How do you eco-drive a diesel ?

[Duffman]

Most shift kits dont change the shift point but increase the shift firmness. I think there is something called a governor that changes rpm in the older tranies, I am at a loss if yours is electronic and how they do that in that type. It could be possible that the tranny does just need a servicing though.

[MazdaMatt]

Increase shift firmness? NO THANKS! This thing kicks like a mule when it shifts gears! It feels like i'm being rear-ended every time up upshift, and like i dropped anchor every time I off-throttle downshift.

[REDNAX]

The post recommending questions posed on specific Ford Diesel boards is the correct answer. Commercial vehicles are spec'd to a different standard than light-duty pickup trucks. They are expected to survive the abuse of low-paid, unskilled drivers and city traffic, with potentially dozens of engine starts per day. And merging into and out of 35-45 mph traffic (and your vehicle sounds about right to me, given your descriptions of its performance) is what it was made for.

One of those three boards, and maybe three or four members will be able to help you determine the best course of action. I have had some experience with this, and know that there is no substitute for experience. It may be that some trans mods will work (personally, I'd NEVER have a full manual valve body on a street vehicle), and certainly it sounds as if some diagnosis is in order.

In the meantime I would get ahold of the service manual -- drivetrain -- for that vehicle and start checking out the simple stuff: linkages, fuel pressure, restrictions that can be done easily from the engine compartment or underneath.

On the other hand, the many box-trucks I've driven (rented by the boss or me) tells me that fuel economy changes are somewhat unlikely, but ensuring factory specs in all areas are dead-on might alleviate some of the fuel burn under certain circumstances.

Reliability trumps pocket-change mpg "improvements".

[MazdaMatt]

Originally Posted by REDNAX

Reliability trumps pocket-change mpg "improvements".

Oh, that's for damn sure... no use improving MPG if after 50 dollars in savings my transmissions explodes all over the highway 500 miles from home.

[instarx]

Warning - more SP, VP, temperature and velocity stuff.

Originally Posted by ConnClark

If you read up on bernoulli's equation air moving across an opening has nothing to do with it. It is directly related to the velocity of the air and nothing to do with an opening.

That's twice now you have condescendingly told me to either "read up on" the issue or to use a computer program so I would understand what is going on. I didn't go to grad school for nothing and I understand the underlying principles just fine thank you. (Yes, it's been 15 years since I used any of it, so I made a few thoughtless errors earlier, but I do know absolutely that the velocity of air in a duct does not change the static pressure in that duct - but it is not intuitively obvious that it does not so I understand your confusion).

Actually that is a commercial science kit sold to and used by universities. Yes it is used to demonstrate Bernoulli's principle. It also demonstrate that just like in plumbing of an intake system with an intercooler static pressure rises and drops according to the velocity of the fluid at different points in it, hence the difference in the fluid levels.

NO, NO, NO! It does not demonstrate that at all - that contraption only demonstrates the Bernoulli effect. Also, you are thinking "I know the velocity is fast in certain areas, and the pressure is lower there, so velocity lowers pressure" - but that is false logic.

If what you say is true would you care to explain why the pressure increases again after flowing through the constriction.

Easily. You have to abandon the idea that the device shown is measuring static pressure - it isn't. It is measuring the relative strengths of the Bernoulli effect at each pressure tap. The last manometer has a lower liquid level (higher pressure) because the velocity of the air moving across its pressure tap is lower than the velocity of the air moving across the tap in the restricted section. I have no idea what the relative static pressure values are in that tube from looking at the manometers, and neither does anyone else.

-------------------
But enough of this VP versus SP versus Bernoulli artifacts stuff - here is the answer to the original issue:

The gas law germane to this problem is

(P1*V1)/T1 = (P2*V2)/T2

simplifying and solving for P2 we get an estimation of the pressure drop caused by any drop in temperature:

P2 = (P1*T2)/T1

where

P1 = pressure upstream fo the intercooler (assuming a 10 psi boost, 25 psi)
T1 = temp upstream of the inter-cooler in Kelvin; (250F = 394K)
T2 = temp downstream of the inter-cooler in K; (150F = 338K)
P2 = pressure downstream of the inter-cooler (the unknown in our problem)
V1 and v2, the volume of the contained air, can be ignored because they remain essentially constant

P2 = (25 psi * 338K)/394K = 21.4 psi

Now since 25 psi - 21.4 psi = 3.6 psi, an intercooler operating at 25 psi that lowers the temperature of its inlet air 100F will also drop the downstream pressure 3.6 psi! That's very close to what the original poster said he was measuring. Therefore, the pressure drop he is seeing across his IC is almost certainly caused by the drop in temperature and NOT from a physical restriction in the IC itself.

If you don't trust my math, here is a little Gas Law calculator I found that let's you solve for various unknowns, including P2:

COMBINED GAS LAW CALCULATOR

Pressure can be in any units, but T must be in degrees Kelvin.

[ConnClark]

Originally Posted by instarx

Warning - more SP, VP, temperature and velocity stuff.



That's twice now you have condescendingly told me to either "read up on" the issue or to use a computer program so I would understand what is going on. I didn't go to grad school for nothing and I understand the underlying principles just fine thank you. (Yes, it's been 15 years since I used any of it, so I made a few thoughtless errors earlier, but I do know absolutely that the velocity of air in a duct does not change the static pressure in that duct - but it is not intuitively obvious that it does not so I understand your confusion).

Lets see what nasa has to say on the subject (See attached). Oops, static pressure does change.

NO, NO, NO! It does not demonstrate that at all - that contraption only demonstrates the Bernoulli effect. Also, you are thinking "I know the velocity is fast in certain areas, and the pressure is lower there, so velocity lowers pressure" - but that is false logic.

Nope, my logic is totally valid

Easily. You have to abandon the idea that the device shown is measuring static pressure - it isn't. It is measuring the relative strengths of the Bernoulli effect at each pressure tap. The last manometer has a lower liquid level (higher pressure) because the velocity of the air moving across its pressure tap is lower than the velocity of the air moving across the tap in the restricted section. I have no idea what the relative static pressure values are in that tube from looking at the manometers, and neither does anyone else.

Nasa and I do

-------------------
But enough of this VP versus SP versus Bernoulli artifacts stuff - here is the answer to the original issue:

The gas law germane to this problem is

(P1*V1)/T1 = (P2*V2)/T2

simplifying and solving for P2 we get an estimation of the pressure drop caused by any drop in temperature:

P2 = (P1*T2)/T1

where

P1 = pressure upstream fo the intercooler (assuming a 10 psi boost, 25 psi)
T1 = temp upstream of the inter-cooler in Kelvin; (250F = 394K)
T2 = temp downstream of the inter-cooler in K; (150F = 338K)
P2 = pressure downstream of the inter-cooler (the unknown in our problem)
V1 and v2, the volume of the contained air, can be ignored because they remain essentially constant

P2 = (25 psi * 338K)/394K = 21.4 psi

Now since 25 psi - 21.4 psi = 3.6 psi, an intercooler operating at 25 psi that lowers the temperature of its inlet air 100F will also drop the downstream pressure 3.6 psi! That's very close to what the original poster said he was measuring. Therefore, the pressure drop he is seeing across his IC is almost certainly caused by the drop in temperature and NOT from a physical restriction in the IC itself.

If you don't trust my math, here is a little Gas Law calculator I found that let's you solve for various unknowns, including P2:

COMBINED GAS LAW CALCULATOR

Pressure can be in any units, but T must be in degrees Kelvin.

These equations are only valid for a closed system. This is your source of error. You cannot just discard the volumes in this equation with out making the assumption the volume on one side of the equation is identical to the volume of the other side of the equation.

With this assumption the density of the air would remain constant. This runs totally contrary to the purpose of an intercooler as an intercooler is used to increase intake charge density.


Do you own an intercooler ?

[vtec-e]

I'm no scientist but how about this for an experiment: Block the intercooler with cardboard. This should eliminate any temp differences that would or wouldn't cause a pressure drop. Of course, a pre/post temp measurement would be handy, if only to make sure the IC is insulated enough. Then if there IS a pressure drop across the IC then it's because of the physical restriction in the IC. If there isn't a pressure drop, then it's due to a lack of cooling. Just my two cents. I'd hate to see things get nasty here.

ollie

[ConnClark]

Blocking the intercooler can lead to engine damage in some cases.

[instarx]

Originally Posted by ConnClark

Lets see what nasa has to say on the subject (See attached). Oops, static pressure does change.

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.

These equations are only valid for a closed system. This is your source of error. You cannot just discard the volumes in this equation with out making the assumption the volume on one side of the equation is identical to the volume of the other side of the equation.

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.

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.

do you own an intercooler?

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

With this assumption the density of the air would remain constant. This runs totally contrary to the purpose of an intercooler as an intercooler is used to increase intake charge density.

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 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.

[instarx]

Originally Posted by vtec-e

I'm no scientist but how about this for an experiment: Block the intercooler with cardboard. This should eliminate any temp differences that would or wouldn't cause a pressure drop. Of course, a pre/post temp measurement would be handy, if only to make sure the IC is insulated enough. Then if there IS a pressure drop across the IC then it's because of the physical restriction in the IC. If there isn't a pressure drop, then it's due to a lack of cooling. Just my two cents. I'd hate to see things get nasty here.

ollie

That would work. You wouldn't want to run it like that forever, but eliminating the temperature variable would allow measurement of the restrictive pressure drop (if any) across the IC. Unfortunately neither ConnClark nor I own the car.