Technical #4 Cylinder is dead…any ideas as to what caused the failure?

IQraceworks

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Jul 7, 2020
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Wow......that random comment from 3 years ago really got someone so butt-hurt that they are still stewing on it today? Not only that, but to take the time to search through other forums and get screenshots? Wow...not sure if that's impressive, or just sad. Thanks for letting me live in your head rent free for the last 3 years.

Talk about emotionally fragile.......
 

SLOWESTN54

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Feb 9, 2021
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Oh my. Definitely a great guy. Shits on others asking for help, yet comes in here asking for help.
As the famous man once said
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IQraceworks

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Jul 7, 2020
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I would LS swap it if I blew my motor.
I thought about doing that....and I've built several LS motors for friends cars. The problem is that it's expensive. By the time you pick up an LQ4 (steel blocked 6.0 LS), rebuild it, put a good set of heads and cam in it, find a new/used transmission, get a Maxx ECU or other standalone, tuning, and mess with all the swap brackets for mounting......you are now into some pretty big money.

For the power im currently making with the N54 (around 575-ish), a set of good forged pistons and rods, and new bearings will set me back about $2k..and then I'm back on the road again. And I shouldn't have any more issues with rings...

An LS swap done right would easily cost 4-5 times that if not more by the time it's all said and done. I'm not saying it wouldn't be cool as hell though....maybe if I win the lottery.
 

martymil

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I thought about doing that....and I've built several LS motors for friends cars. The problem is that it's expensive. By the time you pick up an LQ4 (steel blocked 6.0 LS), rebuild it, put a good set of heads and cam in it, find a new/used transmission, get a Maxx ECU or other standalone, tuning, and mess with all the swap brackets for mounting......you are now into some pretty big money.

For the power im currently making with the N54 (around 575-ish), a set of good forged pistons and rods, and new bearings will set me back about $2k..and then I'm back on the road again. And I shouldn't have any more issues with rings...

An LS swap done right would easily cost 4-5 times that if not more by the time it's all said and done. I'm not saying it wouldn't be cool as hell though....maybe if I win the lottery.

I've built plenty on n54's and you will never do it for 2k, very budget build with many cut corners will set you back at least 3 to 4k building it yourself.

My last parts bill to do it properly with machine work because I cracked the block liners and had to replace the block was 5k not inc labour
and I get dealer discount on all the parts.

To get an LS to run those sort of numbers you dont need much, just a spring/cam package with rods and pistons which can easily be done for under 5k doing it yourself. A manual box is not hard to source or a cheap turbo 400 and you have a killer robust combo making same numbers.

If I ever break my n54 again its all getting turfed out and LS swap it will be, I should listen to my own advice as I rebuilt the engine like 3 times already in my own ride due to fault designs we never knew about the n54 had at the time of build.
 
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IQraceworks

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It all depends on what I find when I pull the head off of my motor. If it's just a broken ring and the cylinder looks fine, I'm just going to hone the cylinders, and put a set of Mahle forged pistons on the stock rods (assuming clearances are ok), install some fresh rob bearings, and button it all back up. According to Mahle, their pistons are sized for the stock bores...but until I can get them in my hands and measure them..who knows.

But if the cylinder walls are trashed....yeah, then it's going to get expensive and an LS swap might start to make more sense.
 
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martymil

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I would do rods aswell as they as weak as the pistons at the power level your at, if your aiming for any more power close deck the block. I would do it anyway and a set of stock size head studs and keep it to 600hp and no more.
 

IQraceworks

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Jul 7, 2020
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Missouri
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07' BMW 335i
Well, I’m finally making some headway on this project. I’m about half way through the “jerking the engine out” process. So far it’s not been all that bad…..just trying to keep track of all of the hardware and wiring, and where it all goes. It really helps labeling things and bagging up all the nuts and bolts.

I’ve watched a few videos, and it looks like the motor should be able to come out without taking the front off of the car…..straight out the top. This is what I’m shooting for, we’ll see how easy it is. I’m planning on leaving the transmission on the car, that should make things a little easier I hope.

J0HISnO.jpg
 

Coupes66

Corporal
Dec 26, 2017
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BMW 335i N54
Well, I’m finally making some headway on this project. I’m about half way through the “jerking the engine out” process. So far it’s not been all that bad…..just trying to keep track of all of the hardware and wiring, and where it all goes. It really helps labeling things and bagging up all the nuts and bolts.

I’ve watched a few videos, and it looks like the motor should be able to come out without taking the front off of the car…..straight out the top. This is what I’m shooting for, we’ll see how easy it is. I’m planning on leaving the transmission on the car, that should make things a little easier I hope.

View attachment 86446
I have changed my engine several times without removing the front or radiator but I removed the transmission. With the transmission removed, the engine comes straight up and out. I didn't remove the hood but made a couple of longer strut replacements made from some pipe to stand the hood straight up. I don't believe the engine can be removed with the transmission attached without removing the front.
 

IQraceworks

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Jul 7, 2020
243
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Missouri
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07' BMW 335i
Well, after 5 months...I finally got the motor pulled out of my car. Between work, family...over overall "life", I've been swamped. I went ahead and pulled it out the top, leaving the transmission and rest of the driveline in the car. It actually came out pretty easy....especially doing it all on my own without any help working the engine lift and/or moving the engine around as it was coming out.

I got tired of talking myself out of getting the stupid motor out...with a little bit of Christmas spirit and some beer, I came up with some extra motivation and just did it.....good lord, such a huge weight off of my shoulders getting that thing out of the car.

Now for the fun part...pulling the head off and seeing what is going on with the piston in cylinder #4. Forged pistons and rods are in the future I think...can't wait to get this thing back on the road! 👍

ieZ1U00.jpg
 

IQraceworks

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Jul 7, 2020
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07' BMW 335i
So......I figured out why cylinder #4 was down on compression. How's that for a cracked ring land? All the ring pieces were sitting down in the bottom of the oil pan.

I measured the factory ring gap and it was right at .009" on the top ring...no wonder the ring decided it had enough. For 550-600hp and 20+ psi of boost, ALL forged pistons manufactures recommend at least .018"-.022" ring gap. At least the cylinder walls were not damaged at all...I lucked out. Not even a scratch..not sure how that happened, but I'm crazy lucky. I checked the cylinder bores and everything is nice and uniform. Looks like all I have to do now is order a new set of rod bearings, forged pistons, and forged rods...and put everything all back together. Still going back and forth on if I should use new stock head bolts...or step up to head studs.... As far as head gaskets...is there one brand that's better than the others?

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wheela

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Jun 4, 2021
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Wow, defintaly lucky to not have damaged anything else.

What's stock ring gap spec? I saw on another forum about 0.005" - 0.012" for the top ring. Does that align with what you've found?
 

IQraceworks

Corporal
Jul 7, 2020
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Missouri
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07' BMW 335i
Wow, defintaly lucky to not have damaged anything else.

What's stock ring gap spec? I saw on another forum about 0.005" - 0.012" for the top ring. Does that align with what you've found?

The top ring gap on that broken piston was right at .009". From everything I've read online from manufactures who make parts for boosted motors....for the bore size of the N54 and boost levels, you want around .020"-.022" ring gap.
 
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wheela

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The top ring gap on that broken piston was right at .009". From everything I've read online from manufactures who make parts for boosted motors....for the bore size of the N54 and boost levels, you want around .020"-.022" ring gap.
Thanks, the bigger gap makes sense for higher power levels.

I was curious where 0.009" landed in the stock clearance range. Since your piston broke and a lot of people push the stock internals to similar power levels, I was curious if your's perhaps fell on the low end of the clearance range compared to others who haven't broken their pistons. I think 0.009" seems to be pretty much right at nominal for the range?

Are you planning on measuring the gaps on your other stock pistons for comparison?