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BMW 3-Series (E90 E92) Forum
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Well...figured out my rough idle issue. Low compression in #4.
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07-11-2023, 12:15 PM | #23 | |
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07-11-2023, 12:18 PM | #24 |
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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.
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07-11-2023, 12:38 PM | #25 | |
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07-11-2023, 01:11 PM | #27 | |
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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
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07-11-2023, 01:18 PM | #28 | |
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07-11-2023, 01:25 PM | #29 | |
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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. |
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07-11-2023, 01:26 PM | #30 | |
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Who really knows....maybe I can tell more after I get the motor out and apart.
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2007 335i, BMS DCI, BMS Chargepipe w/Tial BOV, ARM Catless Downpipes, silicone inlets, Bilstein B12 Prokit Suspension, Whiteline subframe bushings, Front/Rear M3 control arms, G-Plus FMIC, Stage 2 LPFP, Custom E40 tune by Justin (V8Bait), xHP stage 3 transmission flash, RB Two Turbos....10.90 @ 128mph
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07-11-2023, 03:12 PM | #31 |
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...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......
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2007 335i, BMS DCI, BMS Chargepipe w/Tial BOV, ARM Catless Downpipes, silicone inlets, Bilstein B12 Prokit Suspension, Whiteline subframe bushings, Front/Rear M3 control arms, G-Plus FMIC, Stage 2 LPFP, Custom E40 tune by Justin (V8Bait), xHP stage 3 transmission flash, RB Two Turbos....10.90 @ 128mph
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07-11-2023, 05:38 PM | #32 | |
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07-11-2023, 05:45 PM | #33 |
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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. |
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07-11-2023, 06:07 PM | #34 | |
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I would say do what you suggested and get a new piston. |
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07-11-2023, 06:24 PM | #35 | |
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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. |
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07-11-2023, 06:35 PM | #36 |
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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.
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07-11-2023, 11:04 PM | #37 |
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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.
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12-25-2023, 09:51 PM | #38 |
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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! ![]() ![]()
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![]() Last edited by iqraceworks; 12-25-2023 at 09:58 PM.. |
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12-26-2023, 06:44 PM | #39 | |
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12-30-2023, 06:34 PM | #40 |
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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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12-31-2023, 02:50 PM | #41 |
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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.....
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2007 335i, BMS DCI, BMS Chargepipe w/Tial BOV, ARM Catless Downpipes, silicone inlets, Bilstein B12 Prokit Suspension, Whiteline subframe bushings, Front/Rear M3 control arms, G-Plus FMIC, Stage 2 LPFP, Custom E40 tune by Justin (V8Bait), xHP stage 3 transmission flash, RB Two Turbos....10.90 @ 128mph
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01-04-2024, 09:06 PM | #42 |
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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. ![]()
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2007 335i, BMS DCI, BMS Chargepipe w/Tial BOV, ARM Catless Downpipes, silicone inlets, Bilstein B12 Prokit Suspension, Whiteline subframe bushings, Front/Rear M3 control arms, G-Plus FMIC, Stage 2 LPFP, Custom E40 tune by Justin (V8Bait), xHP stage 3 transmission flash, RB Two Turbos....10.90 @ 128mph
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01-09-2024, 07:54 AM | #43 |
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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....
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2007 335i, BMS DCI, BMS Chargepipe w/Tial BOV, ARM Catless Downpipes, silicone inlets, Bilstein B12 Prokit Suspension, Whiteline subframe bushings, Front/Rear M3 control arms, G-Plus FMIC, Stage 2 LPFP, Custom E40 tune by Justin (V8Bait), xHP stage 3 transmission flash, RB Two Turbos....10.90 @ 128mph
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01-10-2024, 01:43 PM | #44 |
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My rods finally showed up. These things are nice! All within 1.5 grams of each other.
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