Already been researching the differences and wiseco pistons they are gonna make a bundle lol. Also learned that 07-early 09 sti's have the same problem cracked ring lands says prolly not an 08 Sti w/o some cracking when leakdown test done tuned and untuned with Hypereutectic pistons also interesting. Also says the zo6 has them and boosted another 150 hp above stock no problem with the same type of pistons and oil squirters.

What are our's not treated? What % silicon are the lnf pistons could not find a thing searching?

 

I never found the % either (was hoping the GM Ecotec Build Book would likst this )....that makes a huge difference in the strength of the piston, but reading the GM build book they pretty much state 300 is the number in whihc the pistons should be replaced, which leads to me believe we have higher silcon values (15-25%).

Pay to play

 

You don't need new pistons over 300. I think you read the SC book because many people are above 300. You probably need to upgrade when you near 400.

 

I think it is less a property of horse power and more boost and temp. With a ported head it is possible to run more power with less boost. So I wouldn't be suprised if boosting 27+ on a hot summer or spring day is the culprit here. Not to mention LNFs are known to have knock, even with the stock tune.

Good luck with the rebuild. Looking forward to seeing that thread and pics.

 

he has an ss/sc or so his about me says

 

http://gmtunersource.com/index.php/r...tec-build-book

Check out page 86...


I found it when I was trying to find the piston composition

Completely agree...just find it funny GM list it @ 300. It has ALOT to do with pressure/temp

 

Im sure you can get a forged piston which is made for the street. They have a different alloy with more silicone to keep them from expanding. Ill check on some and get part numbers as I was a wholesale engine parts dealer before I retired and still have my connections and discounts. Modern engines run tighter clearances.

 

LOL I got some good laughs out of this thread.

first off stock ss/sc pistons will handle well over 300whp, I had mine running 444whp for about a year, and over 410whp for almost 2 years., never had an issue, car still made 190psi compression on all cylinders when I tore the motor down. built motor was another story, but that was my fault.

as for the ss/tc issues, it's direct injection, problem is most people tune em like a standard engine, which you can't do. They do not like too much fuel at all. **** we run 28psi on pump gas on a stock ss/tc motor and only thing that let go was the trans (on a gt3076r mind you) run a 12.8:1 afr no knock, just added meth injection for egt's.

 

Makes sense

 

Big difference in temps when its a K04 vs GT30 @ those boost levels......And as mentioned our pistons are weak to Heat and knock

 

Rich is just as bad for this motor as lean. Trust me under real world loads (not a dyno) running in the 11s will cause rich knock at high loads. You need to learn to think outside the box as far as GDI is concerned. Take everything you know about SMPEFI engines and toss it in the trash If you run safe timing with no knock you can run up to 14.7 A/F at WOT on this motor. It could run leaner than 20/1 at cruising if we wanted to. GM tune is 14.0 at WOT from 2K to 4500. Does that cook the pistons? No. Even the satge kit at 22 psi runs the same A/F as the stock tune at 15 psi. GM feels that 14.0-12.9 A/F is safe enough (even at 22-23psi) for their 7 year 100,000 mile powertrain warranty Understand the design of the engine before you get lost in someone else's misguided ideas. Thinking running 11.8 A/F is safer on this engine than running 12.8-13.0 is far from the truth.

 

I was one of the ones with a cracked ring and cracked piston. https://www.cobaltss.net/forums/2-0l-lnf-performance-tech-153/piston-ring-failure-lots-pics-inside-lnf-196631/

I had Trifecta Infiniboost installed at the time. I drove mainly on stock tune though, which might make my case a little different than most.

In the Houston area alone, we've had no less than three cases ring failures, cylinder cracking, and/or compression loss suffered in TCs that were HPT Tuned. One had to get a new engine and is now going big turbo with forged internals now, another is going to rebuild his with forged internals and going big turbo, and the third just got his repaired but is keeping stock hardware for now. A fourth is showing signs of issues. And that's just this city and the ones I know of.

That stuff will happen as you start getting up there in power, so let's be fair at least. I know you're not a huge supporter of Trifecta, but it's good to have people come out and share things like this so we learn more about the limitations and people can learn about hardware and tune related issues as well as what seems to work best.

I'd be happy to try your tune out, but right now I'm invested in being either stock or on Trifecta, as are many others, so if there's information we can get from this... well... that'd be great for everybody. Make me an offer if you'd like though... I've got many HPT friends that could load it up on mine and it'd be a blast to see what the differences are. Otherwise I'm needing to stay with what I've got and make the best of it.

My cracked piston/ring was causing oil to get by too. I'd love to hear about people's experiences with forged internals. Nobody that I know of has gotten far enough with them or has enough time on them to know how they're working out yet.

I'm wondering if we're seeing a common cylinder 1 issue here. Does anybody think this could be a fuel starvation issue due to it being the last one on the fuel rail and causing a lean condition?

 

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.

 

Dang scott who is having these problems I only know of three people. You, justin had oil in the piston because it had a crack and is now going with forged internals to provent this from happening again. And david that all I know of who else I thought I did to but it was just the o2 sensor that needed to be changed.

 

it was 12.5-12.8 range but i know i wasn't gettin any knock at all during any range of rpm i'm tearin everything down next week i'll start my own thread and all to keep everybody updated

 

There is also an HHR in town that blew cyl 1 on GMS1. Guess what, ring gave way, cracked piston.

 

i just had the same problem with my t/c and i was under warranty,they gave me a new engine,head,everything new under the hood except my turbo and intake and charge piping,i had a cracked piston ring,misfires in cylinders 1,3 and 4 and it was cause i wasnt tuned..soooo get it tuned when you get all this done to it

 

Interesting. So I assume you were fully bolted minus tune, or did you also have something like a manual boost controller? What mods?

 

Brand "W' is he only aftermarket Piston company in the country that Forges it's own inhouse.
You will also have alloy choice for blown/spray or N/A applications.
Superiour ring land flatness to boot.
Several forging desighns also available.
ALL those Monster Trucks you see at Monster Jams use brand "W" not just the decal on the frame. Blown on Alky about 2,500 hp with std. forging.
These Forging's can be set up as tight or tighter than Hypertech or cast pistons. I wish all would get out of there head the 1970 technology that Forgins require more clearance. That is 40 year old technology.

 

i have intense stage 3 blew a hole in # 4 i took all the intense stuff off and put back on the stock stuff took it in under warrenty and got a new engine lol, the old one had 84,000 miles on it and i still have my stock clutch too lol , they came back saying the ecu failed and caused a full system spike and the cylinder had been failing for some time, so im guessing it was intense tuneing that caused it. also the throttle body shorted out to the day it blew as well what sux is i got a new engine with my old sc that has 84,000 miles on it go figure it was the stealership......

 

Back in the day Chevy had a close relationship with TRW Forged piston division in Cleveland.The Ford engine plant was just down the road. TRW sold off the piston division and the owners ran it into the ground. Not sure but much easier to do inhouse Low quality Hypertech pistons inhouse or they mabe outsourced from China.
Putting a Forging division inhouse would be incredibaly expensive.

 

hey term.. whered you go now that more and more people are having the problem and aren't trifecta tuned?

afr's not the only factor in a tune .. thought that seems to be what you bring up all the time..

 

he is in the other thread spouting about his af ratios.

he says 12.7 to 12.8 is the ratio to go with for power, yet ssturbd08 was tuned to that exact af ratio and blew his motor.

I do not disagree with leaning out a motor for more power, but at such high boost levels that are being run, it may not be such a safe idea, especially with a ton of timing.

 

the issue is more going to be with heat and excess boost. theres a reason that zzp runs meth on their setup.. and thats on a turbo that'll run relatively cooler because it's more in it's efficiency range at that boost level then the stock turbo...
yes the fact that trifecta has the ability to run high amounts of boost on the stock setup isn't going to help the issue however time after time vince has said the infiniboost wasn't developed to make it so stock turbo people can run alot of boost.. and advises people against it for multiple reason..

I don't claim to know how T2 tunes at all but theres alot of things to take into consideration

one thing that was mentioned in another thread that people don't seem to address is excess crank case pressure. think about all the high hp lsjs that have put breather filters on their oil caps and done other mods to help this issue.. high EGT's + excess pressure will break the weakest link, it doesn't matter if it's a perfect tune or not thats a formula for issues, thats why tunes across the board are having issues

I would be more concerned about figuring out how to work around the issue/ fix it

if it is an issue similar to the lsj piston 4 issue (though i wouldn't see how but it's awfully odd it's the same piston going on all the cars.) then what about looking into a center feed fuel rail? it would make for better fuel distribution

something like http://www. solstice forum .com/forum/891469-post1.html

 

If it was a fuel feed issue, wouldn't you expect to see a great deal of KR on the affected lean cyl?

When I do see KR step in, (1-3*) it's fairly even across the board or if it's just on a single cyl or two, it moves around the block.