You guys should listen to what mkriebs is saying. Forged pistons are not ideal for daily drivers. Has anyone (meaning someone that logs daily) even tried them in the LNF for a daily driver? I forsee built LNF fail threads in a year.

 

I don't think the forged pistons will cause issues with failing, if the correct procedures are taken with them. For example, don't drive the car til it is 100% warmed up, otherwise you will burn oil like a biatch. The ping from the pistons is going to annoy some people. If you don't like the noise a lightweight flywheel makes, you won't like the forged piston's noise.

Its up to the buyer, of course, but I think whatever vendor that is going to do the group buy, should come up front and tell everyone the complications of having forged pistons.

 

Ok, to the people bringing up 500HP: ZZP ran that... what... once, for roughly 11.5 seconds? Either way, it's not running that reliably for long... much less if it was to be a DD... and the engine's already broken.

I'm planning on taking mine to a road course, where it'll likely face sustained beating far harder on the engine than just 12-13secs of beating. I don't mind warm up.

I appreciate the input (non sarcastic), but when all people have to say is that it's in the tuning, that doesn't actually help, because we have no idea and can't agree on what the "good tuning" is apart from one guy with partial tables through HPT that claims to be the sole person that knows, and yet we still can't rule out other possible causes either.

Just saying. We can't point fingers or claim solutions until we've got more information and evidence.

I'm simply offering people that wanted to buy some pistons a chance to do it a bit cheaper.

 

I agree completely with you, except that ZZP probably had 60-70 dyno pulls at that power. They never broke a piston either.

As for the tuning, there is plenty of info out there. I don't feel like bringing it all in here and cluttering it up. Basically, running to rich seems to be the common issue.

 

...except that every Houston failure except mine and an HHR on GMS1 (which has been said to be lean) has been tuned through HPT, supposedly not running too rich by what many have suggested.

This only helps to deepen the mystery, and is why I find the tuning scapegoat to be a hard one to grasp.

 

What afr were they running? Nothing was posted in the broken piston thread regarding their failure, unless I missed it.

 

12.8-13.0 to my knowledge. 13.0 at one point for sure (as 20Redline mentioned). I can ask them next time I see them for specifics.

Here's a thread that covers a lot of it. https://www.cobaltss.net/forums/2-0l-lnf-performance-tech-153/cracked-piston-possible-build-progress-need-some-advice-199878/

I've got food for thought: Some of the local HPT guys used the pill, bringing up boost, and therefore heat levels too. All of those guys except for one (which later uninstalled it, brought boost down to 17, and used meth) had piston/ring failures. It should be also noted that ZZP used a larger turbo, bringing heat down.

 

There are also alot of guys running the pill successfully. Lets take this to the other thread tho. I would like to see all the info together. Thanks for the link though, I have been keeping an eye on that thread... but i may have overlooked some things. Wait, wasn't that thread, it was a different one. The cracked piston info thread. Take it to there!

 

Agreed.



So... forged pistons. We're looking for at least one more person, to make it worthwhile for a vender. Got 4 people, with a 5th waiting on tax return. Make sure to familiarize yourself with the pros and cons of forged pistons before putting your name down.

 

Knock. I saw one of the logs from a car that that tuner did and the car had a lot of knock. Too much timing for those cylinder pressure levels.

 

The uneducated rule around here.

Keep knock in check, don't drive it wot 100% of the time, it will last. Knock absolutely kills hypereutetic pistons at a much quicker rate than they would a forged. They're quite strong actually but very brittle at the same time.

 

i am down for a group buy for the pistons. i blew my rings on the pill using hpt and my afr was 12.9-13.1 without knock and my maf was dialed in. alot of guys have been blowing their rings lately around here i know at least 3 tuned by trifecta and 3 or so tuned by hpt

 

Do you guys have horrible gas out in Texas or something?

 

im down for group buy def. i just blew my number 4 ring lands, replaced engine under warranty after i put all the stock parts back on

 

THANK YOU! I've been trying to explain this to some of these guys in several different threads on here but nobody is listening.

Alright, that's 6 with a 7th on standby.

 

Nobody is listening because there are plenty of people out there doing it and it IS working. And to bring up ZZP AGAIN, they didnt have a piston failure, the rods bent. Hurry up and start the Rod Group Buy now

 

x2
im gonna do my turbo swap and wait on any engine mods.

 

You're missing my point, the brakes thread is over a dozen pages long...the piston thread is a couple pages and most of it is just banter, not people complaining of a broken piston.

 

just going to say, with ZZP being at 500+whp, the pistons WERE NOT the problem, bending the rods were...

point being, with a good tune you'll need stronger rods LONG before forged pistons

now for guys wanting forged pistons, go ahead, do your thing... but this whole "LNF having piston issues" thing is blown out of proportion... that needs to be reworded to "my tuner isn't what he thinks he is"... because most of the guys who seem to know their way around these engines from top to bottom, aren't having piston issues

fueling issues, most definitely a problem
rods bending, well, the highest output LNF did at over 500whp, so the jury is still out for others to reach that landmark
pistons failing below 400whp.....tune related

 

This has happened on all three mainstream tunes, HPT, Trifecta, and GMS1, with HPT cases not being rich or lean and having no knock. I suppose GM has no idea what they're doing either. We've even had GM Engineers on here state at least twice what they think it is and being too rich for instance isn't one of them.

The brake topic is all on one thread for the most part, while the piston/ring issue spans several threads, with many cases being a simple post that people posted on a sometimes unrelated thread topic. There are many cases that haven't chimed in on that main ring/piston thread, but that doesn't mean they didn't happen or something.

I understand that some of y'all are convinced it's not a hardware issue, but besides one car that ran it for a very short time, what evidence is that based off of? I'm looking at a number of cases that span several tunes, including a manufacturer one, and we've got one case trying to say they're all wrong.

In your minds, is it even a possibility it could be heat? This issue tends to happen in high boost applications, the only surviving pill-running car here was on meth and now isn't running the pill, and in the ZZP case they used a larger turbo, bringing down heat.

 

css = fail thru the new year also...

 

ZZP took them to 500+whp without breaking them. I ran 30 psi thru the stock pistons and turbo for over 10K while running it on the dyno and drag strip PLENTY. AND, I by no means baby my car on my 100 mile daily trek back and forth to work. I live on a mountain, you can imagine the roads are fun, I drive them that way too.

Term is running ~25psi, as well as Broke and PLENTY of others on the HPT forums. Its in the tune.

Taken from another thread/post: https://www.cobaltss.net/forums/show...5&postcount=65

Quote:
Originally Posted by Zander916
Here's an interesting post I found:

"The LNF piston castings are made from a hypereutectic alloy. (high silicon content)
As such they have good strength, and low wear with a favorable thermal expansion characteristic.

Hypereutectic alloy pistons can be fitted to close tolerances since their thermal expansion at operating temperature is minimal compared to a forged piston.
The good cold fitment aids in the NVH department as well as the emissions department.

Now the trade-off: (there's always a compromise)

Hypereutectic alloy pistons tend to be more brittle and lack somewhat in high temperature strength compared to a forging.

What will kill a cast hyperutectic piston quickly is detonation.
The alloy being brittle simply will not withstand continuous hard detonation.
A forging is more forgiving in this respect in exchange for the requirement of looser tolerances and higher cost.

A lot of "horsepressure" can be made with cast pistons so long as detonation is avoided. That is where the knock sensing portion of the engine control circuitry comes in to play.

And don't forget those oil squirters in the LNF that direct cooling jets of oil to the undersides of the pistons, this helps as well.

Bottom line:

Uncontrolled detonation will kill a cast piston in short order.
This usually takes the form of broken (fractured) ring lands and/or skirts.
I speak from experience here. SBC days.

Uncontrolled detonation on a forged piston will beat the heck out of the bearings, crank, wristpins, rods, and will eventually melt pistons and valves.
I know about this too.$$$

Loud exhausts can mask the sounds of detonation.
This in conjunction with some mistuning and you have a perfect recipe for broken parts on any engine.

I speculate that as long as detonation is avoided 400 HP (crank) or more is doable without catastrophic damage to either cast or forged pistons.
And doing this will obviously wear everything in the drivetrain at an accelerated rate.

Cast is generally best for high performance street.
Forged generally best for racing as in long term WOT.

Rickey."

This is a link to that thread: http://www.solsticeforum.com/forum/f...sepower-60783/

Just thought it might help and give even more points of view

Sounds like the causes could be many things - including poor quality fuel for that kind of boost.



My own quote from that thread:
Its in the tune, as this writeup states well! High boost = high cyl pressure + heat, add some knock to the mix and watch the piston beat itself to death.


These cars seem to eat the front O2 sensor since it's in the turbo's exhaust housing. When that front O2 goes bad, the fuel trims go way out of wack and even my own car would have considerable KR thru light accel or WOT when it went bad. I didn't hear or feel it, but because I log the car constantly, I was able to see something was wrong. Then the idle went funky and that was the tell tale sign for the O2.

Im sure there are people out there now running on a bad O2 and don't even know it, especially those without a RPD to monitor KR on the fly.

 

The GM engineers think it is from extremely high cylinder pressures (too much boost). I still think that knock either too much timing or too rich or too lean is to blame.

 

Im not on this list of pill cars?? I didnt even use meth :facepalm:

 

I like... this is good stuff.

I've been looking into a new WB-O2 too, so I'll see if I get some improvement. No O2 codes, but under light throttle it'll sometimes go wacky.


In my post, I was talking about a geographic "here"... as in Houston and surrounding area.