[suspect]

Originally Posted by whyzee125

A failing injector seems pretty likely to be the culprit to me as going lean under high boost produces an insane amount of heat in the cylinder if that were to ever happen. You already know you had a leaky one on that cylinder so seems quite likely that caused it. The O2 sensors only measure across the whole bank so one could easily go a bit lean without throwing your AFR readings off much in a log, especially if the other cylinders compensated.

Wouldn’t a leaky injector cause a rich condition? It might cause other cylinders to lean out because the ECU reduces fuel to them.

[whyzee125]

Originally Posted by suspect

Wouldn’t a leaky injector cause a rich condition? It might cause other cylinders to lean out because the ECU reduces fuel to them.

In theory yes but if an injector is failing, it can cause all sorts of issues. It could cause hydrolock in worst cases, or the car could lean them out, or cut that cylinder off, or it could not realize how much it's flowing, etc. I wouldn't assume that a bad injector is ONLY adding fuel especially if one now has little to no compression on that same cylinder.

[suspect]

Originally Posted by whyzee125

In theory yes but if an injector is failing, it can cause all sorts of issues. It could cause hydrolock in worst cases, or the car could lean them out, or cut that cylinder off, or it could not realize how much it's flowing, etc. I wouldn't assume that a bad injector is ONLY adding fuel especially if one now has little to no compression on that same cylinder.

Is there a way to prevent this in the future? It seems a failing injector can damage the engine at any time. I have the same symptoms on a stock motor. Will find out soon what the compression results show.

[AWD Addict]

Originally Posted by suspect

Is there a way to prevent this in the future? It seems a failing injector can damage the engine at any time. I have the same symptoms on a stock motor. Will find out soon what the compression results show.

Just keep an eye on your plugs for fouling or gasoline odor. Maybe at your regular oil change interval.

[iqraceworks]

Originally Posted by AWD Addict

Just keep an eye on your plugs for fouling or gasoline odor. Maybe at your regular oil change interval.

I never had any fouling issues, or rough start issues, or any gas smell in the oil. Just a rough idle...and after that I pulled all the injectors and found one that just slightly got wet on the end when fuel pressure was put to it. I'm thinking that there could have been something wrong with it...maybe went lean for a split second and cooked that piston.

Here is the log from the 3rd gear pull on the E40 tune I was running...same tune I've been running for 2 years without issues.

I think sometimes when you push these motors to the extreme....any little hicup is enough to cause a problem.

https://datazap.me/u/iqraceworks/v4-...og=0&data=3-20

[whyzee125]

Originally Posted by iqraceworks

I never had any fouling issues, or rough start issues, or any gas smell in the oil. Just a rough idle...and after that I pulled all the injectors and found one that just slightly got wet on the end when fuel pressure was put to it. I'm thinking that there could have been something wrong with it...maybe went lean for a split second and cooked that piston.

Here is the log from the 3rd gear pull on the E40 tune I was running...same tune I've been running for 2 years without issues.

I think sometimes when you push these motors to the extreme....any little hicup is enough to cause a problem.

https://datazap.me/u/iqraceworks/v4-...og=0&data=3-20

Agreed, when you push hardware right to the edge, you remove the buffer you have in stock form for when something inevitably goes wrong. That log looks clean. If there are no other symptoms of a failing injector, I agree that's likely not your issue. I misunderstood and thought you had a confirmed leaky injector.

[oVeRdOsE.]

Originally Posted by whyzee125

That's not what I'm talking about here, his O2's are fine but his piston/ringlands may have been damaged from heat. Yes, people do this with ST manifolds sometimes or there are heat sinks you can buy but totally different issue.

so you saying the reading of O2 on the whole bank can cause lean condition.

If it's the case, is it the O2 sensor or the range or the reaction time? assuming this is not a wideband sensor.

The moment the O2 have a out of range reading they code, and does not mean they are faulty, but what they read can be faulty. Just like issues we have on audi tuned car. Adding a elbow help on heat, spikes thus gives a more linear reading and dont fckup the a/f ratio.

On my car it worked for a while. then i added a stage 2 tune, the tune itself disabled the post-cat O2 and now the car rely only on the pre-cat O2. On a fsi engine. No issue so far, but running meth kit to avoid any lean, detonation and heat issue.

[iqraceworks]

Originally Posted by whyzee125

Agreed, when you push hardware right to the edge, you remove the buffer you have in stock form for when something inevitably goes wrong. That log looks clean. If there are no other symptoms of a failing injector, I agree that's likely not your issue. I misunderstood and thought you had a confirmed leaky injector.

I did find a leaky injector, but if I remember right it was on cylinder #2. My piston/ring problem is in cylinder #4.

Who really knows....maybe I can tell more after I get the motor out and apart.

[iqraceworks]

...hell, the more I think about it. I might run my bore scope down into the cylinder from the top. If it's not damaged, I might just pull the head, pull the oil pan, pull the piston/rod out through the top with the motor still in the car...and replace it with another stock piston and rings.

That sure would be cheaper and easier than dropping $2K+ in forged pistons and rods, bearings, gaskets, etc, etc, etc.....it's just a play car anyways, not my only form of transformation.

Just tossing out some ideas......

[whyzee125]

Originally Posted by oVeRdOsE.

so you saying the reading of O2 on the whole bank can cause lean condition.

If it's the case, is it the O2 sensor or the range or the reaction time? assuming this is not a wideband sensor.

The moment the O2 have a out of range reading they code, and does not mean they are faulty, but what they read can be faulty. Just like issues we have on audi tuned car. Adding a elbow help on heat, spikes thus gives a more linear reading and dont fckup the a/f ratio.

On my car it worked for a while. then i added a stage 2 tune, the tune itself disabled the post-cat O2 and now the car rely only on the pre-cat O2. On a fsi engine. No issue so far, but running meth kit to avoid any lean, detonation and heat issue.

Well what I was saying is that it reads the mean of the 3 cylinders on one bank since those collect into one downpipe/cat. If running lean, it will dump more fuel in all 3 but the only feedback the O2 can give the DME is the whole of those 3 cylinders so it can't accurately calculate one individual cylinder if there is an issue, unless it's by pulling timing or shutting that cylinder down which it will do in extreme cases.

[iqraceworks]

Yep....if one injector acts up and goes slightly lean when the motor is being pushed to the max, the DME might adjust the fuel too all 3 cylinders in the bank, but the lean one will still beat leaner than there others. I'm guessing this is what might've happened.

Not much safety factor when you are pushing close to 600hp at 25psi of boost on cast pistons. I don't think these N54's are really as bullet proof as people think they are.

[suspect]

Originally Posted by iqraceworks

Yep....if one injector acts up and goes slightly lean when the motor is being pushed to the max, the DME might adjust the fuel too all 3 cylinders in the bank, but the lean one will still beat leaner than there others. I'm guessing this is what might've happened.

Not much safety factor when you are pushing close to 600hp at 25psi of boost on cast pistons. I don't think these N54's are really as bullet proof as people think they are.

So your dark sooty spark plug is in #4 not #2?
I would say do what you suggested and get a new piston.

[oVeRdOsE.]

Originally Posted by iqraceworks

Yep....if one injector acts up and goes slightly lean when the motor is being pushed to the max, the DME might adjust the fuel too all 3 cylinders in the bank, but the lean one will still beat leaner than there others. I'm guessing this is what might've happened.

Not much safety factor when you are pushing close to 600hp at 25psi of boost on cast pistons. I don't think these N54's are really as bullet proof as people think they are.

for sure it's not bullet proof has people said. But there's not a lot of report about internal issues, unless people push more than 700whp or doing stupid stuff like cheaping on part and safety.

I read a lot and what all video about this engine before selecting my project.
I was hesitating hard on a B8.5 Allroad audi with a 3.0T S4 6mt drivetrain, or a E91 with a N54 6mt drivetrain. And the N54 was no match. I get a excel sheet on pros and cons and also part and cost of the project.

And after all the research I did not read much ''catastrophic'' failure on that engine , since the 3.0t fsi got way more.

Depends also on maintenance, I own the worst audi engine ever, most forums its filled of issues and blowout engine, touching wood, 93k miles on a aggressive tune, et I had no issue since 2015, no check engine, or anything.

[suspect]

Originally Posted by AWD Addict

Just keep an eye on your plugs for fouling or gasoline odor. Maybe at your regular oil change interval.

Is there any OBD app or device to monitor and flag any numbers outside of limits you can set? My ltft for bank 2 has been -7% all the time when cruising which might have shown a problem earlier.

[whyzee125]

Well a leaky injector is not an engine fault. N54's aren't bulletproof but they are strong engines relative to most other engines out there and can take quite a lot of power. Any engine is going to have failures when running compromised hardware. I don't think you were running too much power for the engine as you didn't bend a rod or anything.

[iqraceworks]

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!

[Shoooter_j]

Originally Posted by iqraceworks

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!

Great job! Looking forward to seeing the rebuild and nice garage setup!

[iqraceworks]

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?

[iqraceworks]

Well, I made some decisions and just got done ordering my new parts.

After looking and all of the info (good and bad) out there online, and considering that the stock parts lasted almost 2 years at this power level before the piston broke, I figured that I should spend some good money on some stuff...but not go totally nuts.

So I ordered....

Mahle Powerpack forged pistons
Manley H-Beam forged rods
King bearings
OEM head bolts
OEM Elring Head Gasket
..and some miscellaneous stuff.

I think that's a pretty reasonable combination of parts that didn't break the bank, and should add a huge amount of strength to the bottom end.

Now I wait.....

[iqraceworks]

Well, my Mahle coated forged pistons showed up today (shout out to CSPRacing for an awesome price ($908) and crazy fast shipping (got them in two days)). I measured them all up with my mic, and they are all +/- .0001" of each other as for as diameter goes. After measuring all of the cylinder bores, I'm going to have a .0025" piston to cylinder wall clearance...which is about perfect according to Mahle.

I think when this is all said and done...I'm going to start a post with all the N54 engine build info in one place. There is lots of great information out there on builing N54's from lots of smart people, but you really have to search for it. Hopefully I can put all the info in and engine build post and make it easier for other DIY'ers to find.

[iqraceworks]

Spent some time last night getting the block prepped, and file-fitting the piston rings. I went with .020" gap on the 1st ring, .022" on the second, and then left the oil rings how they came out of the box. I didn't have to file off much...the Mahle rings already came gapped pretty big. Just waiting for my Manley forged rods to show up....

[iqraceworks]

My rods finally showed up. These things are nice! All within 1.5 grams of each other.