Tach coding plug question

[highoutput]

I know this has obviously been covered, but i wanted to ask directly for clarity.

I swaped an M50 into my '84 318i and the tach is off,....big suprise.
I've read that I just need to get a coding plug from a 325i and "plug it in".

THEN, I read somewhere that you have to have an '87 and up tach for that to work

So can someone give me the real info please?
My tach goes up to 7k, but I don't want to get a 325i coding plug and find out I really need a whole new tach.

Thanks for any help

[Matt-B]

I dont think your cluster has a coding plug, so i think you need a new cluster also...

my 84 had no coding plug, it was "built in" if i remember right

[kalib0y]

yeah the older tachs dont have coding plugs. If I may add a question. Would an E30 M3 coding plug work if I have the e30 m3 cluster? Right now I am using the 325 plug with the M3 tach so my RPMs are about 500 off

[trackjunkie21]

Nope, it sends the signal for a 4 cylinder engine, you need an e28 m5/ e34 m5 one, but that takes a bit more "work"

[RoadHazard]

yeah the older tachs dont have coding plugs. If I may add a question. Would an E30 M3 coding plug work if I have the e30 m3 cluster? Right now I am using the 325 plug with the M3 tach so my RPMs are about 500 off

If you're running a M50/S50 then you need a coding plug from a 6 pot car. It should work with your M3 cluster. I have that setup too. But I don't know why your RPM is off. Maybe you need to double check the PN on the coding plug.

[Adrian_Visser]

It won't work 100% because the m3 tach redlines at 8k the needle will deflect to what it should be at on a 7k tach so it will read low on an 8k tach.

[Chris916]

i was just doing reading on the "coding plug" needed since i found out this weekend my tach on my 91 318is is also off with the m50. does anyone have a picture of this coding plug and where it goes for referance?

thanks

[Matt-B]

i was just doing reading on the "coding plug" needed since i found out this weekend my tach on my 91 318is is also off with the m50. does anyone have a picture of this coding plug and where it goes for referance?

thanks

have you bothered to do a bit of looking around? searching? ;)

[Chris916]

Awesome thanks man. Honestly no i didnt do much searching lol. this thread popped up just as i started searching so i thought ip ask :P

[kalib0y]

If you're running a M50/S50 then you need a coding plug from a 6 pot car. It should work with your M3 cluster. I have that setup too. But I don't know why your RPM is off. Maybe you need to double check the PN on the coding plug.

the tach still sweeps the same as if the 7k 325i tach was in there its just the printing of the numbers is shifted a bit so it reads higher

[highoutput]

Poop.......I dont have a coding plug, for sure. So! Looks like I need a new cluster.
Or maybe I'll get a monster Tach, and drive around like I have a spare tire mounted on my dash.

[kalib0y]

^ thats real racer status there brotha! :)

[RoadHazard]

It won't work 100% because the m3 tach redlines at 8k the needle will deflect to what it should be at on a 7k tach so it will read low on an 8k tach.

Ah. I see. I didn't realize they had different redlines.

[Hobbes]

All E30 dashes have some type of way to change from 4cyl to 6cyl or to change injector size. The older ones had a physical plastic plug thing in the back of them instead of the chip that goes in the front.

Edit: http://www.e30tech.com/forum/showthread.php?t=96921 - See post 7 and 8. IIRC, an eta plug in a 7k dash that is running a 24v or 2.5 m20 will read correctly. I made a dash for a friend from a broken 325e dash and a M10 7k dash and it worked fine on his NVm50.

[highoutput]

Thanks for the info, buy idk where I'd get just that plug ( if anyone has one , let me know). It seems only the old clusters had them so I'm sure theres not to many around. I'm just going to end up getting a new cluster eventually.....