CaSa contributing to LSPI - Turbo/Sprchrgd GDi ?

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wemay

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http://papers.sae.org/2014-32-0092/


Supercharged direct-injection engines are known to have a tendency toward abnormal combustion such as spontaneous low-speed pre-ignition and strong knock because they operate under low-speed, high-load conditions conducive to the occurrence of irregular combustion. It has been hypothesized that one cause of such abnormal combustion is the intrusion of engine oil droplets into the combustion chamber where they become a source of ignition. It has also been reported that varying the composition of engine oil additives can change susceptibility to abnormal combustion. However, the mechanisms involved are not well understood, and it is not clear how the individual components of engine oil additives affect autoignition.

In this study, abnormal combustion experiments were conducted to investigate the effect on autoignition of a calcium-based additive that is typically mixed into engine oil to act as a detergent. The experiments were performed with a single-cylinder 4-cycle gasoline engine using a primary reference fuel (PRF 50) into which the calcium salicylate (CaSa)-based detergent was mixed at various ratios.

The experimental results showed that autoignition occurred increasingly earlier with a higher concentration of the CaSa-based engine oil additive, giving rise to severe abnormal combustion. This indicates that the addition of a CaSa-based detergent to engine oil tends to promote autoignition and abnormal combustion.
 
Interesting. But don't most oils contain a decent dose of calcium these days? Off the top of my head, I can't think of one that doesn't.
 
In the synthetics area, I know Edge and M1 contain less than the others...
 
Hmm... in my application it would have to be Edge 0w-40 or M1 0w-40. Both contain plenty of calcium, 2000 ppm and 3000 ppm respectively.

Unless not all calcium is calcium salicylate....
 
Originally Posted By: Quattro Pete
Hmm... in my application it would have to be Edge 0w-40 or M1 0w-40. Both contain plenty of calcium, 2000 ppm and 3000 ppm respectively.

Unless not all calcium is calcium salicylate....


Hmmm, this might keep me from trying M1 0W-40 in the future.
This is the #1 reason why I didn't try Amsoil Signature 5W-30.
 
Most of the calcium that you see in oils comes from calcium sulphonate and calcium phenate. Calcium salicylate is a detergent that originally found favour in marine lubricants. In recent years it has been used in low SAP automotive applications because unlike suphonates and phenates, it contains no sulphur. Personally I think they should have stuck to putting it into ships as it's a pretty rubbish detergent.
It's a shame that there's no full (and free!) copy of the SAE paper to read so that I could understand quite how they did what they did. All I can say is loads of metals act as combustion catalysts or inhibitors (Pb being the most obvious example). I doubt if this particular bit of R&D will do anything to change how oils are formulated.
 
This is why I wouldn't use Amsoil or Redline in some of these newer engines. They are old school and using 3,500-4,000 ppm of Calcium.
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This is why Mobil went to a low SA formulation yet was somehow still able to make a long drain oil. Mobil 1 is technically more advance than Amsoil or Redline. So is Castrol Edge technically.
 
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