Theoretical n51 to n52 swap

BikeNHV · 10-06-2020, 07:43 PM

Fairly new here despite owning an 09 128i N51/6 speed for over 5 years now. Been browsing various threads absorbing info, but haven't seen this covered exactly.

Let's say, in theory, my N51 died. Seems logical to swap in an N52 longblock and retain the 3SM for an instant upgrade (assuming a proper tune).

If it was your car, what else would you do to that new-to-you N52 block? Or do to something other than the engine that's more convenient while the engine is out?

Parts list off the top of my head:
- Low-mileage N52 longblock - any particular years or donor cars preferable?
- 3SM swapped over from the N51
- MILVs
- Header - worth it or not?
- Tune that will play well with all remaining SULEV stuff in the car.
- Single-mass flywheel and new clutch.
- Engine mounts - are the aftermarket options worthwhile, or just refresh with new stock mounts?
- What else?

wayman519 · 10-09-2020, 12:13 PM

- Low-mileage N52 longblock - any particular years or donor cars preferable?

Engines built between September 2009 to November 2011 need the vanos bolts replaced to prevent catastrophe failure
https://static.nhtsa.gov/odi/rcl/201...4V176-2716.pdf

Engines built prior to 2009 have cam ledge seal issues that require complete head replacement if the grooves are worn. Engines with this issue will suffer power loss and vanos faults.

https://static.nhtsa.gov/odi/tsbs/20...32779-8218.pdf

BikeNHV · 10-12-2020, 10:38 AM

Thanks for those! Hadn't heard about those potential issues. Seems like the vanos bolt issue is easily corrected. Would be a no-brainer to take care of while the engine is on a stand, as well as all the typical oil leak locations.

Jeb_ · 10-22-2020, 09:41 PM

Had my N51 eat a bearing about a year ago and had this done. I left it at the swapping over the 3SM and MILVS. There was definitely a noticeable increase in power but I got used to it pretty quickly. I'll probably do headers sooner or later.

Depending on the age of the donor motor, I'd take the opportunity to do as much of the PITA maintenance items with the engine out. A water water pump service was performed right before the engine failure so I had that moved over to the new engine. Even though I was told the donor's oil pan wasn't leaking, I just changed my oil for the second time since the swap and noticed a leak so I'm kicking myself for not having the oil pan re-sealed when it was convenient.

BikeNHV · 10-23-2020, 08:28 AM

Good info. What did you use for a tune?

Jeb_ · 10-23-2020, 05:20 PM

Quote:

Originally Posted by BikeNHV

Good info. What did you use for a tune?

BPC. They were the ones doing the work on the car and handled the tune as well. So I can't speak to how involved the process is or if anything additional is required for the N51 to N52 swap over their normal tune.

BikeNHV · 10-23-2020, 06:53 PM

Good to know. I'm basically trying to figure out if there's any non-compatibility issues with the SULEV parts (radiator with an extra sensor, special gas tank, etc), but it sounds like its a non-issue.

WDE82 · 10-24-2020, 01:31 PM

I would imagine the DME needs to be coded for N52 vs N51. Of course, the tune for the 3SM probably takes care of that.

Definitely ALL oil seals should be done, maybe even the rear and front main seals if that's not too hard. The oil pan WILL leak eventually. You'll get the VCG with the MILVS install.

Maybe consider putting in the oil cooler OFHG and install the air oil cooler from the 135i? If you're going to track it, it's 100% necessary.

BikeNHV · 10-24-2020, 09:11 PM

Totally agree on the oil seals. My N51 has followed the expected sequence of oil leaks. OFHG @ 69k (previous owner), VCG @ 91k, and the oil pan has been leaking since around 105k. Still is at 121k because I've done nothing about it.

Seems logical to do the mains as well. Knowing myself, I'd be taking everything apart to inspect/clean anyway.

BikeNHV · 12-17-2020, 11:37 AM

I've causally poked around a few online junkyard searches, and it seems like you can get a low-mile N52 from an X5 (has 3SM and better oil cooler) for a reasonable price. Combined with a good tune, sounds like it could be a decent bump for an N51-equipped car.

Does anyone know how far off the X5 N52 is from the 1 series/3 series N52? In terms of mounting/accessories.
Worst case scenario, I guess you could put the 128 motor and X5 motor on stands next to each other, and swap over as many items as needed to make it a drop-in fit.

10-06-2020, 07:43 PM	#1
BikeNHV Private First Class 113 Rep 184 Posts Drives: 128i, F-350, Cooper SE Join Date: Mar 2017 Location: CT iTrader: (1)	Theoretical n51 to n52 swap Fairly new here despite owning an 09 128i N51/6 speed for over 5 years now. Been browsing various threads absorbing info, but haven't seen this covered exactly. Let's say, in theory, my N51 died. Seems logical to swap in an N52 longblock and retain the 3SM for an instant upgrade (assuming a proper tune). If it was your car, what else would you do to that new-to-you N52 block? Or do to something other than the engine that's more convenient while the engine is out? Parts list off the top of my head: - Low-mileage N52 longblock - any particular years or donor cars preferable? - 3SM swapped over from the N51 - MILVs - Header - worth it or not? - Tune that will play well with all remaining SULEV stuff in the car. - Single-mass flywheel and new clutch. - Engine mounts - are the aftermarket options worthwhile, or just refresh with new stock mounts? - What else?
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10-09-2020, 12:13 PM	#2
wayman519 Second Lieutenant 79 Rep 250 Posts Drives: E82 N52 6MT A51 Join Date: Apr 2012 Location: Canada iTrader: (0) Garage List 2018 BMW X2 [0.00] 2009 128i [0.00]	- Low-mileage N52 longblock - any particular years or donor cars preferable? Engines built between September 2009 to November 2011 need the vanos bolts replaced to prevent catastrophe failure https://static.nhtsa.gov/odi/rcl/201...4V176-2716.pdf Engines built prior to 2009 have cam ledge seal issues that require complete head replacement if the grooves are worn. Engines with this issue will suffer power loss and vanos faults. https://static.nhtsa.gov/odi/tsbs/20...32779-8218.pdf
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10-12-2020, 10:38 AM	#3
BikeNHV Private First Class 113 Rep 184 Posts Drives: 128i, F-350, Cooper SE Join Date: Mar 2017 Location: CT iTrader: (1)	Thanks for those! Hadn't heard about those potential issues. Seems like the vanos bolt issue is easily corrected. Would be a no-brainer to take care of while the engine is on a stand, as well as all the typical oil leak locations.
	Appreciate 0 Quote

10-22-2020, 09:41 PM	#4
Jeb_ Private First Class 61 Rep 107 Posts Drives: 2011 128i Join Date: Jun 2016 Location: NC iTrader: (0)	Had my N51 eat a bearing about a year ago and had this done. I left it at the swapping over the 3SM and MILVS. There was definitely a noticeable increase in power but I got used to it pretty quickly. I'll probably do headers sooner or later. Depending on the age of the donor motor, I'd take the opportunity to do as much of the PITA maintenance items with the engine out. A water water pump service was performed right before the engine failure so I had that moved over to the new engine. Even though I was told the donor's oil pan wasn't leaking, I just changed my oil for the second time since the swap and noticed a leak so I'm kicking myself for not having the oil pan re-sealed when it was convenient.
	Appreciate 0 Quote

10-23-2020, 08:28 AM	#5
BikeNHV Private First Class 113 Rep 184 Posts Drives: 128i, F-350, Cooper SE Join Date: Mar 2017 Location: CT iTrader: (1)	Good info. What did you use for a tune?
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10-23-2020, 06:53 PM	#7
BikeNHV Private First Class 113 Rep 184 Posts Drives: 128i, F-350, Cooper SE Join Date: Mar 2017 Location: CT iTrader: (1)	Good to know. I'm basically trying to figure out if there's any non-compatibility issues with the SULEV parts (radiator with an extra sensor, special gas tank, etc), but it sounds like its a non-issue.
	Appreciate 0 Quote

10-24-2020, 01:31 PM	#8
WDE82 Major 815 Rep 1,199 Posts Drives: 2018 440iGC F36 Join Date: Aug 2015 Location: Torrance, CA iTrader: (0)	I would imagine the DME needs to be coded for N52 vs N51. Of course, the tune for the 3SM probably takes care of that. Definitely ALL oil seals should be done, maybe even the rear and front main seals if that's not too hard. The oil pan WILL leak eventually. You'll get the VCG with the MILVS install. Maybe consider putting in the oil cooler OFHG and install the air oil cooler from the 135i? If you're going to track it, it's 100% necessary. __________________
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10-24-2020, 09:11 PM	#9
BikeNHV Private First Class 113 Rep 184 Posts Drives: 128i, F-350, Cooper SE Join Date: Mar 2017 Location: CT iTrader: (1)	Totally agree on the oil seals. My N51 has followed the expected sequence of oil leaks. OFHG @ 69k (previous owner), VCG @ 91k, and the oil pan has been leaking since around 105k. Still is at 121k because I've done nothing about it. Seems logical to do the mains as well. Knowing myself, I'd be taking everything apart to inspect/clean anyway.
	Appreciate 0 Quote

12-17-2020, 11:37 AM	#10
BikeNHV Private First Class 113 Rep 184 Posts Drives: 128i, F-350, Cooper SE Join Date: Mar 2017 Location: CT iTrader: (1)	I've causally poked around a few online junkyard searches, and it seems like you can get a low-mile N52 from an X5 (has 3SM and better oil cooler) for a reasonable price. Combined with a good tune, sounds like it could be a decent bump for an N51-equipped car. Does anyone know how far off the X5 N52 is from the 1 series/3 series N52? In terms of mounting/accessories. Worst case scenario, I guess you could put the 128 motor and X5 motor on stands next to each other, and swap over as many items as needed to make it a drop-in fit.
	Appreciate 0 Quote