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Cold start rattle on LS3

Discussion in 'VF Holden Commodore (2013 - ?)' started by Ron Burgundy, Oct 11, 2017.

  1. monstar

    monstar Donating Member

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    Yes full race build, bathed, tested, honed, bored, machined, balanced, overhauled. But pretty sure LS3 are made in 'Merica, not too much bad to say about the production facilities and protocols.
    Poor oil / air separation (PCV) I think.
    Exactly. But one thing for sure this 2015 6.2 (340) tune is the only difference to previous, never had such an issue like this before now.
    True. Perhaps the solution in light of tune restrictions is to swap in high quality forged asymmetrical pistons:
    Cheaper than supercharging, huge efficiency gains, no noise.
     

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  2. immortality

    immortality Moderator Staff Member

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    Yes via the PCV and the factory system basically has no oil separation at all. The issue I have is that it seems to happen from day one these LS engines and not only high mileage ones like my old V6 which probably still has less oil through the PCV than a newish LS motor.

    My point been that for a new engine to breathe as heavily as the LS engines do there must be an issue with the piston/bore ring seal. It's a well known fact that GM runs a narrow low tension ring these days to reduce friction and improve fuel mileage, clearly they stuffed it up with the original LS1 engine as they were oil burning, heavy breathing piston slapping behemoths but did GM ever truly rectify it or just label it as "acceptable" with slightly higher tension rings fitted seeing as these engines still breathe heavily as they come of the GM production line?
     
  3. monstar

    monstar Donating Member

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    Since February 2011 the GenIV V8 doesn't have the same issue because the passenger rocker cover was revised with half decent air / oil separator. The LSA is a different kettle of fish, needs work per Camaro LE or Z/28. HSV guys go for brands mainly but there are fantastic MAN high efficiency diesel air/oil separators (coincidentally rebranded by Lingenfelter for LSA engines in the US) that actually work to TÜV standards.
    I've not noticed the GenIV engine ever breathing particularly heavily checking via oil filler cap for example?
     
  4. immortality

    immortality Moderator Staff Member

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    I don't think you would particularly notice it via the oil filler cap, if the PCV system is working removing the filler cap will actually create a vacuum leak into the intake because at idle the manifold is at high vacuum and will be sucking on the crank case via the PCV valve.

    I also doubt yours would breathe heavily regardless considering the engine work your has had. BTW, do you know what your piston/bore clearance is?

    Yes I'm aware of the diesel oil air separators, out of Germany originally I think. Big black plastic thing if it's the same one you are referring to. It's a shame OEM doesn't fit a decent catch can system, would alleviate a lot of issues with engines in later life (not that manufacturers car much what happens with engines once they pass warranty mileage).

    Just thinking out loud here for a minute, but we know GM likes to use narrow/low tension rings to improve efficiency, what effect if any do low tension rings have on piston stability in the bore? Taking that further, modern engine run these fancy short skirt pistons with a narrow ring pack positioned very high on the piston with the top ring very close to the piston crown which I believe is done to improve combustion efficiency but what effect does this have on piston stability? All of this is a mute point though because in theory, these modern hypereutectic pistons expand a lot less so in theory should have a much tighter piston to bore clearance than a forged piston (such as yours) and my old school Holden V8 donk.
     
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  5. lmoengnr

    lmoengnr Well-Known Member

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    Both my Redline(L77) and Maloo(LS3) initially had oily intakes in the first 10000k's, but have since 'dried out' before 30000k's.

    I think LS's need 20000k's to properly bed the rings in.
     
  6. immortality

    immortality Moderator Staff Member

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    You're probably right there. I know an ex Holden mechanic that used to do the warranty rebuilds on LS engines here. After rebuilding said engine it was then taken for a drive to properly bed the rings in......

    It probably doesn't help that these engines come with very slippery full synthetic oils from the start. Much better starting with a run in oil and dumping after the first 1000km me thinks.

    The problem is probably worse in cars that get driven to nicely and never really given a decent workout during the run in period.
     
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  7. monstar

    monstar Donating Member

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    About 65-68 kPa vs 101 baro (arr, I'm by the sea).
    No, but those details on file with builder. Pistons are asymmetric per JE video description above.
    I know what you mean, check this pic of the GenV (LT1) piston from underneath:
    Vs mine:
    This gives an idea of how it looks from underneath (Wiseco symmetric vs JE asymmetric):
    Whereas there's a fair bit of meat of course with my compression height but rings well below crown:
    2nd Ring: 1.5mm
    Bore: 102.41mm (4.032 in)
    Oil Ring: 3.0mm
    Top Ring: 1.2mm
    Yes, changed with Gen V but Gen IV was a compromise with inexpensive cast materials (silicone being cheaper than alu) using 40 year old piston design.
     
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  8. Paulie81

    Paulie81 Active Member

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    Mine is pretty much the same and has never worried me. Im guessing the Aluminium block probably makes it sound louder.
     
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  9. 426Cuda

    426Cuda SUBLIME!

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    Excellent post VCoz. Thanks!
    One comment though. The non expansive thermal properties of hypereutectic pistons, sounds, prima facie like a contradiction, when followed by the "prone to noise/slap, rocking before they reach temperature". Of course the piston do expand a little, no doubt, as do the liners. Did you read anything like this in your research?
    Cheers
     
    Last edited: Oct 13, 2017
  10. monstar

    monstar Donating Member

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    If if were the pistons flapping and slapped like an LS1 then it would straight up make the noise on startup. It would clack and carry on like it does on the hundreds of videos on YouTube.

    With LS1 piston slap the noise is there from get go and gets louder and relative to engine RPM until induction / engine case takes over. In other words free revving no load you can definitely hear it.
    This noise described multiple times in text and video in the original thread, occurs only under load when cylinder pressure is high on a new engine - cold and between 1200 and 2700, in open loop, with depressed accelerator pedal position.
    It does not affect all GenIV V8, only the 6.2, and only those with the 2015+ OS in the ECU.
    I propose this is a case of excess cylinder pressure versus massive heat entropy whilst ECU is in warmup mode. If that sounds too wanky and hard to grasp, heat build up during compression vs heat loss to the chamber environment causes crap combustion - knock. As per the previous thread, this cold load knock can be tuned out but this tune is more emissions compliant. Therefore I propose the VFII tune allows the ECU to compensate within more restrictive fuel / spark parameters.
    The VFII noise is matched per RPM, doesn’t get louder with more RPM. Level is easily overcome with induction and crankcase noise 2500+ RPM. Commanding less power via accelerator, or ECU commands transmission shift, the noise is non-existent. In other words doesn’t knock when commanded spark retard...
    So before this turns into a monstar vs the googleverse debate and the sheer weight of info from a decade or so ago dragged in to bear, let’s be clear this is not piston slap under light / typical operating conditions, only under peak cylinder pressure “cold load”, specifically an issue with the manner warmup is handled in the last iteration of the emissions compliant tune (VFII OS only).
    I welcome discussion regarding Pistons, bores, rings, in adequate detail because I’ve studied a bit about these things in order to deal with this stuff.
    Also I whole heartedly believe that knowing what’s making which sound is really important to maintaining the car. Bottom line is it’s noted with Holden as being typical, and Aus Cons Law has your back.
     
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  11. Ron Burgundy

    Ron Burgundy Well-Known Member

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    After obsessing with this for almost a year and reading thousands of web pages I can now confidently say that Monstar's therory seems more accurate than anything else I was told or I have read.

    Monstar's explanation explains well all different variations of this cold startup noise on LS3.

    Given the number of people who experience this cold start rattling it is virtually impossible that these are all poorly built motors with the pistons flapping around.

    In my case...excessive piston to bore clearance does not explain no noise at all on idle, different levels of noise based on ambient temperature and days with no noise at all..Excess bore to piston clearance does not fit with any of this.

    I just wish 'holden techs' knew this and gave people correct info so that the ones prone to overteacting dont waste time trying to solve the problem that does not exist...

    In any case I can't wait to have mine tuned by Sonny ...

    Just need to wait for damn warranty to expire....or do i ?! ;)
     
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  12. immortality

    immortality Moderator Staff Member

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    In your case having it tuned will give you an answer whether or not it's creating the noise. Considering the timing retard table Monstar posted in another thread it's gonna do interesting things.
     
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  13. HemiMagic

    HemiMagic Active Member

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    Sounds like a Duramax......
     
  14. HemiMagic

    HemiMagic Active Member

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    I do not see a disadvantage in a short skirt, except for the lady wearing I suppose.
    I am ignoring the term"slugs"
     
    Last edited: Oct 13, 2017
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  15. HemiMagic

    HemiMagic Active Member

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    Stock GM engines are well known to breathe heavy and put lots of oil through the intake, I wonder what causes that? Worst part is it's not a problem restricted to the V8 engine either as the V6's are just as bad.
    Poor oil / air separation (PCV) I think.

    In regard to the V6, I believe the right bank PCV is very small and worthwhile modifying it larger.
     
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  16. 426Cuda

    426Cuda SUBLIME!

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    Huh, I done get it?;)
     
  17. 426Cuda

    426Cuda SUBLIME!

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    I think you've nailed it Mate.
     
  18. 426Cuda

    426Cuda SUBLIME!

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    Nope. Just do it Ron. Buggered if I'm waiting 7 years! (He says with total optimism)
     
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  19. Ron Burgundy

    Ron Burgundy Well-Known Member

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    I have the money ready but worried to stuff my 5yr factory warranty..
    Really wanna hold onto this.
    The car will be 1 yr old in 2 days ;)
    My brain tells me 'wait'.....but other parts of my body are saying otherwise....
    Not to mention my mrs who will flip the lid... :)
     
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  20. 426Cuda

    426Cuda SUBLIME!

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    Maybe go the Walky route?
    I reckon a reputable tuner and quality parts is a low risk proposition. They're not going to tune it to the point it burns a pistion, detonates like crap, risk throwing a leg etc. These are well built reliable engines and are underdressed and conservatively tuned in standard form. As Monstar has pointed out.many times. Much of the tuning parameters are for regulatory compliance / emissions. So, what are the chances a few bolt ons and good tune are going to contribute to a driveline failure? Slim at best I'd suggest. Holden would have to prove it had caused or contributed to deny a valid waranty claim.
    Get into it Mate. The car will be transformed.
     
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