dexos2 includes an LSPI test???

[OVERKILL]

Originally Posted By: bulwnkl
Originally Posted By: OVERKILL


I wouldn't necessarily claim that it is exclusive to the realm of turbo DI


Great, we agree. Thanks for posting additional references which show that LSPI is not specific to DI nor TDI.


Not quite. I'm saying it is't exclusive to that realm, but what is being investigated by OEM's with respect to dealing with it pretty much is. The actual phenomena itself doesn't require DI or a turbo to happen, in theory. However, in application, where it is being observed and attempted to be dealt with appears to involve both of those technologies. Make sense?

I believe the references support that as well.

So yes, I believe we agree on the fundamental premise, but I'm putting some emphasis on the causation, or rather, the potential for turbo/DI combo's specifically to exhibit this trait almost exclusively in practical application

 

[PimTac]

Going back a few decades, if you had a car with a three on the tree shift and as some people would do, go from 1st to 3rd and skip 2nd gear, depending on the situation you could get a light knock as you accelerated in 3rd gear. My take is that LSPI is exacerbated in TGDI engines but the condition itself was known by other names way back when.

 

[bulwnkl]

Pre-ignition at low speed (lugging). That's Low-Speed Pre-Ignition. (-;

All the sensible and informed references are worded to focus one's attention on GDI without expressly saying the issue is exclusive thereto. I think it would be more intellectually honest to say something along the lines of-- LSPI, a well-known phenomenon, is significantly exacerbated by efforts to increase low-rpm power output and overall power density in gasoline engines, which efforts presently take the form of direct injection + forced induction.

Accordingly, we may focus on DI or TGDI engines when we discuss LSPI. I have no issue with that at all; it's perfectly appropriate. It is not appropriate that I can see to claim that LSPI is somehow _exclusive_ to DI or TGDI.

 

[PimTac]

Originally Posted By: bulwnkl
Pre-ignition at low speed (lugging). That's Low-Speed Pre-Ignition. (-;

All the sensible and informed references are worded to focus one's attention on GDI without expressly saying the issue is exclusive thereto. I think it would be more intellectually honest to say something along the lines of-- LSPI, a well-known phenomenon, is significantly exacerbated by efforts to increase low-rpm power output and overall power density in gasoline engines, which efforts presently take the form of direct injection + forced induction.

Accordingly, we may focus on DI or TGDI engines when we discuss LSPI. I have no issue with that at all; it's perfectly appropriate. It is not appropriate that I can see to claim that LSPI is somehow _exclusive_ to DI or TGDI.




I think you are right. The condition may be more prevalent in the mentioned engines.

 

[wemay]

I did find a small snippet illustrating this phenomenon has been around for quite some time, in high compression engines. The question is, will an oil possessing d1G2 "cure" what ailes Gokhan's car and the millions like it?


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

Quote:
“So these turbocharged, direct-injection vehicles are having these issues with knock – essentially related to the detergents in the oil – and I couldn’t help but think back to the discussions I used to have with old-school engine guys I used to deal with who said to not run detergent oils in high-compression race engines because it can cause them to detonate,” says Speed.

“They knew that detergent oils tended to have knock issues, and non-detergent oils tended to not have knock issues.”

 

[Gokhan]

Originally Posted By: wemay
I did find a small snippet illustrating this phenomenon has been around for quite some time, in high compression engines. The question is, will an oil possessing d1G2 "cure" what ailes Gokhan's car and the millions like it?

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

Quote:
“So these turbocharged, direct-injection vehicles are having these issues with knock – essentially related to the detergents in the oil – and I couldn’t help but think back to the discussions I used to have with old-school engine guys I used to deal with who said to not run detergent oils in high-compression race engines because it can cause them to detonate,” says Speed.

“They knew that detergent oils tended to have knock issues, and non-detergent oils tended to not have knock issues.”

Phew! That's a lot of great interesting information to ponder and absorb, thanks! We now know that the good government people in Oak Ridge National Laboratory are trying to reduce wear in your engine, unlike those EPA/CAFE people who are lowering your oil viscosity or the Hawkins National Laboratory people who are unleashing monsters on you from the Upside Down (not Down Under).

I yet need to try these latest-trend-in-oil-fashion Mg-based oils such as Mobil 1 in my 1985 Corolla. Unfortunately I don't use the car to commute to work these days and it takes forever to reach the end of an OCI and do an oil change -- one of my favorite pastimes.

 

[PimTac]

Thanks wemay for posting that link. Very interesting article. I am curious as to the mentioning of the “poor” 91 octane fuel in AZ. What factors are they talking about?

Gokhan, I’m surprised you haven’t tried the d1G2 oils yet in the Corolla. I’m sure though that there wouldn’t be any instant changes in the engine’s running.

 

[Garak]

Originally Posted By: OVERKILL
Not quite. I'm saying it is't exclusive to that realm, but what is being investigated by OEM's with respect to dealing with it pretty much is. The actual phenomena itself doesn't require DI or a turbo to happen, in theory. However, in application, where it is being observed and attempted to be dealt with appears to involve both of those technologies. Make sense?

Definitely. It's clearly not a problem in these other realms of possibility.

 

[Shannow]

OK...

first there's "end gas autoignition", which is the typical knock that is octane and timing related. The flame starts at the spark ignition point, and as the flame progresses at 50-150 fps, the pressure "wave" in the chambertravels at the local speed of sound, i.e. much faster than the flame front. The unburned portion increases in pressure, and as a result temperature (heat of compression). If this exceeds the octane rating of these gasses, they spontaneously ignite, and you now have opposing flame fronts...when they collide, you get ping/knock....that's the phenomoenon that's tested for by engine knock sensors, and the timing retarded accordingly, to slow the rate of pressure rise.

That's the typical knock that we know. Octane and timing are the usual culprits

There's "Pre-ignition", which is caused by a hot spot (spark plug insulator wrong heat range, carbon deposits, ash deposits, exhaust valve...it ignites the gasses on the compression stroke, meaning that the gasses in the cylinder are burning as the piston rises. It's hot spots...one of my Hot sixes, if I let it idle for 5 minutes after a thrashing, I could turn it off and it would run for 5-10 seconds...lots of carbed cars were fitted with "anti dieseling solenoids" in the emissions control eras. Extensive operation in end gas autoignition can cause localised increases in temperature and lead to knock...that's when you start caving in pistons.

Then there's LSPI, where either a floating piece of deposit, or an oil particle gets into the cylinder, and commences ignition WAY before top dead centre...the piston rises compressing this burning air/fuel mix, until the same thing as happens in End Gas Autoignition occurs, the so called "Superknock" that takes out the ring lands.

Gohkan's engine may be suffering from end gas autoignition (most likely), or pre-ignition (possibly), and it's happening at low speeds. The knocking mechanisms that have been known for a century or more.

But it's NOT what is being referred to in the LSPI in the current problem with DI, high boost petrol engines.

Perhaps he could do us a favour and tak a picture down a plug hole, and see what the surface of the piston looks like...

Piston failure pre-ignition

Piston failure LSPI

 

[Shannow]

Also consider what happens in a "traditionally" fuelled engine.

There is a somewhat homogenous charge, provided by the carb/port/TBI injection. As the piston starts to rise, the crevice volumes (think above and around the top ring), are filled with air/fuel mix, and as the piston rises, they become pressurised, with (say) ten volumes of air/fuel (10:1) compression.

The fuel and oil interact (proven by tracer methods), and as the piston goes down, and the cylinder is depressurised on the exhaust stroke, these vapours are "blown out", into the chamber...the oil vapours arising have an "octane" rating, as they've been partly diluted by fuel, and vice versa.

These vapours are one of the primary sources of unburned HC in a traditional engine, so are the reason that top ring lands got smaller, gaskets fitted cylinders more closely, and squish/quench areas disappeared (not entirely, but look at the "good" kidney chambered heads on the old classics)...

In a GDI engine, the crevices are filled primarily with air (which is why GDI was so attractive), so any oil droplets that pass through aren't "octane enhanced", and if they decide to start burning in the middle of the cylinder, they can act as a centralised ignition source when the fuel gets sprayed into it.

Again, the behaviour/phenomenon in "older" engines is VASTLY different to modern DI engines.

A reason that you don't see the issues in diesel engines, which have been DI for ever is that it probably occurs (the droplet and crevices), but they don't inject the fuel until they WANT it to start burning.

 

[Virtus_Probi]

(Shannow drops mic...)

;^)

 

[Gokhan]

A note: I also noticed that the ORNL researchers at the link above say that thicker oil increases LSPI events because it's harder to scrape with the ring from the cylinder wall. The effect is much less important than the choice of the detergent though.

People are also worried about fuel dilution in these engines. So, there is a tradeoff.

 

[OVERKILL]

Originally Posted By: Virtus_Probi
(Shannow drops mic...)

;^)


Agreed. Extremely well explained.

 

[Gokhan]

Originally Posted By: PimTac
Thanks wemay for posting that link. Very interesting article. I am curious as to the mentioning of the “poor” 91 octane fuel in AZ. What factors are they talking about?

Gokhan, I’m surprised you haven’t tried the d1G2 oils yet in the Corolla. I’m sure though that there wouldn’t be any instant changes in the engine’s running.

I'm only about 2,500 miles into the OCI. Perhaps I'll try M1 EP 0W-20 or 5W-30 next time. It looks like GF-6 won't be here until 2020 but dexos1 Gen 2 is starting to appear.

 

[Garak]

Originally Posted By: Shannow
Gohkan's engine may be suffering from end gas autoignition (most likely), or pre-ignition (possibly), and it's happening at low speeds. The knocking mechanisms that have been known for a century or more.

But not pre-detonation?

 

[Virtus_Probi]

Stopped at O'Reilly on the way home last night and they didn't have any dexos2 oils on display.
Same deal at WM, I know I have seen Pennzoil Euro L 5W30 there before but didn't see a spot for it last night.

 

[Flying_A]

It's not really accurate to say "Dexos 2" is for diesel engines only. The Corvette will require or already requires a Dexos 2 and most Dexos 2 oils are API SN and can come with a variety of different gas engine oil specifications like Porsche A40, VW 502 and so on. It's good to see that Dexos 2 will have a LSPI focus and are addressing it as there are many gas specifications (like the aforementioned specs) that are DI and don't have LSPI constraints on the lubricant.

 

[Virtus_Probi]

Originally Posted By: Flying_A
It's not really accurate to say "Dexos 2" is for diesel engines only. The Corvette will require or already requires a Dexos 2 and most Dexos 2 oils are API SN and can come with a variety of different gas engine oil specifications like Porsche A40, VW 502 and so on. It's good to see that Dexos 2 will have a LSPI focus and are addressing it as there are many gas specifications (like the aforementioned specs) that are DI and don't have LSPI constraints on the lubricant.


Oh yeah, I am interested in dexos2 for my DIT gasoline engine.
I have run M1 5W30 ESP in the past, but I don't believe it was labelled as dexos2 at the time...I still have a couple of one liter bottles around that I could check. It seemed to be marketed as a passenger diesel oil but the M1 website said it was OK for gasoline use.

 

[Patman]

Originally Posted By: Virtus_Probi

Oh yeah, I am interested in dexos2 for my DIT gasoline engine.
I have run M1 5W30 ESP in the past, but I don't believe it was labelled as dexos2 at the time...I still have a couple of one liter bottles around that I could check. It seemed to be marketed as a passenger diesel oil but the M1 website said it was OK for gasoline use.


I have checked the 5w30 ESP bottles at a few stores me and some stores have nothing but the older stuff without the dexos2 labelling, and some have a mix of both. But the interesting thing is that if you look up the specs on the newest stuff that has the dexos2 certification it's exactly the same as the specs on the older stuff that didn't have that spec. So it's possible they didn't need to do any tweaks whatsoever to the formula to meet that specification. I made sure I got the ones with the dexos2 label on it though, just to be safe.

 

[Whimsey]

Originally Posted By: Patman
Originally Posted By: Virtus_Probi

Oh yeah, I am interested in dexos2 for my DIT gasoline engine.
I have run M1 5W30 ESP in the past, but I don't believe it was labelled as dexos2 at the time...I still have a couple of one liter bottles around that I could check. It seemed to be marketed as a passenger diesel oil but the M1 website said it was OK for gasoline use.


I have checked the 5w30 ESP bottles at a few stores me and some stores have nothing but the older stuff without the dexos2 labelling, and some have a mix of both. But the interesting thing is that if you look up the specs on the newest stuff that has the dexos2 certification it's exactly the same as the specs on the older stuff that didn't have that spec. So it's possible they didn't need to do any tweaks whatsoever to the formula to meet that specification. I made sure I got the ones with the dexos2 label on it though, just to be safe.


The same thing with plain jane Mobil 1 5W-30. Dexos 1 versions met the Dexos 1 Gen 2 specs but could not be labeled as such till the Gen2 launch in Sept of 2017.

Whimsey