A.Wayne

Looks like you took in coolant and hydro the rod ....

iloveporsches

First thing my roommate and I thought was hydrolock from coolant. I don't know if that explains the burnt #4 valve, though. Maybe ran lean, raised pressures, blew HG, and burnt valve all on a short period?

Bill

My guess would be that the motor failed from excessive combustion temps. White residue is indicator of excessive heat. Melted valve also shows excessive combustion temps. Piston siezed from heat, metal bits from valve or both. When piston siezed rod failed.

A couple of things can cause excessive combustion temps. Lean AFR, excessive boost, timing, restricted exhaust system. Did this car have an exhaust gas temp gauge? I just read an article in the July 07 Turbo magazine about the Zeitronix ZT-2 meter. I have one in my car and it is a great tool. In the article it noted that Zetronix has come out with the ZAV-1 alarm. It has both a LED and audio warning. The alarm can be programmed to sound or light up under two circumstances. I plan to get one of these if it is compatable with my ZT-2. I would set the ZAV-1 to warn me of boost over 22psi ( I run 21 psi) and egt over 1700-degrees fahrenheit (my car runs between 1250 and 1450). If you had one of these, it may have saved your motor.

Oddjob

For you guys stating hydrolock, what indicators are giving you that impression? Do 1-3 look washed to you?

In order for enough coolant to be drawn into the cylinder on the down stroke, there would have to be a large hole through the headgasket - see anything in the pics of the cylinder or the head that indicates a major headgasket burn through on #1?

I dont have pics, but there is some damage to a small portion the HG on #1. But it looks more like mechanical damage (like from debris flying around in the cylinder), than a burn through or delamination. But it may be a source for the leak...

lart951

I see no signs of hydro lock, # 1 was running too hot also # 4 so it melted the valve and then seized that's it. The white residue is signs of running too lean.

Bill

From the pictures, I do not see an indication of coolant in the combustion chamber. If the car burns coolant for any length of time, usually the piston crown and cylinder head will pit. To me the white residue and burned valve are the key indicators of what happened on in this motor.

Oddjob

Car is basically stock. Running stock boost. No EGT, no aftermarket boost gage. No obvious indication of impending doom before it let go. Temp gage was fine, oil pressure was high (possibly a little abnormally high), felt like it was making normal power, idled fine in the pit lane just 30 seconds before it blew up at turn 3.

I absolutely agree that at least #4 was lean, if not all four - which I am attributing to a fuel system problem; either a single bad injector on #4, or possibly a failing FPR that started losing pressure in the rail, causing all to go lean. Possible that an AFM would give the DME bad air flow data, causing it to run lean?

cruise98

I am with Bill on the excessive combustion temps causing the piston to seize, break the rod and destroy the block. All of the cylinders appear to have been running lean.

Oddjob

Also on #4, hard to see in the pic, but looks like the piston started to burn on the edge too. Or possibly damage from detonation or valve debris (location corresponds to the burned valve).

Bill

Water temp gauge is not a good indicator of what is going on inside the combustion chambers. Too slow. When you have a problem in only one cylinder, it has little impact on the overall water tempature of the motor. Yet that one overheated cylinder can cause a catastrophic failure. EGT is the best indicator. Look inside any factory Porsche race car to see the critical gauges required to assure the motor finishes the race. EGT, Fuel Pressure, Oil Pressure, Ect will be there. Sorry for your friends loss.

Oddjob

Absolutely. My comment was just stating that the car only has the factory gages, and nothing on those gages indicated a pending problem.

If the car goes lean in a full boost/full throttle situation, it will only take a couple seconds to start burning holes. Which is why the EGT alarm you mention is a good idea. Even with an EGT gage, you may not have time to notice the EGTs go through the roof before it melts down.

I do think that a leaking HG would (more often than not) cause the coolant temps to rise dramatically, unless it was an instantaneous/catastrophic HG failure.

Bill

In the case of a leaking head gasket, the coolant temps can definately be increased. The extent of the increase would depend on the size of the leak and the amount of time the leak has occured and has gone unattended.

First and foremost the greatest temp increase would come from low coolant levels due to the leaking head gasket. The second would be an increase in water temp from the lack of a pressurized coolant system. For every 2 psi in pressure increase, it increases the boiling point of coolant by 4 degrees. I think our coolant system operates under 22psi of pressure. Engines like to operate a 190 degrees, and non pressurized coolant boils at 210. Its all in the math.

xsboost90

personally- based on nothing- i would guess that the ring on that piston failed, locked and cocked the piston on that cylinder. Then the crank tryed to push it back up and twisted the rod breaking it off and the rest took out the oil pan. Now HOW the ring seized is a different story. Perhaps the piston became out of round somehow and finally took the rings out. If that cylinder was running lean, it could have burnt the valve, dropped pieces into the cylinder and then....well thats just my speculation.

ross255

For reference I have white soot in my exhaust, and its not running lean, or to hot, and thats looking at a wideband and a EGT, so I think you should take too much notice of it.

tyro

Jim

Something I just thought of:

Fuel. What was in it?

Fuel pump test, did/does it pass in terms of delivery rate?