Wrong Statements Regarding Turbocharging
 

97E300D There were mistakes in the following paragraphs concerning turbocharging.
Member
It will work.......
Rick Miley,

[#1.....I think you should better understand the process of how the EGR valve functions before denouncing the idea on a Turbo. It will work....... Remeber the EGR Valve is still fully fuctioning on this mod.]

[#2.....If you were correct and it would be blowing air out of the "breather filter" then it would also be blowing air out into the exhaust manifold as well, when hooked up in the stock configuration. I don't think the engineers would what to "Create" a manifold leak.]

[#3.....Look at it this way, in order to blow air out the EGR valve and hence out the filter. The intake manifold pressure needs to exceed that of the ambient air pressure 14.7 PSI (sea Level). This may be the case at High RPMS but again at high RPMs the EGR is closed. ]


[#4.....To see it another way there is really no such thing as "suction". In an engine the pistons do not really suck air in through the intake, but rather create a partial vacuum in the cylinder and the outside air pressure rushes in to fill the vacuum at 14.7 PSI. Also as valves open and close faster at higher RPM's there is not enough time for all the air to fill the vacume in the cylinder to make 14.7 PSI a turbo or supercharger can help to balance this out, in an over booted engine it can pump in more then 14.7 PSI. Again the EGR valve would most likly be closed.]

CORRECTIONS BELOW:

#1 Rick Miley is right. Your device will not work on a turbocharged engine. If you hook a pressure gauge to your non-turbo intake manifold you will get a slight vacuum reading. The EGR valve on a turbodiesel is only activated at periods of low boost which is still above atmospheric pressure.

#2 There is positive pressure in the exhaust manifold as the gasses are held back by the energy needed to turn the exhaust side of the turbo. There is also positive pressure in the intake manifold of a turbodiesel. hook up a gauge and see. THIS PRESSURE IS OVER AND ABOVE AMBIENT AIR PRESSURE. IF WHAT YOU HAVE STATED ON OTHER DATES ON THIS TOPIC IS TRUE THAN WHEN YOU HAVE 14.7 POUNDS OF AIR IN YOUR TIRES THEY WILL BE FLAT. A TURBODIESEL HAS POSITIVRE PRESSURE ( ABOVE ATMOSPHERIC) IN THE MANIFOLD. A flat tire has ambient pressure in it!!!! OK?

#3 The intake manifold pressure INDEED EXCEEDS ambient pressure.

#4 There is no vacuum in the cylinders of a Turbodiesel due to the positive pressure created by the turbocharger. Therefore the charge air is forced into the cylinders at a pressure above atmospheric pressure along with additional fuel. How else does a turbocharged engine make 40-50% more power?

Therefore your device will not work on a turbodiesel

Really...
The turbo has a boost pressure above 1 bar or 14.7 PSI ?

WASTEGATE OPENS AT .9 BAR

I found these numbers on the turbo charger. Boost Pressure/Wastegate Pressure: .9 bar (13.05 psi). I take it this is "PSIG" boost which would then be 13.05 psi or 27.75 absolute? If that is the case the I stand corrected but I'm not convinced my friend. Read the boost gauge on a car when it is not running. It reads 1 bar.

Now Read this:
http://www.intendedacceleration.com/tip_1.html

Q. How else does a turbocharged engine make 40-50% more power?

A. Well it is because it supplies the combustion chamber with more air for the fuel/air detonation. My post was not that far off when I said "
as valves open and close faster at higher RPM's there is not enough time for all the air to fill the vacuum in the cylinder to make 14.7 PSI, a turbo or supercharger can help to balance this out, in an over booted engine it can pump in more then 14.7 PSI."

It's all relative the air pressure running through the turbos vains on each side of the engine will still move and pressurize air. It just is lower pressure then that of what is outside. You can still feel the air blowing on a mountaintop; it just takes a higher speed to feel the same as on the ground.


The 14.7 psi is absolute pressures so yes a flat tire is 1 bar and an inflated tire is bar + 32 psi or 46.7 psi absolute pressure. Take a flat tire with no leaks around the bead up 20,000 agl and see what happens. Of course it will be flat when you hit the run way again.

Try this on for size. Fill an empty paint thinner can with 1/4 inch of water heat it until the water is seaming out the opening. You have now displaced the air. put the cap back on and watch what happens when the water condenses back to liquid and leaves a vacuum in it's place. The air pressure around it crushes the can.

When they say the turbo is .9 bar I take it as meaning .9 Bar unless it means .9 Bar of boost above 1 bar. I may be wrong though, just prove it, Let keep this a friendly debate. Typing all caps is sometimes considered rude.

From a technical article at superstreetonline.com:

A turbocharged engine revolves around one central idea, and that is boost. Boost is defined as the increase in manifold pressure above atmospheric pressure. So what the hell does that mean?

Basically, boost is a gauge of the amount of charged air pressure produced by the turbocharger. As boost increases, more charged air is being force-fed into the motor and more horsepower is being made. Boost levels are usually measured in pounds per square inch (psi).

Full text of the article can be found here.

Automotive boost gauges typically read 0 at atmospheric pressure, and boost is always measured above atmospheric. This is even verified by the article you linked to above: "The BAR gauge in the Audi is an absolute pressure gauge and it takes into account the atmospheric pressure. It is an international unit of pressure that is used in most countries. It is equal to 14.5 PSIA or approximately 1 atmosphere. This is why our gauge read about 1 BAR when the engine is off at sea level.
...
Atmospheric pressure can also be ignored when it comes to BAR. Sometimes a european tuner will say the engine is boosted to... or is running 1.1 BAR of boost. In this case he is referring to what we would call 15.9 PSIG boost. He could also say the engine runs at 2.11 BAR."

Notice that they are talking about Audi. Mercedes-Benz ignores atmospheric pressure, and starts the gauge at 0, not 1. Perhaps you will believe the Mercedes-Benz manual for the 300D. The procedure for checking boost pressure can be found here.

Well it sure looks like you got me then :)

I interpreted 1 Bar to mean Barometric pressure not Psi. 1 Bar of boost , "boost" being the key word, means over sea level presure.

But does the ERG valve open when the engine is "Boosted". I thought the EGR valve opened only at lower cruise RPMs when the Turbo was not spooled up. So at what rpms or Man Pressure does it open? The intake is not always boosted is it?

I don't see how attaching a breather filter onto the line feeding the EGR assembly would cause such a "production" for the engine, not thinking theoretically just practically at this point.

Mind you I am keeping this extremely simple, but the EGR valve is exactly that, a valve. IF the EGR valve was to say be open, partially or fully while the turbo is creating boost, that would mean that pressure would be escaping back into the exhaust manifold right?

The amount of flow into the EGR is dependent upon the vaccuum that the cylinders create. It makes no sense for the EGR valve to be open while the turbo is creating boost. The turbo would have to work proportianlly harder to compensate for th eboost lost through the open valve.

If you ever look at the flap on the flap of a non-turbo OM606, you can see that as soon as the rpms start to increase above idle, the flap opens wide to allow air from the airbox, not from the EGR.

I looked at an OM606 turbo this afternoon at the New England GTG. This post is a result of my primative findings. What the worst that can happen while trying this experiment, setting a CEL that will clear after putting things back to normal?

Actually, Turbos and Super Chargers have been around for a long time in aviation even before the Merlins. Today most aviation turbo charging is called Turbo Normalizing which never exceds the sea level manifold presure. So it is never "boosted" except when compaired to the ambient presure outside and always less then 1 bar.

Well I can see the logic behind the pre-turbo exhaust being under enough back pressure, since the turbo is an obstruction to the flow. So that raises the question is the egr inlet pipe before or after the turbo? I would imagine before, in order to match the intake pressure and prevent it from bleeding off addition boost. So that would mean the exhaust side is under more presure to allow it to over come the intakes boost.

Before we can say it won't work The question still needs to be answered " Under what manifold pressure is the EGR valve opened ?"

And do we know if the MAP sensor(s) monitor a drop in pressure and automatically correct the drop by closing the EGR?

We may be on to something else. Since the system seems the be rather sophisticated it may just choose to keep the EGR closed each time it begins to open it. The most sophisticated systems are sometimes the easiest to fool.

What information does the ECU use to open and close the valve? The wires on the EGR valve only tell the ecu if the valve is full open or closed.

An alternative method...
 

Ive been reading up on this topic and am interested it adapting it slightly to work for a turbocharged 98-99. Mr. goodwrench said that air is forced into the intake manifold, well why can we just force air into the egr valve.

In stead of running a seperate line with a filter to atmospheric pressure, one could be plumbed from the egr valve to the intake ducting right after the intercooler. In this manner, the air with be clean, cool, and pressurized, thus eliminating the possibility of air being "forced out" of the egr valve.

This is an interesting topic, I thought of the same thing it should be a very simple solution. Only I think it would react in the same manner as if the EGR valve was just plugged off, a CEL.

The man pressure needs to be at a lower PSI then the air in the Exhaust. This allows the exhaust to displace some of the intake air. If we created a loop as you suggested the pressures would be equal and would have the same effect as blocking off the EGR. I think we still need to understand when the EGR valve opens (pressure wise). The exhaust would seem to be under a higher pressure pre-turbo then the intake since it is the side under restriction, yet this may not be the case. Differing vanes on the intake and exhaust sides could change this some what. It is not so much the speed of each impeller but the pitch of the vanes that do the pressurizing

The sensors, I would think, need to detect a pressure drop within the correct range to not throw a "CEL"

I agree...we definately need to know at what rpms the egr valve is opened and closed at, and if it is pressure sensitive. Once this is known, all that is needed is a bypass that fits the criteria.

As stated above, there is no pressure differential, so this wouldn't work. However, if you tap in before the intercooler, the pressure is higher there so it might have a chance of working. But it would be an awfully long run - diagonally across the engine bay.

To answer some questions above, the EGR is most open at part throttle. The engine is boosted (or overboosted in aviation terms) at that time. Not full boost of 1 bar, but maybe 1/3 to 1/2 bar. The exhaust tap is between the exhaust manifold and the turbo, where there is enough pressure to overcome the intake tract pressure.

Correct me if im wrong, but the pressure before the intercooler and after it should be the same. The job of the intercooler is to reduce the temperature of the hot compressed air coming out of the turbo, if it releaved the pressure too, it would undo the work of the turbo and render it pointless to have one in the first place.

There is a small pressure drop along with the temperature drop. So it doesn't undo all the work of the turbo, just a little.

Has anybody successfully done this with a 98/99 E300TD?

I believe you are correct Rick
(P1*V1)/T1 = (P2*V2)/T2
Control volume of a sample at inlet, exit considered equal: V1=V2 = V
so with a temp drop across the intercooler: Texit < Tinlet
Pressure at intercooler exit is = Pinlet*(Texit/Tinlet)

I've got to get this done on my car.

My car has been running in the stock configuration for 106,000 miles. The manifold has only been cleaned once. I had it off just a couple weeks ago to replace the shutoff valve, and there was just a light dusting of soot. Definitely not enough to affect performance. Bottom line is that the turbo OM606 just doesn't clog up as much as other engines, so it's really not a big deal.

The CDI diesels will detect if the EGR valve is open by monitering the air mass meter for flow changes as the valve opens and closes. The ecu calculates from engine speed and manifold pressure what the air volume is.

If the egr valve is open then the amm volume will be lower than the calculated volume. If the amm doesn't register a change when the valve opens then it know's that the egr valve is either blocked or not opening. Shame really, if I ever had a CDI the first thing I'd do is disconnect the EGR valve, I've never liked the idea of having great air filters yet allowing solids into the intake after the filter :mad: