E30 Speedo How To Guide.

[ThisGuy310]

I would like to preface this by saying much of the info I am typing out has already been figured out by several other people on this forum, so in no way am I trying to present this as new information. I'm simply posting how I managed to get an E30 speedometer to work with my M20 swap with minimal $ invested.

And hopefully this might help out other guys who have issues getting a speedometer to work when using drivetrain parts from cars that did not use mechanical speedos. Some people might not like this approach, and there are several other ways to go out about this, but this ended up being the easiest way for me to get a working speedo (that still looks factory IMO) into the stock e21 dash without having to spend $800 on a 323 transmission.


The parts I ended up using to get this to work:
-Complete Motometer cluster from E30 325i
(other clusters may work but I will explain why I chose the Moto)
-Rostra Precision Controls 250-4165 speed sensor (26 bucks on Summit)
-VSS Vehicle Speed Buffer TPI TBI --- 25071437 (25 bucks on ebay or free if you can find one at the boneyard )


To start things off disassemble your Motometer cluster.
You want the Motometer cluster because unlike the VDO cluster the Moto speedo has a potentiometer on the back that can be used to calibrate the speedo.

The issue you will notice right away going from an e21 speedo to an e30 is that the e30 speedo is approximately 1/4" smaller in diameter. Because of this I ended up making a spacer ring to fit around the e30 speedo.
I simply used the plastic panel from the cluster and cut out what I needed.


The e30 cluster is more of a grey color whereas the e21 is kind of a semi gloss black. I gave the ring a quick rattle can and then hot glued it to the speedo. I know this is a bit ghetto but it does the job.

Now the spacer ring should fill the opening in the e21 cluster nicely and you'll be wondering how to mount the speedo as there is not way it's going to fit.
This is what I ended up doing, but if I had to do it over again I would simply make this bracket entirely out of metal. What I did works but it is a PITA and could easily be improved upon.
I cut out the mounting piece from the e30 cluster, and then cut out the bracket from the e21 cluster so that the e30 plastic piece sort of fits into it.


I glued the blue plastic piece to the metal bracket, but like I said, If I could do it over again I would simply use the blue plastic piece as a template to make a small piece out of metal and weld that to the e21 bracket instead.
Anyways here is a shot of how the gauge ring looks within the cluster.




This is how I ended up tackling the electrical side of things.
I needed a power source for both the speedo, and the speed buffer amplifier unit. You could use existing wiring for all of this but I ended up making a small fuse box that I used to power a few other things as well.

I borrowed the idea of the buffer unit from another website, essentially he experienced poor performance out of the magnetic pick up unit at low speed. He explains everything here, as well as the wiring diagram for the buffer.
http://duster318.freeservers.com/tec...iversalvss.htm

Next I mounted the pickup on the driveshaft, I simply followed the manufactures instructions.

I routed the wires to the buffer unit.



As for wiring the speedometer, beyond the circuit board in the cluster, the speedo simply has a 5 pin connector. Two of these pins are for the OBC I believe but the three I was interested in were power, ground, and signal input.
Looking at the speedo, + pin is your 12v power input (which I took from my fusebox) pin 31 is your ground, and pin 31b is the signal input which I took from the buffer unit.


Getting a good connection on here was kind of tricky but I ended up cutting apart the e30 connector and shortening the three pins I wanted.

I then used heat shrink butt connectors to attach my wires to the inout pins. (orange=12v from fuse box, green=ground, black=output from buffer)


View of the back of the cluster, I used spade connectors to make it somewhat removable.

Pic of the connectors to plug into the cluster.



I just drove the car today, and without any adjustment yet to the potentiometer it reads within 10 mph, so I am hoping there is enough adjustment to fix that. The movement of the needle is very smooth and linear. I'll update the thread after I try and calibrate it to see how close I can get against a GPS.

Picture of it mounted (I had to switch back to the stock tach unfortunately)
I should also note that due to the depth of the e30 speedo the air duct is in the way. I got a bit frustrated with this so I just took a heat gun and warmed it up a bit and bent it out of the way. It only needs to be adjusted a half inch or so.

For now I just wedge the buffer up in the glovebox, and I'm planning on just sticking the fusebox up somewhere in the glovebox so that it is accessible.

[Jester323]

Good job & thanks for a clear write up.

I hope that hot glue holds up for you!

[lasvegascop]

Good job brother.... I like it...and I personally didn't know about the difference between the VDO and MOTO units. Dang it, if I knew it, I would've used the same as you....

Anyways....Since you're there man and obviously know how to go around electronics, just use the E30 tach too.....I dropped it into my E21 cluster and it looks good. I think? It's on my build thread so you can check it out if ya like to see what it looks like? (I have a feeling you already seen it tho ahhahahah)

[bflan2001]

Very nice...on an unrelated note, I'll give you a grand for those Zender five-spokes. Where did you find those?

[ThisGuy310]

Good job & thanks for a clear write up.

I hope that hot glue holds up for you!

Thanks, the glue is definitely not the right way to do it, but it does work. When I pull the cluster out to try and better calibrate the speedo, I probably will just replace the blue plastic with a metal bracket.

Good job brother.... I like it...and I personally didn't know about the difference between the VDO and MOTO units. Dang it, if I knew it, I would've used the same as you....

Anyways....Since you're there man and obviously know how to go around electronics, just use the E30 tach too.....I dropped it into my E21 cluster and it looks good. I think? It's on my build thread so you can check it out if ya like to see what it looks like? (I have a feeling you already seen it tho ahhahahah)

I definitely watched your build thread, and your cluster came out great. I couldn't quite figure out how you got the E30 circuit board wired up. You make a good point about using the E30 tach, but I kind of want to keep the stock clock. But I might change my mind as the 320 tach reads about 8-1200 rpm high.

Very nice...on an unrelated note, I'll give you a grand for those Zender five-spokes. Where did you find those?

I have lots of brand new old stock sets of zender wheels, they are from a good friends collection and I'm helping him sell them.
Unfortunately all but 1 set are either 4x108 or 5x112.
I have complete sets of four for all of these wheels pictured. Most sets have the original boxes/packaging.
Everything is for sale except the white turbos.

PM me if you want more info.

[Zan320]

Nice work. Also, could'nt you just swap the face of the 323 tach onto the 320 tach? I remember reading somewhere of a guy doing this. Done by carefully removing the needle and two screws.

[02inTheRockies]

Great write up and BTW- I got the intake boot yesterday (looks great), thanks for helping me out with that

[ThisGuy310]

Nice work. Also, could'nt you just swap the face of the 323 tach onto the 320 tach? I remember reading somewhere of a guy doing this. Done by carefully removing the needle and two screws.

You probably could swap the face, but the calibration would still be off. I adjusted the 320 tach with the potentiometer, but it needs an internal resistor to be changed to be accurate.

Great write up and BTW- I got the intake boot yesterday (looks great), thanks for helping me out with that

Glad you got it.

[davetech74]

Hi I am just swapping in an e30 5spd this morning and woul love to see some pics of this thread. Can anyone direct me to them?

[hotdish]

Hi I am just swapping in an e30 5spd this morning and woul love to see some pics of this thread. Can anyone direct me to them?

Use this: https://www.bimmerforums.com/forum/showthread.php?2354628-Photobucket-Hyperlink-Embedded-Photo-Fix!

[dups]

dang, not working for me. I restarted the browser. Need to reboot?

[dups]

aha! gotta run a quickclean (Mcaffee users) or just delete your browser image cache after adding it to chrome.