tditom
Top Post Dawg
- Joined
- Sep 5, 2001
- Location
- Jackson, MI
- TDI
- formerly: 2001 Golf GL, '97 Passat (RIP) '98 NB, '05 B5 sedan
Revisiting this thread since coming back to the forum after several years. Some of this is very pertinent to the ongoing issues of CR HPFP failures. The links to the original data sheets are broken. I tried to fix one but it was a problem, so if you want you can look at the items in my album about fuel lubricity here:
Original thread follows****************************************
I have been concerned about diesel fuel lubricity, especially with ULSD coming on the scene.
As you know, the high pressures inside our fuel injection systems require very close tolerances between the pump components. The only lubrication these components receive is from the diesel fuel. The process of lowering the sulfur content also lowers the lubricating properties of the fuel. When the implementation plan of ULSD was being developed here (the U.S.), a push was made for a lubricity standard for US diesel fuel.
The test for fuel lubricity is performed on a High Frequency Reciprocating Rig (HFRR). Here is a description of the test (LINK -you will need to search on hfrr):
Here is a presentation from Bosch in 2003 that detailed the issue of lubricity, and gave an assessment of US fuel supply at that time. Remember that this was before ULSD was on the scene. They were pushing for a fuel lubricity standard to be implemented for LSD, which has more "natural" lubricity than ULSD. Note on slide 8 that 80% of US fuel stations tested had a wear scar >460 microns. Take a look at the photos of FI components that were run with fuels that had varying lubricity properties.
Here is a summary of ASTM's process for arriving at 520 micron max wear scar.
I was able to contact one of the author's of the Bosch presentation, and he was actually on the ASTM committee that set the 520 standard. He could not explain why he agreed to the more lenient spec when his presentation clearly had 460 as a MAX allowable wear, and <400 preferred. My conclusion is that the other ASTM members wore him down and convinced him that the fuel distributors would sufficiently protect the FI equipment. He also told me that he was more concerned with people over-doing it with additives, and causing more potential problems than benefits. For this reason he advised against using additives. He verified that additives for lubricity must be added to ULSD to bring it to spec, and that those additives are applied at the fuel terminal, when the fuel goes into a tanker truck.
I have been using biodiesel mixtures for a long time, partly based on the lubricity tests done using various concentrations of biodiesel. Here is a paper on that. The takeaway is any biodiesel concentration above 2% will adequately protect your fuel injection components with D2 that meets the ASTM standard for lubricity. Note that VW (and most other diesel mfrs) recommend that you limit biodiesel to 5%.
In a recent thread discussing additives, I was noting that I could find very little data from additive manufacturers. I contacted Power Service and asked for some data. A few days later I got it in the mail. I was unsure if I was seeing retail pump fuel or not. So I called PS and talked to the guy who sent me this data. He verified that this was in fact untreated fuel, so that was somewhat of a relief. (Ironically, this was the same test method used by Spicer in his test.)
The following data sheet is for raw (fuel that has no additives applied at the terminal) LSD:
[/IMG]
It should be noted that the HFRR results were way over spec before PS Diesel Fuel Service "DFS" (white bottle) or Diesel Kleen "DK" (silver bottle) was added. This gives us an idea of what kind of fuel our vehicles could have seen before 2005!!
The following results were for raw ULSD:
[/IMG]
Note that the HFRR result for this untreated fuel was actually better than LSD. See the resultant HFRR results after treatment with DFS.
Next, see a horrendous example of raw ULSD (for an idea of how important lubricity additives are with this fuel). Again note the benefits from DFS:
[/IMG]
During this conversation he told me that because of testing repeatability and variability, the passing mark for HFRR was actually 560! So now we're talking about fuel being ~22% worse than the MAXIMUM wear results allowed by the people who manufacture our FI equipment!!
I asked the guy at PS to send retail pump fuel data, so we could see what PS products do in the real world. He emailed me a couple of results from retail pump fuels. He explained that the data was generated for a fuel that was subsequently cut with biodiesel, but assured me that the HFRR results were taken before biodiesel was added, so the lubricity improvement shown was strictly from PS products over retail fuel that had already been additized at the fuel delivery terminal.
First results:
[/IMG]
So here we have lubricity that is just a bit above the allowable limit coming out of the pump. Note the improvement shown using DFS.
Here is the last data sheet:
[/IMG]
These results show a fuel out of the pump that barely meets the standard, and that it was brought down 130 microns by DFS.
Besides FPPF, this is the only additive manufacturer data that I can find real numbers on. If you have links to other data, please post them on this thread.
Here is "data" from FPPF:
OK, so what all of this tells me we should use some sort of fuel lubricity additive, being careful to stick to the recommended dosing. I would recommend an additive that actually provides data. The only ones I know of at this point are biodiesel, Power Service (both white and silver) and FPPF. I do NOT trust the fuel supply system in this country to take care of this for me. If anyone has a link, or data for another additive manufacturer, please add them here. Thanks.
Original thread follows****************************************
I have been concerned about diesel fuel lubricity, especially with ULSD coming on the scene.
As you know, the high pressures inside our fuel injection systems require very close tolerances between the pump components. The only lubrication these components receive is from the diesel fuel. The process of lowering the sulfur content also lowers the lubricating properties of the fuel. When the implementation plan of ULSD was being developed here (the U.S.), a push was made for a lubricity standard for US diesel fuel.
The test for fuel lubricity is performed on a High Frequency Reciprocating Rig (HFRR). Here is a description of the test (LINK -you will need to search on hfrr):
The maximum wear scar acceptable in Europe and Canada is 460 microns....The instrument uses an electromagnetic drive to oscillate an upper 6 mm diameter steel ball bearing against a stationary lower steel test plate. The reciprocation frequency and stroke length are controlled to 50 Hz and 1 mm respectively throughout the 75 minute test. The contact is fully immersed in the test fuel which is maintained at 60°C. The ball is loaded against the plate by means of a suspended 200 gm weight. All test parameters are controlled automatically through a PC via a custom electronic interface. The friction coefficient, electrical contact resistance and temperature are displayed in
graphical format as the test proceeds and the test data are saved to file. The performance of the fuel is assessed by measuring the diameter of the wear scar formed on the ball using a 1 micron resolution microscope. The test result is sensitive to the moisture content of the atmosphere, consequently an adjustment is made depending on the ambient conditions or the atmosphere is controlled e.g. by enclosing the instrument in a humidity controlled cabinet...
Here is a presentation from Bosch in 2003 that detailed the issue of lubricity, and gave an assessment of US fuel supply at that time. Remember that this was before ULSD was on the scene. They were pushing for a fuel lubricity standard to be implemented for LSD, which has more "natural" lubricity than ULSD. Note on slide 8 that 80% of US fuel stations tested had a wear scar >460 microns. Take a look at the photos of FI components that were run with fuels that had varying lubricity properties.
Here is a summary of ASTM's process for arriving at 520 micron max wear scar.
No rationale was given for not adhering to the FI manufacturers' recommendation. The bolded statement at the end of the excerpt indicates what the influence was.excerpt said:...Revision of D 975-02 Specification for Diesel Fuel Oils to include a lubricity specification
PLEASE READ THIS NOTE AND THE SUPPORTING DOCUMENTS BEFORE VOTING.
...¸ Most members believe that we need to adopt a lubricity specification at ASTM to protect injection equipment from excessive wear.
...¸ The CRC Diesel Performance Group has committed to conduct a research program to provide additional supporting data to adjust this level if necessary, especially for the new high-pressure common-rail injection equipment.
Data and Discussion Supporting the Proposal: One technical supporting document for the proposed level is an SAE Technical Paper 2001-01-1928. An interpretation of the data in Table 5 by Ken Mitchell results in an average scar diameter of 517 microns for a passing pump rating of 3.4.
Since the lubricity correlation is not an exact science at this time, we also can find documents that conclude HFRR at 550 or HFRR at 500 microns. The proposed level of 520 microns based on the above document is a reasonable technical compromise to ensure proper protection for injection equipment.
It is worth noting that, although the correlation between SLBOCLE and HFRR is not close to perfect, most supporting documents and field data indicate that the proposed 520 micron HFRR level does not result in lower lubricity when compared to our previous proposal of 3,100 gram SLBOCLE level. In many cases it should provide better fuel lubricity.
...
Steps Beyond the current Proposal: This proposed specification will provide a starting point that would protect the injection equipment without creating harmful side effects and unnecessary cost to the fuel suppliers. ...
I was able to contact one of the author's of the Bosch presentation, and he was actually on the ASTM committee that set the 520 standard. He could not explain why he agreed to the more lenient spec when his presentation clearly had 460 as a MAX allowable wear, and <400 preferred. My conclusion is that the other ASTM members wore him down and convinced him that the fuel distributors would sufficiently protect the FI equipment. He also told me that he was more concerned with people over-doing it with additives, and causing more potential problems than benefits. For this reason he advised against using additives. He verified that additives for lubricity must be added to ULSD to bring it to spec, and that those additives are applied at the fuel terminal, when the fuel goes into a tanker truck.
I have been using biodiesel mixtures for a long time, partly based on the lubricity tests done using various concentrations of biodiesel. Here is a paper on that. The takeaway is any biodiesel concentration above 2% will adequately protect your fuel injection components with D2 that meets the ASTM standard for lubricity. Note that VW (and most other diesel mfrs) recommend that you limit biodiesel to 5%.
In a recent thread discussing additives, I was noting that I could find very little data from additive manufacturers. I contacted Power Service and asked for some data. A few days later I got it in the mail. I was unsure if I was seeing retail pump fuel or not. So I called PS and talked to the guy who sent me this data. He verified that this was in fact untreated fuel, so that was somewhat of a relief. (Ironically, this was the same test method used by Spicer in his test.)
The following data sheet is for raw (fuel that has no additives applied at the terminal) LSD:
It should be noted that the HFRR results were way over spec before PS Diesel Fuel Service "DFS" (white bottle) or Diesel Kleen "DK" (silver bottle) was added. This gives us an idea of what kind of fuel our vehicles could have seen before 2005!!
The following results were for raw ULSD:
Note that the HFRR result for this untreated fuel was actually better than LSD. See the resultant HFRR results after treatment with DFS.
Next, see a horrendous example of raw ULSD (for an idea of how important lubricity additives are with this fuel). Again note the benefits from DFS:
During this conversation he told me that because of testing repeatability and variability, the passing mark for HFRR was actually 560! So now we're talking about fuel being ~22% worse than the MAXIMUM wear results allowed by the people who manufacture our FI equipment!!
I asked the guy at PS to send retail pump fuel data, so we could see what PS products do in the real world. He emailed me a couple of results from retail pump fuels. He explained that the data was generated for a fuel that was subsequently cut with biodiesel, but assured me that the HFRR results were taken before biodiesel was added, so the lubricity improvement shown was strictly from PS products over retail fuel that had already been additized at the fuel delivery terminal.
First results:
So here we have lubricity that is just a bit above the allowable limit coming out of the pump. Note the improvement shown using DFS.
Here is the last data sheet:
These results show a fuel out of the pump that barely meets the standard, and that it was brought down 130 microns by DFS.
Besides FPPF, this is the only additive manufacturer data that I can find real numbers on. If you have links to other data, please post them on this thread.
Here is "data" from FPPF:
OK, so what all of this tells me we should use some sort of fuel lubricity additive, being careful to stick to the recommended dosing. I would recommend an additive that actually provides data. The only ones I know of at this point are biodiesel, Power Service (both white and silver) and FPPF. I do NOT trust the fuel supply system in this country to take care of this for me. If anyone has a link, or data for another additive manufacturer, please add them here. Thanks.
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