RPM's going crazy

[rs4pro3]

Ok I just installed a piggy back computer into my 85 325e, but the problem is the rpm display on it is going crazy, it jumps all over the place, the tach is staying where it should and reading the correct rpm's. I connected the rpm input for the piggyback to the black wire pin #1 on the c104 plug by the ecu. Any ideas why it's not reading correct and jumping all over the place?

[RobertK]

Sounds like you got your SAFC in today...

I think you're supposed to have one wire go in to the piggy back and one going back out to the DME but I'm not sure because I have not had the pleasure of playing an SAFC.

[rs4pro3]

for the AFM wire yes, I figured it out, my Plasma booster and the Apexi wern't playing along together nicely. I undid the ground for the booster and grounded it to the frame instead of the coil, and now it reads just fine. I just have to find a MAF(i damaged the one I had installing a temp sender) and buy a wideband o2 and I'll be good to go.

[rs4pro3]

I should ad the SAFC-II is so easy to tune, I just have it in monitor mode right now, untill I get my wideband o2 and maf. But all it takes is a few button pushes and you can adjust the signal where needed.

[RobertK]

Silly boy.. when working with cars I NEVER share grounds in a DC environment. Glad to hear you worked it out. Next time we meet up I want to play with it.

BTW.. do you still want that 17 inch computer monitor?

[rs4pro3]

sometime yes, there is talk right now of a dragon run monday so I could pick it up then.