Topic: LNF engine failed

[Arabas]

bad news from Greece.
a friend had a problem with his LNF engine. the idle was rough, car started not working properly, and there was a lot of smoke coming from the engine.
he drove to the dealer and after seeing that in cylinder one there was no compression, they had to open the engine and see whats going on.
today, they reported to him.

piston is melted and there is a small scratch in the cylinder...
they still haven't decided if they will cover it under warranty or not.

Any ideas of the possible cause or any similar incidents?

[Carbon Sky]

Melted piston is likely from running too lean.

bad news from Greece.
a friend had a problem with his LNF engine. the idle was rough, car started not working properly, and there was a lot of smoke coming from the engine.
he drove to the dealer and after seeing that in cylinder one there was no compression, they had to open the engine and see whats going on.
today, they reported to him.

piston is melted and there is a small scratch in the cylinder...
they still haven't decided if they will cover it under warranty or not.

Any ideas of the possible cause or any similar incidents?

[DeepBlueGXP]

Agree

[Arabas]

running too lean sounds reasonable to me.
could this be from bad gas, incorrect tune, fail of spark plug, fail of fuel rail or something else?

any similr incidents you ve heard of Carbon Sky?

[Carbon Sky]

Likely a result of the tune, asking for unsafe air fuel ratio mixture.  If not that, it could be they defeated overboost safeties, and as a result, it was boosting more than the fuel system could deliver.  I doubt this is the problem because the injector's at full tilt, on a stock turbo, barely hit high 30%, maybe low 40% duty cycle.  So they should be able to deliver enough fuel to prevent this problem, unless the tune is preventing it from doing so.

Could be bad gas, or dirty gas rather, partially clogging the fuel system, not allowing it to deliver sufficient fuel.

Odds are high that it was simply a bad tune.

running too lean sounds reasonable to me.
could this be from bad gas, incorrect tune, fail of spark plug, fail of fuel rail or something else?

any similr incidents you ve heard of Carbon Sky?

[Arabas]

if it is the result of the tune, wouldn't all pistons be damaged (some more, some less)?
i have been thinking of all these possible causes and i was counting on a bad fuel rail on cylinder 1 (i don't know if i m using the correct english term here)

[Carbon Sky]

My guess is that is likely a part of the fuel system, that becomes an issue beyond originally designed operating range that tends to affect cylinder 1 before the rest.  In most of the LNF engine failures, they've primarily been melted pistons.  And most of the time, it has been cylinder 1.

if it is the result of the tune, wouldn't all pistons be damaged (some more, some less)?
i have been thinking of all these possible causes and i was counting on a bad fuel rail on cylinder 1 (i don't know if i m using the correct english term here)

[Yogi]

Here's a similar story for you, Arabas:  http://www.solsticeforum.com/forum/f63/burnt-pistons-63665/

Pls let us know if you figure it out!   

[Critterman]

There have been several instances of this happening always #1, probably because of the way fuel is delivered from the back to the front.  Do a search on the skyroadster forum, and the BB solsticeforum.

They are probably in the archives.

[Kelu]

There are tons of reports like this over Cobalt forum, most referring to #1 piston. The statistics were like same % between stock engine, gmpp engine, hpt tuned, trifecta, so it's about the engine.
I wouldn't blame the tune, the most users affected by this were in Texas area where is known for bad gas.

Arab: just for the record, what tune he had, what gas? He was logging it from time to time?

[LatinVenom]

I agree about jumping a little to fast and blame the tune.

[Kagem]

Our friend has the same tune as we do. Just tune nothing else, the rest of the car is stock. We know that there might be many reasons that concluded to this result, but all this time we thought our engines could handle up to 400+ horsepower with stock engine parts and that is the reason we seem to be surprised with what happened. We hope everything ends up well for our little friend, positive thoughts and wishes needed....

[2kwk4u]

hmmm  I'm not sure that #1 being at the end of the fuel rail NECESSARILY means anything.  I'd be more inclined to believe that this could be a design fault of the fuel rail itself.  If all 4 injectors were firing at once, I'd buy the distance from the fuel pump as a factor.  My guess is if the pump or pressure regulator was failing it wouldn't always be #1 that melts.

[Mac]

Our friend has the same tune as we do. Just tune nothing else, the rest of the car is stock. We know that there might be many reasons that concluded to this result, but all this time we thought our engines could handle up to 400+ horsepower with stock engine parts and that is the reason we seem to be surprised with what happened. We hope everything ends up well for our little friend, positive thoughts and wishes needed....

"but all this time we thought our engines could handle up to 400+ horsepower with stock engine parts"

From what i have read from gm the number is 300hp not 400hp. over 300 they recommed forged pistons, and the list grows from there. considering 2liter and 150hp per it seems asking alot to expect 200hp per liter or 100hp per hole. and not expect it to wear out rather fast or burn up. Back in the day i raced my z28 at OCIR just for fun with 427's i would break 2 to 3 a year. If you play hard you pay too.   


Seems that GM is pushing stock limits with the gmpp tune.  I know here in AZ 91oct  gas is not enough to keep it out of detonation under mid rpm wot. Even with a auto that down shifts as needed. I run half a tank of sunoco 100 uleaded and it runs so much better. In fact with the 91 rot gut they sell today compared to a full tank of 100sunoco it is like having the GM tune or not. Issues with detonation are much worse when it gets to 120degrees. but we have 100 to 110 pump gas at about every station here in town, but it aint cheep starts at 6.19 a gallon.

[Kelu]

but it aint cheep starts at 6.19 a gallon.

That is exactly how much we pay for a gallon of our top fuel around this part of the world. Our top fuel is "similar" to your 93, sometimes worse, sometimes better.
Believe me, you don't want to live in Athens or Bucharest (my city) and had to drive everyday in the city. I average 13 mpg because of the traffic.
So, we should be the ones complaining

[Mac]

you know that is how i justify, spending 6+$. so how much is sunoco or other racing fuel there? if it can be found?  i only use sunoco as it is the least expensive here and the station is just down the street by the lake. the performance boat guys put about 100-200gal in those boats. good thing i do not have a cigar boat that has that kind of need. 600-1200 bucks to go for a cruise, the solstice about 90$ if i fill it up, last about 3 weeks. they can burn those tanks out in a day.

[NormSky]

If the injectors are near static or open just about all the time, a drop in needed pressure would result on the furthest injector on a stock or GMPP tune. The root cause would be low pressure at the injector because of the rail design or the open injectors. There could be a temperature increase on the cylinder also. Even a single, cooler range spark plug might save the engine.

Norm

[LatinVenom]

That is a good point about the colder plug. This is the reason why I do not understand why GM went to the hotter plug.
The original plug was a colder plug and that is what is on my car. (GXP 2007)
If it ever needs changing it will be replace with the same cold range plug, available from other manufacturers since the 102's can no longer manufacturer.

[seal9]

I would be looking at a water/meth injector set up to add octane ( 50/50 mix should give 100) , and cool it out a bit ..seal9

[shabby]

If the injectors are near static or open just about all the time, a drop in needed pressure would result on the furthest injector on a stock or GMPP tune.

The lnf injectors run at around 25% duty cycle.

Btw Arabas what tune did your friend have?

[Mac]

Seal9

I have thought about that, but i know little about the set up and how that would work with the GMpp tune. If someone makes a stand alone setup that wont need a special tune that would be a less costly way to go in the long run.

Colder plug for sure will help but if you live in a cold area it may not start very easy and or run rough could even foul up if not run hard enough, i think the later wont be an issue

[2kwk4u]

The lnf injectors run at around 25% duty cycle.

Btw Arabas what tune did your friend have?

It wouldn't make sense in a direct injection engine for the injectors to run much more than a 25% duty cycle if you think about it.  You're spraying fuel straight into the combustion chamber.  If the injector is firing during the exhaust stroke, for example, you would be pushing fuel straight past the exhaust valve.  I guess up to a 50% duty cycle would be feasible (spraying on intake and compression strokes).

[sunnygator]

Not sure I understand why colder plugs would help significantly, unless you think the problem was caused by early ignition from overheated plugs, and that's not what I' hearing.  Or do you think the colder plugs suck out enough heat to make a significant difference?  Just wondering.

....and my curiosity is peaked by the fact I've had clogged injectors creating misfires in the past, as well as the hotter plugs......

Sunnygator

[Gentleman Jack]

Sunny,
I was wondering the same.

Is the recomendation that everyone change to colder plugs?  As far as I know I still have the original plugs and haven't seen any problems.  I thought the change in plugs was for folks who drive short distances often and don't heat up the engine enough?

What did I miss?

GJ

[Sol Asylum]

A hotter plug will retain more heat at the electrode part of the plug.  The porcelain part of the plug is shaped so that it has more surface area before it joins the body of the plug which makes it harder for the heat to transfer to the body and be dissipated.  Because the plug is hotter it makes it harder for carbon to form on the electrode and reduces carbon fouling, which is what causes the hard start and rough running.  The down side to this is that you now have a hotter hot spot in the cylinder which can cause pre-ignition or knock/ping.  Higher octane fuel will help reduce the pre-ignition.

Pre-ignition actually is trying to drive the engine back wards which causes a lot more stress on the engine and if you think about it hot gases will actually be present inside the engine for a longer time before they get exhausted.  This causes higher cylinder temps which only makes the pre-ignition more likely the next go around and things get worse.  You could be literally pouring fuel on the fire.