How does the type of magnesium used between HDMO's and PCMO's vary? At least one of them must be using magnesium sulfates?
Magnesium type used
- Thread starter vinu_neuro
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Thanks jack, but that's from 05 and doesn't talk about which types of Mg are used in pcmo's as detergents and dispersants in hdmo's. Sounds like industry moved away from Mg detergents back then. And we're back to it now. I'm sure a lot has changed.
MolaKule
Staff member
Slightly off topic but from the Mikhail responder on Noria:
Quote:
This formulation provides a unique valve seat deposit. Magnesium containing components of the valve seat deposit are unstable, decompose, and do not remain on the valve seat. Thus, the valve seat deposit is thinner with this specific magnesium--calcium detergent oil. A thinner deposit on the seat results in a lower valve seat temperature because there is less insulation between the valve seat and the cylinder head. As previously described, the thinner deposit prevents localized loss and channeling of the deposit, and subsequent valve failure.”
OK, let’s examine the lack of logic here.
If the Magnesium does not remain on the valve seat, due to decomposition, then there is less so-called insulation anyway.
Except in the case of engine shutdown, how long is the valve in contact with the head, via the valve seat, in order to transfer heat energy?
Back to the DD question:
Detergents and dispersants are a class of additives called deposit control agents and stabilizers.
The role of detergents is to suspend polar oxidation products and neutralize oxidation-derived acids.
The role of dispersants is to suspend by-products of combustion, such as soot, and lubricant degradation, lacquer, and carbon deposits.
Detergents are predominately metal-based additives whereas dispersants are ashless, high molecular weight polymers.
Magnesium phenate or Magnesium salicylate are often used with reduced sodium or calcium sulfonates to reduce the total sulfated ash content that might be deposited.
Quote:
This formulation provides a unique valve seat deposit. Magnesium containing components of the valve seat deposit are unstable, decompose, and do not remain on the valve seat. Thus, the valve seat deposit is thinner with this specific magnesium--calcium detergent oil. A thinner deposit on the seat results in a lower valve seat temperature because there is less insulation between the valve seat and the cylinder head. As previously described, the thinner deposit prevents localized loss and channeling of the deposit, and subsequent valve failure.”
OK, let’s examine the lack of logic here.
If the Magnesium does not remain on the valve seat, due to decomposition, then there is less so-called insulation anyway.
Except in the case of engine shutdown, how long is the valve in contact with the head, via the valve seat, in order to transfer heat energy?
Back to the DD question:
Detergents and dispersants are a class of additives called deposit control agents and stabilizers.
The role of detergents is to suspend polar oxidation products and neutralize oxidation-derived acids.
The role of dispersants is to suspend by-products of combustion, such as soot, and lubricant degradation, lacquer, and carbon deposits.
Detergents are predominately metal-based additives whereas dispersants are ashless, high molecular weight polymers.
Magnesium phenate or Magnesium salicylate are often used with reduced sodium or calcium sulfonates to reduce the total sulfated ash content that might be deposited.
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Originally Posted By: MolaKule
Slightly off topic but from the Mikhail responder on Noria:
Quote:
This formulation provides a unique valve seat deposit. Magnesium containing components of the valve seat deposit are unstable, decompose, and do not remain on the valve seat. Thus, the valve seat deposit is thinner with this specific magnesium--calcium detergent oil. A thinner deposit on the seat results in a lower valve seat temperature because there is less insulation between the valve seat and the cylinder head. As previously described, the thinner deposit prevents localized loss and channeling of the deposit, and subsequent valve failure.”
OK, let’s examine the lack of logic here.
If the Magnesium does not remain on the valve seat, due to decomposition, then there is less so-called insulation anyway.
Except in the case of engine shutdown, how long is the valve in contact with the head, via the valve seat, in order to transfer heat energy?
I think the logic is fine but the word "seat" in "valve seat" is wrong and it should be "valve head" instead. The valve seat is the metal ring in the cylinder head casting that the valve head seals against.
The valve head is against the seat more than 500 degrees of 720 in a 4 cycle engine, so that's lots of time for the valve head to cool down if the heat can travel into the head casting through the seat. An insulating layer will theoretically increase the valve head temperature. Whether the effect if pronounced enough to be noticeable is open to question.
Slightly off topic but from the Mikhail responder on Noria:
Quote:
This formulation provides a unique valve seat deposit. Magnesium containing components of the valve seat deposit are unstable, decompose, and do not remain on the valve seat. Thus, the valve seat deposit is thinner with this specific magnesium--calcium detergent oil. A thinner deposit on the seat results in a lower valve seat temperature because there is less insulation between the valve seat and the cylinder head. As previously described, the thinner deposit prevents localized loss and channeling of the deposit, and subsequent valve failure.”
OK, let’s examine the lack of logic here.
If the Magnesium does not remain on the valve seat, due to decomposition, then there is less so-called insulation anyway.
Except in the case of engine shutdown, how long is the valve in contact with the head, via the valve seat, in order to transfer heat energy?
I think the logic is fine but the word "seat" in "valve seat" is wrong and it should be "valve head" instead. The valve seat is the metal ring in the cylinder head casting that the valve head seals against.
The valve head is against the seat more than 500 degrees of 720 in a 4 cycle engine, so that's lots of time for the valve head to cool down if the heat can travel into the head casting through the seat. An insulating layer will theoretically increase the valve head temperature. Whether the effect if pronounced enough to be noticeable is open to question.
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MolaKule
Staff member
I understand the heat transfer theory, I was referring to the "If the Magnesium does not remain on the valve seat, due to decomposition, then there is less so-called insulation anyway."
If we are discussing heat transfer paths, the exhaust valve will be heated by the gases and the heat will travel from the valve, to the valve seat, then to the head upon closing. More heat will only transfer with longer closure times.
Something seems to be missing from his quote or the author failed to include some additional information from the paper he was citing.
If we are discussing heat transfer paths, the exhaust valve will be heated by the gases and the heat will travel from the valve, to the valve seat, then to the head upon closing. More heat will only transfer with longer closure times.
Something seems to be missing from his quote or the author failed to include some additional information from the paper he was citing.
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