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#4533724 - 10/04/17 11:30 AM Can someone explain how oil protects against LSPI?
ZZman Online   content


Registered: 03/17/08
Posts: 5791
Loc: Michigan
Wouldn't it be the proper computer/timing that would do the protecting or stopping of it?
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#4533732 - 10/04/17 11:35 AM Re: Can someone explain how oil protects against LSPI? [Re: ZZman]
ZZman Online   content


Registered: 03/17/08
Posts: 5791
Loc: Michigan
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#4533754 - 10/04/17 11:56 AM Re: Can someone explain how oil protects against LSPI? [Re: ZZman]
Virtus_Probi Offline


Registered: 06/25/15
Posts: 3970
Loc: New England
I don't know that the exact mechanism is completely understood even now, but the chemical composition of oil can strongly affect uncontrolled ignition of the air/fuel charge through oil droplets and/or tiny solid particles from oil combustion in the cylinder. Since it is Low Speed Pre Ignition and tends to occur in high torque conditions, I can only assume that relatively low RPMs during periods of high stress on the engine basically give the unwanted ignition more time to occur in any given combustion cycle...and these DIT engines are generally pretty good at producing a lot of torque at low RPMs.

I know, the whole thing seems weird...I doubt very much that anybody working on early mass market DI systems even remotely saw this coming.
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#4533757 - 10/04/17 11:59 AM Re: Can someone explain how oil protects against LSPI? [Re: ZZman]
Garak Offline


Registered: 12/05/09
Posts: 24620
Loc: Regina, Saskatchewan, Canada
Is it really protecting against it, or minimising what is causing it? I gather there would be no LSPI if there were no deposits whatsoever in the first place.


Edited by Garak (10/04/17 11:59 AM)
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Plain, simple Garak.

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#4533760 - 10/04/17 12:02 PM Re: Can someone explain how oil protects against LSPI? [Re: ZZman]
bigj_16 Offline


Registered: 07/03/17
Posts: 1268
Loc: Douglas County, Colorado
Originally Posted By: ZZman
Wouldn't it be the proper computer/timing that would do the protecting or stopping of it?

Oil doesn't protect against LSPI. The oil and/or some components of the oil are possibly contributing to LSPI. They are trying to either get rid of or mitigate the components that do possibly contribute. In early testing, it looks like higher levels (1500 or above) of calcium MAY be a possible contributor. So, the manufacturer either lowers the calcium, or raises ,say, magnesium, moly, or ZDP, or some combination thereof, to mitigate this. This is all early on, so nothing is set in stone.

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#4533763 - 10/04/17 12:05 PM Re: Can someone explain how oil protects against LSPI? [Re: Garak]
Virtus_Probi Offline


Registered: 06/25/15
Posts: 3970
Loc: New England
Originally Posted By: Garak
Is it really protecting against it, or minimising what is causing it? I gather there would be no LSPI if there were no deposits whatsoever in the first place.


My understanding is that there is no LSPI if there is no oil present in the chamber, but I can't prove that and I'd think it would be very hard to test without quickly seizing an engine. That would say that proper oil composition is minimizing the problem since oil is the cause of the problem.
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#4533851 - 10/04/17 01:18 PM Re: Can someone explain how oil protects against LSPI? [Re: Virtus_Probi]
Garak Offline


Registered: 12/05/09
Posts: 24620
Loc: Regina, Saskatchewan, Canada
Yes, if the oil wasn't there in the first place, it shouldn't be an issue. But, yes, running an engine with no oil wouldn't be terribly practical. wink
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Plain, simple Garak.

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#4533871 - 10/04/17 01:29 PM Re: Can someone explain how oil protects against LSPI? [Re: ZZman]
ARCOgraphite Offline


Registered: 05/17/09
Posts: 11970
Loc: N.H, U.S.A.
Ok. Run Krytox pfpe in the experiment.

Ill go ahead and blame the high static compression AND low octane fuel. They hoped a stratified charge would allow good ignitability ( a late puff of fuel rich mist near the sparker) but the lean boundary charge may be prone to pre-ig due to burn carryover from exh cycle in the ring land area - now rings are closer to the crowm.

All speculation on my part here, but drawn from building hi comp engines in the late 70's
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#4533919 - 10/04/17 02:21 PM Re: Can someone explain how oil protects against LSPI? [Re: ZZman]
CT8 Online   content


Registered: 10/09/14
Posts: 11010
Loc: Idaho
There seems to actually be no concrete answers. Additives, Base oils engine components who knows.
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#4533958 - 10/04/17 03:06 PM Re: Can someone explain how oil protects against LSPI? [Re: ZZman]
CourierDriver Offline


Registered: 12/27/09
Posts: 4953
Loc: Tn.
Now I have PTSD OVER LSPI, now what? There will be 1000s in here losing sleep not to mention millions of googling over it....lol Did we ever solve PS "piston slap"?
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#4533969 - 10/04/17 03:26 PM Re: Can someone explain how oil protects against LSPI? [Re: ZZman]
ZZman Online   content


Registered: 03/17/08
Posts: 5791
Loc: Michigan
I guess to be safe run premium.
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#4534004 - 10/04/17 04:10 PM Re: Can someone explain how oil protects against LSPI? [Re: ARCOgraphite]
A_Harman Offline


Registered: 10/01/10
Posts: 6921
Loc: Michigan
Originally Posted By: ARCOgraphite
Ok. Run Krytox pfpe in the experiment.

Ill go ahead and blame the high static compression AND low octane fuel. They hoped a stratified charge would allow good ignitability ( a late puff of fuel rich mist near the sparker) but the lean boundary charge may be prone to pre-ig due to burn carryover from exh cycle in the ring land area - now rings are closer to the crowm.

All speculation on my part here, but drawn from building hi comp engines in the late 70's


Strange that you should mention Krytox grease. When I was running oil consumption tests at Cummins back in the mid-90's, one technique that we used was to shut off all the oil going to the cylinder head of the test engine, to see how much oil was being lost through the ring pack alone. When we shut off the oil, we packed the rocker arm pivots, valve tips, and pushrod cups with Krytox grease, then ran the engine at idle for 100 hours to get a stable oil consumption reading. The natural gas C-series engine I was testing was shown to be using about half of its oil through the multi-lip valve stem seals. Switching to single-lip seals cured that problem.
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#4534057 - 10/04/17 05:25 PM Re: Can someone explain how oil protects against LSPI? [Re: CourierDriver]
Virtus_Probi Offline


Registered: 06/25/15
Posts: 3970
Loc: New England
Originally Posted By: CourierDriver
Now I have PTSD OVER LSPI, now what? There will be 1000s in here losing sleep not to mention millions of googling over it....lol Did we ever solve PS "piston slap"?


STBY!!!
;^)
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#4534382 - 10/05/17 08:24 AM Re: Can someone explain how oil protects against LSPI? [Re: CT8]
zeng Offline


Registered: 09/01/15
Posts: 2189
Loc: Malaysia
Originally Posted By: CT8
There seems to actually be no concrete answers. Additives, Base oils engine components who knows.

+1
........ and a low viscosity xW20 grade oil is contributing to LSPI phenomenon too ?

https://www.oronite.com/products/lspi.asp

Edit:upload


Edited by zeng (10/05/17 08:27 AM)

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#4543285 - 10/14/17 02:44 PM Re: Can someone explain how oil protects against LSPI? [Re: ZZman]
4ever4d Offline


Registered: 01/02/10
Posts: 953
Loc: North Carolina
According to Lake Speed Jr. at Driven Racing oils in cooperation with the Oak Ridge National Labratory, sodium in mixing with moisture from the combustion process is the cause. Investigating Oil Composition and Low Speed Knock


Edited by 4ever4d (10/14/17 02:52 PM)
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