.

 

[sathackr]

Is the volume of the engine fixed from the cylinder volume only, or the intake and cylinder volume. Since the valve is closed and the cylinder volume only becomes available when the valve opens and only for a short period of time. Would this set up a pressure pulse in the intake of which the compressor woudl have to work against?

Then would we need to figure in leakage past the compressor wheel since we are not using a positive displacement pump.

Just some questions? I may be stupid as well and just not know it so I am asking.

Slim - I think there would be a slight pressure spike, similar to water hammer when you shut off a faucet quickly, though not nearly as violent since air compresses much better than water. To consider all variables I think would likely need a mathematical model running on a supercomputer. Variable such as:

Remaining pressure in cylinder after the exhaust valve closes.
--Even if it closes exactly at TDC of the exhaust stroke, there is still volume in the precups.
--Less backpressure = less exhaust mass remaining in the cylinder.
--(I think this is what Slim was referring to) Say there is a bunch of backpressure and the mass in the precups is at 40psi. When the intake valve opens, would that cause a minor pressure wave causing a short-lived reversal of the intake air flow? Obviously the pressure would quickly drop as the piston continued down it's intake stroke but what effect does that have?

Compressor efficiency/turbo maps. I know nothing about these. I see people talk about operating a compressor closer to its efficiency peaks, but I don't understand the relation of that to the temperature of the compressed air. I've always thought compressing a fixed amount into a fixed space would generate a fixed temperature rise unrelated to the device actually performing the compression.



To the other argument...I've lost track of what's what and who's who. I think everyone's on the same page they are just describing it differently. I think I can help and I was a little off in my previous post regarding the definition of a cubic ft of air.

The NIST(National Institute of Standards and Technology) defines a cubic ft: "A standard cubic foot of gas is defined as a cubic foot at a temperature of 21 ºC (70 ºF) and a pressure of 101.35 kilopascals (14.696 psia)" Pg 125 Uniform Regulation for the Method of Sale of Commodities

Therefore, a given volume that flows x cfm can flow a higher cfm at a higher pressure even though the volume is the same. More pressure at the same temperature = more cfm. Same pressure at lower temperature = more cfm. When something is rated at X,XXX cfm, that rating is done at 0psi(or 14.7, depending on how you look at it)

The only way you can flow more air mass/cfm at the same volume and pressure is by reducing the temperature. If Turbo A produces 20psi of boost at a 300ºF IAT and Turbo B produces 20psi of boost at a 150ºF IAT then Turbo B will move more air at the same pressure. I don't feel like doing the math to determine exactly how much air but I don't think it is the primary source of power increase of Turbo B. I think the primary power increase comes from the reduced backpressure. I also don't understand enough about compressor wheels to understand how one wheel can produce the same boost at a lower temperature than another. Maybe someone who does could help out with that?


When volume, temperature, and pressure are kept constant, mass remains constant as well.

Take a normal scuba tank. It's volume is about .5cu ft. It holds 80cuft(at 14.7psi) of air, at 3000psi. When it's filled, it gets hot. If you open the valve on it and let the air out, you will have an ice-covered valve shortly. Scuba shops typically overfill them slightly. 3300psi in a hot tank = about 3000psi in a cool tank. Pressure changed, air mass did not. No air left the tank even though the pressure went down 300psi. The same volume at a lower temperature can contain a greater mass of air.

 

[Slim Shady]

Thank you, I think that there are a lot of variables that need to be considered. Not just simple enought to say this works because the numbers say it does. Forget one part of the equation or get one number wrong and it all is trash. Super computer is something we all have (it is called a brain) just some are better at somethings than others and to be good at something and slam someone for not being good at it is a bad thing. It always amazed me seeing people write music from scratch, now that is super computing.

 

[THEFERMANATOR]

OMG, you are kidding me. Just because you cannot comprehend the written English language does not mean you should jump into a thread to discredit the truth of how things are ENGINEERED. This is not complicated, and if you are going to come to a thread about turbochargers you better be prepared to back up your claims. So far you have actually made several false staements and now trying to reconcile them. The simpified view is not the truth, and cannot be trusted when making design choices.

How many times do I have to say colder air has more mass, I have said it every step of the way and you have ignored it, I explained why you air tank has difference pressures based on mass. Maybe you havent figured it out, but just because it says 80cuft on it, doesnt mean someone put 80cuft of air in it, they put the required amount of volume in it, to get the right mass, and so it doesnt explode from overpressure if it heats up after filling. That might be 60cuft, it could be 90cuft of ambiant air based on the temperature when filling. The reason I harp on this is because people keep preaching CFM, which is volume, not mass. I showed you that the same volume could have less mass when it was hotter. What more do I have to say so you understand it? If youre going to talk turbo tech, you have to speak in terms of both CFM and mass flow. That is if you want to be correct.

I tried to explain this a few years ago, and it was painfully obvious no one wanted to understand it then. So I will leave you to understand it how you would like to.....unsubscribed

So then lets cut the bullshit, heres a yes or no question for you. Is it possible for 2 different turbos to flow 2 different amounts of air on the same engine under the same boost and envirmental conditions?

 

[littleboy]

Thank you, I think that there are a lot of variables that need to be considered. Not just simple enought to say this works because the numbers say it does. Forget one part of the equation or get one number wrong and it all is trash. Super computer is something we all have (it is called a brain) just some are better at somethings than others and to be good at something and slam someone for not being good at it is a bad thing. It always amazed me seeing people write music from scratch, now that is super computing.

People that write music from scratch are talented for sure! I know nothing about music so i leave that to those that know music. Some days i feel like i have a half decent understanding of engines so i occasionally get these ideas and i grab parts and throw an engine together. If it doesn't run like i want it to i tweak things till i get the results i want. This is how i learn.... keyboard racing doesn't get engines built an parts tested. :hihi:

 

[THEFERMANATOR]

People that write music from scratch are talented for sure! I know nothing about music so i leave that to those that know music. Some days i feel like i have a half decent understanding of engines so i occasionally get these ideas and i grab parts and throw an engine together. If it doesn't run like i want it to i tweak things till i get the results i want. This is how i learn.... keyboard racing doesn't get engines built an parts tested. :hihi:

And is why desktop dyno software can be off as much as 20%. There will ALWAYS be a difference between theory, and reality. Just because something works on paper, doesn't mean it will work in the real world.

 

[buddy]

So then lets cut the bullshit, heres a yes or no question for you. Is it possible for 2 different turbos to flow 2 different amounts of air on the same engine under the same boost and envirmental conditions?

YES!!! and I have never said otherwise, but you fail to understand the basic concepts that allow that to be true. The use of CFM or volume where air mass applies and using them interchangeably is a big clue that someone doesnt truly understand. It is not always true, and has everything to do with operating within different compressor efficiency islands and whether or not you are cooling the intake charge. Technically for one to flow more air at the same pressure, they flow out the same volume of air (CFM), with different air mass. They would in flow different volumes (CFM), the one with lower post compression IAT having taken in more ambiant volume to make the same boost pressure. That is because the turbo would have transferred less heat to the intake charge, thereby less of the boost pressure due to air volume expansion from heat. So its also easily possible that two different turbos also flow the same air mass at the same pressure, if having the same efficiency.

Compressor efficieny tells you how much the compressor will cut your AIR MASS, by contributing heat to the air charge. The more efficient the compressor the less heat it contributes. So although a fixed volume will compress with same heat, the compressor is adding heat as well.

These calculations are not like designing a whole engine, and its no wonder someone that doesnt understand all of them must do by trial and error. But getting them most correct, understanding how to engineer the entire system and interdependencies gets you to the most correct solution first, with some inevitable tweaking I agree. But this discussion of just air mass vs air volume is so intricate to fuel combustion and so simple compared to an entire engine design, that these are not some rough estimations. You test how much fuel you have, or its spec'd, and you buy turbos with tested specifications. And since diesels are very fuel to air ratio tolerant you get away with a lot of crap. But these numbers are very accurate in this respect when you already know the fuel mass and air mass demand. We talk in terms of fuel volume a lot, but when it comes to actually calculating air demand, you have to convert it to mass as well, and determine air mass required. THEN, with knowledge of your IATs (intercooler or not and compressor efficiency) you can determine how much air volume you need, but we discuss air volume in terms of engine displacement and boost pressure. So there are so many conversions you have to understand how to apply them. In fact, we havent calculated anything in this thread because we can't get past how to calculate it, because so many people don't understand how and want to argue with those that do. It makes no sense why people argue with physical facts rather than try to learn them!

And I realized unsubscribe is in the thread tools, so you can chew on that

 

[littleboy]

Lmao, all along i and other engine builders have been measuring mass air flow in cfm. Guess we will have to totally refigure everything now ..........
Buddy, you are a total contradiction to yourself!

 

[THEFERMANATOR]

YES!!! and I have never said otherwise, but you fail to understand the basic concepts that allow that to be true. The use of CFM or volume where air mass applies and using them interchangeably is a big clue that someone doesnt truly understand. It is not always true, and has everything to do with operating within different compressor efficiency islands and whether or not you are cooling the intake charge. Technically for one to flow more air at the same pressure, they flow out the same volume of air (CFM), with different air mass. They would in flow different volumes (CFM), the one with lower post compression IAT having taken in more ambiant volume to make the same boost pressure. That is because the turbo would have transferred less heat to the intake charge, thereby less of the boost pressure due to air volume expansion from heat. So its also easily possible that two different turbos also flow the same air mass at the same pressure, if having the same efficiency.

Compressor efficieny tells you how much the compressor will cut your AIR MASS, by contributing heat to the air charge. The more efficient the compressor the less heat it contributes. So although a fixed volume will compress with same heat, the compressor is adding heat as well.

These calculations are not like designing a whole engine, and its no wonder someone that doesnt understand all of them must do by trial and error. But getting them most correct, understanding how to engineer the entire system and interdependencies gets you to the most correct solution first, with some inevitable tweaking I agree. But this discussion of just air mass vs air volume is so intricate to fuel combustion and so simple compared to an entire engine design, that these are not some rough estimations. You test how much fuel you have, or its spec'd, and you buy turbos with tested specifications. And since diesels are very fuel to air ratio tolerant you get away with a lot of crap. But these numbers are very accurate in this respect when you already know the fuel mass and air mass demand. We talk in terms of fuel volume a lot, but when it comes to actually calculating air demand, you have to convert it to mass as well, and determine air mass required. THEN, with knowledge of your IATs (intercooler or not and compressor efficiency) you can determine how much air volume you need, but we discuss air volume in terms of engine displacement and boost pressure. So there are so many conversions you have to understand how to apply them. In fact, we havent calculated anything in this thread because we can't get past how to calculate it, because so many people don't understand how and want to argue with those that do. It makes no sense why people argue with physical facts rather than try to learn them!

And I realized unsubscribe is in the thread tools, so you can chew on that

You started out good, but then your comprehension skills went to shit. I asked a simple question, but yet you still had to go into an in depth arguement to prove yourself to be the supreme intelect. I've known what you've been saying all along, but your muddying it up with these long contradictory paragraphs afterwards. All you had to say was YES. Then you could have simply said but due to the different air densities. Instead you go into a whole big spiel to try and prove yourself to be "above" the rest of us somehow. You know there are many of us who DO get this stuff, but also understand that all of the extra is NOT needed. As I have been saying all along, KISS. You don't have to give a physic lesson to give the answer, but for some reason you can't figure that out. And then make derrogitory statements like

I tried to explain this a few years ago, and it was painfully obvious no one wanted to understand it then. So I will leave you to understand it how you would like to.....unsubscribed

which are completely uneccesary as you are NOT the only person here who DOES get it.

 

[Dylly]

You started out good, but then your comprehension skills went to shit. I asked a simple question, but yet you still had to go into an in depth arguement to prove yourself to be the supreme intelect. I've known what you've been saying all along, but your muddying it up with these long contradictory paragraphs afterwards. All you had to say was YES. Then you could have simply said but due to the different air densities. Instead you go into a whole big spiel to try and prove yourself to be "above" the rest of us somehow. You know there are many of us who DO get this stuff, but also understand that all of the extra is NOT needed. As I have been saying all along, KISS. You don't have to give a physic lesson to give the answer, but for some reason you can't figure that out. And then make derrogitory statements like which are completely uneccesary as you are NOT the only person here who DOES get it.

Just a heads up, Buddy didnt contradict himself once. Everything in that post is consistent, and correct. Its to bad we have the attention span of a golden retriever, otherwise maybe a post that was longer than 4 lines might have the chance of being understood.

 

[THEFERMANATOR]

Just a heads up, Buddy didnt contradict himself once. Everything in that post is consistent, and correct. Its to bad we have the attention span of a golden retriever, otherwise maybe a post that was longer than 4 lines might have the chance of being understood.

Then how are posts like 2 turbos will flow exactly the same amount air at the same boost pressure, but then 2 sentences later say that they can flow different amounts of air IF the IAT is different NOT contradictory? My WHOLE point all along was to keep it simple rather than to look like a smartass trying to show off. The WHOLE equation could have been explained simply and precisely, but for some reason it is believed that a physics lesson must be given to explain, or to show how you have the only proper explanation of it. I can obviously tell who here has spent there time reading and studying the logic behind it, rather than doing and learning what it does. It just takes me back to my days of dealing with engineers, and my distatste for them as they always acted like they knew it all yet couldn't figure out because there books couldn't give them the answer.