How do you eco-drive a diesel ?

[tasdrouille]

I have been running since July with cross flow to the IC blocked. Haven't noticed variation in pressure with or without the block. There is not even much variation in IAT between stock and blocked. No variation at all driving on flat terrain. I noticed a 18 F difference on a one mile 6% grade at 60 mph, but that's pretty much it, I never boost for extended period of times.

[instarx]

Originally Posted by tasdrouille

I have been running since July with cross flow to the IC blocked. Haven't noticed variation in pressure with or without the block. There is not even much variation in IAT between stock and blocked. No variation at all driving on flat terrain. I noticed a 18 F difference on a one mile 6% grade at 60 mph, but that's pretty much it, I never boost for extended period of times.

That makes sense. If the turbo isn't being used then the intake air is not being compressed/heated and the IC becomes just another part of the ductwork.

[groar]

What I wasn't understanding is why I can save 33% in the megane without FCD, while I can save only 20% in the scenic with FCD...

After 3 tanks in the scenic, it seams I'm improving myself, noticeably as the temperature is dropping. Thanks to the onboard computer I can say that when the ICE is cold it consumes 5.2L/100 (10% saving from the 5.9L/100 rating), while when it's hot it consumes only 3.5L/100 (40% saving).

At 70km/h I can find the sweet spot at 2.3L/100, and at 80km/h it's at 3.0L/100. Now these hot spots are so volatiles that any change in road level or a truck overtaking me and the consumption increases by 10-20% and/or the speed decreases by 5-10% !!!

3 possibilities I imagine :

• the heavier weight and greater Cd and FA of the scenic make it more sensible to road conditions.
• as I drive nearer from scenic's sweet spots (as I drive by looking at the FCD), the gas waste is smaller and doesn't permit to absorb the changes in road conditions without generating a speed change.
• the high grade diesel (cetane 55 instead of 51) has less impact in scenic's more complex common rail turbo diesel engine than in megane's simpler turbo diesel engine.

As my wife and I are swapping our cars regularly, from tomorrow I get the megane back Since I'm eco-driving, I prefer the megane which is lighter, while my wife prefers the scenic which is higher.

Denis.

[ConnClark]

Originally Posted by instarx

Oops, indeed.

Read the title: "Inviscoid, Incompressible Fluid". An incompressible fluid means water or some other liquid, not a compressible fluid like air. You picked an inappropriate diagram to support your position. Seems you and NASA are talking about different things.

Yes the calculations for this were done using an incompressible fluid model. They did this to simplify the problem so that it was easier to teach. Sort of like how you are applying the combined gas law which is a generalized application of the ideal gas law which assumes your working with an ideal gas ( Ideal Gas Law ). Note, air is not an ideal gas.

Bernoulli's principal applies to compressible and incompressible fluids alike. The full text of the Nasa example is here chapt3 . If you wish to expand upon it and calculate compressible flow effects I suggest you read this http://www.freestudy.co.uk/thermodynamics/t7201.pdf .

So Nasa and I are talking about the same thing.

The equation is the Combined Gas Law, and it applies to ALL systems - closed, open and in between. No exceptions. The Gas Laws: They're the Law, not Suggestions.

It does???

"The combined gas law states that for a closed system ......"

Combined Gas Equation-cs

As for ignoring the volume component: There are not two container volumes in this system, only one. It just happens to be a long, thin container where hot air is cooled as it passes through the container until it exits the other end. The values for V1 and V2 are therefore ignored.

The volume of the container isn't relevant. The volume of a unit of gas is.

"There is one more technique you need to know to apply the gas laws to things like the atmosphere.

In all the scenarios considered in section 1, the volume V was just the volume of the container. So the question is, what is the relevant V when we are talking about the atmosphere, or any other system where there is no relevant container?

The answer is that we talk about a parcel of gas. That is, take some region of space, and imagine marking all the gas that is initially within that region. We then follow the parcel of marked gas as time goes on. The parcel will move. The parcel will change shape, but that doesn’t matter, except insofar as the volume changes (compressing or expanding the parcel). The boundaries of the parcel might become a bit blurry, as molecules diffuse across the boundary to/from adjacent parcels, but this won’t greatly affect the properties of our parcel, especially if neighboring parcels have approximately the same properties anyway."

Gas Laws

Yes I do. It's attached to my car. What does that have to do with anything.

I asked because I thought you might like to make measurements.

With this one I am through. The IC cools the air. Cool air molecules have less energy therefore they exhibit less pressure and can be packed closer together. Cold air is more dense than hot air.

This contradicts your statement in post #55 "V1 and v2, the volume of the contained air, can be ignored because they remain essentially constant". Density of the air could not change and still have your calculations in post #55 be valid. In order to pack lower pressure air molecules together and make the air more dense you must raise the pressure

This is basic, and is entirely consistent with the gas laws. This gets back to my very first statement that the pressure drop measured across the IC is due to the drop in temperature. I have shown that the drop is predicted by the Gas Laws, and that the Gas Law even predicts the amount of temperature drop correctly. The equation is simple enough for anyone to understand. I gave a reference. I gave a link to a calculator for anyone to use. Yet you still want to argue that the temperature drop isn't responsible for the pressure drop. Fine.

If for some reason you refuse to accept the proven fact that lowering the temperature also lowers the pressure, it is not my responsibility. Believe what you will. If you want to argue that the Gas Laws are wrong, go dig up Robert Boyle or Jacques Charles and argue with them.

Your narrow view on how the combined gas law can be applied totally neglects the Charles' Law form.

Charles's law - Wikipedia, the free encyclopedia

In fact the way you describe things working it could be construed as a denial it exists.

If you had an ideal intercooler working on an ideal gas this would be use to describe its behavior because it results in the the maximum reduction of volume of the gas. This is the behavior engineers try to approximate when designing an intercooler. Unfortunately they cannot design one without flow restriction and the pressure drop across the intercooler varies in proportion to the square of the amount of air flowing through it.

[ConnClark]

Originally Posted by tasdrouille

I have been running since July with cross flow to the IC blocked. Haven't noticed variation in pressure with or without the block. There is not even much variation in IAT between stock and blocked. No variation at all driving on flat terrain. I noticed a 18 F difference on a one mile 6% grade at 60 mph, but that's pretty much it, I never boost for extended period of times.

How are you measuring the IAT? If it is based of a reading from the car's computer the temp sensor is usually located before the turbo either as part of or very close to the MAF sensor. Also if you have working EGR it raises intake temps.

[tasdrouille]

The IAT sensor is in post IC piping. I don't see the point of having the IAT before the turbo. The air gets compressed, then cooled by the IC, if the ECU wants to know the IAT for anything useful it's got to take it after the IC. My experience has been that IAT sensors near or integrated with the MAF are mostly seen on N/A cars.

The cooled EGR does not affect the IAT readings as it's located right at the intake manifold.

[ConnClark]

Originally Posted by tasdrouille

The IAT sensor is in post IC piping. I don't see the point of having the IAT before the turbo. The air gets compressed, then cooled by the IC, if the ECU wants to know the IAT for anything useful it's got to take it after the IC. My experience has been that IAT sensors near or integrated with the MAF are mostly seen on N/A cars.

The cooled EGR does not affect the IAT readings as it's located right at the intake manifold.

Most MAF sensors need the temperature of the air right at the MAF in order to accurately figure out how much air is flowing through them. In a modern diesel actual manifold air intake temps aren't usually needed as they know how much air is going into the engine from the MAF reading. This is usually sufficient for emissions control.

I'm not familiar with the volkswagon engine and emissions controls so I'll take your word for where the iat sensor is located.

[Piwoslaw]

Here is something about how much an intercooler gives in a turbodiesel.
My Peugeot 307 has two versions with a 1.6 turdodiesel engine: 90hp and 110hp. There are also 407's with the same two engines and 307 with 2.0 liter, 90hp and 110 hp engines. I have the 110hp engine and was wondering about differences between it and the weaker version. I found this thread on the Peugeot-Klub Polska forum, and in it two links:http://tdi.pl and http://www.psc.com.pl. It's all in Polish, but the last link is supposed to have some charts (my browser doesn't like them).
It turns out that the 90hp version doesn't have an intercooler. Someone took a stock intercooler from the 110hp version and installed it in the weaker one. This gave about 9hp. The increase was in the mid range of rpm's, at lower and higher rpm's the power and torque were the same or slightly lower. Nothing else was changed. If the compression ratio was increased to compensate for the extra drag in the air supply, then you should get the 110hp engine.

Unfortunately, neither turbos, nor intercoolers, help much in the 1500rpm range where my engine is usually at

[Big Dave]

If the objective is increased engine efficiency, the best way to deal with the EFR is to block it off. If if never opens, the combustion process is not poisoned by the exhaust gas and the whole combustion event yield more heat into the cylinder. Higher temperature = higher efficiency.

[Big Dave]

MazdaMatt:
If I sat down and tried to design a fuel-guzzler the only improvement I could offer (make the MPG worse) is to get one with a gas engine.

Modding that beast to get 15 MPG would take Warren buffet's ransom.

Suggestions:
Drive it as little as possible or
Trade it in - you can get some fabulous deals these days