# How to avoid piston damage in 16.5 Cruze



## Fuhnominon (Mar 19, 2015)

Hi everyone, I have a 2016 2nd generation Cruze on way to me via a shipper that I bought online. I have been doing some reading and am very fearful of the Piston damage that I've read is very prevalent with some gen2 cruzes. Can anyone suggest things i could do to if not completely eliminate piston damage then at least give best chance of not suffering that fate?


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## HBCRUZE2017 (Jan 25, 2018)

nope goodluck i had mine happen at around 30k on my 17 lt on the way to work doing 75mph in cruise control

i heard that if you dont use the autostop start function and use 91 it helps but who knows


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## Fuhnominon (Mar 19, 2015)

HBCRUZE2017 said:


> nope goodluck i had mine happen at around 30k on my 17 lt on the way to work doing 75mph in cruise control
> 
> i heard that if you dont use the autostop start function and use 91 it helps but who knows


Oh no!! Thanks for the input. What is 91 may I ask


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## Drmilr (Mar 28, 2016)

Octane rating


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## jblackburn (Apr 14, 2012)

Run a good quality synthetic oil (I've run Amsoil XL and SS in mine since 15k, and Pennzoil Platinum before that), and run 91/93 octane in it.

38k and counting on mine. @*UpstateNYBill* has over 100k on his 17.


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## Fuhnominon (Mar 19, 2015)

Thanks so so much guys. I will try these tips and hope it has as much success for me as it has for you. I have no idea what state the engine is in as I haven't received the car yet but I hope the pistons are ok but I will do exactly as you have directed.


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## Ma v e n (Oct 8, 2018)

Stick to a high quality Dexos1 Gen2 or comparable oil (Amsoil, Mobil1, Pennzoil Platinum all good choices.) I'm a fan of shorter oil change intervals to keep fuel dilution low, others go extended drain intervals with certain oils. Run 91 or 93 octane, whatever you have available, from Top Tier grade fuel stations (TopTiergas.com)


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## Fuhnominon (Mar 19, 2015)

I appreciate these pointers so much. Thanks a million ?


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## UpstateNYBill (Jan 14, 2012)

jblackburn said:


> Run a good quality synthetic oil (I've run Amsoil XL and SS in mine since 15k, and Pennzoil Platinum before that), and run 91/93 octane in it.
> 
> 38k and counting on mine. @*UpstateNYBill* has over 100k on his 17.


108,000 by tomorrow. I don't do anything special other than run premium gas.


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## snowwy66 (Nov 5, 2017)

Call the dealer and have them look up the VIN to find out what work has been done to it. 

I bought a yamaha only to find out there was a recall on the trans. I called the dealer and was told the recall had been performed.


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## XtremeRevolution (Jan 19, 2012)

Ma v e n said:


> Stick to a high quality Dexos1 Gen2 or comparable oil (Amsoil, Mobil1, Pennzoil Platinum all good choices.) I'm a fan of shorter oil change intervals to keep fuel dilution low, others go extended drain intervals with certain oils. Run 91 or 93 octane, whatever you have available, from Top Tier grade fuel stations (TopTiergas.com)


I would not even group those 3 oils together. AMSOIL's performance is not even close to Mobil 1, for example. Mobil 1 AP showed some woefully disappointing shear stability results recently in standardized testing. Mobil 1 EP has showed absolutely awful thermo-xodiation performance in standardized testing performed a couple of years ago, and Mobil 1 vanilla has shown poor oxidation stability in my own customers; oil analysis reports. I wouldn't go anywhere close to a Mobil 1 product for a direct injected engine. I'm not yet convinced that PP provides the same LSPI protection that AMSOIL does, but they at least appear to have better oxidation stability. 

Furthermore, oil change intervals have very little bearing on fuel dilution; that is determined almost entirely by driving conditions. I've had to address this topic enough times that I wrote an article on it. Instead of repeating myself, I'll direct you to it: 

Gasoline Engine Fuel Dilution Trends | XTREMEREVOLUTION.NET

When you can get 4.4% fuel dilution (anything over 5% is critical/severe), with only 950 miles on a change of oil, the suggestion that anyone should shorten their service intervals to keep fuel dilution low flies right out the window, especially when the previous analysis interval at 4100 miles had lower fuel dilution.


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## Ma v e n (Oct 8, 2018)

There's no debating that Mobil1 and Pennzoil products meet or exceed GM specs and are licensed D1G2 products. They are widely available, in brick and mortar, at virtually every garage in the USA and of course online, at very reasonable prices. There's no other oil in the $4/qt range(5qt jugs routinely go on sale for sub$25 at multiple retailers) that's worth the effort to or is able to be argued offers any real advantage other than brand loyalty. (M1 v PP v QSU v CE v ad infinium)

I have very few problems with Amsoil or it's use...You know this. I've advocated it's use numerous times. It's "grouped" together with those because I have a finite amount of time and effort to spend online. It should be clear to virtually all that Amsoil is a different beast. From the price, cost/benefit ratio, to availability at service centers, general brick and mortar, and typical online availability at popular and trusted e-tailers, to actually being licensed(obviously a hotly debated subject....But a concern to many and not a point I mention for any other reason than many other people make it....I know you have X,XXX customers that use it, I've got it in some of my own vehicles as well..)

You can't have a discussion about oil and leave out XMO, SOPUS or Amsoil so they all get mentioned. You also cant negate cost with most people, so the fact that Amsoil averages somewhere between 80% and 200% more expensive than more readily available and licensed options means it's worth offering alternatives to, even if it is arguably the best choice. Especially since I've yet to see a carbon or LSPI related failure in my area on a vehicle run on a steady diet of any "aftermarket" synthetic oil. It's ALWAYS oils that specifically labeled as blends or on bulk ACDelco Dexos


Fuel dilution....Sure you're not wrong. Adjusting OCI to make sure fuel dilution never exceeds 3% is not only expensive and potentially wasteful it is for all reasonable efforts impossible without constant monitoring. 

However....That doesn't mean I want to, or advise running around at 4% for 15,000 miles just because it never goes over 4%.


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## XtremeRevolution (Jan 19, 2012)

Ma v e n said:


> There's no debating that Mobil1 and Pennzoil products meet or exceed GM specs and are licensed D1G2 products. They are widely available, in brick and mortar, at virtually every garage in the USA and of course online, at very reasonable prices. There's no other oil in the $4/qt range(5qt jugs routinely go on sale for sub$25 at multiple retailers) that's worth the effort to or is able to be argued offers any real advantage other than brand loyalty. (M1 v PP v QSU v CE v ad infinium)
> 
> I have very few problems with Amsoil or it's use...You know this. I've advocated it's use numerous times. It's "grouped" together with those because I have a finite amount of time and effort to spend online. It should be clear to virtually all that Amsoil is a different beast. From the price, cost/benefit ratio, to availability at service centers, general brick and mortar, and typical online availability at popular and trusted e-tailers, to actually being licensed(obviously a hotly debated subject....But a concern to many and not a point I mention for any other reason than many other people make it....I know you have X,XXX customers that use it, I've got it in some of my own vehicles as well..)
> 
> ...


I never said they don't meet or exceed D1G2 specifications; what I'm saying, and have said before, is that *it's just not enough.* In fact, I'd argue that bare minimum specifications are rarely, if ever, enough. You are getting exactly what you're paying for; don't fool yourself into believing otherwise just because those companies made better products in the past. I've seen enough of Mobil 1 oxidation and shear stability in recent years that would steer me away from those products for at least five more. 

I know you don't have a problem with AMSOIL, and I don't have a problem with pennzoil platinum, but I do have a problem with Mobil 1 based on the test results I have seen. 

Even AMSOIL's OE and XL options offer the same LSPI protection claims according to D1G2. Those are claims not repeated by M1 or PP. If they could make those same claims, I'm sure they would, but they're not focused on doing better than the bare minimum required; they're focused on marketing. 

I can get you in touch with my buddy Austin whose Malibu dropped a piston on Mobil 1 and was diagnosed as LSPI by the dealer just last year, but I think you trust me enough to not waste my time with that. 

OCI has nothing to do with fuel dilution. You can't adjust OCI to make sure fuel dilution never exceeds 3%; you can only adjust your driving conditions (and even then, that's often unreasonable to expect). These higher end oils also handle fuel dilution far better; are able to release it more quickly (from my observations) and are able to continue protecting better while diluted. Fuel dilution is becoming a fact of life; you can't get away from it. If you're scared of 4% fuel dilution, you'd be changing your oil every 500 miles. 

I had a lengthy discussion with a technical lead from AMSOIL's development team about this topic and he said that in their testing, the only side effect he's seen with higher fuel dilution is varnish, but it does not affect their recommendations. Furthermore, their reformulation actually removed the "severe service" designation for turbocharged engines. He maintained quite strongly that AMSOIL will protect very well for 15,000 miles in severe service or 25,000 miles for normal service. 

I understand this is a bit to wrap your head around given what we are normally comfortable with or exposed to in the American automotive industry, but your hesitation to want or advise running 4% fuel dilution for 15,000 miles, *on AMSOIL's signature series,* is simply unfounded. 

I really don't want to make this whole thing an AMSOIL sales pitch so I'm trying to remain technical here. I would say this about any oil that had similar capabilities. Take Pennzoil Platinum for example; your biggest issue is going to be oxidation. The fuel (containing ethanol), with short trips (more heat cycles), will introduce more moisture in the crankcase which will be absorbed by the ethanol, which overnight will deplete some of the additives in the oil. That's really your only issue dictating service intervals where fuel dilution exists. If you were running Pennzoil Platinum, for example I would have no reservations changing it at the OEM recommended intervals, with or without fuel dilution. 

The biggest thing I'd like you to take away from this discussion is that fuel dilution is not cumulative and can actually reduce over the course of an oil's service life.


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## 17Cruzer (Apr 18, 2017)

Oil is cheap....even Amsoil compared to a new engine and install. Change oil every 5K (or less). Done.


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## HBCRUZE2017 (Jan 25, 2018)

i use torco in my camaro but whatever dealer uses in my cruze lol let it blow up again they will fix it


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## theshiftyjelly (May 26, 2018)

I got bit today. 20k on a '17 Premier. Very disappointed in the brand. Regular maintenance and fuel as described in the manual shouldn't result in magor engine failure at 20k. Last Chevy I buy. 



HBCRUZE2017 said:


> nope goodluck i had mine happen at around 30k on my 17 lt on the way to work doing 75mph in cruise control
> 
> i heard that if you dont use the autostop start function and use 91 it helps but who knows


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## snowwy66 (Nov 5, 2017)

theshiftyjelly said:


> I got bit today. 20k on a '17 Premier. Very disappointed in the brand. Regular maintenance and fuel as described in the manual shouldn't result in magor engine failure at 20k. Last Chevy I buy.


According to the forum. Chev isn't the only brand with the problem.


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## theshiftyjelly (May 26, 2018)

Very true, point taken. Guess I should say last 4 cyl. turbo.



snowwy66 said:


> According to the forum. Chev isn't the only brand with the problem.


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## Farmerboy (Sep 2, 2012)

17Cruzer said:


> Oil is cheap....even Amsoil compared to a new engine and install. Change oil every 5K (or less). Done.


One reason I use Amsoil with its possible 15,000 mi Oci is that at 33,000 mi/yr that 7,500 comes around in 3 months. When I’m busy on farm it’s hard to find time to change oil so twice a year helps a lot.


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## 17Cruzer (Apr 18, 2017)

Farmerboy said:


> One reason I use Amsoil with its possible 15,000 mi Oci is that at 33,000 mi/yr that 7,500 comes around in 3 months. When I’m busy on farm it’s hard to find time to change oil so twice a year helps a lot.


Understood, and with your amount of road miles in a 3 month time span, twice a year is perfectly acceptable.


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## adamc91115 (Sep 22, 2018)

My 2016.5 just broke 100k and haven't had any issues. I use Valvoline Modern Engine 5w30 with Trifecta tune. I try to only use 93 octane but it does get the occasional tank of 87. 


I'm definitely not easy on this car, and my wife is even worse lol. It has been an extremely reliable car for us, just like our 2014 was.


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## booyakashao (Dec 7, 2018)

Okay let's collect some info.

I have a 2016 Gen 2 with no piston issues.
Built in Ohio.
Mileage: 62k.
Gas: 87 with octane booster, 89, and 93
Oil used: (5w-30) valvoline, (5w-30) warren distribution, and (0w-30) amsoil
Spark plugs replaced at 51k
I do have a trifecta tune and a k&n air filter.


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## Terry B (Oct 18, 2018)

My 2017 Premier dropped a piston at 25K going 25 mph. Dealer took care of it, replaced all 4 pistons and called it a design flaw - it has to do with the type of engine in the Cruze. *LSPI is an abnormal combustion event in which the fuel-air mixture ignites before intended, causing excessive pressures inside the engine's cylinders. In mild cases, this can cause engine noise, but when severe enough, LSPI can cause engine damage.*


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## snowwy66 (Nov 5, 2017)

Just to clarify.

No such thing as 16.5. It's either a 16 Cruze limited gen 1 or cruze gen 2. ?


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## JohnUber (Feb 7, 2019)

I have a 2015 Cruze 1.8 liter manual transmission. I have intermittently put Lucas Upper Cylender Lubricant in my tank, as well as Berryman’s B12 Chemtool, or O’Reilly Auto Prts brand octane booster from time to time. It is easier to measure out to exact using a turkey blaster or the perfect size travel size shampoo bottle from Walmart or other stores or just eyeball it as I have done many times. I am a full time Uber driver starting at about 20,000 miles on my car. As of this moment I have 162,523 miles. I think it is cheaper to buy an octane booster or an upper cylinder lubricant than high octane gas at the pump. However a lot of the comments also were indicating they had a stop start feature on their car. Maybe that system makes the engine run too lean after each cycle. If that is the issue then it is in the programming.


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## jblackburn (Apr 14, 2012)

JohnUber said:


> I have a 2015 Cruze 1.8 liter. I have intermittently put Lucas Upper Cylender Lubricant in my tank, as well as Berryman’s B12 Chemtool, or O’Reilly Auto Prts brand octane booster from time to time. I am a full time Uber driver starting at about 20,000 miles on my car. As of this moment I have 162,523 miles., and the pressing issue I have is not pistons, but the “intake manifold tuning valve connecting rod” regularly coming off.


The 1.8 is totally unrelated to the Gen 2 1.4T.

The intake manifold tuning valve has a couple threads on the site here that will turn up with a quick search.


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## dak10ssb (Feb 4, 2013)

Piston damage is usually detonation from cheap fuel and has been 4 ever
Alcohol has no mercy just saying
I have a 2011 on my airboat which I do run HARD always put 93 in it and have had no trouble not to say I got 34 # of boost ecm holes it to 28#
Running rpm at 5400 
Be kind to ur Cruze put 93 in it and ride on


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## Farmerboy (Sep 2, 2012)

Maybe someone more knowledgeable than me could give us a little info on the exact fuel injection process on these DI Gen 2 engines. I can understand that in the Gen 1 the fuel is pulled in with the air on the intake stroke and is present in the cylinder during the entire compression stroke. Easy to understand how higher octane would effect preignition. On Gen 2 when does the inj. event take place? If fuel is injected only immediately before the spark plugs fire there is less time for preignition to happen. If it is mostly the oil droplets causing it, why all the misinformation about high octane gas helping. Seems I remember some reporting piston breakage while using 93 octane.


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## HBCRUZE2017 (Jan 25, 2018)

you shouldnt have to run 91/93 in an economy car tho to avoid engine detonation lol that is dumb i run 87 all day ran 91 once and i didnt feel or see any different 

ill save the $$ to put 91 in my camaro


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## Ma v e n (Oct 8, 2018)

The problem is this isn't typical detonation. It's not related KLSA(knock limiting spark advance) or any other of traditional forms or modes of knock or ping. It's a new phenomenon that can't be mitigated on the fly by the ECM. 

Many people drive cars that detonate over and over everyday, for months or years with minimal I'll effects or notable degradation of the engine. 

LSPI is literally oftentimes a one-and-done type of scenario. Like fentanyl....Once and your dead, maybe


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## Ma v e n (Oct 8, 2018)

The Cruze may be an economy car, but that doesn't change the fact that it sports an engine making 110hp/Liter(1.8hp/cubic inch). A number unimaginable in a street engine not too long ago.
The 2010 ZR1 only managed 102hp/L
BMWs N54, N55 and B58 inline-6 3.0L Turbo engines made it through life from 2006 to now with anywhere from 100-110hp/L in most vehicles. 

Comparisons can go on and on and on...

The LE2 is a high performance modern engine. only gets sold as the "base" engine in the car here. It's a performance option elsewhere.


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## Farmerboy (Sep 2, 2012)

Ma v e n said:


> The problem is this isn't typical detonation. It's not related KLSA(knock limiting spark advance) or any other of traditional forms or modes of knock or ping. It's a new phenomenon that can't be mitigated on the fly by the ECM.
> 
> Many people drive cars that detonate over and over everyday, for months or years with minimal I'll effects or notable degradation of the engine.
> 
> LSPI is literally oftentimes a one-and-done type of scenario. Like fentanyl....Once and your dead, maybe





Ma v e n said:


> The Cruze may be an economy car, but that doesn't change the fact that it sports an engine making 110hp/Liter(1.8hp/cubic inch). A number unimaginable in a street engine not too long ago.
> The 2010 ZR1 only managed 102hp/L
> BMWs N54, N55 and B58 inline-6 3.0L Turbo engines made it through life from 2006 to now with anywhere from 100-110hp/L in most vehicles.
> 
> ...


 All of this is very reasonable but does not at all address my question about injection event timing.


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## 17Cruzer (Apr 18, 2017)

Farmerboy said:


> All of this is very reasonable but does not at all address my question about injection event timing.


Fuel injection event timing has no bearing on LSPI (but it does aid in cooling the combustion chamber),......very fine oil droplets from the PVC system, blowby and/or a leaking turbo seal does as well as a lean AFR. We need to use a catch can to help offset LSPI and limiting the fouling of the intake valves.


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## Ma v e n (Oct 8, 2018)

Sorry Farmer...I did the see your post.

So, yes technically speaking the DI engine does just spray fuel "right before" the secondary ignition spark event.
Let's just say our timing is 20degrees BTDC compression stroke for giggles. That means we have to be done spraying fuel somewhere sooner than 20dBTFC, lets say 30degressBTDC compression.

And under normal circumstances we'd never want to be spraying fuel into the exhaust...So that means we can't start til the exhaust valve has closed, which due to overlap may be 20 ATDC Exhaust, or 20 degrees into the intake stroke. So we'd wait til 30 ATDC exhaust.

That means there's a window from 30 ATDC exhaust to 30 BTDC compression we can spray into.

Simple maths tells us if we eliminate the first 30degrees of out intake stroke as usable injection time, and the last 30 degrees of our compression stroke, we are left with a 300 degree injection timing window. 

We could call this 41.7% injector duty cycle in porrt fueling terms. (300d/720d x 100 = 41.66)

A port fuel injected engine might want to run 85% duty cycle...Or 612 degrees of injection window, but that's because port injection can just spray into the closed intake valve, and that built up fuel will enter once the valve opens. However the engine can still only fill the cylinder with fuel during the time the intake valve is open. So on a forced induction engine we are limited to camshaft intake duration in order to fuel the cylinder (anywhere between 180-210degrees for most street engines)and on a naturally aspirated engine you'll have potentially less time as the upstroke of the piston on compression may create positive cylinder pressure in some engines near intake valve opening.

The direct injected system has enough pressure to be able to get all that volume of fuel into the cylinder in less than half the injector on time. And uses less fuel because unless we are warming up the cat, we don't allow fuel out the exhaust valve. This isn't something a PFI engine can accomplish without limiting duty cycle significantly. 

There's a much larger injection window than most people would think. It shrinks as ignition timing advances and camshaft overlap increases, but it's not this tiny fraction of what a PFI engine has.


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## Ma v e n (Oct 8, 2018)

17Cruzer said:


> Fuel injection event timing has no bearing on LSPI (but it does aid in cooling the combustion chamber),......very fine oil droplets from the PVC system, blowby and/or a leaking turbo seal does as well as a lean AFR. We need to use a catch can to help offset LSPI and limiting the fouling of the intake valves.


Um no...Mostly.


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## 17Cruzer (Apr 18, 2017)

Ma v e n said:


> Um no...Mostly.


Mostly? Explain. 

https://www.summitracing.com/parts/mor-85682/all
Watch the video


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## Farmerboy (Sep 2, 2012)

Ma v e n said:


> Sorry Farmer...I did the see your post.
> 
> So, yes technically speaking the DI engine does just spray fuel "right before" the secondary ignition spark event.
> Let's just say our timing is 20degrees BTDC compression stroke for giggles. That means we have to be done spraying fuel somewhere sooner than 20dBTFC, lets say 30degressBTDC compression.
> ...


 A very informative post but it still does not say when the (CRUZE Gen2 1.4) fires the injs. If done immediately before the spark plugs fire there is very little time to preignition. Therefore the oil vapor seems to have more effect than fuel. Seems that is what GM thinks also with revised oil specs.


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## Ma v e n (Oct 8, 2018)

17Cruzer said:


> Fuel injection event timing has no bearing on LSPI (but it does aid in cooling the combustion chamber),......very fine oil droplets from the PVC system, blowby and/or a leaking turbo seal does as well as a lean AFR. We need to use a catch can to help offset LSPI and limiting the fouling of the intake valves.


Timing has a bearing on LSPI firstly because a late or short injection event results in poor atomization of the fuel and droplet formation. These droplets mix with the oil to create the compound which ignites.(not related to catch can)

Cooling of the combustion chamber is notable because the less thermal energy available, the less likely unintended combustion events occur.(not catch can related)

Lean AFR is another contributor to cylinder temp. And isn't affected by a catch can.

Turbo seal leakage(if you think that's really a notable contributor), blowby, and normal characteristic cylinder wall and piston ring lubrication are not affected by a catch can.

A catch can MAY catch some of the oil droplets in the PCV system and mitigate their entry into the intake. But LSPI occurs even on engines without sealed/recirculating emissions spec crankcase ventilation systems. 
A catch can on an LE2 is also a tricky endeavour to get right because the system used two pipes that can feed oil fouled air into the intake, and one of them flows in two directions, a challenge for most cheap cans.

And that brings us to most cheap cans.

They simply can't remove oil vapors from the crankcase gas flow in any meaningful manner(if the car has any notable oil particulate to begin with) they need to be a coalescing air/oil separator to do what those who claim they are needed, need them to do. At best they are typically a wire mesh(relatively coarse), more often than not they are no more than a baffled canister, perhaps with some stainless steel/brass wool material in them.

That video is neat to look at, but that's a port injected, overhead valve 6.2L V8 being raced....Not exactly a directly analogous hardware setup to what we are talking about, nor is it even remotely the conditions which contribute to the event we are discussing.


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## 17Cruzer (Apr 18, 2017)

Ma v e n said:


> Timing has a bearing on LSPI firstly because a late or short injection event results in poor atomization of the fuel and droplet formation. These droplets mix with the oil to create the compound which ignites.(not related to catch can)
> 
> Cooling of the combustion chamber is notable because the less thermal energy available, the less likely unintended combustion events occur.(not catch can related)
> 
> ...


Pre-igition is created by an ignition source other than the ignition system, as long as there is fuel and air in the combustion chamber. Oil IS combustible with air present (it can also act like a glow plug!), it is a source contributing to LSPI. That, and too lean AFR, and lugging the engine are the other factors in LSPI. An additional factor is oil introduced via the PVC system. More on that below.....

All direct injection vehicles will experience fouled intake valves because no fuel is injected ahead of the valves as it is in a port injected engine. Gasoline injected ahead of the valves act as a cleaning and cooling agent. In direct injection, gasoline is injected directly to the combustion chamber, by-passing the intake valves. Oil vapors from the PVC system will accumulate on the back of the intake valves and on the piston tops. Lastly, leaking turbo seals will also add oil vapors to the intake. 

Catch cans.....will reduce the amount of oil vapors from the PVC system entering the air intake system. They help reduce oil fouling of the piping, sensors, intercooler, throttlebody, intake valves, and piston tops. Catch cans have no effect on blow-by, the fuel system, or the ignition system. 

There are different styles of catch cans, avoid the cheap ones, but even they are better than no catch can. Air/oil separator catch cans are desirable, and they must be a closed loop type.


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## Ma v e n (Oct 8, 2018)

Farmer, it seems as though you want the EXACT time the ECM commands an injection event, there isn't just one. It's a dynamic system. Both the intake and exhaust camshaft have variable timing, and of course ignition timing is variable. The ECM determines injector firing event starting point in crankshaft/camshaft degrees(position), injector pulse width and fuel pressure on the fly to account for engine speed, load and desired emissions/fuel economy.


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## snowwy66 (Nov 5, 2017)

I highly doubt injection occurs just before spark. 

That's not enough time to get everything mixed up. For a more complete burn.

For years fuel was pulled in with air on the intake stroke. Mixing up on the compression stroke.


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## 17Cruzer (Apr 18, 2017)

snowwy66 said:


> I highly doubt injection occurs just before spark.
> 
> That's not enough time to get everything mixed up. For a more complete burn.
> 
> For years fuel was pulled in with air on the intake stroke. Mixing up on the compression stroke.


Direct injection is under much higher fuel pressure than port injection and doesn't need as much time to "fill" and fully mix with air in the combustion chamber. The injector duty cycle is much shorter in duration than port injectors.


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## snowwy66 (Nov 5, 2017)

17Cruzer said:


> Direct injection is under much higher fuel pressure than port injection and doesn't need as much time to "fill" and fully mix with air in the combustion chamber. The injector duty cycle is much shorter in duration than port injectors.


According to the torque pro app. Our direct injection system is running at the same 60 psi fuel injection started with in the 80's. When throttle body injection was introduced for a couple of years before switching to the port injection system we're all familiar with now. 

Higher compression is more resistance. Thus today's smaller spark plug gaps from when High Energy Ignition first came out. Which started at .045 and increased to .060 with the higher voltage systems. And now dropped to .028

The carburetor and the throttle body and the port injector required a full stroke to mix up the mixture intake. There's no way a direct injection is going to squirt just before spark and have a proper stirring up for combustion.


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## plano-doug (Jul 1, 2015)

snowwy66 said:


> According to the torque pro app. Our direct injection system is running at the same 60 psi fuel injection started with in the 80's.


That's 60psi the from the tank pump. There's another, much higher pressure pump under the hood, which boosts it up for DI. I have the LFX with DI in my 2013 Impala, but I haven't wrenched on it much, so I can't claim more than a little knowledge about it, but I know it has two pumps.

If you think about it, with the compression stroke and the heat, the fuel pressure must be quite high, or it won't be able to overcome the pressure in the combustion chamber.

Doug

.


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## Ma v e n (Oct 8, 2018)

Injection rail pressure is several hundred psi minimum. Up to around 2000psi at max pressure. 


17Cruzer, I'm not sure what point you're trying to make anymore. Are you still claiming injection timing has nothing to do with LSPI or are you now just reiterating information that many of us already know, and that was literally just talked about in this thread?

If you believe that any of the readily available catch cans would work(just as a proper functioning air/oil separator, ignoring LSPI for a minute)Id like to know which one and how you'd intend to plumb it.

As for catch cans being an important part of a strategy to eliminate LSPI....I guess that depends on whether one believes a functioning emission spec closed PCV system is a statistically relevant contributor to LSPI. I don't. 

Id also debate the cost/benefit ratio when it comes to keeping valves clean...


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## Taxman (Aug 10, 2017)

Speaking of dirty valves, is it the PCV, the EGR, or both that makes the mess in the first place?


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## Farmerboy (Sep 2, 2012)

I’m saying what I don’t know much about but dsl engines fire inj only when compression has heated air enough to ignite fuel. Way high pressure vaporizes the fuel immediately.


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## 17Cruzer (Apr 18, 2017)

Ma v e n said:


> Injection rail pressure is several hundred psi minimum. Up to around 2000psi at max pressure.
> 
> 
> 17Cruzer, I'm not sure what point you're trying to make anymore. Are you still claiming injection timing has nothing to do with LSPI or are you now just reiterating information that many of us already know, and that was literally just talked about in this thread?
> ...


A catch can will not *eliminate* LSPI. It can reduce a small amount of oil entering the intake track at the stock PVC entry point (just in front of the turbo inducer) if plumbed correctly, and thus help reduce the number of LSPI events or perhaps reduce the severity of the event. Less oil in the combustion chamber the better. Also note that some catch can applications such as the WRX, use 2 catch cans. 

The type of catch can I am talking about is this: PVC air/oil separator (functions with the PVC). 









Not this:


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## IndyDiesel (May 24, 2015)

There is no darn way I am putting premium fuel in my 18 premier, if I need to do that to get longevity. These threads put me to sleep. Smiles.


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## 17Cruzer (Apr 18, 2017)

IndyDiesel said:


> There is no darn way I am putting premium fuel in my 18 premier, if I need to do that to get longevity. These threads put me to sleep. Smiles.


The static compression ratio on the LE2 is 10:1, plus boost!


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## Ma v e n (Oct 8, 2018)

Taxman said:


> Speaking of dirty valves, is it the PCV, the EGR, or both that makes the mess in the first place?


It's definitely both, but the argument could be made that the EGR or EGR functionality of certain VVT setuos is a larger contributor. 




Farmerboy said:


> I’m saying what I don’t know much about but dsl engines fire inj only when compression has heated air enough to ignite fuel. Way high pressure vaporizes the fuel immediately.


Yup, the diesel uses the heat of the cylinder to cause ignition, we don't want that in our gasoline engines. Gasoline engines fire the spark plug to start combustion WELL before peak cylinder pressure/temperature is reached. And rely on a mixed air/fuel charge to propagate a flame/pressure smoothly through the cylinder and evenly raise the cylinder pressures. 
Diesels are definitely different though. 
The fuel itself has different flash point, and autoignite points. There's significantly higher cylinder pressures (and as a ratio of cylinder volume, smaller combustion chambers) in a diesel, and significantly higher in cylinder temps, before and during combustion. This is a major reason why our gas direct injection engines can get by with ~2000psi injection pressure, but a diesel may have 30,000psi. 

The diesel engine will actually start burning fuel at the first autoignition of the initial vapors and this initial burn can vaporize the remaining liquid fuel , diesel engines are not uncommon to have the injector spraying fuel into the cylinder while a combustion event is actually already occuring, this is something we'd NEVER want in a standard spark ignition engine. 

Basically, we need a nearly fully gaseous mixture at the right temperature sort of evenly dispersed throughout the cylinder. We can't accomplish that with very late injections into a hot cylinder to my knowledge.


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## Ma v e n (Oct 8, 2018)

IndyDiesel said:


> There is no darn way I am putting premium fuel in my 18 premier, if I need to do that to get longevity. These threads put me to sleep. Smiles.


Every direct injected vehicle I currently or have ever owned, gets a steady diet of 93octane from TopTier stations, only.


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## IndyDiesel (May 24, 2015)

Ma v e n said:


> Every direct injected vehicle I currently or have ever owned, gets a steady diet of 93octane from TopTier stations, only.


I only use top tier and normally use 87. Everyone said the same thing when I had a 14 eco manual, I never had issues there either. Most everyone had emissions issues with the diesel and I didn’t have any emission issues other than an EGR sticking open. I just don’t worry about what could happen. If I am going to buy premium fuel it’s going to be a mustang Gt, not an economy car. Just my view.


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## Ma v e n (Oct 8, 2018)

I don't worry about my fuel either. Everything gets 93. Cruze, Impala, HHR SS, Silverado. As far as I'm concerned there's only one octane. My Cruze is the economy car, it gets 38mpg on my commute where the Silverado only musters 17mpg. 


I run 93 because I see measurable economy differences, idle quality differences and reduced knock retard. The LFX, LNF and LE2 all pull timing constantly to much higher degree on 87 than 93. Reducing ignition advance reduces power output and efficiency. If the recommended fuel reduces power output and efficiency it's the wrong recommendation. Just because it "will" run on 87, doesn't mean it "should"


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## Farmerboy (Sep 2, 2012)

And that is what I find interesting about these cars. I have never seen measurable difference in mpg or drivability in either my previous ‘12 Eco or this ‘17 Lt on 87. I know a lot of others said they did but some also reported broken pistons with 93. There must be some difference in cars, programming, climate, driving style, etc. that makes a difference.


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## snowwy66 (Nov 5, 2017)

I"m going to go out on a limb and say elevation is probably the big difference between people seeing improvement or not. 

Those that live at sea level would probably notice more then those of us that live in the mountains @4400 feet. 

12.7 atmospheric pressure vs 14.7.


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## snowwy66 (Nov 5, 2017)

plano-doug said:


> That's 60psi the from the tank pump. There's another, much higher pressure pump under the hood, which boosts it up for DI. I have the LFX with DI in my 2013 Impala, but I haven't wrenched on it much, so I can't claim more than a little knowledge about it, but I know it has two pumps.
> 
> If you think about it, with the compression stroke and the heat, the fuel pressure must be quite high, or it won't be able to overcome the pressure in the combustion chamber.
> 
> ...


There was another gauge in torque. I beleive it measured 2200 and I thought it was full of crap. Now I know.


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## Ma v e n (Oct 8, 2018)

Farmerboy said:


> And that is what I find interesting about these cars. I have never seen measurable difference in mpg or drivability in either my previous ‘12 Eco or this ‘17 Lt on 87. I know a lot of others said they did but some also reported broken pistons with 93. There must be some difference in cars, programming, climate, driving style, etc. that makes a difference.


Local weather/climate, altitude, driving style, fuel, driving style. All definitely make a difference. These thing are all different in Southern Cali, than they are in Kansas, than they are in Connecticut.

My Silverado does that care if it's Exxon, or Shell, local convenience store, or megamart fuel. It gets no less than 17.2mpg and better than 17.8mpg on my commute as long as weather is within 10F. The Cruze is more particular, it prefers Conoco, by as much as 2.5mpg over the others. Exxon gives it a cold idle stumble.
The Impala needs spark plugs at 110k, but besides that, it's okay with anything top tier, it will throw a CEL if it has to run a full tank of local convenience gas(Wawa)


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## HBCRUZE2017 (Jan 25, 2018)

IndyDiesel said:


> There is no darn way I am putting premium fuel in my 18 premier, if I need to do that to get longevity. These threads put me to sleep. Smiles.


lol i agree this is dumb even asked after i got my engine rebuilt they said 87 i said got it !


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