Replacement turbo

[guybb3]

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.

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

Art

Art, I'm an engineer and I did very well in Physics and Math but I have a huge headache after reading this thread!!

 

[Matt Bachand]

I took it as this-

The boost gauge is read on top of my intake.

If my intake is pressurized to 10psi of boost, it really doesnt make a difference where that source of pressure is coming from, its going to be 10 PSI, from a ATT, from a holset, from any source, intake pressurized to 10psi is what it is. Exactly that. Intake pressurized to 10psi.

Now.

ATT has advantage because it takes less energy (exhaust backpressure) to make that 10psi, leaving more power available. It appears to do this with lower IAT's as well, which makes the 10psi more effective.

 

[buddy]

Exactly correct Matt! More engine power available and less heat transfer to intake air.

 

[buddy]

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.

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

Art

There certainly is a time and place for anologies, and when those anologies are correct they are good. Some anologies can make you think you understand.

It would be safe to say that your feeling from the drivers seat is as has been paraphrased as more power at lower boost, and more of a reserve capacity at a boost value. But if you go into trying to explain why it feels like that there is a lot of science and math that the anologies do not accurately depict.

And there are different types of engineers/scientists, not all of them study aerodynamics, pressure, flow, etc.... Mechanical and Aerospace engineers are more adept to looking at systems as a whole and applying assumptions on stuff like this, although anyone can use the information out there to do the same.

You can trust that the turbo works better, and its not by a miracle of pushing 7000CFM through a 1000CFM engine. The theories and equations applied are sound and do explain how the efficiency of larger turbos improve the power of the system, and it is not by a large CFM intake increase.

 

[ak diesel driver]

my .02 cents because of the lower backpressure it's like have a bigger hole for the exhaust to escape. in which case you could have more cfm flowing with the same psi. Not sure how much but it should be measureable. More accurate than psi would be to have a flow meter. Then there is no math involved

 

[NVW]

Also the IAT with the ATT is lower, therefore more dense. So less psi with ATT should equate the same air as a GM turbo.

 

[buddy]

my .02 cents because of the lower backpressure it's like have a bigger hole for the exhaust to escape. in which case you could have more cfm flowing with the same psi. Not sure how much but it should be measureable. More accurate than psi would be to have a flow meter. Then there is no math involved

The exhaust exits faster which is part of the reason its better. But the intake CFM, engine CFM and exhaust CFM is all different, because there is conservation of mass, and no conservation of volume.

More dense as in mass is part of it as well, but that has nothing to do with CFM.

 

[Turbine Doc]

IMO the simple explanation is better, and it's not because I'm simple minded, nor is not that I do not understand the math & theorums which you citing, however you wish to wrap it up in detailed explanations.....;

A turbocharger is a pump, a bigger pump moves more fluid, it takes more energy to drive the bigger pump, but the bigger pump still has capacity to move more fluid, this case being air (which is a compressible fluid), providing sufficient energy to drive the larger pump.

All of the internal engine dynamics you are describing do have an impact if the extra fluid can be used and when it can be used or is just wasted effort.

On top end with GM-X there is wasted effort, vs. ATT on bottom end the GM-X with it's WG uses available energy better, as there is insufficient available energy to spool as effectively as GM-X.

But the margin of lost energy is negligible due to the better internal flow dynamics of the ATT with it's dual scroll setup minimal loss is something that still works well with the 6.5.

This from Turbonetics website may help some to the overall discussion for those lost in the theory written for gassers but close enough to help with turbo operation in general.

Q: What is boost?

A: "Boost" is the amount of pressure, measured in pounds per square inch (PSI), kilopascals (101.285 = 14.7 PSI, or BAR (based on 1 BAR equaling 1 atmosphere of pressure - 14.7 PSI) that the turbocharger is forcing into the engine/intake manifold/cylinders. PSI tends to be the most common way of measuring boost pressure but the Japanese market frequently uses BAR and many high end engine management programs utilize kilopascals.

Think of boost as how hard the turbocharger is working. When looking at a compressor wheel map to decide what trim to use, you will notice that there are oval lines (efficiency islands) that are drawn on the maps.

Attached to these efficiency islands are speeds that the wheel is turning at a certain efficiency and air flow. The faster the wheel turns "boosts", the harder it has to work to flow air.

So at its basic level, boost is just how fast the compressor wheel is turning at any given time. It would be ridiculous to have readings such as, "Hey man, how much boost are you running?" - "I'm running 120,418"...dont you think?

It is important to remember a few things in regards to boost:

1. Boost DOES NOT equal horsepower. Lots of air, plus fuel in the cylinder and a timely ignition spark equals horsepower. (take note also per Turbonetics) A small turbocharger can be running at 20 PSI and make less horsepower than a turbocharger larger than it running 10 PSI.

This does not mean that sizing a larger turbo is necessarily better though. The opposite can hold true as well. A turbo sized too large can make less power than a unit much smaller. But lets get back to boost. (IMO this is where the balance off ATT sizing comes in sacrifice a small level (tiny) performance on bottom end netting significant gains on top end for the 6.5)

2. Boost at the turbocharger and boost in the intake manifold may not be the same. Be careful where you measure boost pressure from. The system is only as strong as its weakest link. If you have an intercooler that is too small then the turbocharger will be working (remember above) "boosting" more than the air inside the intake manifold.

This is because the intercooler is too restrictive to flow the correct amount of air to make a certain HP at a given PSI. Or think about if you had a leak in your intercooler piping. What if a clamp was loose and air was escaping without you knowing.

The turbo would have to work (theres that word again) extrememly hard to make the "boost" that you want it to. On a side note overspeeding of the turbocharger is a leading cause of its death and destruction.

3. Once pressure is applied to air the measurement CFM (cubic feet per minute) can not be used to calculate airflow. The density of the air changes, and this means that PPM (pounds of air per minute) must be used to determine the volume/flow of air at a given PSI or "Boost" pressure.

We haven't even discussed density of the charge here, which is another piece of the equation, the size and efficiency of the bucket does matter, and efficiency of the turbine that drives the bucket.

The ATT is better turbo than the GM-X because it provides more air, more efficiently at the power load the 6.5 likes to work at

Earlier Buddy you said my data was skewed by setting of my WG via TM, that only set the upper limit when going for maximum power and it kept when I was stock programming from opening WG too early on bottom end, I still have plenty of data showing where at cruising speeds say 70 mph the GM-X was working harder making more boost for that speed than the ATT does.

I.E. towing a hill in OD with a enclosed 7x6x12 utility trailer loaded up in cruise control slight increase in fuel and trans does not kick down into lower gear, with GM-X I would have to take it out of cruise to stop what I call boost dance (fuel on/off-boost up/down) to maintain speed because in cruise control the delay in engine speed sensing let the power come down to climb the hill then chop the fuel half way into the climb, then back into fuel when it slows again. With ATT same load & even heavier, same hill I am able to pull in OD, no kick-down into 3rd, nor having to come out of cruise.

That is real world dynamics, where did the power come from, more CFM of air sustaining the engine, the GM-X would sustain the hill climb but @ 8 psi boost with more fuel & EGT & IAT, vs 6 psi boost with the ATT,.

And as far as ability to fully understand systems and interactions, hmmn I must be doing sumthin rite, not too many K1500 6.5's capable of pulling 18K loads and surviving to 198K miles so far.

 

[buddy]

Density has been mentioned many times, as part of why the ATT works better.

Density provides more mass per volume. Having a more dense air charge has no effect on CFM, but you get more mass of air.

And the wastegate also sets your low boost amount, with the high. Because if its not loose enough to drop boost at a fuel rate then its going to boost more than you really need and be parasitic to engine power. Another reason the vacuum system can outperform the spring

The problem is focusing on CFM, there isnt a bunch more CFM and that would be a misunderstanding of how it all works. A larger turbo can provide more power at lower boost but its not because its pushing more CFM at a given boost level, its because the engine isnt using as much of its own power to make the boost.

Everyone agrees, the GMx uses more energy to make your boost. This is the simple explanation of why you have more power. There is less parasitic enigne power loss with the ATT than the GMx, so your engine has more available power with the same amount of air than it did before.

 

[tanman_2006]

After some thought (Not Much to be Honest) I think I will be spending in the neighborhood of $1,139 by the end of the summer! Looks like a good deal for a freakin awesome set up! :thumbsup:

Now back to the regular programed Physics Class.

 

[GJF]

So, basically that "thingy" that spins compresses alot more of "that stuff" to make my truck fasterer??

 

[Matt Bachand]

Density has been mentioned many times, as part of why the ATT works better.

Density provides more mass per volume. Having a more dense air charge has no effect on CFM, but you get more mass of air.

And the wastegate also sets your low boost amount, with the high. Because if its not loose enough to drop boost at a fuel rate then its going to boost more than you really need and be parasitic to engine power. Another reason the vacuum system can outperform the spring

The problem is focusing on CFM, there isnt a bunch more CFM and that would be a misunderstanding of how it all works. A larger turbo can provide more power at lower boost but its not because its pushing more CFM at a given boost level, its because the engine isnt using as much of its own power to make the boost.

Everyone agrees, the GMx uses more energy to make your boost. This is the simple explanation of why you have more power. There is less parasitic enigne power loss with the ATT than the GMx, so your engine has more available power with the same amount of air than it did before.

Plus the heat transfer to IAT's is LESS, thus the density factor comes in I think.

The lower IAT factor is huge here. I think that is where most if not ALL your extra air comes into play that the ATT can provide.

I think we're all on the same page here now..... Over a year later and a couple hundred posts :grouphug:

TD & Buddy ... I think you two should just meet at the Salt flats with your 6.5''s and line em up

 

[Turbine Doc]

Plus the heat transfer to IAT's is LESS, thus the density factor comes in I think.

The lower IAT factor is huge here. I think that is where most if not ALL your extra air comes into play that the ATT can provide.

I think we're all on the same page here now..... Over a year later and a couple hundred posts :grouphug:

TD & Buddy ... I think you two should just meet at the Salt flats with your 6.5''s and line em up

Nope to either; not talking it to the salt flats this is my daily driver, from the Flats to MS is a long walk should I break down pushing the envelope, nor do I agree that improvement on parasitic loss is THE reason

To me, the word parasitic would work with a supercharger as energy is taken directly from the engine via a belt drive. A turbo recovers lost energy that would just go out the tail pipe but does not add to engine load in a parasitic manner, ATT recovers waste energy better than the GM-X so more efficient & more air flow capability from ATT.

Those are my observations and I'm sticking to them, Buddy & I obviously won't share the same view in total but a group hug is long overdue :grouphug: I'm done, I don't really care to debate the who is more correct any longer.

Bottom line ATT works, IMO for multiple reasons, Buddy has a different take on it, more power to him & his calculator, I think overall a very good discussion, albeit a long one .

Gotta log off for now I've got some steam table calculations to run through before class tomorrow.

 

[Veg_Out]

I love that we are arguing about why the turbo is better!

 

[GJF]

I think that everybody is pretty much on the same page. I also think, including myself some have used the gas laws incorrectly (not intentionally). I know how and why it works, but after consulting with a friends Physics Professor, I have some redirecting to review. Luckily I have been provided with some very good reading material to aide me to better understand.( The professor is a big aviation nut. We talked about turbos in aviation and luckily we had something in common ) I am inclined to think that aspirated combustion engines do work well using these laws and equations. But once forced induction is thrown in the mix by going from a single atmosphere to multiple, a different means of measure is required. The compressor wheel spins at accelerating loads at 100K RPM's. By increasing the physical dimensions of the wheel the amount of air moved/pumped/compressed/pushed however you want to call it is going to be greater than the small dimension wheel at the same RPM's. I do respect the the desire to have information explained correctly using the correct terminology. Agreed, misleading information causes havoc, chaos and mass confusion.

 

[buddy]

When accounting for density gain from somewhat lower IATs, a larger turbo can push the same CFM as a turbo that transfers more heat to the intake, at a slightly lower pressure. This is because the CFM in the turbo is not the same as the CFM through the engine and is not the same as the CFM through the exhaust. This only becomes significant at high boost levels, and increases with temperature differences. So although the 6.5 at 4000rpm is displacing 1000CFM, and it cannot flow any more than that, the air the turbo itself took the same amount of ambiant air to put the same more mass in.

So the ATT may double (over N/A) the mass input into the cylinder at 18psi boost at 150F intake temps, and the turbo itself used 2000CFM ambiant to run that 1000CFM of double mass air into the engine.

Lets assume the GMx transfers more heat to the intake air, and at 180F it takes 19.5psi boost to double the mass of air in the cylinder, even though the engine is only passing 1000CFM the GMx passed 2000CFM as well.

Thats a large IAT difference and high boost pressures and higher RPM than any of us likely take our 6.5s, just to demonstrate. The CFM of the engine and the intake post turbo is still limited by the engine displacement and RPM. At lower pressures and intake temperature differences this difference becomes negligible. This benefit is only from lower IATs, and not turbo capacity. It is attributable to more efficient exhaust flow transferring less heat through the compressor housing and blades. WMI, intercoolers, and larger exhaust pipes all have the same effect.

Now design your 6.5 to run at 5000rpm and 20+ psi and this effect can become much more significant.

Turbos are absolutely parasitic. They utilize waste heat, but the piston has to do the work to drive the turbine. The less turbine drive pressure needed the less engery is wasted during combustion stroke of other pistons to push the exhaust stroke creating backpressure to drive the turbine. No such thing as free energy.

So at 4000rpm and boost levels beyond most people use and very optimistic temperature differences there is less than 5% more CFM using the ATT vs the GMx, the amount gets very small at lower boost and rpms. CFM through the engine is fixed by rpms.

So density is the real story, but offers a slight turbo CFM increase, and the engine is at a lower pressure, but any turbo is equivalent at the same air temperature.

The major gain comes from less parasitic loss, and better exhaust scavenging, which can add about 5% more volume of fresh air (rather than exhaust gases left sitting at higher backpressures that expanded in the piston vacuum) in the engine at high boost levels. The exhaust valve closes prior to TDC, so the exhaust gases left in the cylinder are at the pressure it equalized at with the exhaust manifold, which more pressure means more expansion during intake stroke and less volume for fresh air. This leftover exhaust in the cylinder also reduces engines CFM from optimal.

 

[Matt Bachand]

I value the input of everyone. Thinking about things from different angles is always key.


Slim whats you're outlook??

SmithvilleD? How about yours?

 

[Slim Shady]

I value the input of everyone. Thinking about things from different angles is always key.


Slim whats you're outlook??

/quote]


The A-Team Turbo works, does what it is designed to do, and if it doesn't and the purchaser is not happy, I will make it right.

I have to ask why the engineers do actual prototype testing. I have asked a lot of engineers and the consensus was the math will get you very close to the answer, but real world testing and prototype work is done so that all the unknown parts of the equation then become apparent.

I am not an expert in math, I build things by old fashioned trial and error, and seat of the pants performance. Does it work in real life or not. I wonder how the old racer guys did it before they had engineers, guys like Richard Petty, Rousch, and others?

I think both work, and have a similar outcome.

 

[NoDak]

I believe what slim is talking about is the marriage of art and science. I recall a really good article to that topic in an Open Wheel magazine I read several years ago. Basically, the math and science gets you on the target, but the tinkering testing and trial & error get you to the bulls eye.

One can't forget, that knowledge is good, and that knowledge of what does not work, is just as valuable as knowledge of what does work. You know the saying, I won't do that again!? But one also can rely on a scientist to disect the "oops" projects, to tell us why they really failed, so we don't avoid future areas to improve. Hmm? Pre-combustion chambers, ports, size, shape? What's next?

It is clear to me why the GMx came to be... the science led them to a different goal. I'm pretty sure they achieved that goal that involved economics and exhaust quality.

Just for the record... I don't believe anyone pointed out that the turbine flow on the GMx is only a part of the exhaust flow. There may be very little wasted exhaust flow at low speeds and fueling, but at the higher speeds/fueling/loads when the waste gate is fully open, I suspect there is a significant wasted opportunity to recover energy. This is completely seperate of the backpressure, exhaust restriction or whatever you wanna call it. I suspect for this discussion, one could be simply looking at the GMx turbo and waste-gate as "one" unit.

I now have about 4,200 miles on my first ATT and Kennedy Diesel programming. My fuel mileage average is much improved even though I've been driving it like a stolen rental car! I don't have any towing in the mix yet, but that season is just starting. And as the "new" wears off, my driving might very well return to normal, and the true improvement potential will prevail. I really hate to share my actual mileage numbers until I have more data. The great thing about it is the improved range on a short box fuel tank! Now it's not hard to reach 400 and some miles on most every tank.

Rock on!!!

 

[Badaxe]

Has anybody tried the Banks Sidewinder Turbo for the 6.2 on their 6.5?