LSPI
- Thread starter RINGER
- Start date
I think I'll just keep putting the correct fuel in, and driving it! 
Unfortunately the publisher is Elsevier, so don't expect much except a teaser. No data or maths are attached.
The paper has examined oil droplets being formed from piston ring bypass, and their effect on low speed pre-ignition.
The paper has examined oil droplets being formed from piston ring bypass, and their effect on low speed pre-ignition.
Hi.
I skimmed the article previously. It is of little relvance to most members on this forum.
The salient details are that with the trend to smaller displacement, turbocharged engines, tiny oil droplets from the piston rings sidewall area can mix with the air/fuel mixture and increase the onset of Low Speed Pre Ignition (LSPI). Diluted crankcase oil exasperates this. The upshot is that the API is going to develop a new classification SN Plus, for oils that have less CA additive.
Cheers.
I skimmed the article previously. It is of little relvance to most members on this forum.
The salient details are that with the trend to smaller displacement, turbocharged engines, tiny oil droplets from the piston rings sidewall area can mix with the air/fuel mixture and increase the onset of Low Speed Pre Ignition (LSPI). Diluted crankcase oil exasperates this. The upshot is that the API is going to develop a new classification SN Plus, for oils that have less CA additive.
Cheers.
I only looked this up as I was considering a salvage repairable write off 2018 Holden Astra with a bad engine. These cars it seems have a propensity of this condition from using wrong oil & folk using fuel with lower than required RON fuel. Pulling tops off pistons?
A knock sensor isn't all that smart. It's just a microphone that "listens" for loud noises, the question being where do you set the "loud" threshold. Too low and you will end up with false positives, retarded timing, poor performance and economy. Too high leads to chronic detonation and engine damage.
Perhaps the Astra engine has a lot of noise at its knock sensor in normal conditions and so the sensor doesn't detect very mild knock.
In any case, the knock sensor retarding the timing for low-octane fuel is a bit of a hack. It doesn't prevent damage, it prevents further damage. You have to have detonation before it can detect it; a bit like the old Yamaha cylinder head torquing instructions: tighten it up till it strips, then back it off a quarter turn.
Have fun,
Rob.
Perhaps the Astra engine has a lot of noise at its knock sensor in normal conditions and so the sensor doesn't detect very mild knock.
In any case, the knock sensor retarding the timing for low-octane fuel is a bit of a hack. It doesn't prevent damage, it prevents further damage. You have to have detonation before it can detect it; a bit like the old Yamaha cylinder head torquing instructions: tighten it up till it strips, then back it off a quarter turn.
Have fun,
Rob.