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I found out today that BMW is denying the warranty claim. Apparently cylinder 1 is scored and it appears that the ring or ring land is damaged. Compression on cylinder 1 was 85 while the others were normal. The ECU also indicated overboost at some point (not clear exactly when that occurred in relation to the problems with cylinder 1). BMWNA concluded that the overboost was caused by the Dinan tune and that the overboost caused the damage to cylinder 1. Based on my limited knowledge of engines, it seems that BMWNA’s conclusion requires that the overboost caused pre-ignition or detonation in cylinder 1. However, isn’t the BMW ECU and knock sensor support to adjust fuel and timing to prevent this? I don’t know enough about how Dinan piggyback tunes work, but the car did not feel any different immediately before I noticed a problem with the engine. In other words, it didn’t feel like there was any more boost than normal. Does this mean that a Dinan tune will always cause overboost readings? Or would an overboost reading only happen if something went wrong with the car and/or the tune? It also seems possible that the overboost did not happen in connection with the cylinder problem, but popped up sometime in the past. The dealer did not know when the overboost occurred or even if it happened on the same day as the engine problem. Right before the issue occurred, I did notice the car hesitate slightly at higher rpms (I was accelerating into the highway). Could the issue have actually been fuel delivery, which caused the cylinder to run lean? BMWNA as indicated that they have not seen any similar issues with any B58s so it must be the tune, but it seems that fact could justify the opposite conclusion. The issue hasn’t appeared in stock or tuned cars, which would indicate that there may have been a rare defect with a BMW part. That conclusion would make more sense if BMWNA said we have seen this before and only on tuned cars. Sorry for the long update, just a little frustrated.
Fortunately my BMW dealer has been very cooperative and understanding. They have definitely earned my future business. My Dinan dealer has been equally cooperative and helpful. I have recommended them to others in the past and I will definitely continue to do so. My car is going to be towed to the Dinan dealer for further evaluation and repair (hopefully). I have not received confirmation for sure, presumably Dinan wants to verify the cause before it makes a determination. I’m assuming they will take it up with BMW if they think or can demonstrate that BMW reached the wrong conclusion?
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