The Official OBD1 vs OBD2 argument thread.

[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]

^ 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.

[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.

[328ijunkie]

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

[metris228]

Is it as simple as this with the M54 engine and MS43 ecu?
Just flash out a heaps of options from the ecu?
Am I able to buy a harness adapter for this?

I already have a 330i wreck so already have everything I need... and I have no issues with mounting and running the drive-by-wire throttle.

[nmlss2006]

In all of this I have not yet seen hard data on how the OBD II ECU would be 'smarter' or 'cleaner', when you remove the air pump, the tank pressure sensor etc. You do have the more immediate diagnostics advantage, coupled with the more substantial advantage of not having to convert the engine IF you can get it with all the parts, certainly, but you have to weigh that against the fact that the swap is a lot less documented and supported by vendors.
By the by, the OBD I Bosch is certainly not 1980s technology as some poster up here has offered, perhaps some research is warranted.

[328ijunkie]

2 bank o2 sensors. Short and long term adaptation for each bank. Smarter idle control and knock detection...

[cmeptb13]

Why do you need an OBDI fuel rail? I'm running the OBDII rail on mine along with the FPR that was under the car on the e36.

You're right. The only reason you would need OBD1 fuel rail is if you're doing the m50 intake manifold swap. That's why it's offered with the m50 manifold swap kit.

[328ijunkie]

^You can run a OBD2 fuel rail on the OBD1 manifold easily...

[cmeptb13]

That's good to know. Thanks. So is the OBD1 rail simply for the use with the plastic cover then? Is there any reason at all why you'd need OBD1 fuel rail?

[nmlss2006]

Two O2 sensors, OK, how is the adaptation different and how is the idle control and the knock sensing smarter? Genuine question, mind, because as far as I know the differences are not material except in an emissions sense and then only if you use everything that was supposed to be there, but we're all here to learn.

[etxxz]

The computer itself is different, it processes much more data and i'm sure the bmw engineers took advantage of that capability to refine things. What - i probably will never know and we'll never understand. There's a lot more to just running than knock sensing and idle control. I work in a company that designs and tests motorcycle engines. You'd be surprised the endless amount of parameters we have to deal with to run a tiny itty bit better than a previous test.

^You can run a OBD2 fuel rail on the OBD1 manifold easily...

I second this. Its very easy (AND CHEAP) to DIY your own kit. OBD2 with M/S50 manifold. No problem. This where all if not most of the gains of the "obd1" swap come from anyways.


on a bad side of things. I have sold all my e30s. i'm out of the e30 world. will probably move onto e46 fanatics... If anyone should need obd2 support or wiring schematics pm me. I tend to receive emails on that ; | happy moddin to all.

[nmlss2006]

As an engineer by training, 'different' and 'much more data' will not encourage me to make claims about 'better' especially when coupled with 'we'll never understand'.
I don't mean to sound snarky, it's a statement of fact: if we're going to state that A works better than B, we should be able to give reasons and numbers. Or at least reasonable predictions for numbers. Because it may very well be that the 'different' is actually working worse when it has the typical idiotic intake, the typical idiotic exhaust, is running 10C cooler than it should, again typically etc - and it may very well be that the more advanced electronics cope less well with having out of spec conditions. This would actually be fairly realistic. So far, it's all speculation and I'll take it as such - with no offense intended.

[etxxz]

well here the big facts. OBD2 was introduced for emissions regulations. The OBD1 engines could not make the same power so BMW bumped up the displacements and restricted intakes to make up for this. So, as an already engineer that designs engines for a living you're gonna have to research on your own to compare the obd2 Siemens MS (41.0?) vs the obd1 Bosch unit. You can surely find online are dyno #s from multiple bimmerforums and r3v members. The bigger intake and less restrictive the exhaust, as idiotic as you think that is, also make big difference.. a hotter engine will typically make more power and run more efficiently than cooler one. I have extremely accurate data from many many engines with so many sensors it takes a whole day to connect everything and no you can't have it.

The thing is, define "worse" - more emissions, less power, higher cov, combustion instability, higher bsfc's?

Some, ie track junkies like me, could care less about these parameters as long as my car 1) ran well and 2) was faster than it was before. Ofcourse you ask me during work hours and i will answer differently.

[rThor432]

^^Like you said, I could care less if I'm running OBD1 or 2 as long as the thing runs right. I had OBD1 on my last S52 and it never missed a beat. Very simple setup. I'm running OBD2 on my new S52 because 1- Some tuners (read: the one I'm using) prefer the extent of some adjustments vs OBD1 and 2- I prefer the diagnostic interface that ISTA/D gives with OBD2 vs. OBD1.

Maybe I'll read through this thread and be convinced otherwise. Haven't hooked everything up yet and I've got OBD1 and OBD2 setups in my parts department.