AW - Concentration or Total Amount Available?

[Peter_M]

Antiwear compound content such as ZDDP is generally talked about in terms of a proportion of the total mass of oil. ie 1400ppm or 0.011% etc.

Because of the mechanism of protection, isn't the most important thing being the total quantity of ZDDP in the sump of the engine that is available to form the protective film under heat and pressure?

To illustrate this question more, assume I have two identical engines except that one has twice the oil capacity to the other. If the large sumped engine contains 10 litres of 700ppm ZDDP oil and the other contains 5 litres of 1400ppm ZDDP oil, if all else is equal, won't the protection afforded by the ZDDP be the same in both engines?

Thanks
Peter

 

[MolaKule]

NO, because the concentrations are different.

You have to realize that ZDDP is an ester containing Sulfur, Zinc, and Phosphorus. ZDDP is an Anti-Wear chemistry in the PI package that also acts as an anti-oxidant agent because of the correct ratios of S-Z-P.

 

[Olas]

Good question

. If the only variable was sump capacity then you would expect them to both have the same volume of additive.
If this proves to be true it could lend weight t the oversize filter argument.

 

[MolaKule]

The main advantage of a large sump over a smaller one is oil cooling.

The other advantage would be reserve capacity in case of a leak or oil evaporation.

 

[HTSS_TR]

The other advantage is longer OCI ?

 

[CT8]

Originally Posted By: MolaKule
The main advantage of a large sump over a smaller one is oil cooling.

The other advantage would be reserve capacity in case of a leak or oil evaporation.
Taking longer to heat up?

 

[MolaKule]

Originally Posted By: CT8
Originally Posted By: MolaKule
The main advantage of a large sump over a smaller one is oil cooling.

The other advantage would be reserve capacity in case of a leak or oil evaporation.
Taking longer to heat up?


A larger mass of oil usually means a larger sump capacity which in turn usually mean a larger (deeper) oil pan which dissipates more heat.

The larger the oil pan, the more surface to cool the oil, reducing oil temps.

If you can reduce the oil temps, the oil oxidizes slower over time, and OCI can be increased, barring any other variables.

 

[Peter_M]

Originally Posted By: MolaKule
NO, because the concentrations are different.

You have to realize that ZDDP is an ester containing Sulfur, Zinc, and Phosphorus. ZDDP is an Anti-Wear chemistry in the PI package that also acts as an anti-oxidant agent because of the correct ratios of S-Z-P.


Molakule,

Could you explain your answer about the AW chemistry a little more for me please?

Could we also ignore the other advantages of additional oil capacity and assume the temperatures are same/steady state to nullify any other effects.

I do appreciate your thoughts.

Regards
Peter

 

[MolaKule]

Sure thing but what facet?

Regarding the ppm vs. volume or the AW additive chemistry of ZDDP?

 

[Peter_M]

Probably ppm vs volume first please?

But I will take you up on the AW additive chemistry of ZDDP at a later date!

Thanks
Peter

 

[tudorart]

Peter allow me a shot please.
Here's how I see it
If you have the smallest elemental unit for oil on the dS(smallest element of surface) at an instant unit of time dt your concentration is all that matters.

The rate at which the AW is replenished on the surface is dependent on the concentration and not overall volume and it has to be higher than the rate at which it's being exfoliated (which is particular to each design and use).
Hence the metal limits set for protecting exhaust treatments are also expressed in percentage or ppm.

 

[weasley]

These discussions overlook the fact that there is more than just ZDDP competing for the surface. If your ZDDP dosage is lower then there is likely to be something else at a relatively higher dosage. Could be detergents, friction modifier, corrosion inhibitor.... A relatively higher dosage of ZDDP will tend to give it a better chance of getting at the surface.

Unless you consider the relative surface activity of each molecule type - you can reduce Zn/P levels but change the molecule type, making it more active. You can't think about these things as simple mass balances.

 

[MolaKule]

Quote:
To illustrate this question more, assume I have two identical engines except that one has twice the oil capacity to the other. If the large sumped engine contains 10 litres of 700ppm ZDDP oil and the other contains 5 litres of 1400ppm ZDDP oil, if all else is equal, won't the protection afforded by the ZDDP be the same in both engines?


This may help.

We'll call your first oil (10 litres of 700ppm ZDDP oil) Oil A.

We'll call your second oil (5 litres of 1400ppm ZDDP oil) Oil B.

Let's take a 1 Liter sample of Oil A. When we analyze it, it will show 700ppm of ZDDP.

Let's take a 1 Liter sample of Oil B. When we analyze it, it will show 1400ppm of ZDDP.

Let's take a 100 milliLiter sample of Oil A. When we analyze it, it will show 700ppm of ZDDP.

Let's take a 100 milliLiter sample of Oil B. When we analyze it, it will show 1400ppm of ZDDP, etc.

The sample volume does not matter. It is the total concentration of a specific additive in the oil at blending time that matters.

 

[aa1986]

So when a drop of oil hits an engine part, oil A will behave differently to oil B.

The drop size is the same, but each oil has differing amounts of AW.

Is that correct?

 

[MolaKule]

That is correct, each has differing amounts or centrations of AW, all else being equal.

Whether it is 5000 gallons, or 1 microdrop, it doesn't matter, the percentage (ppm) of the AW will be the same.

It doesn't matter what the additive may be, because the amount of additive to be added is based on a dosing of either percent of weight or of Percent by volume.

For example, one of my full synthetic PI packages has a dosage of 9.3% by volume, which means that for whatever volume I add it to, the additive percentage (by volume) has to be 9.3%.

We know 1 quart = 946 milliLiters.

So to get the proper additive yield for 1 quart, I would have to add 80 milliLiters of the additive for each 866 milliLiters of base oil to get the specified concentration of additive in that one quart.

The analysis would look like this:

Calcium - 2,070 ppm
Moly - 51 ppm
Nitrogen - 1,100 PPM
Phosphorus - 800 ppm
Zinc - 900 ppm


If I was working with a 5 gallon jug of oil, I would have to add 400 milliLiters of additive to each 4.3 Liters of base oil.

(1000 milliLiters = 1 Liter)

The analysis would look like this:

Calcium - 2,070 ppm
Moly - 51 ppm
Nitrogen - 1,100 PPM
Phosphorus - 800 ppm
Zinc - 900 ppm

And so on. If I were mixing for a 10,000 gallon tanker of blended (fully formulated) oil, the I simply scale up the numbers.

The analysis of the 10,000 gallon tanker of oil would look like this:

Calcium - 2,070 ppm
Moly - 51 ppm
Nitrogen - 1,100 PPM
Phosphorus - 800 ppm
Zinc - 900 ppm

 

[MolaKule]

Dang timeout got me again.

Quote:
If I was working with a 5 gallon jug of oil, I would have to add 400 milliLiters of additive to each 4.3 Liters of base oil.

(1000 milliLiters = 1 Liter)

The analysis would look like this:

Calcium - 2,070 ppm
Moly - 51 ppm
Nitrogen - 1,100 PPM
Phosphorus - 800 ppm
Zinc - 900 ppm

And so on. If I were mixing for a 10,000 gallon tanker of blended (fully formulated) oil, the I simply scale up the numbers.

The analysis of the 10,000 gallon tanker of oil would look like this:

Calcium - 2,070 ppm
Moly - 51 ppm
Nitrogen - 1,100 PPM
Phosphorus - 800 ppm
Zinc - 900 ppm


Should read:



If I were working with a 5 quart jug of oil, I would have to add 400 milliLiters (0.4 Liters) of additive for each 4.3 Liters of base oil.

The analysis would look like this:

Calcium - 2,070 ppm
Moly - 51 ppm
Nitrogen - 1,100 PPM
Phosphorus - 800 ppm
Zinc - 900 ppm

And so on. If I were mixing for a 10,000 gallon tanker of blended (fully formulated) oil, I would simply scale up the numbers.

The analysis of the 10,000 gallon tanker of oil would look like this:

Calcium - 2,070 ppm
Moly - 51 ppm
Nitrogen - 1,100 PPM
Phosphorus - 800 ppm
Zinc - 900 ppm

(1000 milliLiters = 1 Liter)

 

[Peter_M]

Originally Posted By: tudorart

The rate at which the AW is replenished on the surface is dependent on the concentration and not overall volume and it has to be higher than the rate at which it's being exfoliated (which is particular to each design and use).


Sorry all, this is closer to my intended question! I apologise I wasn't clearer earlier.

Why is the rate of replenishment dependent on the concentration of the AW and not the total amount of AW flowing over the particular journal/slipper/lobe? Is there some sort of time criteria?

I appreciate all your responses to date. Thank you

 

[aa1986]

The rate of flow is the same regardless of it being a 5qt sump or a 10qt sump.

The flow does not increase because the sump is larger, so the only way to replenish more is to increase the concentration.

The only difference with a 5qt sump and a 10qt sump with the same concentration of AW will be for how long the oil is able to replenish the AW.

 

[MolaKule]

Good question Peter_M, but I still think you're confused about ppm concentrations and total oil flow or volume.

The concentration in ppms for any additive component will be the same regardless of oil flow moving past or between surfaces, measured in Liters/second.

Let's get down to the molecular level for a moment and see if that helps.

In the case of ZDDP, the sulfur, zinc, and phosphorus elements disassociates from the total ZDDP molecule.

The sulfur molecule, along with the zinc molecule, helps with the anti-oxidation task and the sulfur molecule helps the phosphorus molecule attach itself to the ferrous (iron) surface.

When the phosphorus element attaches itself to the ferrous (iron) surface, it forms a Plastic film of mainly ferrous phosphates that reduces contact wear.

However, these "associations" can't stay friends forever because heat, mechanical shearing, and oxidation degrade these associations over time.

A higher concentration of the ZDDP molecule (or any additive chemistry) means the molecule can give up more of its elements to do their job.

What I have described is just one additive component. There are many different additive chemistries in lubricants, so concentrating on just ZDDP is not really constructive.

It is the total package, consisting of base oils and additives, that determine the performance of a commercially formulated lubricant.

 

[MolaKule]

Quote:
Peter_M: Is there some sort of time criteria?



Quote:
However, these "associations" can't stay friends forever because heat, mechanical shearing, and oxidation degrade these associations over time.


"Rate" implies effects over time.

The higher the heat, the more the oxygen, and the more the mechanical shearing, the higher the RATE of degradation.