As of this past weekend, I’ve finally parted out at least one of every one of these three chassis. Having the most experience in the E30, I figured I would like it best overall. This write up is purely based on working on the cars themselves and not about performance in any way. Subtext under headings are the order of my preference.
E36 OBD1 -> E30 -> E36 OBD2 -> E46
I split the E36 because the split between OBD1 and OBD2 because the electronics and emissions equipment are so different.
The Image isn’t completely accurate. The OBD2 bay has the OBD1 intake manifold and the OBD1 bay appears to be an OBD2 engine swap (or at least the valve cover) but it maintained the OBD1 electronics. The reason I like the E30 better than the OBD2 E36 engine is the lack of emissions/nannies. The reason I like the OBD1 E36 engines better is because their intake manifold is significantly easier to take off. It also lacks the M20’s “bitch tube” that frequently leaks.
The E46 is at the bottom of the list simply due to all the vacuum lines, emissions bits, and stability control attachments. So many of these hoses and clips become brittle over time and need to be replaced. Seriously, who runs the starter power wire THROUGH the intake manifold? On the plus side, the E46 has quick disconnect cooling hoses. It’s a huge improvement over the E36’s spider web of coolant hoses. The down side of the E46 quick coolant hoses is that old hoses had distended O rings that made connecting the hoses back up impossible.
Engine electronics is interesting. The M20 puts the ECU above the glove box. The E36 stores it behind the firewall but still behind the glove box. The E46 stores the ECU in a weatherproof box on the driver’s side of the engine bay. The E46’s method greatly simplifies wiring and is a huge plus. The OBD2 E36 seems to route wiring everywhere and it’s mildly more annoying than the OBD1 counter part to remove the engine.
E46 -> E36 -> E30
The E30 engine bay is simply cramped. On the plus side, there isn’t much there. The E36 has this cabin air cowl that hovers over the #6 cylinder that makes things a pain. It’s removed with external torx sockets. It’s annoying. The E46 has that section off with a few hand clips and some normal headed bolts. Both the E46 and E36 have removable front core supports. This is great for engine removal. I do enjoy the E30 clam shell style hood better. Regardless, the E46 has much more room and I’ve never had an issue getting to bolts. The E46 also had a much simpler brake/footwell area to work on. There were quick connectors for hoses and removing the brake master/booster was quick and intuitive.
E46 -> E36 -> E30
For simplicity, the E30’s rear suspension is infinitely easier to work on. But that’s because it has trailing arms and nothing else. The E46 rear suspension is mostly identical to the E36 but has a few changes that make bolt access and general maintenance much easier to work on. I wasn’t fond of the E46’s method of supporting the diff cover (non M models).
The front suspensions are identical for most parts. The E36 and E46 have separate struts from spindles. The E46 has this weird hex design for the front control arm bushing. In my experience, it’s a horrible design. Poly/nylon inserts wear out quickly as that area has to flex. I had a set of THR CABs that wore out after 6 months and started to clunk under acceleration. But the control arm is aluminum so that’s nice.
E46 -> E30 -> E36
Again, the E30 is only good in this area because it simply has much less. The E46 seemed to have a better plan for running wiring and connections were easy to find. The interior wiring bits are mostly the same among the three chassis. So far from my experience, the E46 has fairly standard wiring diagrams like the E30. I’ve found several conflicting wiring diagrams over the years for E36s. Vanos, non vanos, OBD2, OBD1, auto, manual, and so on.
E46 -> E30 -> E36
The E46 simply has more space. The drive tunnel is larger and shielding is much easier to get out. I found that the routing of the exhaust and how the bushings were mounted made the exhaust simple to get out. The E36 bolted things oddly but was still fairly straight forward. The E30 exhaust was terrible to work with and was super heavy. The reason I rank the E30 higher is due to simplicity. It’s more cramped but there is less stuff there to unbolt. I’m not fond of how the shifters are mounted for the E36/E46. I much prefer the E30 way of mounting. All three are terrible though.
Yes I hate on the E36 pretty well. The OBD1 engine is a dream to work on though. I find it that awkward stage where BMW started getting more technologically advanced and went through some growing pains with the swap to OBD2 and stricter emissions rules. The E46 is just an E36 but updated and roomier. The E30 will always have a special place in my heart but much of the car is an annoyance to work on. Its only saving grace is that it doesn’t have much to over complicate things.