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Engine: Stock bottom (~15k miles, 3k on boost), Alaniz head (minus port/polish), Vortech at 10PSI, 650cc, EMS (9500 timing cut, 9700 fuel cut), Proflow 70mm, Toda Header, test pipe, Spugen dual, stock plugs. 380whp@9000rpm
Scene of the crime: Long stretch of flat road, multiple high speed runs (150+mph). On the third run after a few mins of 9000+rpm 150mph driving, car was driven over a flat bridge (with pavement changes) and lost oil pressure directly after.
The Aftermath: Dip stick popped out, oil all over driver's side of engine bay/frame rail. Checked the oil and it was at the 4th X. No holes in block, all oil appears to have come out of dipstick hole.
Car is towed home and we begin to break it open. Removing the plugs begins to tell the story. Plug #2 has no electrode and all other plugs are black but intact. Pulling the head reveals this:
Damage to piston(and rings) #2 and sleeve #2. Other 3 cylinders look fine and head looks fine:
It is clear that the electrode breaking off caused the damage and ruined the rings on piston two. What is not clear is how the spark plug blew out.
Theory 1: Spark plug failed due to prolonged high boost pressure. Stock plugs were clearly not made to handle boost.
Theory 2: Spark plug heat range not cold enough, high combustion chamber temperature due to long high RPM run caused knock and melting of electrode.
Theory 3: Rapid unloading/reloading of engine/drivetrain from uneven bridge surface changes and 100% throttle position caused some kind of mechanical overrev or failure.
Thoughts? We are trying to rebuild in a way that will prevent this from happening again.
I would guess there was detonation in #2 but it would take more investigation to determine the cause. Certainly you want to check the injectors, ignition, etc. Could have been a plug issue as well. The subsequent ring breach certainly pushed high pressure through the crank case forcing oil out.. so you will need to check critical oiled parts for damage.
Um, is this (9500 timing cut, 9700 fuel cut) rpms? Unless you had internal work (tested and balanced etc) that's a bit high. You should have your fuel cutoff at 9200 or 9300 rpm. Any higher than that and your asking for trouble.
Besides that, didn't anyone ever tell you not to run 150mph on a public road? The states don't have an autobaun.
Um, is this (9500 timing cut, 9700 fuel cut) rpms? Unless you had internal work (tested and balanced etc) that's a bit high. You should have your fuel cutoff at 9200 or 9300 rpm. Any higher than that and your asking for trouble.
The limitation on revving an F20C is in the head. The possibility of valve float was eliminated with the use of double valve springs and Ti retainers. The head was capable of 11k RPM. Again, there was NO signs of valve to piston contact.
Besides that, didn't anyone ever tell you not to run 150mph on a public road? The states don't have an autobaun.
Agreed, but that is not what this thread is about.
I would guess there was detonation in #2 but it would take more investigation to determine the cause. Certainly you want to check the injectors, ignition, etc. Could have been a plug issue as well. The subsequent ring breach certainly pushed high pressure through the crank case forcing oil out.. so you will need to check critical oiled parts for damage.
We had hoped to determine the condition of the injectors/coils during the incident by reviewing the logs from the AEM but we have been unable to interface with it. Perhaps it is because all of the sensors in the engine bay are disconnected?
Originally Posted by Fyrestrike,Jan 9 2006, 11:28 AM
The limitation on revving an F20C is in the head. The possibility of valve float was eliminated with the use of double valve springs and Ti retainers. The head was capable of 11k RPM. Again, there was NO signs of valve to piston contact.
Agreed, but that is not what this thread is about.
my guess is detonation. but that's a loose theory based upon the story and the pictures. there is some obvious burning going on inside not just the #2 cylinder, but all the cylinders.
if the porcelain has black or grey spots, then that's also a sign of detonation. however, if there is a dry soot on the porcelain of the spark plugs, that can indicate running too rich.
Since the piston is melted, that would be a timing/detonation issue.
Do you think the plug broke apart, chipped the ring land... and then high RPM load melted the piston right where it was chipped?
The spark plug breaking out should have caused some mechanical damage somewhere else? Did it just magically disappear through the valves not damaging anything? Did you check your catalytic converter to see if the sparkplug piece is stuck in front of it?
The tough part about diagnosing this scenario is that what appears to be the two failure modes (broken ring land and broken spark plug) for your motor, are probably the two most common occurences with catastrophies for boosted motors.
Regardless, sorry for your troubles. At least this way you can build the motor you have always wanted to now!
01-09-2006, 05:34 AM
Blown Engine
