Engine/Transmission (1998.5 - 2002) Aeroturbine Claims Defy Physics

[Lube Man]

The Aeroturbine may be an efficient muffler in its ability to reduce sound. It may have less restriction to air flow compared to some other mufflers. And it may sound "cool". All valid reasons to buy it. But performance claims are unsubstantiated. There is no way it can accelerate air flow as seemingly claimed. Air velocity and pressure within the unit may be different at different points within the unit as it flows through the two chambers. However, to accelerate air through the unit would require an external source of either mechanical or heat energy.



The only way to substantiate the manufacturers claims is by laboratory testing using accepted enginnering practice and instrumentation. This must be done by an independent lab. Testimonials by users are no substitute.

 

[Forrest Nearing]

thank you!!!



to quote Homer Simpson, "Young lady, in this house we follow the laws of thermo-dynamics!"

 

[BTowler]

Thank you very much! I work in a field that is rife with exaggerated claims, misting systems (which operate on the principle of thermal-dynamics), which is why I was so perturbed with Aero Turbines claims. You will never get anything from me but honesty as to what my products can do and why!

 

[Lube Man]

Well, no overwhelming response. That's good. Maybe people will analyze things rather than make rash statements. Human nature is to defend anything you bought otherwise the ego could be affected!

 

[swampfox]

Well you can, Kinda... ... . By reducing pipe diameter you cause the air/gas to accelerate, then by opening the pipe to a much larger diameter you create a partical vacuum... . i. e. venturi effect... . which sucks the air/gas behind it... i. e. more aceleration. The energy for this comes from the heat in the gas... . temp of gas drops as it passes through the ventri..... however in a muffler you have a problem... ... reducing pipe diameter to get the ventri effect causes backpressure up the line..... then you have the exhaust gas pulses in the line and finally you have several feet of tailpipe after the muffler... ... . all of which may have a negative effect on the venturi effect. You might, with a very good computer and a very good engineering staff design a COMPLETE exhust system in which a venturi effect along with tuned gas pulses would contribute to a "faster" more efficient gas flow but it would have to be individually designed for each truck/engine combination... . and it would only be really efficient at a very narrow rpm range.

 

[Lube Man]

Whoa, you lost me on the vacuum. Reducing pipe size will require more pressure to allow same airflow as coming in. Then increasing pipe size again will require less pressure to maintain same airflow through the enlarged section. No vacuum is created. The classic venturi effect (as discovered by Bernouli) is where a fluid passing through a conduit will create negative pressure at an opening in the conduit. I guess this could be considered vaccumm pressure. This negative pressure will then draw fluid out of the opening into the main stream.



To digress, years ago I worked in a boat yard. We often used a bilge pump where you took a water hose hooked up to a water supply, ran it into the bilge and then over the side. There was another hose connected at 90 degrees that lay in the bilge. The flow of water through the main hose would suck additional water from the bilge and be dumped over the side. . Very reliable as it was not subject to power failure. Municipal water systems are a lot more reliable than electric utilities.

 

[Lube Man]

Sorry, Bernoulli is the correct spelling in case anyone is searching the encyclopedia.

 

[mmclaughlin]

Lets see if I can remember this correctly - I believe that if you take a gas and pass it through a pipe of some diameter, you start with subsonic flow, then you can decrease the diameter of the pipe to get to a sonic condition, then once you increase the diameter the airflow becomes supersonic. As it goes to a larger diameter after the sonic condition, the flow rate increases, somewhat counter intuitive to decrease diameter to increase flow rate, but it does work. Obviously you would have to figure out the specific diameter and flow rate, but it can be done. Now you would just have to figure out what the diameters would have to be for our exhaust rates - my guess is that the diameter would be much less then 4"

 

[Lube Man]

Here are some comments from an engineer friend of mine. He has extensive experience as a manager of the marine division of a large corporation and was heavily involved in testing equipment for both industry and the U. S. Navy:



Hi again,

I didn't notice the website till after I had sent the last e-mail.

Initial feeling is that they should offer test data run in independant, certified test facilities that have no commercial ax to grind.

Test data shown does not satisfy me. For example, how do they know they get increased engine longevity? Did they take a new engine down and mic all of the major wearing components, reassemble, test run for several thousand hours then remeasure all parts. Did they do the same thing with a standard engine of the same mfg. using a standard muffler for comparison?

I would anticipate that they could readily measure backpressure, on both systems.

Fuel economy and temperature could also be readily measured by running both engines on a Dynamometer for the same time, with the same measured amount of fuel. If their claim is valid, the standard equipped engine would run out of fuel first. Such a test should be rerun several times and averaged out for best results.

Keep in mind, that with computers and graphics today, anyone can punch out some pretty good looking graphs and you and I can't contest it because we lack the where-with-all to run tests etc. that would or could prove otherwise!

That is why I say test data should be run preferably at nationally recognised test facilities.

The question of torque and horsepower could be answered by running each system for a prescribed period of time at say 250 or 500 RPM increments above idle and load til the engine starts to drag down

I like the idea of a stainless muffler. It would probably outlast the vehicle. Would suggest all stainles exhaust piping to compliment the muffler.

Gotta go eat.

Fred

 

[snowracer69]

Originally posted by mmclaughlin

Lets see if I can remember this correctly - I believe that if you take a gas and pass it through a pipe of some diameter, you start with subsonic flow, then you can decrease the diameter of the pipe to get to a sonic condition, then once you increase the diameter the airflow becomes supersonic. As it goes to a larger diameter after the sonic condition, the flow rate increases, somewhat counter intuitive to decrease diameter to increase flow rate, but it does work. Obviously you would have to figure out the specific diameter and flow rate, but it can be done. Now you would just have to figure out what the diameters would have to be for our exhaust rates - my guess is that the diameter would be much less then 4"

Kinda... .



Actually, you can only accelerate a flow to Mach 1 by decreasing the area it passes through. After that, it is strictly determined by the backpressure at the exit what the flow will do from there. There are many different possibilites, but the main ones are these:



1. The flow will, after going sonic at the throat (smallest diameter, where dA=0), continue to go supersonic and the flow will be considered "matched", that is, there is no need for a shockwave anywhere inside the nozzle or outside the exit (or expansion waves outside the exit) to match the pressure at the exit to the backpressure outside... this is a perfect case, and while the shockwaves are still there, they are perfectly parallel to the flow exiting the nozzle (very difficult to obtain).



2. The flow will, after going sonic at the throat, decrease it's speed to a subsonic condition to match the backpressure at the exit. There will be no shockwaves, as they can not form in subsonic flow.



3. The flow will, after going sonic at the throat, go supersonic in the diverging portion of the nozzle, but due to the backpressure being at a certain value a shockwave will form inside the nozzle causing a jump in the pressure (and a decrease in total pressure) to match the backpressure (flow will normally again be subsonic after the shockwave).



There are others, with shockwaves outside the nozzle and expansion fans outside as well.

 

[y-knot]

Personally, I could care less if it speeds the air up, spins it around or dances with it. I bought the thing to see if it would help with the DRONE, it did, so I am happy. It also changed the sound of the trucks exhaust, which is cool, I never wanted to be like everyone else. The thing looks like no other muffler I have ever seen, and the claims make sense to me. Granted I have never really studied physics (low level college courses), but they seem valid and just as reasonable as the famous TAG unit. At least I can see the logic behind their claims, and yes even I know that air, when forced to split it's flow of half going straight and the other half over a curved surface, will create a pressure differential.



Have you taken the time to buy and use the product? I am in no position to prove anything they claim, but for me it did what I wanted, which is more than I can say about several other products.

 

[snowracer69]

Originally posted by y-knot

Granted I have never really studied physics (low level college courses), but they seem valid and just as reasonable as the famous TAG unit.



At least I can see the logic behind their claims.

Two problems:



Since we haven't hashed this out in a while but from what I remember: 1, no, what they claim does not seem valid (ok, maybe they're valid claims, but they sure as I TRIED TO BY-PASS THE CUSSING FILTER defy physics!) and 2, I don't see the logic behind it... . not in an exhaust where minimal backpressure is desired and free flowing would be the best.



I'm glad it did for you what you wanted, and if you're happy, then I'm happy... but the theory isn't there, UNLIKE the TAG (of which I am not affiliated, nor do I own their product).

 

[Lube Man]

Yep, I agree, the TAG does not defy physics. I am not saying that the Aeroturbine is not a good muffler. But I have a real problem with the claim that it accelerates exhaust. Again, to repeat myself, if the inlet and outlet diameter of the Aeroturbine are the same, the only way to accelerate the flow of exhaust is to introduce additional energy either by heat or mechanically.



As my friend Fred said, the only way to validate the manufacturer's claims is by testing, which they apparantly have not done or they would be promoting the test results. I have no vendetta against Aeroturbine. I would love to buy one if the claims can be substantiated. But as an engineer, I have to be convinced. If my comments are in error let someone step forward and present sound engineering reasons.

 

[Forrest Nearing]

my problem is that it's like $200...



you could obtain the same or better results for $50 or less...



Forrest

 

[BTowler]

I wonder how much it costs to produce? $20-30 maybe?

 

[Lube Man]

Does anyone know of a muffler that would have the same dimensions as the stock muffler (requiring minimum installation work) but with less back pressure?

 

[snowracer69]

Why not give Rip Rook a call and see what he has to say about it? www.sourceautomotive.biz Heck, just go 4" all the way back and be done with it!

 

[Forrest Nearing]

it probably costs more than $20-30 to build as it's T304 stainless and has a fairly complicated internal design (compared to other mufflers)



I don't doubt that it's a quality piece, but it's not worth the money they're charging IMHO.



Forrest

 

[Lube Man]

I think it would be worth the money if the claims were true. Hard to put a price on technology. But so far the claims are unsubstantiated thus no technology premium.

 

[BTowler]

If it is made here it might approach $60-70, even out of 304 due to mass production costs, but if it is sourced out overseas you would be amazed at how cheaply it can be made.



BTW, what is the website for the tag? I would like to see what it is like.