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N52 Swap Discussion

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    By the way, hubcapboy.... Nice work.

    I especially like your transmission mount.

    Those parts were laser cut right?


      Daaaaang this is cool work. hoveringuy is going to suggest that the best way to meet in the middle is if you do similar work to this, except starting with my prototype mounts instead of the Z4 mounts. I'm not saying lets do it, I'm saying hes gonna say do it.

      I just did the most basic of research digging around here and both of my port-side engine arms are 2211676031505, which is the E90 version and mounts one "position" further back on the block than the e85 it looks like. I think this is probably some of the reason I wasn't eager to trust any distances... I knew my arms were a different shape, and they wouldn't BE a different shape if they expected motor mounts in the same location. Sorry for my waffling there. Another reason I was brushing the offset aside is I wanted to use hydraulic e46 motor mounts (I think the same as Z4) which you can see in some of the shots above.

      I fooled around with 3/16 plywood at lunch today and got nowhere.

      Edit to save a post: Yea. All these parts were cut locally on laser. I'm super eager to have an excuse to order more pieces. I reached out to probably 5 different laser and waterjet places and this one had the parts done before some of them answered my email.


        At the moment, I'm still going off the premise that the Z4 mounts worked fine with the exception of the 'slice and one inch back' part.

        Since I have those same mounts, that's all I can go off of. You're further ahead in the process. I'm trying to give some input, even if it's just ideas.
        Last edited by LukeJ; 07-14-2020, 04:44 PM.


          I think the engine mounts will sort themselves out soon enough. Once hupcapboy has some good fitting prototypes I think we'd be well-served to digitize it and come up with the best "production" solution.

          An important clarification here is rear sump vs front sump, and I believe he's going for a front sump design which will leave the sub-frame and sway bar untouched.

          I ran an e34 oil pan on my M54 swap for a while and tolerated it because it was the only solution at the time, but it pretty much sucked. The plan I heard was for a shallower front sump with wings and oil control trap doors. I don't know if front or rear sumps are inherently better from an oiling perspective, but I currently get occasional flickering oil light only under hard braking downhill with my rear sump.

          There's definitely some smart folks on this thread, excited to see where this goes!


            Just so I understand the 'advantages' of the ArcAsylum subframe (if they were available)... The smaller diameter cross tube that's pushed forward allowing more space for the oil pan and the sway bar mounts on the front. The engine mounting points don't move position, do they? The steering rack doesn't move forward, does it?

            I read somewhere recently about someone using an E36 sway bar mounted in front and they welded mounting pads to the frame. I can't remember where I viewed it.

            I've already repositioned my oil pickup and from what I've measured I have about two inches to take off the front of the oil pan, if I move the sway bar. 3.5" if I don't. Yard stick tolerances.

            Whatever I cut off the front, I plan to try to replace volume-wise to one side or both.

            I don't think anything else needs to be modified.

            What am I missing?


              This is my car

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              You can see that the ends are the original subframe, so motor mounts are identical. Only the center is changed to be skinnier. Steering rack is unchanged.

              What you don't see on this on is the sway bar tab that cantilevered forward and just sucked. Mine broke and I spun. I now have a Bayside Fabrication frame weld-on mount and it's great.

              Bottom line is that a modified subframe is necessary for a rear sump, but I'm not sure rear sump is even best. If we're making a pan from scratch there's lots of room out front.

              Also, I keep adding oil but it seems to just pour out of the bottom of the engine...


                The front sump vs rear sump question is an interesting one. When I first started thinking about this swap I considered whether I was adapting the chassis to the engine, or the engine to the chassis. Right off the bat, based on the BMP conversions and arc asylum work it looked like any attempt to adapt the chassis to the engine... also required adapting the engine to the modified chassis. If it had been practical to re-design the subframe to accommodate the unmodified rear pan without moving the steering rack, I would have been ready to do that. The real answer to LukeJ's question "what am I missing" is you aren't missing anything... if you're happy to modify both the pan and the crossmember that's about the magnitude of the changes. I don't think there's any reason not to take this approach, it's just not the path I went down.

                At first hack, building a pan might seem more complicated than modifying the subframe, but as I thought about it, the job of the pan is really much less complicated than the subframe, and getting geometry slightly wrong doesn't matter. if the bottom of my pan is two degrees out of level... big deal. If my steering rack is two degrees out of level, I'm going to get a weird look when I take it for an alignment.

                From a "what were they thinking" standpoint... I don't have any evidence that BMW moved to a rear pan design for any performance or engine design reason. Looking at the e30 (front pan) vs the e36 (rear pan) and comparing what changed between the two models, I think the pan was just an accommodation for wanting to move the front wheels forward.

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                We could argue for a few pages about whether the common reference lines between the two chassis are meaningful (rear bumper? why is that important?) but it starts to become obvious that the seat bases, rear wheel, steering wheel, and firewall are all generally common, but the front wheels are waaaaaaaay out there. I can't imagine the reasoning here was "a rear sump design is so important that we're going to move the front wheels forward and re-design the front suspension to accommodate it." If that were the case, they would have taken the opportunity to move the oil pump to the rear at the same time. The newly-designed 24v DOHC engines were so different that they're leaned over an additional 10 degrees, but the oil pump is still at the front? That makes me think that the reasoning was "put the oil pump where it makes the most sense mechanically for the engine, put the sump where it makes the most sense for the chassis."

                Ford and GM V8's both had factory pans that moved the sump forward or backward depending on which chassis the engine was installed in. I've heard an argument for rear sump to supply oil under heavy acceleration when all the oil *rushes* to the back of the pan. That's just about the only argument I dismiss... Braking forces are significantly greater than acceleration in any car that feels safe to drive. Porsche used to say that they size their brakes to be 4x as powerful as the engine.


                  I tried to multi-quote but it just isn't working. I can't wait to ditch this awful forum software...

                  anyway, yes the ix has a swaybar. They just moved it to the front of the subframe, and mirrored the steering rack. The links attach to the struts like the M3, instead of the control arms. The ride height comes from the struts/springs, but BMW moved the inner ball joints down to keep them horizontal at stock ride height. I suppose you could use an IX subframe, but lowered with RWD struts that control arm angle is going to cause issues.

                  As far as rear vs front sump, I don't think it matters - except on the earlier people doing 24v swaps, in usually lowered cars, that E34 pan hung out really badly and often got smacked on things. From that perspective a rear sump is better, but if you can make a pan with enough clearance I'd think front is just fine.

                  I think you are on to something with that diagram. Actually, the newer cars have pretty much kept the same firewall/shifter relationship, but the front wheels have moved waaay out. That's why I can't just use a modern front differential and oil pan because everything is like 6" off.

                  That oil pan flange looks awesome! I wonder how much easier/cheaper it would be to have an aluminum one made and a cut up ix pan welded to that, instead of what I was going to do (merge the ix and RWD/Auto N52 pans). That is still, to this day, where I've been stuck..
                  Build thread



                    Hoof... I'm starting to appreciate some of the challenges of the ix swap now that I'm bumping into 6 years of nando's posts while I search for stuff.

                    Maybe this is the dumbest idea in the entire world, but bear with me... if you took this pan, which is e90 ix:

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                    Cut most of the flange off, but leave the inside edge as a flat, and set an aluminum cut flange (like, say, from a guy you know just south of you) on top of it, and then slid the flange forward a known distance (the distance between where that axle is now and where you want it to be longitudinally) could re-weld the perimeter and cut the back of the pan off and end it with a plate.

                    This makes more sense than adapting the m20 ix pan, as you get the correct angle already (you don't have to build a 10 degree wedge between the two pieces) and you get the newer (presumably better) diff.


                      Maybe, but the hole spacing is probably wrong, the diff is also further to the drivers side (won't line up with the transfercase), and it will probably all foul the steering rack, subframe, etc.

                      Basically, the newer cars are heavier, longer, wider, and just bigger. Utilizing anything other than the engine is (which stayed the same size, doubled in power, and lost weight - arguably the only improvement) is a waste of time.
                      Build thread



                        Is there not an e90 325xi manual? I don’t think you can retain your e30 trans and transfer case because the 24v clocks it over 10 degrees, right?


                          Originally posted by hubcapboy View Post
                          Is there not an e90 325xi manual? I don’t think you can retain your e30 trans and transfer case because the 24v clocks it over 10 degrees, right?
                          Yes but it doesn't matter. None of that stuff will fit, it's not even close. Believe me, I've tried (as have others).

                          I spent $1500 (seems cheap now, lol) on a Getrag 260 specifically built for a 325ix transfercase and a 24v bellhousing for a reason (yes, it will work). The oil pan is solvable (I have mocked it up) but which is the best Frankenstein path, and even more important, who can actually fabricate it are more difficult to solve.. I can weld but I know my own limits. :(
                          Last edited by nando; 07-15-2020, 10:01 PM.
                          Build thread



                            I used to complain that I was only able to work on stuff like this in the dark after the rest of the family went to sleep... Now that I'm coming out here at lunch and it's mid-80's (shut up, I'm from Washington... that's hot) I'm looking forward to picking this back up when the sun goes down.

                            Someone asked a few posts back if there was a guide to the wiring harness. There isn't that I've found, but for people who've done a lot of 24v swap wiring it won't look that daunting (although... that isn't me). E30 and E36 cars have very clear engine to chassis harness connectors where all the important stuff goes into the dash. Swapping the M5x 24v out of and E36 into an E30 isn't simple, but the wiring relies a lot on most of these interfaces being in the same place, and most of the signals being the same.

                            Rather than swapping the C101 connector onto an OBD1 M50 harness, this job looks like its going to be a lot more of locating the relevant signals within the N52 harness and "adding" a C101. A lot of the juicy stuff comes from the DME on the x60001 connector, which as far as I can tell just disappears into the e90/e85 dash harness and probably isn't worth splitting out of there unless you're really motivated to do so. This connector also has some of the connections you're going to need to add chassis side for the DME, like the accelerator pedal, brake switch, speed signal, clutch signal (if you want cruise control) and (whoop) exhaust flap.

                            On top of that, there's some e30 dash wiring that'll need to be added to the N52 harness, such as the temp signal for the dash display and the oil level signal. My preference at the moment (I think I mentioned it way back) is to use an old fashioned low oil sensor and dipstick rather than the n52 oil level. Unless the output from these two senders is similar and the level sender can be adapted to the low oil indication on the check panel. I haven't checked to see if the flange is the same and if this is a pan-design decision that needs to be made.

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                              The good news for everyone else I expect is I don’t see myself being able to do this confidently without fully diagramming both harnesses and marking what I’m eliminating. There’s some suspicious looking connectors that just pop out of the harness that I expect are either modules we don’t need or are harnesses I’ll want to add.

                              The power side of the n52 harness and relays and fuses is pretty impenetrable to me without sitting down with a diagram.

                              I don’t see any utility in trying to retain the e30 diagnostic port, although it might be cool to re-use it as an under-hood OBD if the other end of the connector users available.
                              Attached Files


                                I'm on a phone, but I have some thoughts. I won't go into detail until I'm at a keyboard, but..

                                I've considered wiring but haven't written anything down because I see that as the easiest part. Engine mounts, oil control and cooling are the biggest difficulties. Obviously, I have been involved with all of the N52 swaps to date (and N54s that don't require the entire chassis harness and every module swapped over). I have also built many adapters and harnesses for various E30 swaps. I don't mind sharing everything I know.

                                Regarding coolant and oil level - the easiest answer is GT Peterson's CAN board. It should be able to translate any of these signals, including cruise control, without issue. N52 swap programming uses CAN11h mode, which is what the E46 - and relevant swaps use. So I also see that as a relatively easy problem, that only needs documenting, and at worst a firmware update.

                                Funny enough, I built an E46 M3 cluster for a swap, but I keep thinking I'd rather have the simplicity and originality of the stock E30 cluster. The E46 cluster would "just work", including the variable redline - but I feel increasingly that I don't want to give up all of the E30s original character.
                                Last edited by nando; 07-20-2020, 06:23 PM.
                                Build thread