Engine Dr.'s: Need help with autopsy of blown motor (w/ PICs)
#16
Originally Posted by Oddjob
One of the keys here: are 1-3 lean, or washed from coolant?
In discussion with some local guys - the ideas that have been tossed out:
1) running lean on all 4 - clean piston crowns and chambers, white soot in exhaust, burned #4.
2) blew headgasket, #1-3 are clean from coolant in the chambers, not lean. White soot in exhaust if from coolant, #1 hydrolocked and blew apart.
3) missing rod nut on #1 was loose. Car ran lean, burned #4, changing engine balance/increasing vibration at high rpm, rod nut fell off blowing engine apart.
4) running lean, #4 burned, #1 detonated/knocked and cracked the oil scraper ring, which stuck the piston.
In discussion with some local guys - the ideas that have been tossed out:
1) running lean on all 4 - clean piston crowns and chambers, white soot in exhaust, burned #4.
2) blew headgasket, #1-3 are clean from coolant in the chambers, not lean. White soot in exhaust if from coolant, #1 hydrolocked and blew apart.
3) missing rod nut on #1 was loose. Car ran lean, burned #4, changing engine balance/increasing vibration at high rpm, rod nut fell off blowing engine apart.
4) running lean, #4 burned, #1 detonated/knocked and cracked the oil scraper ring, which stuck the piston.
#18
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.
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.
#19
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...
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...
#20
Originally Posted by 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...
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...
#21
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.
#22
Originally Posted by 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.
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.
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?
#24
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).
#25
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.
#26
Originally Posted by Bill
Water temp gauge is not a good indicator of what is going on inside the combustion chambers. Too slow.
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.
#27
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.
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.
#28
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.