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Is sodium the cause of LSPI and ecoboom?

RubyRed15

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Very interesting article, from October '17, suggesting that sodium content in engine oil may be the cause of LSPI. I searched here and didn't see it, so here it is.

http://www.enginelabs.com/engine-tech/oil-composition-direct-injection-low-speed-knock/

So the first logical question is, "which oils are low in sodium?" I can't find any tables or comparisons, and it seems the mfrs are not posting this data to their websites (at least not the few I looked at).
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Brian V

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At last theory that I have read the thoughts were explaining that Calcium was the possible igniter ..
Stochastic Pre- Ignition has been around for a century and has been studied in a scientific experiment using trial and error proceeses as of recently . Past few years .

There are probably a few theories around .. best guess is that it has to do with these additive packages that are added to these oil formulations .. yeah the cleaning agents ..
Given these ideas the fuels used along with the oils very well may lead to the likely cause of a Pre-Igniton .
 
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markmurfie

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The first logical question is as an engine guy, why do they not know the difference between detonation and preignition. Describing preignition as a detonation event so large it could destroy the engine in one event is not much better.

Detonation occurs after ignition when fuel ignites from increased heat and pressure from the flame wave propagation. These second ignitions cause pressure spikes. The ringlands being the weak part of the piston usually end up cracking. a fuels octane rating is telling you how much it can resist self igniting in those high heat and pressure times.

Pre ignition is when the fuel mixture ignites before spark ignition. This usually happens early in the compression stroke from a small hot spot, like carbon build up or sharp metal edges. Having air and fuel burning while the piston is compressing usually leads to a hole melted through the top of the piston.

LSPI low speed pre ignition is common in turbo charged DI engines. The exact reason is not well understood. Very hot EGR gases and increased back pressure from the turbo with relatively slow exhaust valve motion?
OEMs limited engine load to work around it. Recently it was found that oil additives can help these engines resist LSPI. So what ever ford is recommending for oil to use in your ecoboost follow what they say and don't start experimenting with oils.

The fact they thought it was detonation then spent a bunch of time seeing what effect different engine oils had on detonation made me chuckle. Require a higher octane or lower the compression ratio, low speed detonation problems solved.
 

Coyote Red

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You guys really impress me sometimes with your science knowledge and research skills, just sayin.
 

Brian V

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You guys really impress me sometimes with your science knowledge and research skills, just sayin.
We are just readers of these interesting subjects . We do a lot of background searching looking for documentation and theory .

Even our own Sun is going to burn out some day might as well study up on the subject .
 

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Brian V

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There is another factor involved . ( heat )
The compounds may have to reach a volatile temperature to ignite the fuel air mixture .
 

TorqueMan

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Detonation occurs after ignition when fuel ignites from increased heat and pressure from the flame wave propagation. These second ignitions cause pressure spikes.
To add a bit of clarity, detonation occurs when the fuel/air mixture is ignited either simultaneously, or nearly simultaneously by both the spark plug AND another ignition source (can be a hot spot in the cylinder, but is usually increased heat/compression from the initial spark plug-induced ignition event). The key to understanding the danger is knowing detonation produces two flame fronts/pressure waves in the cylinder that collide and produce a sudden, potentially catastrophic rise in cylinder pressure accompanied by a characteristic ping or knock sound. If left unchecked, detonation will destroy your engine just as effectively as pre-ignition, as each subsequent ignition event is influenced by the increased heat generated from the previous.

Luckily, our engines are protected from detonation by the computer, which reduces power demand, and thus heat, when it senses a knock event. If everything is working as designed, most of us will never notice detonation beyond a power loss. As mentioned, the computer assumes a certain fuel octane as it manages the engine through these events, which is why it's important to know whatever tune you are running is properly programmed AND that you are using the octane the computer expects.

Pre-ignition occurs when the fuel/air mixture ignites prematurely, but it can also generate enough heat to result in detonation. How's that? You may experience a pre-ignition event on one cycle that doesn't destroy the piston, but does heat the piston enough to prompt a detonation event on the next (or subsequent) cycle. This is especially dangerous because the computer may not protect the engine as designed. Detonation usually starts out mild and progresses, giving the computer time to respond and prevent damage. A pre-ignition event may not trigger the computer to reduce power demand, so the subsequent detonation event it causes can easily result in catastrophic failure.

So yes, pre-ignition and detonation can be a devastating one-two punch that causes a dreaded ecoboom.

Recently it was found that oil additives can help these engines resist LSPI. So what ever ford is recommending for oil to use in your ecoboost follow what they say and don't start experimenting with oils.
GM has been working on an oil standard--called dexos1 Gen 2-- specifically addressing LSPI. Oils meeting this standard also meet or exceed the standard required by Ford for our engines. You can find a list of oils meeting the dexos1 Gen 2 standard here:

http://www.centerforqa.com/dexos-brand2015/

Require a higher octane or lower the compression ratio, low speed detonation problems solved.
You mean low-speed pre-ignition. :D
 

Marvinmadman

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Limit boost via the wastgaste solenoid. Alter ignition and fuel timing. Reduce the actual throttle body actuation degree. Number of ways they can deal with it.
 

TorqueMan

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How do they do that ? If the car is moving along at 2000 rpm in 6th gear, and you floor it, what will the engine do ?
LSPI is a relatively new (since the advent of small-displacement, high-output, turbocharged, direct-injected engines) phenomenon which engineers are still struggling to fully understand, particularly what precisely causes it. In-cylinder observation has shown that it occurs randomly throughout the combustion chamber, which makes it very difficult to pin down its cause, and therefore develop effective mitigation strategies.

What IS known is that LSPI arises due to interaction between engine lubricant and fuel under fairly specific engine operating conditions--most often low engine RPM (hence the "low-speed" portion of the name) and high power demand. The most widely accepted theory to date is that when fuel is directly injected into the combustion chamber it can dilute already present oil enough to create a combustible fuel-oil mixture which may then ignite during the compression stroke under the right temp/pressure conditions--such as under high boost at low RPM.

Because the whole point of small-displacement, high-output, turbocharged, direct-injected engines is to enable a relatively fuel-efficient 4cyl engine to produce significant power at lower RPMs, manufacturers are struggling to devise answers to the LSPI problem. As far as I know, the only situation under which the computer limits power output is when it senses knock, or detonation. There is no way to "sense" LSPI, so the computer can do nothing to prevent and/or limit it other than to keep the engine out of operating regimes where it occurs. What happens when you do that? You wind up with a small-displacement engine that cannot make power at lower RPMs--and you sell a lot more V8s.

In short, as far as I know, mitigation strategies are focused on oil forumlations and perhaps changes to combustion chamber design, because limiting power output at low RPMs would defeat the engine's primary design goals.
 

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ElAviator72

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Something tells me that if you're leaking enough oil into the combustion chamber to cause LSPI in the first place, that there's bigger problems afoot elsewhere in the engine. I suppose if you blew the right turbo seal, your turbo could hemorrhage oil into the intake...
 

jtmat

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Even our own Sun is going to burn out some day might as well study up on the subject .
I read two websites and now I'm a subject matta eXPurt.

After spending 40k and 50k on a mustang, some people better know some sht.
 

Regs

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I think it has something to do with tuning the car past its limits and tolerances.
 
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RubyRed15

RubyRed15

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Something tells me that if you're leaking enough oil into the combustion chamber to cause LSPI in the first place, that there's bigger problems afoot elsewhere in the engine. I suppose if you blew the right turbo seal, your turbo could hemorrhage oil into the intake...
It's not an oil quantity issue; it's the contents, according to the supposition in the article. Read the section that talks about the top ring and fuel atomization.
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