flyboyX's obd2 s52 engine swap blog

[mongule]

For wiring make sure you wire the correct wire for engine speed to the dme
Depending on your car you might have to splice into the back of the cluster.

It is different then Obd1 cars and will not let you rev higher then 5000 rpm if you dont wire it in correctly.

I forget which pin exactly it was on the dme itself but check the Etm. Took me a while to troubleshoot this so just a heads up for your swap.

[jahnaboi]

EDIT: I'm dumb. Lets get this project on the way!

[flyboyx]

the obd2 cars have an egr valve attached to the exhaust manifold. this valve is connectied to a hose that goes to a filtered air pump located on the passenger side next to the ecu box. below is a photo. the wiring for this air pump is located in the s52's engine harness. initially, i planned to delete this pump. i haven't seen any conversions where it was maintained. after spending sometime thinking about it, i believe i am going to relocate my convertible's battery to the trunk and mount this accessory in the battery locaton. can't seem to think of a good reason not to install it.

the mz3 had asc traction control and i have no intention of installing that system on my car. the x6031 plug has 4 wires associated with asc. they are pins 9,10,11, and 12. instead, i will be using a couple of these wires to route the oil level sensor signal into the cabin. oddly, the mz3 didn't have an oil level sensor, but the e34 oil pan does. the m42 also had one. i will just route the wires i need from the ecu to the sensor on the engine side. on the body side, i plan to route some of the wires associated with asc over to the instrument cluster so the signal can go to the light on the dash.

lots of guys make a harness adapter to morf the x20 plug of the s52 engine harness to the c101 of the e30 body. i intend to use both sides of the x20 and x6031 to route my wires into the body harness. i will cut the c101 out of the e30 harness and repin or solder the wires to the body side harness plug of the e36. i think this will look a lot closer to the way it would come from the factory.

the obd2 reader/data port interface is an easy one. there are four wires coming off the obd2 port. two are brown chassis grounds, one is red/yellow power in to the port(goes to a 5amp fuse in the fuse box), the other is wht/vlt with yellow dashes. this one routes from the ecu through the x6031 plug at pin #4.

[hoveringuy]

Looks like you've done your homework. There are not a lot of well-documented OBD2 swaps here so kudos to you. I'm interested in seeing your progress!

[flyboyx]

this week i started getting serious about getting that engine in my car. i have asked quite a few questions here and received lots of good answers from fellow r3vers. since there is not a lot of thorough documentation about obd2 swaps, i thought i would try to get as much down in this thread as possible. this is my way of paying forward to all of you that have helped get me to this point. if you have constructive comments to make this a better thread, please post them here. if you have individual questions about some point for your swap, please pm me for that because i would like to keep this thread as clean and on topic as possible. if it is something that will improve this thread, i will post that up as well. updates may not come every day or every week, because of other life obligations like work, divorce, renovating a house flooded by hurricane ike, time with new girlfriend, etc, but i will try to post updates here every time i make progress.

ok, with that said, my car receiving the transplant is a 91 318i convertible. my donor car is a 46,000 mile wrecked 2000 MZ3 that i found on local craigslist for a stupid cheap price.

the engines have been out of the cars for a month now. the m42/getrag 240 was sold right away and shipped to a guy in north carolina. my s52 is hanging on an engine stand in my garage next to the e30. i removed the oil pump and windage tray so i could pull off the main bearing caps to check the inserts. i was planning to buy all new bearings and rod bolts, but the main bearing inserts look new, so i have decided to not touch the rods and just put the mains back together and retorque them. i guess i will spend that part of the budget on a stage 3 clutch. i am waiting for my gaskets to arrive in the mail so i can get the engine back together.

i have a nice close ratio zf 5 speed that came with the mz3, but i have elected to use a getrag 260 out of one of my e30 parts cars. my reason for doing this is because the car is a convertible. i will never race it on a track. my only plans are to run it on the street. i wanted the .81 overdrive that the getrag affords for fuel economy and quieter drivability during highway use. i am going to use the dampered e36 flywheel and upgrade to a 6 puck stage 3 clutch and pressure plate. of course, it goes without saying that i put the z3 shifter on the getrag.

my e34 525i oil pan and dipstick tube came from various local junk yards. i spent about 60.00 here. i intend to buy the oil pump pickup tube new.

i found an obd1 manifold from a 93 325i in the local pick a part junk yard. it included the hoses, mounting brackets, throttle body, injectors, and also the plastic cover that goes over them. after a little flirting with the hispanic girl that prices the parts, i walked out of there only paying 75.00 for the assembly. i know that i wont use the throttle body or the injectors, but i will need the rail and some of the hoses undearneath.

for the exhaust, i plan to use the stock mz3 exhaust from the resonators forward. this includes the cats and all four o2 sensors. someone on this forum told me that it should bolt up with little or no modification. we will see. after the resonators i plan to have a stainless custom 3"single pipe made to get the exhaust back to the muffler. i have already purchased a 3" inlet to dual 3" outlet black vibrant muffler from verocious motor sports. lots of people seem to really like that muffler and i wasn't very expensive. about 140.00 shipped.

the differential is the 3:25 lsd from the mz3. unfortunately, during the accident, the finned aluminum cover plate was broken beyond use, so i used the cover from one of my e30 parts cars. one of the axle shafts poped out during the accident and had been that way for some time. unfortunately, this means i have to take the diff apart and clean out all the dust and grit.

my convertible e30 325i parts car had a new driveshaft, so that is going in my swap.

i will be modifying my trans mount and the shifter linkage in the near future.

smaller brake booster came from said junkyard above. it is out of an early model vw rabbit. the bolt pattern on the master cylinder side and also the firewall side is exactly the same as e30. of course the input shaft was too long and unfortunately, after the threads, it was about 1/16 of an inch larger diameter. this making it very diffacult/impossible to rethread. my solution was to take both boosters apart and swap the e30 input shaft into the rabbit booster and put everything back together. i will have to let you know how it works out.

plan to use the e36/mz3 radiator. i still have the m42 rad, but cant see any reason to reduce the capacity as the e36 version seems to fit perfectly in the late model e30 mounting brackets.

i had to purchase e36 engine mounting brackets from a junk yard because mine were both broken from the accident. i ordered a new set of e34 525i mounts. they are so cheap(like 10.00 each), i can't imagine anyone reusing an old set.

all of my new parts associated with the engine are coming from pelican or bma auto parts. i priced everything at bav auto, bma and the dealer. bma auto was close to the same as pelican, bav auto was slightly more. as you can imagine, the dealer was much more expensive. everyone i talked to was very professional and helpful, though.

i have lots of suspension upgrades to the car but they really aren't assocated with this swap, so i will list all of this in another thread sometime down the road.

the most important part of the swap is the wiring and i am still working on getting it figured out. i downloaded the electrical troubleshooting manuals online from a couple of different sources. it is amazing how different two etms that are suposedly from the same make and model can be. hmmm....

as i stated above, this is going to be a completely stock obd2 swap with ews 3.(except i will use an obd1 manifold) i have spent a lot of time studying the mz3 etm. i have elected to strip the entire body wiring harness from this car. this seems like the easiest way to go because there are a lot of wires in there i need to use. in the top left corner of the photo below, is the sub wiring harness for the fuel tank pressure sensor and also the sensor itself. hard to see in the photo, but the sensor is connected to a hose that goes to two orifices. one is in the filler neck and the other in the top of the tank. the wiring for this sensor are pins 5,6 and 7 of the x6031 plug. i have not had the tank out of my e30 yet, but i will find a way to attach the sensor to the tank and post the info here. i intend to swap the 14ish gallon tank with the 16.4 gallon tank from one of my parts cars anyway.