Reason for Zero Compression

[TalonJohn94]

What do you guys think was the culprit?
Bad tuning and/or just old worn valve?
Most likely burned or most likely chipped?

Please help.

(The cylinder in question is #2, but the 3rd picture is cylinder #4)

 

[TOONAH]

There is no visual evidence of overheating, so I'll rule that out. If you look at the corresponding notch on the piston crown is there evidence that the valve hit it? If so timing might have been off. Stock valves, right? Were you thrashing the engine, over revving it? Valve "float" at high rpms does occur. I would check the valve height and the spring for proper tension. Perhaps the lifter stuck?

 

[TalonJohn94]

• There are no visible markings on the pistons.
• I know the engine wasn't overheated while this happened.
• I wasn't over-revving, just doing about 75 mph on the interstate. The car actually ran fine after the damage while cruising at a constant speed/rpm on the freeway, just no acceleration and poor idle of course.
• Yeah, all stock valve train.

 

[1sick91tsi]

I have seen a bad headgasket cause this. I think the coolant creates like a electrical current from the plug and acts like a cutting torch or something. Thats what I would guess.

 

[TalonJohn94]

If it is, in fact, DETONATION - why would this have occurred given my mods and the fact that I barely did my own tuning and erred on the side of rich?

 

[TalonJohn94]

Also, would it be wise to send my injectors out for testing to see if a bad injector was the culprit?

 

[TOONAH]

Well detonation is also known as pre-ignition, meaning that the air fuel mixture detonates for some reason and not at the prescribed tuning, say 5 degrees BTC. When the AFR is lean the resultant gases reach a higher temperature and even little bits of hard white carbon glow hot enough into the next cycle causing detonation usually prior to the prescribed timing (5BTC). So this if our valve is still closing when
the detonation occurs and if the rpm and the resonant frequency of the valve spring is causing valve 'float', the valve is basically slammed against the seat and breaks. Valve 'float' is something I have studied over the years. I am using Manley valves and springs which are superior quality to Mitsubishi OEM valves. Valve float is best described as a set of condions that occurs (usually) at high rpm's. Any moving part in a mechanical reciporcating machine is said to have a resonant frequency.
Just as speakers do. Engineers use "F sub r" = 1 over the square root 2pi L C squared formula in electronics to make sure that the resonant frequency of the speaker is less than its normal intended range. If the F sub r occurred at say 1KHz the speaker would have a power dropout at that frequency or conversely it could go into an exponential sympathetic oscillation untill it ripped itself apart.
So usually the F sub R is 10 Hz less than what the human ear can hear, say 40 Hz.
Well the same is true of mechanical parts. Essentially in the case of the valve, if say 7500 rpm occurred at the F sub r of the valve spring, the result is the loss of spring tension at that given instant. So if detonation also occurred say 10 BTC and the valve was still open by 2-4 mm it would be slammed against the seat and fracture. Well of course the Mitsubishi engineers would not design it that way. But we all know how metal tempering works, so repeated momentary overheating of any steel part changes
its characteristics. Springs and exhaust valves especially.
When you get it fixed, do yourself a favor and get a data logging UEGO so that you can see exactly what is happening over time.
Hope you will forgive me for going on about resonant frequency, but it is a very powerful concept. It is exactly how a wine glass can be shattered by applying a sound of the correct volume and pitch at which the glass is resonant. Somehow energy is added to the sympathetic oscillations in the glass and it goes into a form of self destructive energetic runaway. In Electronics we call it "thermal elibriation".
It is therefore possible to cause any electro-mechanical device to self destruct, simply by injecting some current, in the correct phase and frequency into the system at the correct point of entry.
What I am saying is that it is possible for a machine to shake itself apart if all the components F sub r's are not factored into the design equation.

 

[blackrosenova40]

Post a picture of all your spark plugs.

 

[TalonJohn94]

Ok, I'll do that. Btw, I can already tell you that the cylinder in question's spark plug was black.

Doesn't that suggest a rich condition?

 

[BogusSVO]

I have seen burnt valves for several reasons, most likely the valve was not seating fully, due to a heat warped valve, cracked seat, carbon build up around the valve stem around the guide area....

when it happens, when combustion happens, the air/fuel mix acts like a torch and cuts thu the opening causing it to enlarge.

 

[TalonJohn94]

So, essentially a rich condition (visa-vie carbon buildup) can cause this sort of valve destruction?

 

[TOONAH]

Not likely. A lean (extra heat) condition causes carbon deposits to become hard and brittle, grey/whitish in color. The hardened carbon acts like a glow plug and can cause pre-ignition on the next compression cycle.
Guess no one likes the valve "float" theory, huh?
It is scientific and is well documented. Besides your valves don't look burnt.
The nature of the missing piece looks like it hit hard and shattered along fracture lines. It may have been faulty out of the box. Take it out and have take an x-ray photo of it taken, (anybody got an x-ray camera!) I'll bet you $100 you will see more fractures in it.
Have you checked the oil pressure in the head? It the automatic lash adjuster (lifter to you yanks) failed to pump up on that stroke the excessive lash in the valve could have caused it to slam into the seat with enough force to break a piece out of it, especially if it came out of the mold flawed. Yes OEM valves are cast while Manley valves are forged.
Please feel free to challenge me if you want, but I think I have more science backing my idea.
In my many years of troublshooting some highly complex electro-mechanical devices, I have come to learn that many radical and terminal failures are caused by multiple events occurring at a simultaenious moment in time.

 

[TalonJohn94]

Well, I can't check the oil pressure in the head anymore. However, I will try to check the lash adjuster and I might even have access to an X-Ray machine because a friend of mine does aeronautic welding.

So, if this is a result of a lean condition rather than anything else - how do I prevent this in the future with my level of tuning capability? I mean, I was just tuning for zero knock in high throttle conditions and perpetually struggling to lower the other two fuel trims from 139% to 110% at best?

 

[TOONAH]

Gold Diamond,
The message I was trying to get across is that it probably is not a tuning issue.
Other than looking a little oily, the valves look normal. Not black and sooty, not pure off white either. There is some hardened grey/whitish carbon deposits on the valve. What I think is that the valve was had hairline cracks (faults) right out of the box. It just took the right conditions to finish it off. Get some good forged stainless steel valves. Do not bother porting a 1G head. The exhaust valve bowl/port is too thin to bother machining any off. Just had one blow a pinhole coolant leak.

 

[TalonJohn94]

TOONAH,

I think I understand your position now. Here's my plan:

New (3g) lifters
New forged stainless steel valves (Any suggestions?)
New valve seals
OEM Head gasket
ARP Head studs
Trim the engine mount to accommodate the studs
New exhaust manifold studs and crush washers
New valve cover gasket
Install AEM WB O2

Other Notes/Questions:

The timing components/water pump are only a couple thousand miles old
Do you suggest new valves "keepers" or guides?
Is there a way to test my valve springs before reinstalling?

Thanks again

 

[BogusSVO]

you may want to change the seats in that cylinder of the head also....

 

[turbotsi92]

TOONAH,

I think I understand your position now. Here's my plan:

New (3g) lifters
New forged stainless steel valves (Any suggestions?)
New valve seals
OEM Head gasket
ARP Head studs
Trim the engine mount to accommodate the studs
New exhaust manifold studs and crush washers
New valve cover gasket
Install AEM WB O2

Other Notes/Questions:

The timing components/water pump are only a couple thousand miles old
Do you suggest new valves "keepers" or guides?
Is there a way to test my valve springs before reinstalling?

Thanks again

If you are going with the above i would not go with the OEM Head Gasket, go Cometic.

 

[TalonJohn94]

you may want to change the seats in that cylinder of the head also....

You think this is necessary even when valves weren't bent?

If you are going with the above i would not go with the OEM Head Gasket, go Cometic.

Why exactly?

 

[MY1GDSM]

If you are going with the above i would not go with the OEM Head Gasket, go Cometic.

A Stock gasket with some copper spray & APR's will hold 30Psi All day long... .
If he did Go with a MLS head gasket I'd say get an OEM MLS long before a Cometic

 

[turbotsi92]

You think this is necessary even when valves weren't bent?



Why exactly?

If you are going to go with the ARP head studs (i am presuming you are thinking from a high boost perspective), then I say Cometic for the exact same reason. If you don't have any plans to run high boost then why even put the head studs in there.

QUOTE=turbotsi92;152019651]If you are going with the above i would not go with the OEM Head Gasket, go Cometic.

A Stock gasket with some copper spray & APR's will hold 30Psi All day long... .
If head did Go with a MLS head gasket I'd say get an OEM MLS long before a Cometic[/QUOTE]

Why would you say go that route before a cometic. Dacowgod (tuners member) is running 44PSI on a Cometic, and he put down 574AWHP at the shootout on Buschur's Mustang Dyno. I am not saying that OEM with copper spray is not a good option, but the Cometic's have always been bullet proof from my experiences.

 

[TalonJohn94]

Just to be clear, I don't plan on going much further than current mods other than a front mount and better tuning. I know people say that, but I'm certain. The most boost this cylinder head will ever see is 24-25psi from my E316G.

but the Cometic's have always been bullet proof from my experiences.

But will it definitely seal even if I don't get the head decked?

 

[TalonJohn94]

Does anyone think I need to check or replace my valve springs in this situation?

 

[dsm-onster]

That valve just doesn't looked burned. Sorry. It's not a simple burned valve problem here based on the pics shown. It looks like it flaked apart. Something contacted it. Or it was weak.

Detonation, which is not preignition, could have done it. But not likely in the least. . .

You springs should be fine. But I'd of course check them. . .

As mentioend DEFINATELY DEFINATELY DEFINATELY check the valve seat. burnt valve or any valve damage means that theres a HUGE chance the seat is forked. You will need to have it replaced 99.999% of the time.

 

[TalonJohn94]

Oh wow, I didn't know the seats were that commonly replaced. What's the checking procedure?

 

[TalonJohn94]

Please define the valve seat being "forked."

Also, yesterday I checked for cracks in the cylinder head with some special dies which showed no cracks.