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E30 325iX twincharged build - [video #7]

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    E30 325iX twincharged build - [video #7]

    2005/02 Prologue
    My first car a few years earlier was E30 316, but in 2005 I saw a 325iX for the first time properly at the Bimmer Tuning Club of Finland ice track days. The iX-thing hit me, I had to get one some day. A pic of the iX in question, even though it isn't and wasn't my car and is only loosely related to this.

    2016/08 The search
    12 years passed by without getting my own four-wheel driven E30, instead I had about a dozen of beemers and another dozen of some other cars. After daily driven a Jeep, a pair of VAG torsen all-wheel drives and E61 530xd I wasn't really keen of going back to rwd any more, at least not for a dd. The old E30 iX-thing hit me again and I began seeking for one. After about half a year a prefacelit 325iX (1986/04) that met the (loose) criteria was found, although it was not 2-door, red, and far from flawless... well, I was't going to make a full restoration anyway. According to the seller, the tc lock was broken, but another transfer case was part of the deal. The car had a rollcage, loud exhaust etc and the car felt it had really loose rear end for awd, just like rwd E30 (the reason for this was to be found out later on). Despite this I bought the car and drove it ~300km home.

    The first thing I did was to switch the H&R iX lowering springs to less lowering Lowtec ones with thick rubbers both up and down. At this point I found out the car had stock shocks and the bumpstops were not shortened so the car had about 1 cm (less than half inch) of inbound travel. The car had been mostly on ice track use so the sound insulation was all removed.

    2017/03 - 2017/06 Rust
    It was supposed to be a few weekends' job to weld the rotten rear arches. Typically, when pulling it apart, the actual damage was surprising, both positively and negatively. The good thing was that the car did not come to Finland until around 2004 and the ice track is not salted. Among other things, I viewed the side skirts from the inside with an edoscope and found out they were good enough that I didn't want change them at that point. As there is no time and no facilities to give attention to every little detail, the rust repairs in general were done with the mentality that after about 10 years I will be stripping the whole car into a bare shell and give the repairs more attention to detail.

    One of the bad things were the poorly done job to cover the inoperability of the ABS (using a blinker relay), the strange little dents here and there, the rollcage had not been welded properly etc...

    At this point, I decided to replace all the chassis bushings and joints, brake pipes and hoses, drive shaft boots etc. For future purposes, I replaced original prefacelift fuel pumps with Walbro 450 inside the tank.

    In June, the car passed MOT and I was able to drive it a bit so I wouldn't lose motivation for the thing.

    2017/07 - 2017/10 The sad end of center diff viscous coupling
    I added adjustments for the rear axle, M20 got a new starter and distributor. I bought a 1000hp-proven extended front drive shaft from a Finnish iX entusiast and replaced the seals and bearings in the spare transfer cases. Out of the car I tested that the viscous lock is in really tight condition.

    However, after I installed the transfer case in car, there was a strange whining noise coming from somewhere in transmission/tc/diff area. Didn't drive much, I took the transfer case out of the car and back on the table but found no reason for the sound. Everything looked ok.

    I put everything back in place and the noise was still there. As the garage I had in my disposal was about 40 km from my home, I drove it for probably 200 km until a crazy idea for source of noise came into mind. The 325iX with all it's variants was manufactured with few different diff gear ratios... but wait, no, surely no-one could be stupid enough to put different ratios in front/rear.. I used reflective tape on the rims, jacked the car up, started and put it in gear, the laser rpm meter confirmed what I feared.

    Unaware of this in time, I ruined the good viscous diff lock. It no longer worked nearly as well after the incident. The reason sound was not heard before was because the previous viscous was completely broken and there was basically only an open differential in the center, which allowed difference in gear ratio. The good viscous then tried to brake this "slippage" and of it took a lot of heat, the sound then came from the front diff which because the tires and drive shaft tore the gears at different speeds all the time. A suitable front diff (matching the rear ratio) was found in a couple of days.

    I then opened the transfer case that was in the car when I bought it and found a desperate attempt to lock the center differential. The halves of the viscous crown were welded together, which has no effect on the locking, but the viscous and differential could not be separated without a grinder. So most likely one of the previous owners had swapped the front or rear diff, ruined the viscous and then "fix things" by trying to weld the center diff. This all was very annoying as good viscous are very hard to come by.

    2017/11 - 2018/01 Restoring a bit of comfort
    I bought ugly greed but otherwise okayish facelift floor carpet with sound insulation, painted it black and at the same time added some sound insulation material in place of the removed bitumens. This all added some 20 kg of weight, but will be compensated in the future. The iX is terribly fat anyways compared to any rwd E30.

    Until this the ABS was not working, and I started designing an Arduino-based controller/software for diagnosing ABS signals as there are no handheld testers etc. Before it was completed, it turned out that the indicator light was controlled by a flashing relay, both relays on the hydraulic unit had been removed and in addition the front sensor pins were in the wrong pins on the ABS ECU (connected to pins used in rwd E30, the iX has a different ECU with more pins). The ABS became fully operational after this.

    More comfort was sought by installing a BT stereo and retrofitting E34 cruise. The E30 cruise sets are hard find but the operation and functionality of early E34 cruise is basically similar (looking at ETMs), so it just needed adapted wiring harness. Testing cruise functionality and especially troubleshooting problems in the car is typically tricky, so I quickly sketched Arduino tester to simulate the rear speed signal for the instrument cluster on the table so I could test the operation. It seemed to work on the table, so I installed it in the car and it worked as expected.

    2018/02 Own prototypes
    Alpina and other similar additional displays for E30s are great, but they cost a damn lot and they can't show any custom information one could want. I bought a cheap multicolor touch screen and prototyped the previous ABS signal solution to gather some more data and visualized the information to the display, unfortunately that two-part glued frame broke and has not been in place since then by the priorities time low. Will come back yet and then there will be a little more involved.

    The iX likes it when driven in the winter. Getting one for summer use only is a shame ;) Trying to avoid salt is a bit stressing though..

    2018/04 - 2018/10 Preparations for engine/driveline swap
    I've known that the front diff is the weak part if looking for more power. I also knew that the E34 525iX has a stronger one, paired with a M50 engine, but adapting diff into M20 or the whole package in E30 are both quite involving. However, the destruction of the viscous lock of the original transfer case kinda took the other option out. Conveniently one E34 525iXA with overheated engine and visually not so good shape appeared on sale in my home town, and I bought it. I replaced the cracked head and drove the car a bit to get verification that there are no other underlying tech problems.

    In the summer, I also found a 525iX manual trasnsmission and matching transfer cases. The biggest difference to the E30's original AWD technology is the transfer case lock, which is a magnetic clutch-based instead of a viscose lock. Also the power distribution is marginally 1 % more to the rear. Once again, I used a microcontroller and quickly sketched software as a tool, I measured the effect of different duty % and frequencies on the static locking torque, with one output locked and the other turned with a torque wrench. I topped my ~250Nm torque wrench at about 50 % duty, and until that the tq/f ratio was quite linear.

    Big thanks to Nisse Järnet who shared some valuable information about the swap, including that the fact E34 front drive shafts could be used in E30 if the outer ends were modified a bit in a lathe. I drew custom ABS rings with E30 tooth profile and the inner diameter of those E34 outer ends with CAD and had them laser cutted.

    A fellow E30 entusiast welded the aluminum parts of the shortened E34 phase linkage to fit the package :yep:

    I bought Z3 188 torsen rear diff with ratio matching the front one. The original M20 with 280 kkm on the odo started smoking at the beginning of the year, and at this point it already smoked so much that I was ashamed to drive it in traffic. One plug became covered with oil almost instantly after cleaning. I used the endoscope and peeked that there was clearly oil on top of the 4th piston. This winter was rest for the iX.

    2019/03 - 2019/06 Engine/driveline swap
    M20 out and M50 in.

    It's a bit more complicated than M50 swap for a rwd, eg the engine and hence the firewall had to be moved 3 cm further back around cylinder head, I had to use poly engine mounts (as Nisse told me to, but I had to try with rubber ones and find out myself they just won't do). Clearances to rack, firewall, subframe are all 2-3 mm and the M50 really has just one specific location it fits -- but that's enough. Naturally, the engine and transfer case mounts custom made, amongst many other small brackets.

    M50 intake manifold / throttle body didn't clear brake fluid reservoir as the engine was moved backwards, and J-Spec intake plenum was an easy workaround here (although I'm considering changing to M52 manifold now). Some room had to be done in trans tunnel, fan cover and surrounding area.

    I upgraded brake booster and master cylinder with those taken from the E34 525iX, the radiator to a bigger aluminium one, coolant expansion tank to a new facelift model etc. Some engine seals were replaced and the clutch was upgraded with Sachs SRE 765 for future plans.

    I knew from previous experience that with a lazy fit, that 765 is a pain in the *** in terms of comfort and feel, but also almost like a standard one with a proper adjustment. I made a measuring tool in place of the slave cylinder to properly measure the point at which the clutch starts to disengage, and with the measures an extension to pivot pin and a longer rod for the slave.

    MOT passed and ready to go again

    2019/06 - 2019/12 Speeduino
    I was excited to try Speeduino as an adjustable motor control because it was open source so custom features and flexible integration to external things could be achieved. I assembled it on Pazi88's M50 pnp pcb, initially had difficulties to get it running due to fake coil driver components. Pazi88 spotted the fakes from a photo I sent and with genuine drivers the thing fired right up. I then added wideband lambda and a flex fuel sensor, pump gas to E85 and the standard injectors were already small when n/a.

    Injectors were changed to 630cc EV14 ones, Speeduino to newer design which took advantage of new firmware development to allow fully sequential injection etc.

    2019/12 - 2020/01 Control unit for the center diff lock
    What started as ABS dianostic helper tool was evolving to a control device to diff lock, and for that it needed few more features, like ECU (Speeduino) integration, a 9DOF / acceleration sensor, 14 other outputs, 13 analog measurements, and 14 digital inputs. Not all of those are yet in use, but I've designed this to monitor engine and driveline status and alert when things go bad -- I don’t want visible extra aftermarket gauges that I don’t have time to look at.

    In the early winter, the rearward bias of open center diff (at the time without lock control) became noticeable, a couple of times the went quite sideways surprising the driver. The normal E30 thing, which I wasn't expecting with awd and open diff however. That is actually just a good thing, with the unlocked diff the car goes much more neutrally in corners than standard iX and, if necessary, the sizzling of the rear end can be cured with more power to the front. However, not all torque can be removed from the front as in xdrive.

    In late January, I got first test drives with the controller

    Adjustments and control strategy evolved with having the wheel speeds, diff lock control % and conditions in the same Tunerstudio log along with Speeduino engine data. Here is an example of a situation where the rear end is trying to slip but controller notices, controls the lock and the driver does not notice anything.

    2020/02 - 2020/06
    I continued to enhance lock control for winter conditions. The aim was and is to make it turn more easily and letting it go a bit more sideways than the viscous lock allowed it to, without losing the predictability in behaviour that the mechanical one has.

    From the clip of a log, one can clearly see how the speeds tend to get the difference when accelerating (especially between the wheels of the open front) and how the ABS squeaks after releasing the throttle.

    Last edited by muuris; 08-20-2021, 05:51 AM.
    1986 325iX
    2006 530xd

    2020/06 - 2021/01
    I added some calculations for the iXMega controller, including gear detection, acceleration rates, fuel consumption etc not so relevant. Also coded control strategy for the upcoming E90 pwm controller fan (not installed in car yet). The next step is the addition of a steering wheel angle sensor to make the behavior turn a little more agile. We expect the E39 Touring's level / headlight level sensor from the post office, try it first (rod to shoulder shaft, or wherever the lever arm fits now).

    Next evolution of the pcb will be having additional ESP32 for automatized datalogging and a web-UI (via hotspot) for changing settings on a pad/laptop/phone. These are proven to be working on the table, also not in car yet but maybe this year. These things take a lot of time and until finished there's really not much to show

    For winter 2020-2021 the car won't be driven to avoid salt contamination.

    Next up.. it needs some more power :)​
    1986 325iX
    2006 530xd


      Excellent progress over time, very interesting work on the controller. Keep it going!


        I ordered some new PCBs for this, the first is for the bigger iX-controller and the other one looks something like this:

        So it's a replacement for the SI-board inside instrument cluster. As this is the first prototype it has some placeholders and for sure many things to be done in a better way, but we'll see how it goes. The main purpose for the board is that I wanted to be able to freely control what used to be econometer:

        It has some other features as well, including
        -ability to control speedometer based on ABS-signals with tyre size compensation (data from iX-controller)
        -parallel control for oil pressure warning light (ie based on pressure sensor in addition to factory switch)
        -control of inspection lights (ie based on lambda or oil temperature, haven't decided yet)
        -controls for some additional warning/status indicators
        -reading out signals from fuel tank sensor and engine temp sensor (don't know if I will actually have any use for these though)
        1986 325iX
        2006 530xd


          Didn't have time much for this last year, only things were passing yearly MOT and attending Finland's E30 meeting.

          I had intention to boost this last year, but as it didn't happen, I figured it has to be done twice to compensate (turbo + supercharger). Won't be targeting for huge hp, but instead decent response and drivability.
          I started fabricating exhaust manifold:

          1986 325iX
          2006 530xd


            Great read.


              Turbo exhaust manifold sketched:

              ..and fabricated:

              This took quite a bit of time, not only as exhaust manifolds usually do, but this was also my first tig-welding thingie. Wastegate pipes come to a flange and both channels are divided all the way to the valve face. I also added 6x EGT probe bungs and 2x EMP bungs. It is quite a tight fit to get the manifold in place, as M50 tilt angle, big iX front shock towers and front drive shaft are all on the way.

              Also made a timelapse video of the manifold fabrication:

              Last edited by muuris; 03-09-2022, 03:58 AM.
              1986 325iX
              2006 530xd


                Love this build! Custom electronics mixed with E30 are my kind of thing!

                Would you be willing to share the photo file you made for the boost gauge econometer overlay? I'm wanting to do something similar to mine, although will likely develop a different electronic solution then you are using.
                My Build Threads:
                '87 BMW E30 325is (restomod)
                '98 BMW E36 328i
                '90 Mazda Miata NA
                '04 Jeep TJ
                '05 Yamaha R6


                  Originally posted by Panici
                  Would you be willing to share the photo file you made for the boost gauge econometer overlay
                  Send me a pm.

                  For heat soak and packaging reasons I decided to switch to a plastic M52B28 manifold. The main reason I originally went for the aluminium plenum was the clearance issue with brake reservoir:


                  I cut the original throttle cable mounts, swapped them 180° and also moved it further away from the throttle body. For this I also had to made a spacer/shaft extension parts for the throttle:

                  Next clearance issue was between throttle linkage and brake booster vacuum connector/check valve. Made a custom connector for booster so that the check valve will be attached on the hose:

                  Brake reservoir was remotely located with mainly 2002 parts and so the M52 manifold and tb had room to go in:

                  I was planning to install Eaton M62 in place of the original AC compressor but unfortunately there just isn't enough space in the iX. It would be possible only if engine mount would be relocated in the front subframe but this was out of the question for me. So the plan became swapping alternator into AC compressor location and installing SC in the alternator location. The bad thing about this is that plumbing SC with intercooler isn't really feasable, but I'm using E85 and the use of SC is only very momentary.

                  One day of playing with a spirit level and a laser and now I have bracket to mount Eaton in place:

                  1986 325iX
                  2006 530xd


                    That is a serious project, props! Would love to see it in action.
                    '85 Alpine Weiß 2-door with m20b30 ground up build


                      Originally posted by gnmzl View Post
                      That is a serious project, props! Would love to see it in action.

                      This has had E34 140 A alternator previously, but now it'll be replaced by a smaller 70 A version from E36 316i compact. The size different isn't huge but just enough to squeeze it where I want to:

                      This means the serpentine belt route will be altered and will hence need two additional idler pulleys. At first I'll try the Eaton with just one eccentric pulley. The belt in pic is too long, will be shorter one:

                      I decided not to use exhaust manifold wrap or ceramic coating, but aluminium heat shielding instead. I only had 3 mm thick material laying around, so these are quite heavy duty :D Will be painted, not left shiny:

                      I needed to get the big crank bolt open for the turbo oil return so I made a crank locking tool. The first version wasn't too succesful as it bent badly (but managed to get the bolt open with it nevertheless):

                      Exhaust camshaft was swapped for a M50B25nv intake cam:

                      Turbo oil return into traditional place, but it had to be angled as the alternator is quite close to this:

                      Crank locking tool v2 (10 mm thick steel and some old halfshaft):

                      Next up is some paint for the fabricated parts and starting to put it together a bit so I can start making boost piping.
                      1986 325iX
                      2006 530xd