[BXL4]

My 2015 328i has blown up. Cylinder #4 showing no compression. The others are fine. Two different shops say "replace the engine" and I may do that but neither can tell me what, exactly "blew."

I have a Stage 1 Bootmod ECU tune. Aftermarket chargepipe and downpipe along with a larger intercooler. I've practiced good, regular maintenance including new plugs and coils just recently and have never had a problem until now. 2 borescope reports same "we don't SEE a burnt valve."

I probably will repair this car as I still really like it but am puzzled as to why diagnostics are proving to be so hard to come by and would much rather fix something relatively minor than a wholesale engine swap, possibly inheriting some hidden problems in the replacement.

It did happen at a BMW Club track day but I'm a rookie and was driving with a club instructor learning the lines. Noticed a big loss of power exiting a turn at about 3500rpm and mid-throttle.

Thanks a million for your diagnostic ideas or personal experience with this engine.

[Billfitz]

Zero compression could be a number of things, none of them good. The only way to find out for sure is to tear the engine down, and if that reveals something that's not worth trying to fix you've wasted the cost of tearing it down.

[sspade]

More than likely a hole in your piston due to detonation (LSPI). Although not super common, its been reported on this very forum. Be sure to follow up if you do decide to open the engine!

[sqwinny]

Originally Posted by BXL4

It did happen at a BMW Club track day but I'm a rookie and was driving with a club instructor learning the lines. Noticed a big loss of power exiting a turn at about 3500rpm and mid-throttle.

My guess is going to be a mixture of inconsistent gas (winter this shows to be true), maintenance when racing ( coil + plugs + injectors), and/or oil starvation.

Remember when tracking and beating on the car, you are leaning on it to make more power.

Otherwise I could just have been sheer bad luck. N20/n26 has a history of not being the most reliable due to castings in the block, the oil pump pickup being smaller than your thumb, age of the car/motor. These things are at 10 years these days if not over.

[gameson]

no compression can not be due to timing chain?

[Billfitz]

Not likely, unless it was collateral damage.

[Polo08816]

Originally Posted by BXL4

My 2015 328i has blown up. Cylinder #4 showing no compression. The others are fine. Two different shops say "replace the engine" and I may do that but neither can tell me what, exactly "blew."

I have a Stage 1 Bootmod ECU tune. Aftermarket chargepipe and downpipe along with a larger intercooler. I've practiced good, regular maintenance including new plugs and coils just recently and have never had a problem until now. 2 borescope reports same "we don't SEE a burnt valve."

I probably will repair this car as I still really like it but am puzzled as to why diagnostics are proving to be so hard to come by and would much rather fix something relatively minor than a wholesale engine swap, possibly inheriting some hidden problems in the replacement.

It did happen at a BMW Club track day but I'm a rookie and was driving with a club instructor learning the lines. Noticed a big loss of power exiting a turn at about 3500rpm and mid-throttle.

Thanks a million for your diagnostic ideas or personal experience with this engine.

Track/road course is probably the hardest use case for an engine and when you factor an aftermarket tune in, it's likely a significant contributing factor.

If gaining power was that easy with no detriment to reliability, BMW would have already done it from the factory.

[MaverickCruise]

I think it was the sudden burst of torque that destroyed the piston position.
Most of the N20s I have seen were damaged at 3-4K RPM after full throttle. With the stock turbo, this rpm will reach maximum pressure, which may reach 25psi in an instant.
If you plan on rebuilding the engine, I highly recommend replacing it with forged piston connecting rods, as well as a brand new block.
I built a closed deck block and used it for 1 year with pressures up to 28psi and I am currently working on another wet cylinder liner

[vitofrompoland]

What was your oil level before? Was it at max or between max and min?
I heard, that in N20/26/55 engines, extremely right turn (like on a track) can cause loss of oil pressure, due to centrifugal force. I don't know if this is true.

[BXL4]

Originally Posted by Billfitz

Zero compression could be a number of things, none of them good. The only way to find out for sure is to tear the engine down, and if that reveals something that's not worth trying to fix you've wasted the cost of tearing it down.

That's the consensus and I'm ready to swap out the engine but it is frustrating to learn that while it might be something inexpensive (head gasket) learning for sure could make the ultimate repair cost much higher.

[BXL4]

Originally Posted by vitofrompoland

What was your oil level before? Was it at max or between max and min?
I heard, that in N20/26/55 engines, extremely right turn (like on a track) can cause loss of oil pressure, due to centrifugal force. I don't know if this is true.

It showed right at full on the electronic gauge (N20s don't have a dipstick).

[tgk007]

I have an n26 with 110k miles on it and after letting someone other than me drive it for a month I get it back and there is no compression in cylinder 2. Cylinders 1, 3, and 4 have normal compression. The engine had a custom tune, was full bolt on, had a stage 3 pure Turbo. I'm not sure exactly how hard this individual drove the car bc I wasn't there, but from what I've gathered she basically dogged it out. No respect at all for all the time and money I put into the car. I know the oil level was slightly low (a half quart low)...i.cant even say she was using 93 octane gas...considering the tune was for 93 OCT plus 50/50 water/methanol injection that would've been devastating. Check out.these pics of the second cylinder piston. I tore the engine down myself. Notice the chunk missing from the right side of the piston. What could cause this?

[sqwinny]

You answered your own question here. all these things can lead to other things. without a log or you driving the car could be anything.

“I know the oil level was slightly low (a half quart low)...i.cant even say she was using 93 octane gas...considering the tune was for 93 OCT plus 50/50 water/methanol injection that would've been devastating.”

[tgk007]

I meant what would cause that chunk to get blown off the piston? Some type of abnormal detonation?

[cfm56d7b]

BXL4 This is one of those “pay to play” cautionary tales.

It simply happened to you instead of another BMW enthusiast. No fun of course but the risks are always higher when adding something that BMW engineers did not plan for.

Engines can fail even under normal driving conditions. It’s rare but it happens. Manufacturing defects do occur and just when conditions are right (extra boost helps wear down the already compromised part) the failure happens.

Hope the new or repaired engine will be installed soon and you will enjoy the car again.

[sspade]

MaverickCruise exactly!

[sspade]

sqwinny the N20 was offered in NA Market up until (and including) MY2018... there are many out there with under 10 years on them.

[sqwinny]

Originally Posted by sspade

sqwinny the N20 was offered in NA Market up until (and including) MY2018... there are many out there with under 10 years on them.

Steven please reread the post by OP. 2015 car. If motor is original that means motor was assembled in 2014. OP made this post in December ‘23. 2014 -> 2023 is ~10 years. It’s not worth it to quote me in this thread on over technicalities of 2-5 months of a potential engines age of being built at the factory…

[G35POPPEDMYCHERRY]

Originally Posted by vitofrompoland

What was your oil level before? Was it at max or between max and min?
I heard, that in N20/26/55 engines, extremely right turn (like on a track) can cause loss of oil pressure, due to centrifugal force. I don't know if this is true.

N20 is a shit engine
My sisters totally lost compression cylinder 1 out of where

Piston ring was broke. Piston 1 and 2 were replaced.

Although it’s had some instances where it’s ran hot. Debri causing radiator failure, and one time ran out of fuel due to faulty pump. How does a girl driving around the city back and forth to work stock, fry a piston ring.

Lots of folks with timing chain issues.

[sqwinny]

Originally Posted by G35POPPEDMYCHERRY

Although it’s had some instances where it’s ran hot. Debri causing radiator failure, and one time ran out of fuel due to faulty pump. How does a girl driving around the city back and forth to work stock, fry a piston ring.

Lots of folks with timing chain issues.

We can point fingers but one of the most known piston ring issue motor of all time is the VQ Nissan motors and the famous VA ea888 early Gen motors.

Piston rings can be due to too many occuring knocks, bad gas, low oil level as a turbo motor WILL burn an amount oil eventually. Those 10k miles oil changes were the dumbest thing BMW started. so crappy gas + low oil + limited fuel can cause issues from one occurrence or over time.

If you run out of fuel because of a pump that happens from time to time. Fuel pumps are a forever components.

Although n20 has it faults, it’s not exactly any different from other cars. If you have a German car you play by German rules. If you don’t you are in for a bad time.

[G35POPPEDMYCHERRY]

Originally Posted by sqwinny

We can point fingers but one of the most known piston ring issue motor of all time is the VQ Nissan motors and the famous VA ea888 early Gen motors.

Piston rings can be due to too many occuring knocks, bad gas, low oil level as a turbo motor WILL burn an amount oil eventually. Those 10k miles oil changes were the dumbest thing BMW started. so crappy gas + low oil + limited fuel can cause issues from one occurrence or over time.

If you run out of fuel because of a pump that happens from time to time. Fuel pumps are a forever components.

Although n20 has it faults, it’s not exactly any different from other cars. If you have a German car you play by German rules. If you don’t you are in for a bad time.

agreed, any engine can have its faults. those oil change intervals was the ultimate fuck you to less educated consumers but alas they saved money by doing less CBS. so win win for BMW. My n52 still says 15k for oil changes

curious how low fuel or running out of fuel can cause piston ring trauma.

[sqwinny]

Typically the n20 and PWG n55 share many of the same components. When you have a customer who is driving and doesn’t check things every so often, these cars require maintenance on the schedule. You have to play by the German rules. If you say well I can stretch this out by 500 miles you are playing the not if but when game for lifespan of parts/fluids/etc. many people forget fuel injectors you can’t clean on Direct injection motors without removing them 100% and doing a supersonic clean or replace them every 50k miles or so.

Initially the n20 had plenty issues with the high compression motors. Some quality control, some manufacturing, some pure bad luck. With low oil pressure/fuel issues you can cause little and non feeling in the cabin knocking / but also at the same time LSPI is possible.

Bmw didn’t learn their lesson and did the same thing with the first gen b46 which was in the mini and high compression versions of the b46 in the f chassis. Needless to say the low compression pistons don’t really have an issue for n20/n26/b46/b48.

Sometimes it can be just sheer bad luck. In your other comment with the missing PCV hose, it’s clear your sister doesn’t work on cars or took it to get serviced recently and had an overall inspection done as the PCV hose was just hanging in the engine bay completely sheered off.