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Replacement turbo

GJF said:
Yes, It is the same volume displacement wise. And no, the volume is greater just compressed into the same given area. Yes, pressure will be greater in the area but not from the compressor.
Click to expand...

Volume is size as in area. 1 cubic foot is 1 cubic foot regardless if it is at atmospheric pressure or two times atmospheric. The engine only displaces so much volume. The turbocharger does the work to increase the mass of that volume. So yes the turbocharger is flowing more air. The equation much be balanced such that what went in is what went out, so 2000 cubic feet went in at half the mass of the 1000 cubic feet that went into the cylinder.
 
It would probably be better stated that a smaller turbo that is only 60% efficient to supply 10psi of boost, and changing the compressor to a larger compressor that is 90% efficient at 10 psi thus allowing a more efficient air charge into a given area. So while not increasing pressure you are only changing efficiency and in turn filling the area closer to it's capability creating more energy.
 
Turbine Doc said:
Buddy,

Not a myth, possibly a difference of how we view the same data let's focus on the etc.

Now I know you have issue with the claim of 2x delivery at same speed, that I can agree with you is a subjective statement and probably incorrect, to know with certainty what the real dynamic flow delta is we need some device for measuring air flow.

If it's only 1.5x, I'll take that as it is still an .5x or even if just .25x improvement and engine isn't struggling as hard to get it, it's all good.

What I can say there is more reserve boost available with the ATT past 1500rpm it happens more quickly with the ATT, than with my GM-X when cruising @ 70 mph my ATT does it with 1.5-2psi vs 2-4 psi required from the GM turbo.
Click to expand...

Trying to make analogies is useless when math, physics and chemistry can explain it all. And youve done none of that analysis in trying to make claims or more flow at less boost. The ATT provides a slight flow increase but it has nothing to do with the engine intake and everything to do with the engine exhaust.

The reason your boost is lower at cruise has nothing to do with compressor flow, but how your turbomaster was configured. I can easily cruise 70mph at 1 psi boost with lots of reserve power using the vacuum system tuned to do that and go up to 17psi when I need it. The current homemade controller I am using is only 2 psi at 70mph and will still spikes to 17psi, all depends on spring you use. The ATT still outperforms under load and at 15psi, because it requires engine to do less work to puts in more dense air, and a few percent more more volume.
 
GJF said:
It would probably be better stated that a smaller turbo that is only 60% efficient to supply 10psi of boost, and changing the compressor to a larger compressor that is 90% efficient at 10 psi thus allowing a more efficient air charge into a given area. So while not increasing pressure you are only changing efficiency and in turn filling the area closer to it's capability creating more energy.
Click to expand...

Its going to fill the areas the same volume and flow, the only difference is the amount of backpressure (more efficient means engine does less work and slightly less exhaust gases left in the cylinder). If its 60% efficient then it takes nearly 17psi turbine backpressure to make 10psi of compressor boost.

And 90% obviously only little over 11psi turbine backpressure to make 10psi boost.

This is EXACTLY why ATT is better. Not because it flows 1.5 or 1.25x the air, because it doesnt. The engine is freed of some work with the ATT, so it does have more reserve power at higher RPMs and load, but not because it has significantly larger reserve air flow capability.
 
If you would put your theory in to practice it would be like making a turbo using a ATT turbine section with a GM8 compressor. Or even worse a GM4 compressor. And then when you put that on your engine the peformance would be exactly the same. By your theory only a more efficient turbine section makes a difference and the compressor is just along for the ride???
 
Wow, I'm sorry I started this. You math guys kill me. Can someone just tell me in simple terms if my ATT is better than the GM-8 was?
 
I just want people, including the experts, to actually understand the science and not the dumbed down version that proliferates common misconceptions.

It matters to me that I understand how a system works to know how it impacts the rest of the system and then what other modifications may complement or negate the positive affects.
 
There is about 650 posts with some great Tech real world application, provided by more than competent 6.5 experts, that say the ATT is better......Some very well respected 6.5 die hards have already gave it the stamp of approval.
 
I still don't understand your thinking..
The Ideal gas laws explain

PV=ntr

That with a constant pressure volume will change with change in temperature.
As volume increases pressure remains the same as temperature increases.

Boyle's Law, a principle that describes the relationship between the pressure and volume of a gas. According to this law, the pressure exerted by a gas held at a constant temperature varies inversely with the volume of the gas. For example, if the volume is halved, the pressure is doubled; and if the volume is doubled, the pressure is halved. The reason for this effect is that a gas is made up of loosely spaced molecules moving at random. If a gas is compressed in a cylinder, these molecules are pushed together; thus, the gas occupies less volume. The molecules, having less space in which to move, hit the walls of the cylinder more frequently and thus exert an increased pressure.

Boyle's Law actually applies only to an ideal, theoretical gas. When real gases are compressed at a constant temperature, changes in the relationship between pressure and volume occur. However, the law is accurate enough to be useful in a number of practical applications. It is used, for example, in calculating the volume and pressure of internal-combustion engines and steam engines.

Even in a controlled enviornment volume does not stay constant with pressure. Volume can increase with the same pressure or better yet volume can exceed a given amount (mass) while running a lower pressure in relation to temperature.
 
you have to put the equations into the proper context. The volume is fixed, and PV=nRT is for the gas or air. The engine is the volume. No extra air goes through it that doesnt go through the cylinder in a cycle that gets combusted.

Flow is a volume over time.

If volume is fixed and pressure increases with no flow of new air/gas, then temperature is going to increase to balance the equation.

n happens to be a measure of mass, so when there is flow of more air/gas and pressure increases in fixed volume and temperature is held constant then the mass increases to balance the equation.
 
I wish I paid better attention in Physics! I understand some of this but some of it is just too much.

Maybe it is just because I read that whole thread in the past 2 days. Good job on the ATT I hope to invest in one of these soon.
 
But we are refering to the volume created by the turbo. We know the displacement of the engine IS fixed. Temperature is never fixed as it is constantly changing depending on the load the engine is bearing. The volume of a turbo is only fixed based of the parameters the turbo is capable of. And a turbo is a variable volume dependant of load and substained boost.
Flow is not volume over time, flow is a variable dependant on the flow cababilities of the inlet tract.
Bottom line if all variable were fixed then it would stand correct. But we are talking about a diesel engine where all the variables constantly change and the only thing that could be considered constant is the end boost setting as long as the load and rpm is maintained. Simply said volume can be more without pressure change. No different that filling oxygen tanks, oxygen is kept at a constant pressure but volume increases while it is compressed to ultimately fill the cylinder. The fill rate is stopped at a pressurized level so the cylinder will not fail or exceed it's capability. The only way the tank can be filled faster is A: more pressure or B: increase the fill orifice.
 
The issue is not how fast you fill something, but how much you can fill it. one turbo at 10psi is going to fill a cylinder exactly as fast as another turbo at 10psi.

And you are not applying the equations correctly. n is moles, a measure of mass you have to take into account in balancing the equation. When pressure goed up and volume goes down the mass increases to balance the equation along with temperature fluctuations (putting it constant was just to make the point in theory). Flow is exactly volume over time, it takes no account of mass in it, which is why the density of the air has no impact on a CFM value. The engine volume is not variable, flow through the engine is constant at any RPM (if assuming cylinder is at same pressure of intake when intake valve closes) Flow of the turbo is different, as it does the work to compress the air to make it more dense so in the fixed volume flow engine you can get more oxygen for more combustion.
 
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Talk about chasing your tail around. Too much contradicting for my taste. I'll have to say I have better things to do. Good luck.
 
If you laid out the entire model and balance the equations it would become more appararent. You have to understand the relationship between gas laws and flow, where mass has no bearing on a flow value, but laws of conservation apply to the system.
 
buddy said:
I just want people, including the experts, to actually understand the science and not the dumbed down version that proliferates common misconceptions.
Click to expand...

But, you see........ It needs to be "dumbed down" for people like me and perhaps a large percentage of our community. With the math, you just lose me..... With TD's analogys, I can get a better understanding and a picture in my mind of how things work. Maybe I'm just getting to be an old fart. :D

Just my $.02.....:smile5:

Art
 
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