Noobs Guide to a 24v swap. (WIP) by 328iJunkie

By stevegolf
( 1 )

13 minute read

Noobs Guide to a 24v swap. (WIP)

Compliments of 328iJunkie @ 

DISCLAMER!: I take no responsibilty for anything said below or anything you may do with this information. This is not a completely detailed workthough, more of a guide.

So you wanna throw a baller engine in your E30? There are some things you're gonna need to think about and research. 

First things first. You're going to spend a lot of money on this. More than you plan to. You can ghetto rig the hell out of it and then it won't work or it'll be as reliable as a British car. There's not all bad news in this area though. There are a few different ways to do the swap that can cut some costs down and this will be discussed.

Engine: What you gonna do here? This will change a lot of things later down the line so you have to decide this first. 

M50B25: Cheap as hell, damn near bullet proof, usually haven't been beat on but also rare (91/92 525, 92 325 E36). The most rustic and old of the 24v motors. Dual Valve springs, no variable valve timing, and brick internals (very similar to the M20's) this makes them good and bad for a number of reasons but basically the least powerful of the bunch. Utilize their own wiring harness and ECU so you don’t have a lot of choices there (at least not simple ones).

M50TUB25: The most common of all 24v swaps. Again pretty bullet proof, updated electronics, valve train and internals. Has VANOS!. Came from 93-95 325s/525s. Run OBD1 and can use a few different harness/ecu combos. Also very cheap to find. Smidgen more powerful than the NV motor.

S50B30 (US):

M52B25/M52B28: Seems like the new thing to do, very similar to the M50TU but with the B28 you get an displacement bump. Came in 96-98 328s (B2 , 96-98 528's (B2 , and 96-99(E36 only) 323s With this motor BMW started doing some changes, namely of which is OBD2 tuning. This we will discuss later. Some other changes are different cam Trays, late 96+ motors are missing a 3rd port in the cyl head, extra hole in the block for a crank sensor, and a metal (better) coolant pipe. Also they changed the oil filter housing to a plastic lid which sometimes isn't a big deal but is annoying when you look for a powersteering pump as they mount a little different. Some other big changes are the valve cover, CCV/PCV system and coil design. You can spot the change by the flipped (Front vs. Rear) oil filler cap. Other changes are the lame M52 Manifold and attached parts, which I will also discuss later. 21.5lb injectors (pink tops) and a different fuel rail. Another big change with the flip to OBD2 is EWS but as it turns out ill discuss easy solutions for that later.

S52B32: Mad Powa!, This is basically the most powerful of the E36 24v swaps. found in 96-99 M3s it also runs OBD2 and uses vanos. Very similar parts to the M52 in a bunch of ways. So see all the poo I said for that engine. Differences include the Cams and displacement obviously. Also runs OBD2.

Euro Engines:



Wiring/Tuning: This is feel is the next big thing to decide. Depending on which engine you chose you may have a choice or not. If you chose a M50NV you can really only easily run the NV harness/ECU. M50TU/S50 engines run OBD1 so you're also limited there a little, the M52/S52 guys have tons of choices though so ill discuss that more. 

OBD1 vs. OBD2: So you don’t know what the hell I'm talking about, in 1996 the govt decided cars were destroying the earf so they said hey lets require everyone to do this standardized system to make engines pretty and clean to said earth. This changed BMWs a ton as they redesigned their engine line to compensate for the change. ECUs became a lot more complicated and thus so did tuning and wiring. They added tons of emissions BS and other annoyances, but I'm not gonna rip OBD2 completely as I run it in a lot of my customer cars. 

You M52/S52 guys will have a big choice to make here that could completely change not only the cost of your swap but the headache involved. So where to start? Well first off your motor came OBD2, so it would seem logical to keep it that way right? Not so fast. Keeping the entire OBD2 system is extremely complicated from running a remote FPR to the EWS system and secondary air pump. So the new thing to do is have a tuner play with the ECU a little to make your life easier. There are many tuners out there that can do OBD2 stuff the two I know of/deal with are Technica Motorsports and The Racers Market Both located here in GA. Another little issue with OBD2 is they're chipless. This requires you to send your ECU somewhere to get "tuned" or "flashed" as it's called in the OBD2 world where as an OBD1 ECU is socketed so you can do something easy which is referred to as "chipping" the ECU. 

Basically the biggest thing that needs to first be addressed to make your life easier is the EWS system which basically a security system that BMW began using as early as 95. There is a chip in E36 key and on this chip is some crazy mystical code. This code has to match up to the Code in the EWS box (which is under the steering column on 96+ E36's, and the code in the ECU. If those codes don’t "align" then your car won't start, no matter what you do. So you can either A: Implement the entire E36 system or B: Check the little EWS delete box when you choose to get your tune done on your ECU. 

Other things you can have them "play" with are the secondary air pump system and evap system. Another issue with OBD2 is the O2 sensors… of which there are 4 of. 2 PRE-cat (the ones the ECU needs to see how the engine is running) and 2 POST-cat (the ones the ECU needs to see if your Cat converter is working). Federal law requires I state you have to run all 4 of these……

So if you decide to keep OBD2 you get to keep all your cool OBD2 stuff that may have come with your motor like the harness/ecu/sensors. If not then you will have to do what is called an OBD1 conversion. 

This requires a few things:

OBD1 Conversion: Requires an OBD1 Harness (from a 93-95 325 or 95 M3) and ECU (people prefer the RED 413 because it doesn’t have EWS, the SILVER 413 does but all you have to do to get around this is get an EWS delete chip for it). Other big things you need are the OBD1 sensors which consists of the OBD1 Crank sensor (which now moves to the front timing cover instead of in the block), OBD1 cam sensor, OBD1 knock sensors, OBD1 O2 sensors, and OBD1 IAT sensor. Other people will tell you 324234 other things are required from the injectors to the OBD1 coolant line, this is not true. The other big thing you'll need is a chip for your newly acquired 413 ECU. Why you ask? Well the 413 ECU's (depending on the chip) were designed to run the 2.5L 325 or 3.0L M3. You're now running a 2.8 or 3.2L engine with different injectors and whatnot so you'll need a chip from a "tuner" to match the setup you're running. 

Again choosing OBD1/OBD2 is a cost factor because you'll need to pay for all that stuff I just mentioned so choose wisely!

Wiring part duex: Another big thing you will now encounter now that you’ve decided which tuning direction to go is WIRING! if you have no idea what the hell is going on then you'll usually find someone else to take care of this for you. Many people and vendors sell wiring adapters or will rewire your E36 harness. Basically the problem is the E36 harness has a plug on it called a X20. This will not plug into the E30 body plug called the C101. If you want the engine and other things to work you have to get them to plug into each other somehow. If you DO know what's going on you can simply make your own adapter or rewire the E36 harness yourself which will save you some coin. Wiring guides can be found all over R3V and E30tech and the rest of the intranets.

So now that we've got all that covered we move on to other things. What trans you gonna run?

Transmission: This may seem like a small choice but it has a lot of decisions associated with it. Do you want to run an E36 or E30 transmission? You can run a variety of transmissions: G240,G250,G260, or ZF310/320. E30 318's (M42) came with G240s, E36 325's came with G250s, E30 325s came with G260s and the E36 M3's and 328s and E39 528s came with ZF's. The G240 and G250 are regarded as weaker than the others. The ZF is the strongest of the bunch. The decision you make here will have tons of choices that follow it from the clutch to the shifter to the actual trans mount. The easy logical thing would seem to be run the trans that came with my car! If you have a E30 325 which most of you will this would be the G260. Running this trans has some issues though. First off is the 10 degree tilt difference between the E36 engine and E30 transmission. This will require you to run a custom transmission mount (which some people here sell), and bend the shift linkage around a little. Another big issue with running this transmission is you CANT get the oil pan off the E36 engine with the trans still attached so don’t forget to take care of that gasket! There were also a few different variants of the G260 that I don’t feel like talking about but just keep in mind they're not all the same. Running an E36 trans may seem a lot easier then but don’t just the gun too quick. 

The bases you have to cover in trans choices are: The Trans, Clutch/FW setup, Shifter, and Driveshaft. All of these things change based on the transmission you choose. If you use the E30 trans as I mentioned you'll have to play with the shift linkage and trans mount but you can run your original clutch/fw setup and driveshaft. You basically want to use the driveshaft that was originally mated to the transmission you're using. There are some variants to this but that’s the basic jest of it. Same goes with the shifter. The clutch/FW setup however you have some choices on, you can keep your M20 or M42 setup or go with an E36 one but basically the rule of thumb is the Clutch/FW/PP and starter all have to have come from the same thing, so use M3 clutch? Then you use M3 flywheel/Pressureplate and E36 starter. 

The other big thing that goes along with choosing a transmission is rear gearing. The E30 transmissions used an Overdriven 5th gear which makes using original rear gearing work well (3.73-4.10) but the E36 trannies used a non overdriven 5th (1:1) so unless you don’t mind spinning 23423423 RPMs on the highway you'll want to swap the rear end to a lower ratio (2.93-3.46). Not gonna discuss diffs in too much detail because that’s an entire new box of worms but yeah. 

Other Engine Stuff (cooling system, PS system, AC, etc): So now you’ve chosen your engine, trans and tuning. Now before you throw your lump in there you need to figure out the rest of the stuff.

Cooling System: Again the logical choice would be to use the original setup. This may work great or may not. If you have an <87 325 then your cooling system is designed wrong compared to the E36 motor (hot and cold sides of radiator are flipped) so you'll either need to upgrade to the late model setup or do the infamous M42 radiator mod. This I will say is common but I don’t recommend it. Although it cleans up the engine bay nicely and plumbs everything easier you have to keep in mind that the radiator was designed to cool a 4cyl so its smaller but integrates the coolant res into the side of it. You'll need to figure out a fan setup as well. The E30 clutch fan (325) can be used but sits EXTREMELY close to the radiator so it's best to go electric and put one in front of the radiator/AC condenser. 

PS System. You basically use the E36 pump with some chopped and bent E30 lines. You mount the res on the e36 engine mount arm and go from there!

AC: This one is annoying at times but can be easily addressed. But basically what you want to do is get an E36 compressor/tensioner/belt setup. You now have to figure out a way to hookup your R12 E30 lines to the E36 compressor. Some people sell adapters, some people have the lines fabbed to fix the issue but basically the Issue is the lines and no you don’t HAVE to lose AC to do this swap. 

Getting the damn thing in!: So now you’ve decided on an Engine and Trans and tuning. Now you have to figure out how to get the motor in the car!

Some things you'll need to address: The original brake booster is in the way. Replace it with a better/smaller (overall diameter) one or move it out of the way. The E36 oil pan DOESN’T work easily, the one you need to get is out of a 91-95 525. The original motor mounts don’t work easily as well. The common ones to get are E28 535i ones. Exhaust will also need to be worked out. Nothing will really bolt up 100% easily and there are a bunch of a different choices of headers but just keep in mind you'll have to address it. 

Some other things to do are to clean paint and prep the motor on a stand. Replace wear items like gaskets, thermostat, and the water pump.