I've been tasked with making a harness for an '82 SC 3.0 going in a 914. This is a Lambda O2 sensor engine with an ECU. The customer didn't think it was an ECU engine when we talked, and I don't think he's got an ECU.

With his core harness on the bench, I'm mapping it out, I don't see it working without an ECU.

I've done a couple non Lambda CIS harnesses, but this is the first one with an ECU. On a 911 the ECU is under the passenger seat and is connected to the engine and the fuel pump via the chassis harness.

Anyone walked down this path before?

If it does have one it's originally a narrow band.
Many WB meters put out a "simulated" narrow band signal, it's one wire, usually in the dash connection wiring. The WB meter/gauge itself still works as intended.
The ECU on early cars is just looking for stoch, 14.7:1 AFR

The lambda on an 81 sc controls fuel pressure modulation.. Most disconnect with no issues.. I can tell you this it really is not an ecu but rather just makes small changes in pressure to adjust mixture.. I had this initial setup in my 77 911 that eventually became a 3.2 ss turbo engine with megasquirt and 400 whp.. That was 15 years ago though..

If the fuel distributor has a frequency valve on it you'll need the control system to make it work. With the O2 sensor disconnected the control unit runs the frequency valve at a median value. With no signal the valve doesn't cycle between open and closed, greatly affecting the mixture. With the control unit across the top this diagram shows there's a few other components you'll need.

Click to view attachment

I had unhooked my o2 sensor to mess with the mixture on my 82 sc - forgot to hook it back up. Seemed to drive just fine for who knows how long..

I've done a little reading on this, and one guy had 22% lower MPG, which isn't good for the engine. I'm waiting to hear back from my customer for more details