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Discussion Starter · #1 ·
My car went to limp mode, thought was bad coil or plug
Turns out cyl 6 is not happy

Now a short block from bmw is insane price

Should i opt to tear it down and fix or get 2nd hand motor?

Wondering can i replace the one piston and check the head if engine is in car?

Is oil likely to have metal in it from this? Drove it 30km like this

How much are the oversize pistons from bmw .2mm oversize and a rehone??

Just trying to work out cheaper option


 

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My car went to limp mode, thought was bad coil or plug
Turns out cyl 6 is not happy

Now a short block from bmw is insane price

Should i opt to tear it down and fix or get 2nd hand motor?

Wondering can i replace the one piston and check the head if engine is in car?

Is oil likely to have metal in it from this? Drove it 30km like this

How much are the oversize pistons from bmw .2mm oversize and a rehone??

Just trying to work out cheaper option


WOW.. sorry about your situation. What was going on when this happened? If it was me I would just get a used motor, chill for a little bit then sell the car. Really depends on your budget amd how you like the car.
 

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It is only a broken ring land, from the carbon build up on top of piston susceptible to detonation if you have a tune. Cylinder wall looks pretty good, you need to remove protruding burr/gouge to get piston out.
I think it is good to go even with a used piston
 

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With the high port velocity of the bmw cylinder broken off ring land should’ve got through exhaust valves cleanly on following exhaust stroke
 

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Open it up, and go from there. Your best case here is new piston, flush, and button up. Worst - new motor. That wall looks bad, but might be actually not that bad in reality. Go in hoping for the best but ready for the worst.
 

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Sorry for the dark day.
You can do as @ticat928 mentioned, in addition if you are lucky that chunk didn't damage the compression area, valves.
To replace the piston you would need to drop the subframe so inspect+clean the oil and Vanos pump. May flush the oil 3 or 4 times with clean filters and later clean the Vanos solenoids and it's filters, change the Vanos filter in the lower block. May also consider replacing the rods bearing, it is an investment in the hope of saving the engine.
 

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It is only a broken ring land, from the carbon build up on top of piston susceptible to detonation if you have a tune. Cylinder wall looks pretty good, you need to remove protruding burr/gouge to get piston out.
I think it is good to go even with a used piston
@ticat928 can you please explain what you meant about detonation as I don't know enough to understand? That is a lot of carbon build-up from op's images and op's signature shows he was running a tune. Are you saying the tune caused detonation which resulted in the carbon build-up or did you mean something else?
 

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Discussion Starter · #11 ·
Yep fast attack motorsport tune
Ill be loading stock tune after that!

I do drive pretty hard

Last time ill be tuning a car i think ive had way too many issues with these tuners
 

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yep unless the tuner discloses exactly what maps they've changed, and you can verify it yourself, not worth it.
 

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Discussion Starter · #13 ·
Can the head be removed
With engine in car?
Or just remove whole motor and start to strip down?
 

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Yes it can. But no point. U have to bore out the cylinders and get oversized pistons.
Do you really think he needs to bore? Scratch does not look bad enough to me, but hard to say with just a picture.
 

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Discussion Starter · #18 ·
Its fams tune

Not sure how to check
All i got from jim is it should not ping as the car has ionic knock sensing

$20k au this is costing me for unknown km motor but new rod bearings changeover
 

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Discussion Starter · #19 ·
I can assure you i have a knack for breaking things lol i am hard on my cars but not abusive and preventative maintenance is very big for me
 

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@Craze i remember seeing your posts in the infinity tune thread and it confused me. If i recall correctly, you are running 98 octane out there, right? If that’s the case, based on your previous repeated issues with pinging, even before this piston thing i was thinking there MUST be something else wrong w the motor. It would be really really tough to make a sorted s85 ping with 98... even if you tried to! Even w fams tune i would think. I could be wrong and I apologize if I’m misremembering anything (I’ve had some wine). But it would be a shame if you replaced your motor and this happened again due to an unresolved issue.
 
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