S52 OBD1 Conversion Complete...here's what I learned.

[SG_M3]

like that?

[///M3///M5]

like that?

Exactly

[///M3///M5]

Check your wiring.

Mine works now.

[SG_M3]

Check your wiring.

Mine works now.

I probably have it wrong, sad since its only two wires.

[///M3///M5]

I probably have it wrong, sad since its only two wires.

Also, I never did anything with the road speed sensor and it works fine.

[SG_M3]

Also, I never did anything with the road speed sensor and it works fine.

most chips delete this function. Mine works without it.

[vjlax18]

Great write up, but there are a couple of things you don't need to do. One is the rubber coolant hose instead of the metal. Leave the metal and just plug the end that goes to the TB and then plug the head were it goes to the TB. Dremel the valve cover down a bit so that the coil wires sit under the OBD-II cover. For a track car, you can also plug the vac lines going to the TB and the OBD-II ICV connector. Take apart the factory hose that clips to the vent on the front of the valve cover and run 3/4" tubing to a catch can.

[UDM Motorsport]

sorry to post on this thread...but figured i'd ask as i'm abit confused.

I'm installing a M52 in my 95 M3. I know the above instructions is on a 99 M3.
Does all the same steps apply? Meaning i'll have to replace all the sensors on the M52?

thanks
franklin

[jmitro]

M52 or S52? either way, i believe since the M52 is obdII you would have to use the OBDI sensors from the 95 M3, just as you would for an OBDI conversion for S52

[UDM Motorsport]

thanks....just wanted to make sure before i spend money on the sensors.

[vinnymac]

M52 or S52? either way, i believe since the M52 is obdII you would have to use the OBDI sensors from the 95 M3, just as you would for an OBDI conversion for S52

Yup...

[vjlax18]

Put the S50 crank in it and call it a 2.9L. Everything is the exact same when doing the conversion with the M or S motors.

[sprnova]

9. PCV – The OBD2 crank case vent is setup up differently than the OBD1 vent. There are several options to address this issue. If you are using the OBD2 valve cover, you can keep your OBD2 PCV setup and figure out a way to mount the breather valve (cone shaped plastic valve with round breather on top) under the intake manifold. If you are using the OBD1 valve cover, you should use the OBD1 breather valve that clips on to the crankcase vent port. The OBD1 valve has a vacuum line that connects to the plug that joins the ICV to the intake manifold and a large oil drain line that runs to the dipstick. The last option is a hook up a hose to the crankcase vent and run a breather catch can. I picked up a small length of 1” rubber hose and connected it to my OBD2 valve cover and hooked up the other end to the OBD1 breather valve and use a barbed connector to join the oil drain line to my dipstick.

Where did the larger of the 2 hoses coming off of the PCV valve go to prior to your conversion? I am reassembling my 3.2 OBD1 motor and I have the larger hose marked as going to the dipstick and I thinks its correct. But others have said it is supposed to go to the T-Body boot. I am not running tractional control so I purchased the '95 M3 boot that has to holes in it. One hole is for the Idle Control Valve hose but I dont know what the second one is for. Does anyone know??

[M3zie]

sorry to post on this thread...but figured i'd ask as i'm abit confused.

I'm installing a M52 in my 95 M3. I know the above instructions is on a 99 M3.
Does all the same steps apply? Meaning i'll have to replace all the sensors on the M52?

thanks
franklin

Hopefully you mean S52?

[bmxcm]

One hole is for the Idle Control Valve hose but I dont know what the second one is for. Does anyone know??

it is not needed, seal it up

[sprnova]

it is not needed, seal it up

That is the confusing part. Some people post that the larger of the 2 hoses plugs into the second hole on the bottom of the boot, while other say it goes to the dipstick pipe. Trying to figure out which one is correct.

[bmxcm]

That is the confusing part. Some people post that the larger of the 2 hoses plugs into the second hole on the bottom of the boot, while other say it goes to the dipstick pipe. Trying to figure out which one is correct.

i really don't think it matters, i would rather have it go to the oil pan tho than the intake, less mess

[sprnova]

i really don't think it matters, i would rather have it go to the oil pan tho than the intake, less mess

Problem is, what is it for? To vent off oil and air, or to get fresh air from the TB boot?

[checkerboard6]

For those who have done this (or understand the procedure), would the write up be drastically different for an s52 into an OBD1 car (325is)? I'm in the process of determining if the current s50 swap will survive the money-shift with a rebuilt head? If the motor is toast, I have many of the components from the s50 to work with.

[Serious]

For those who have done this (or understand the procedure), would the write up be drastically different for an s52 into an OBD1 car (325is)? I'm in the process of determining if the current s50 swap will survive the money-shift with a rebuilt head? If the motor is toast, I have many of the components from the s50 to work with.

http://homepage.mac.com/aceves/OBDI/OBD_ONE1.htm

[slcook54]

Great write up Vinny, I remember when I bought an OBDII supercharger kit on the basis that 'only' electronics were different, that was a costly mistake. Great to see some solid information!

[joon]

This is the best OBD-I conversion thread around! I have a few questions for the guys who've done this conversion.

Is it possible to reuse the OBD-II coolant hose at all? I intend to plug up the throttle body and bypass the heater core so that ought to simply the coolant circuit.. (it's hot and humid here all year round) I was studying the hoses and it seems possible, I'm sure I missed something though.. the reason I'm asking is that the hoses on my 16 year old OBD-I engine are rather rotten, and the low mileage donor S52 still has really nice hoses

[vjlax18]

I wouldn't bypass the heater core since it's nice to have in an overheat situation. You can and should use the metal pipe. Just double clamp a bolt in the end of a hose and clamp the hose onto the pipe that goes to the TB. Or if you're really handy, switch over to the euro style cooling system that's self bleeding.

[vinnymac]

This is the best OBD-I conversion thread around! I have a few questions for the guys who've done this conversion.

Is it possible to reuse the OBD-II coolant hose at all? I intend to plug up the throttle body and bypass the heater core so that ought to simply the coolant circuit.. (it's hot and humid here all year round) I was studying the hoses and it seems possible, I'm sure I missed something though.. the reason I'm asking is that the hoses on my 16 year old OBD-I engine are rather rotten, and the low mileage donor S52 still has really nice hoses

You definitely can but it would require a few modifications and some creativity in plugging the lines you don't need and routing some hoses for the lines you do need to retain.

I would stick with the metal hardline if you can since it's more robust. However, there isn't any short term risk if you switch to the rubber OBD1 cooland hose.

[vjlax18]

Both the rubber and the metal have the same amount of connections. However, to switch to the rubber one, you need the Turner adapter. Stick with the metal, it's easier and cheaper.