Ash content corrolations to Pre-Ignition

[vex]

This information may be old, but does anyone have anything else to say about it?

I'm reading a paper on Engine oil lubrication for the Rotary Engine (RE), and there seems to be a strong correlation between ash content and pre-ignition events.

For instance an oil that contains <0.05 Sulphated ash % by weight took more than 40 (2.5 hrs run time = 1 cycle) cycles before the first pre-ignition event. For the second run it took 35, for each consecutive run there were no pre-ignition events. Compare that to oils that have relatively high ash contents (1.2, 0.9) which experienced their first pre-ignition event within 8 cycles.

On the market today, how many oils are there that have a lower Ash content similar to the <0.05? Do synthetic oils use base stock with that low of an ash content? I tried looking at Royal Purples website, but they offer no insight on the ash content of their product.

[Cp1]

i can tell you without a doubt that knock goes up when plugs start to get fouled even a little bit which in turn causes them to foul and even cake up even faster.

[vex]

So how do we tell the ash content of oils? I tried looking up the API ratings, and they only dictate ash content on diesel oils.

[Cp1]

good question do they not put that info on motorcycle or 2-stroke oil?

[vex]

I'll check. I'm still looking, but I found an engine oil that does list it's ash content from the ASTM D 874 to be 0.88

http://www.nulon.com.au/products.php...day_Engine_Oil

That's rather high, and not good engine oil for our motors... so beware.

http://www.api.org/certifications/en..._Oil_Guide.pdf

Is a good guide, but only references Ash in the CJ-4 rating.

Still looking:
http://www.purvisbros.com/supduty.htm
Pennzoil Supreme Fleet Oil has 1.4%

There's a second good reason you shouldn't use car oil in your motorbike - sulfated ash. It's common in many American & Canadian modern oils; without burnt oil discoloring it, it normally has a light-gray to pale-tan colouration which may become visible if you shear a bit of the debris. When coloured by oil, it looks like the dreaded sludge. Unfortunately, the API SH-SL ratings are not strict enough on sulfated ash content. It's an issue that's fairly well known in some motorcycling circles, and the Japanese motorcycle industry recognized the issue very early on, creating a new oil specification specific to their needs (one, that among other things, caps the sulfated ash content very low): JASO-MA, recently revised further into to JASO-MA1 & JASO-MA2. For motorcyclists, the sulfated ash content poses a secondary issue: it means higher quantities of sulfuric acid if water gets introduced into the oil (such as from condensation within the galley spaces); since most motorcycle engines share the oil with both the engine and the transmission, the sulfuric acid is particularly problematic as the metals used in the transmission selector forks are made of cheaper steels that don't stand up to the acid nearly as well as most engine components.

The most informative I could find so far.

[vex]

I've been picking the brains of my local car club about this and it seems like we'd want to run diesel oil (CJ-4 rating). This is what I got from there

People run diesel oils (HDEOs) all the time in gas engines, it's rarely any issue at all. In fact, I believe in many benefits to this for turbocharged gas engines because these oils typically are more tailored to turbochargers. They typically have higher TBNs as well which means longer oil life and a better base oil to start with (rather than just souping up crappy base oil with additive pack). The only way to know for sure what the ash content is, is to look at the UOAs (Used Oil Analysis) on a place like BITOG. There are specific forums for HDEOs as well as Sx-class oils. Many HDEOs meet SM or whatever specs anyway, so it doesn't matter much.

[Max777]

Very interesting stuff right there!

[vex]

completely procrastinating my studying for Operational methods test tomorrow:
These are from Bob Is The Oil Guy website/forum. All are Virgin oil analysis'.

[vex]

Although slightly off topic those who are running Two Stroke oil (aka, premix). I'm curious what you think about this:



If you notice, the apex wear is about 19.6 Micrometers/hour of operation which is roughly 17.4 more micrometers/hour of wear when compared to conventional oils. Is it really beneficial to go to Premix with these statistics?

[NoDOHC]

tell me if i am wrong, but wasn't that being compared to ATF and found to have half the wear?

If I interpreted the data correctly, 19.6 um/ 2.5 hours with only 1.5 mm allowable wear (8.0 mm stock, 6.5 mm allowed) gives about 200 hours (12,000 miles) before wear becomes a problem on a premixed rotary (which I really don't believe). Granted, this is full-throttle useage, but that number seems out there a little.

I have seen 150,000 mile rotaries with 6.9 mm of apex seal left.

I am not sure that these are 2.5 hour cycles.

[vex]

Originally Posted by NoDOHC

tell me if i am wrong, but wasn't that being compared to ATF and found to have half the wear?

If I interpreted the data correctly, 19.6 um/ 2.5 hours with only 1.5 mm allowable wear (8.0 mm stock, 6.5 mm allowed) gives about 200 hours (12,000 miles) before wear becomes a problem on a premixed rotary (which I really don't believe). Granted, this is full-throttle useage, but that number seems out there a little.

I have seen 150,000 mile rotaries with 6.9 mm of apex seal left.

I am not sure that these are 2.5 hour cycles.

I'll have to double check what the cycle times were for the endurance run. But yes, that was comparing ATF to Two Stroke.

[vex]

Here's the procedure for the endurance test:
A succession of mixed low-speed/low-output (2500 rev/
min and 20 hp) and high-speed/high-output (6000 rev/
min and 100 hp) sequences followed by idling, for 96 h.
Each individual sequence lasts 6 h.


Which mean's it's 19.6/96h = .204167 micrometers/hour compared to the 13.5/96h = .140625 micrometers/hour, which is significantly less than the two stroke. Redoing your math we have:
1500/.204167=7346.94 hours assuming 60 miles/hour of operation speed gives us a little over 440,816 miles.
1500/.140625=10666.767 hours of operation assuming 60 mph of operation gives us a little over 640,006 miles

Using standard oil instead of two stroke has the theoretical ability to last 1/3 longer than two stroke.

[NoDOHC]

I think I am confused. I read 38 um / cycle wear for ATF and 19.6 um / cycle wear for two-cycle oil. Is the 13.5 published somewhere else that I can't immediately see?

The 96 hour cycle makes a lot more sense, but I am still confused about the above numbers.

Also, this test was likely done with the same quantity of each oil injected through the stock oil injection system. This data does not prove that additional two-cycle oil increases seal wear.

[vex]

Originally Posted by NoDOHC

I think I am confused. I read 38 um / cycle wear for ATF and 19.6 um / cycle wear for two-cycle oil. Is the 13.5 published somewhere else that I can't immediately see?

Yes, the 13.5 is published in the sae paper, but I didn't copy/paste a picture of the chart.

The 96 hour cycle makes a lot more sense, but I am still confused about the above numbers.

Also, this test was likely done with the same quantity of each oil injected through the stock oil injection system. This data does not prove that additional two-cycle oil increases seal wear.

Volumes are measured as you can see in the previous posted image--but not constant. The volumes differ from one to the other, but may be based upon viscosity and other possibilities. However, since both instances of the engine were run per cycle (96 hours), and greater wear was indicated with two stroke it is only plausible that running two stroke for lubricating the apex seals is not as efficient when it comes to lubrication of them. That is not to say that it's not beneficial to run two stroke for the lubrication of the apex seals since ash content would be reduced to nill, and would burn cleaner than regular oil.

[Barry Bordes]

Vex, the NSU paper spoke of their "prime candidate" oil having half the wear, and the "Typical Marine Cylinder Lubricant" in fig. 16 showed extremly low wear data. Do you have any idea which oils these are?

From your analysis of the "CAT New Oil" charts above which oil would you think is best for rotary engines?

Thanks for the information backup to your original questions. You presented this well.

Barry