S/M50 and S/M52 Knock Sensors Interchangeable… or Not…

[IMSARS69]

Have noted that there are two different types of Knock Sensors for the M and S engine series. The M50 and S50 uses a pair of separate two wire single sensors [ at ~$90 ea. ], while the M52 and S52 is a Siamesed pair of sensors with a single four wire connector [ at ~$90 for the assembly, or half the cost for the same ‘knock sensing coverage’ ].


The S/M50 setup with separate sensors, two wire connectors ea. looks thus:

14 Ping Sensor 2 12141738667 $90.58

Also shown in several pics here as aftermarket from Advance Auto - Single Sensor - Two Wire

The S/M52 setup with dual sensors, four wire combined connector looks thus:

16 Ping Sensor 1 12141703276 $90.58

Also shown in several pics here as aftermarket from Advance Auto - Dual Sensors - Four Wire

Question is, can one use either setup for the 50 or the 52 so long as the wiring is properly connected by splicing or splitting as required. That is, are the sensors the ‘same’, only the wiring pigtail and harness being different. BMW is noted for their propensity to revise wiring harnesses especially during the time frame of these engines, i.e. the mid 90’s, ex. best I can tell they had three or four different ‘Front Harnesses’ during a three or four year period.


What do folks who’re swapping an S52, with the dual Siamesed sensors w/ single four wire connector do to adapt to OBDI specs using an OBDI harness having two separate connectors for the separate sensors?


IF the sensors are compatible then it seems all one needs to do is splice / connect the appropriate wires from the respective pigtail(s) to the harness connector(s).


IOW can I use a Dual Sensor setup designed for the S/M52 with the four wire connector [ for one price ] with my S50 engine and splice it into my M50 OBDI harness having (2) two wire connectors. The ECU is a Red Label w/ appropriate Turner chip.


This source http://ddurrelltech.com/bmw/e30_to_m...rsionlist.html implies they are NOT compatible and it can’t be done in that it recommends the following [ snipped from complete swap parts listing ]:

§ M52/S52 conversions: To go full ODBI (if desired), all the ODBI sensors will be needed, as well as [ snip ]. Need both knock sensors and other miscellaneous things

§ Parts list to convert from ODBII to ODBI

o ‘92-‘95 M50 harness

o Knock sensors (2)

That confusing nuff… ‘;) What say Ya’ll? Can it be done… or Not…

TIA…

[Farbin Kaiber]

Search in this forum quickly finds...

http://www.r3vlimited.com/board/showthread.php?t=248023&highlight=obd1+knock+sensors

And,

http://www.r3vlimited.com/board/showthread.php?t=228185&highlight=obd1+knock+sensors

[e30rapidic]

nope

[IMSARS69]

Thanks to Farbin and e30rapidic for their responses...

Search in this forum quickly finds...

http://www.r3vlimited.com/board/showthread.php?t=248023&highlight=obd1+knock+sensors

And,

http://www.r3vlimited.com/board/show...+knock+sensors

Appreciate your humoring me here... I frequently find searching forums a real PITA since they seem to have a rather limited 'filtering' capacity which generates huge numbers of unrelated 'hits'... of course I may be overlooking something with the searching feature but don't think so since I've been mess'n round with forums since 1200bps modems...

When I think to, I use the Google search 'work around' where ya put in the forum URL and then the search parameters... that sometimes works wonders...

To be honest I'm not sure if I did due diligence on R3VLtd or not as I was covering the three Bimmer sites I frequent and easy to lose track... being an OF with chronic CRS and 'ol Timer's Disease an all... ';)


The links you provided definitely covered the issue, wish I'd picked up on them and saved Ya'll the trouble... and me for that matter... ';)

Appears to be as I thought it might, that is the 'pingers' are [ probably ] NOT 'block / engine specific', but ARE 'electronics specific'...

nope

Gotcha... see above...


FWIW I got the following very reasonably priced source for Knock Sensors from Jakobie1086 on Bimmerfest at:

1992-1995 BMW 325i Knock Sensor Bosch for $57 ea. This doesn't show the '95 M3, but cross ref of PN 12141738667 (Ping Sensor) on RealOEM shows they're all the same...


Thanks again...

[nando]

knock sensors are highly tuned devices. it might "work" with a different sensor, but because they are tuned for specific frequencies it's unlikely it will function correctly.

[IMSARS69]

knock sensors are highly tuned devices. it might "work" with a different sensor, but because they are tuned for specific frequencies it's unlikely it will function correctly.

Thanks for the input, however based on what I found as noted above, and personal knowledge and belief, that's not the reason for not being interchangeable, since in fact they are 'interchangeable' on the various engine blocks and need to be when swapping an S/M52 over to an OBDI setup... If frequencies were an issue that wouldn't be possible...

Which is to say the 'pingers' are [ probably ] NOT 'block / engine specific', but ARE 'electronics specific'...

OCTJMO... ICBW...

[nando]

Which is to say the 'pingers' are [ probably ] NOT 'block / engine specific', but ARE 'electronics specific'...

OCTJMO... ICBW...

that's exactly what I'm saying. the DME is tuned to look for specific frequencies from the sensor, which actually comes across as some sort of electrical signal. If that signal isn't identical then the DME will be tuned for the wrong signal and it's not going to read knock correctly.

the blocks are pretty much the same, and economically it wouldn't make sense to change the connector on the sensor just for the heck of it. I would assume that the signal (voltage, resistance, whatever it is) had changed between OBD1 and OBD2. at the very least, I'd expect the resolution to be much higher on OBD2.

[Farbin Kaiber]

Thanks to Farbin and e30rapidic for their responses...


Appreciate your humoring me here... I frequently find searching forums a real PITA since they seem to have a rather limited 'filtering' capacity which generates huge numbers of unrelated 'hits'... of course I may be overlooking something with the searching feature but don't think so since I've been mess'n round with forums since 1200bps modems...

When I think to, I use the Google search 'work around' where ya put in the forum URL and then the search parameters... that sometimes works wonders...

To be honest I'm not sure if I did due diligence on R3VLtd or not as I was covering the three Bimmer sites I frequent and easy to lose track... being an OF with chronic CRS and 'ol Timer's Disease an all... ';)


The links you provided definitely covered the issue, wish I'd picked up on them and saved Ya'll the trouble... and me for that matter... ';)

Appears to be as I thought it might, that is the 'pingers' are [ probably ] NOT 'block / engine specific', but ARE 'electronics specific'...

Thanks again...

Glad to be of service, I know many have issues with the search feature here, but for me, I feel pretty confident with it, so no problem on my end, glad to be able to help someone find something needed.

[e30rapidic]

Hey IMSA, I got a PM notification from you in my email but no PM.

I've been to VIR many times but never taken the cabrio. I think roll bars look out of place in them and I don't want to spoil mine. I've been around VIR in a lot of different cars, including my old 325is. As for racing, I've got close to 30 years under my belt but mostly Late Model Stock Car stuff around here. Orange County, Wake County, South Boston, Myrtle Beach, etc.