Cold start rattle on LS3 - piston slap :) Engine replaced

[Ron Burgundy]

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.

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 ?!

 

[Immortality]

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.

 

[HemiMagic]

Sounds like a Duramax......

 

[HemiMagic]

We all love a nice short skirt on our slugs. But, they do have their disadvantages.

I do not see a disadvantage in a short skirt, except for the lady wearing I suppose.
I am ignoring the term"slugs"

 

[HemiMagic]

↑
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.

 

[426Cuda]

I do not see a disadvantage in a short skirt, except for the lady wearing I suppose.
I am ignoring the term"slugs"

Huh, I done get it?

 

[426Cuda]

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.

I think you've nailed it Mate.

 

[426Cuda]

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 ?!

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

 

[Ron Burgundy]

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

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...

 

[426Cuda]

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...

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.