The Official OBD1 vs OBD2 argument thread.

[328ijunkie]

New: http://www.r3vlimited.com/board/showthread.php?t=258532

[evandael]

couple wiring questions for the guru's ITT. for reference, i'm swapping an OBD2 S52 into an early model 325is and i'm NOT running EWS.


when i wire up the coolant temp sensor for the E30's cluster, will I need to tap the head and use a brown-top single pole sensor to run to c101p4? the stock e36 sensor is a dual temp so i don't understand how it interfaces with the E30's chassis electronics. please advise!

i did some scouring through the ETM's and it seems like VSS can come from x20p9 and x6031p3. no real advantage to doing that, but i'm wondering if i'm correct.

do both the x20pin18 ignition wire and the x20pin15 starter wire get connected to the E30 ignition?

still trying to figure out the a/c idle bump and aux fan wiring. i think that x20pin5 will interface with the E30's c211 (like this). additionally, wiring through x20pin6 is how the DME tells the compressor to engage on the E36 but because the E30 does this in the body harness, I wager it won't need to be connected.

for the aux fan, i'll be using 328ijunkie's information to run it as a full-time fan that's switched when the thermostat opens.



all in all it doesn't seem very different or more difficult from OBD1 wiring if you aren't running EWS.

[DesertBMW]

^ good read

So with your flashing setup you have to keep the SAP relay installed in the harness? This is good to know as most of the harnesses i prep i rip it out of... hrm...

No, you don't need to have it there. DME will never use it and will not trow a code for it.

[328ijunkie]

^ good read

So with your flashing setup you have to keep the SAP relay installed in the harness? This is good to know as most of the harnesses i prep i rip it out of... hrm...

[DesertBMW]

Ok so you found cheap wrecked 1996-1999 E36 donor car and you got nice 1984-1991 E30 that you want to do the 24v engine swap. Sense not much information is written about OBD2 conversion into your OBD1 project car, I decided to write what is needed and what is not when compared to OBD1 and OBD2 conversions.
Lets say that you already did one 24v swap in your E30 with 1993-1995 OBD1 system and you know it works. So that the only information that I will say here is the info that you need to know when putting in OBD2 engine management system from 1996-1999 E36.

Argument: what is better the 93-95 obd1 engine management or 96-99 engine management?

If you got 1992-1995 OBD1 donor car then it would be the best way to go with OBD1. If you already spent a lot of money getting all the OBD1 parts for your OBD2 donor engine then keep it OBD1.
If your donor car is OBD2 then it would be better to stay with OBD2 with your E30 swap. This way it will be cheaper to stay with OBD2 than to look and spend time and money getting all the OBD1 parts.

Siemens MS41.1(OBD2) DME is better and more powerful unit than Bosch 3.3(OBD1). There are many features that MS41.1 does better like: More precise ignition timing because on M52/S52 crank sensor is mounted on the block and reads directly off the crankshaft, while OBD1 reads the timing from the front pulley and timing teeth are mounted on the rubber harmonic balancer that vibrates and not better than solid tooth gear mounted inside the engine on the crankshaft, more precise injection with ability to turn off each injector if the coil goes bad on that cylinder to prevent fuel flood, bigger injectors, running loss valve with remote fuel pressure regulator, helps reduce fuel vapor and temperature, better on board diagnostics. Quality knock sensors that never go bad. And more…

OBD2 conversion does not cost more money than OBD1 conversion. Lets say you bought the M52 engine and want to buy all the OBD1 parts, the first problem is knock sensors are expensive and you need two of them, used ones are not good because most of them crack, they are very poor quality. Plus you will need a tune for that red 413 ecu for your M52, so just the cost of those two parts will pay for quality OBD2 dme flash for your swap.

With a proper OBD2 MS41.1 ecu flash your OBD2 engine management will be the same as if you were installing obd1 engine management. DME can be programmed so that it does not look for these emissions components and not
throw a check engine light:

You will NOT need to run/have super heavy OBD2 dual catalyst converters nor the rear oxygen sensors! OBD2 ecu can be flashed so that only runs on two 02 sensors that are in the exhaust manifolds, or it can even be programmed like OBD1 just to run on one 02 sensor.

You will NOT need to run/have SAP air pump, nor the SAP valve, just weld the manifolds or use block plate, or simply run aftermarket header system.

You will NOT need to run/have fuel tank pressure sensor, nor charcoal canister valve, nor exhaust muffler flap solenoid

SAP pump purple relay will need to be there, but it already comes on the OBD2 harness already so just keep it there, do not plug in any other relay there or you will burn the harness.

SAP valve vacuum solenoid will need to be plugged in, but It already comes installed on your M52 so just keep it there, if you use the M50 intake manifold then It can be flashed out of the ecu also. Plug the vacuum line in the manifold. Remove the vacuum canister junk.

Remote fuel pressure regulator with running loss valve is a form of an upgrade, run it if you can, it reduces the fuel temperature, and fuel vapor bubbles, saves you fuel, or it also can be flashed out of the ecu.
You will use the OBD2 purge valve that is located under throttle body, and just run the line to your E30 charcoal canister output

No need for ASC/ABS signals connected to the ECU

EWS can be turned off and you don’t need to have any of the EWS junk components, no need to cut any wires. If you want EWS then use the EWS junk and let it just control the starter for anti theft protection. E30/E36 locks are not easy to crack, so the need for EWS is just an overkill

There are few OBD2 tuners in the US, but I can only speak of what I can tune and code, so if you have any questions please private message me. I have plenty of OBD2 ecu units ready to roll, no need send me anything, keep your own obd2 ecu, sell it along with the matching ews junk on ebay and use the money to buy quality flashed ms41.1 and it almost comes out free cost at the end.

You can just wire the OBD2 plug to your 20 pin diagnostic connector under the hood so that you can check the codes with regular obd2 scanner, no need to run the wires all the way inside the car.

These photos are to show you what I am talking about:

EWS2 module plug, bridge starter wires if you have E36


SAP pump relay leave it plugged in, comes on the OBD2 harness anyway



SAP valve solenoid, leave it there, just plug the vacuum port on the manifold



3 way running loss valve, it is an upgrade, run it if you can, it is small and compact, fits anywhere



Post cat. 02 sensors, you don’t need them, but if you want to run dual cats then just run them



Fuel pressure sensor, you don’t need this at all


Carbon canister valve, you do not need this, E30 already had the charcoal canister in the front, and valve is mechanical integrated in the fuel tank.


Muffler flap valve solenoid is flashed out of the ecu.


This is my testing car , with stack of OBD2 ecus ready to be custom flashed with quality tunes. And Tuning/Flashing software. I have the ability to flash any MS41.1 ecu to whatever tune or car, even 528i, make ms41.1 ecu into ms41.2. As long as it says ms41.1 on the side I can do it. MS41.2 is the ms41.1 with different software for S52, just minor difference in the software nothing major. I can make the ms41.1 software work same as ms41.2.



I hope this answered all of your questions,

[Slovik]

It will work but if you don't use the OBD2 FPR you will end up with a CEL, there is a plug on you harness for it, they are real cheap at the junk yard and every e36 seem to have the same one 3 bolts and a snip.

[325e10]

Left Mine OBD2 since I already had all the bits, was super easy really.

[328ijunkie]

^ Good to hear.


And yes, you can run OBD1 TB and OBD1 Fuel rail just fine. The ECU doesnt know the difference as the TPS is basically the same and the FPR is 3.5 bar just like the OBD2 one.

[Farbin Kaiber]

Just jumping in to say I'm also going OBDII s52.

[plain325]

Only solution ive found to ^ problem is early E39 OBD2 fuel rail. Its an obd2 rail with integrated FPR just like the OBD1 one.

Can i run a regular obd1 rail on my obd2 swap if i dont care about the fuel rail cover? I believe the odb1 regulator is a 3.5 bar unit, same as obd2.

[mammoth_e30]

i think that's a good idea. My once awesome OBDII / EWSII kamasutra thread is now utterly abandoned with most pictures/links down. I will take some time this weekend to shine it up and update some of the info such that i can be loaded to the 24v wiki page. I'm 6 OBDII cars in fully functional with Diagnostics port and all, plus who knows how many other cars used my thread so its worthy.

Imagine i did it up in 2007! first car i ever wired..

This would be a great addition! :D

A collection of correct OBDII swap info is much needed period. There is lots of searchable info here and the web but you can't count on it being correct.

I've got a S52 drive line with harness and dme sitting in the garage awaiting its turn in the chassis. Since I'm currently running a M50NV it makes complete sense to stay OBDII and avoid sourcing misc bits to run it on old technology.

I've never edited a wiki page but I created an account and it doesn't look very hard to follow the existing format. I don't want to jack this thread to talk about it, lets take it off line or make a new thread.

[328ijunkie]

Only solution ive found to ^ problem is early E39 OBD2 fuel rail. Its an obd2 rail with integrated FPR just like the OBD1 one.

[Gooch]

No not needed, just makes for a simple setup if you have extra OBD1 parts handy. Honestly I could go either way with the fuel rail, I just prefer the OBD1 FPR in the fuel rail.

Robert, have you physically used an OBDI rail on an OBDII motor? Please see my post #67. Are you running the fuel rail cover?

[328ijunkie]

Hmm. Maybe ill make a writeup on my site.......

[aplinweiss_is]

We could organize an OBDII section on the 24v wiki page....

This would be a great addition! :D

A collection of correct OBDII swap info is much needed period. There is lots of searchable info here and the web but you can't count on it being correct.

I've got a S52 drive line with harness and dme sitting in the garage awaiting its turn in the chassis. Since I'm currently running a M50NV it makes complete sense to stay OBDII and avoid sourcing misc bits to run it on old technology.