ok, what do you make of this???? HG Failure....

[jc052685]

Ok, here is some pics of my recent HG failure and I am looking for some input on the cause of the failure. This gasket had about 6-7 miles on it before making 12 or so pulles on the dyno till there was a missfire. This was the cause. This failure is between cyl 3/4.

 

I saw no sign of detination in the head or piston surfaces. However if you look at the last few pics there is some deformity in the gasket.

 

 

 

 

 

 

 

[jeffer949]

Looks like classic detonation to me. IF you had a Metal headgaske in there your pistons would of probably gone.

[jc052685]

Looks like classic detonation to me. IF you had a Metal headgaske in there your pistons would of probably gone.

 

why?

[BRAAP]

100% sure, detonation!

 

Why? L-series are "hyper" sensitive to detonation as it is, and like any other engine, the addition of boost only exaggerates detonation, i.e. failed parts in very short order! This linked below discusses my theory of why the L-series is so hyper sensitive to detonation;

http://forums.hybridz.org/showthread.php?t=125186

 

Typical culprits for detonation are;

1) Too much ignition timing for the conditions, (boost, combustion/air/coolant temps).

2) Fuel quality too low of octane for the boost/temps/overall conditions.

3) Too much boost for the fuel and ignition settings.

4) Too lean of mixture for the boost levels run.

 

When running more than stock levels of boost, extreme care must paid to the tune, ie. fuel mixtures are rich enough and ignition timing is retarded enough for the boost levels, compression ratio, engine and IAT's, etc. Add to that the L-series hyper sensitivity to detonation and the tuner has to be very good at his job making sure the tune is "safe"!

 

ARe you running cast pistons? If so I'd be concerned about busted piston skirts or at least collapsed skirts. If you find big chunks of aluminum in the oil pan, that would be the pistons skirts.

 

 

Two things about your gasket reveal the story.

 

1) The bulging/deformed pushed out gasket.

2) Fretting/scuffing on the face of the fire ring.

 

Detonation severe enough that the head bolts/studs stretched as well as the cylinder head flexing enough to relax the clamp on the gasket allowing the pressures in the chamber to push the gasket outwards. It had lifted enough for the gasket to squirm on a few occasions hence the fretting/scuffing on the fire ring itself indicating the gasket was squirming between the head and block, this was happening over and over, not just once.

 

Between cylinders #3 and #4 is the hottest region of the head due to exhaust valves being adjacent to each other. Your head more than likely lifted in that region the most causing the gasket to completely fail right there allowing the combustion process to communicate between the cylinders through the gasket, effectively a blow torch between the cylinders.

 

 

 

As mentioned, a metal head gasket would’ve contained the detonation better than the FelPro resulting in the more obvious melted piston tops, possibly bottom damage as well. keep in mind detonation is not something you want to contain, in fact, you don’t it at all because it is BAD with a capital B!

Edited December 30, 2009 by BRAAP

[jc052685]

Ok, I agree with everything stated Paul. Now here is my question.

 

From my arrows could one say the gasket was not corectly aligned with the bore? Thus causing the fire ring to be exposed the the cumbustion chamber directly.Then the fire ring could then become a "hot spot" being a direct cause of detination its self?

 

It just looks to me like some of the fire ring was left exposed in the chamber....

 

 

 

 

 

 

[rejracer]

When exposed to that much heat the metal in the gasket will deform. When a gasket fails between cylinders like this, during the combustion process the high pressure of the firing cylinder forces very hot and burning gasses to the adjacent cylinder. To give you an idea of the temps involved, NOX starts forming in combustion process at about 2500*F. Detonation starts above that point, How much above I don't know..

 

At 4000 RPM the failed section of the gasket was seeing 4000 pulses of 2500*F gases being forced through it per minute. You are seeing the result of the failure, not the cause. Notice the discoloration at the break point, and that after .5" it returns to normal color.

 

The gases being forced through the gap is still in the combustion process, which means there's still quite a bit of oxygen in the mix. High temps + Oxygen + material = rapidly burning material. Steel burns just fine with high temps and Oxygen. Paul's analogy of a blowtorch is not an exaggeration.

 

How long was the car run after the gasket blew?

[jeffer949]

Ok well lets look at the name of the "fire ring" Its called that because it actually see's fire from the combustion. Do you have an over bore? If not then i doubt that it was actually in the combustion chamber.

 

Im trying to find my camera and I cant to show you a picture of what happens when the detonation is contained in the combustion chamber by a MLS HG. But i can't so ill try later. But picture what happened to your HG but down the side of my piston taking all the rings and ring lands along with it. Ill try to find the picture.

 

Also how much boost are you running and are you running ARP head studs?

[jc052685]

 

How long was the car run after the gasket blew?

 

 

We stoped the dyno run as soon as we noticed the misfire. I asume it was a slow blow that let a small amount of combusting gases past and into the next cyl untill there was enough loss in compression to cause a misfire.

 

I drove it home about 5-6 miles only with the injectors to 3/4 disconected.

 

Notice the discoloration at the break point, and that after .5" it returns to normal color.

 

Yes, this is what happens when the gasket material is burnt out from within the fire ring.

 

Ok well lets look at the name of the "fire ring" Its called that because it actually see's fire from the combustion. Do you have an over bore? If not then i doubt that it was actually in the combustion chamber.

 

+1mm over

 

also it is meat to see fire on its inner most surface and to dissipate this heat with the other 2 faces.

 

 

Also how much boost are you running and are you running ARP head studs?

 

 

14psi, did 309whp & 329ft/lb

[ktm]

You seem all set in your mind that the fire ring was within the cylinder. It most likely was not. You need to look for the obvious answers first, not the esoteric explanations.

 

Rejracer gave a great explanation as to what you are seeing when coupled with Paul's description of detonation. The detonation you experienced could have been brought about by: carbon build-up on the valves or pistons in the cylinder; too hot of a spark plug; transient lean condition caused by a loss of fuel (voltage fluctuation at the pump, clogged injector, clogged filter, etc.); too much timing advance; engine temperature too hot (especially since you are a dyno - 12 pulls!); bad gas; etc.

 

It's the detonation you don't hear that you need to worry about such as this case. I've seen my fair share of blown head gaskets!

[jc052685]

sounds good to me. Gonna pull a deg of timming out of the whole thing and fatten it up some around peak tq.

[ktm]

You said the HG only had 6-7 miles on it. Did you re-build the engine? You said that there was a 1mm over bore, while not drastic it is an increase in volume and your fuel map may need to be adjusted accordingly. In other words, you may have been lean afterwards if you used the same map.

 

Maybe a slightly leaner mixture coupled with dyno runs caused the detonation that would not have normally occured under normal circumstances. It's hard to say.

[ozconnection]

Do you have data logging with your engine setup?

 

Time to review your files and see 'whatsup'

 

Until you isolate the problem, keep using those cheap gaskets....it's what's saving your engine from complete failure. I'm actually pretty surprised that they can hold that sort of power and torque....(maybe not for long, like you found out) .

[jc052685]

You said the HG only had 6-7 miles on it. Did you re-build the engine? You said that there was a 1mm over bore, while not drastic it is an increase in volume and your fuel map may need to be adjusted accordingly. In other words, you may have been lean afterwards if you used the same map.

 

Maybe a slightly leaner mixture coupled with dyno runs caused the detonation that would not have normally occured under normal circumstances. It's hard to say.

 

 

Well, I was duking it out with a single turbo built g35......kept turning up the boost till pfffttt.

 

Junkyard motor that was rebuilt by some previous owner.

 

 

The car was on the dyno being tuned.

[ozconnection]

Well, I was duking it out with a single turbo built g35......kept turning up the boost till pfffttt.

 

Junkyard motor that was rebuilt by some previous owner.

 

 

The car was on the dyno being tuned.

 

Tuned?

[jc052685]

Tuned?

 

http://dictionary.reference.com/browse/tuned

[ozconnection]

http://dictionary.reference.com/browse/tuned

tuned

 

 

1. mod.
   tipsy; drunk. : Willy was a little tuned so Sally swiped his car keys.
   

I like this one the best!

 

Thanks for the definitions....Now I'm perfectly clear about you and your situation!

[jc052685]

tuned

 

 

1. mod.
   tipsy; drunk. : Willy was a little tuned so Sally swiped his car keys.
   

I like this one the best!

 

Thanks for the definitions....Now I'm perfectly clear about you and your situation!

 

lol.....

 

 

 

 

Anyway. Got the car all back together the other day. Finally drove it today and POP. Fresh Nissan HG dead. Got maybe 3 miles out of this one. So pretty much gonna burn this car to the ground!

 

 

Not really. Gonna double check the timming again since the oil pump gasket is leaking. I added some fuel @ peak tq but did not pull any timming to I will have it apart and back together before Sunday si I will report back.

[Zmanco]

I just skimmed over the thread again but don't see the timing table. Perhaps you can post it?

 

And are you sure that you have it calibrated properly? In other words, have you confirmed with a timing light that what you have entered in the table matches what you measure with the light?

[woldson]

Have you had the opportunity to see the new damage? Please post pics, or better yet, comparison pics.

[ktm]

Your timing is off. Adding fuel does very little for detonation resistance assuming that you are already tuned for boost. By that I mean if you are already tuned for an AFR of 12 to 12.5, adding more fuel will not help. You need to start pulling timing.

 

Do not simply pull 1 degree and try again, but rather pull 5 degrees. Start low and work your way higher, not the other way around.

 

I learned the very hard way trying to tune for California 91 octane. It acts more like 89 octane and my map was setup (based on others here) for 91 octane. As a result I blew quite a few head gaskets due to aggressive timing.