Quick/Specific DB Gauge and LC-1 Install Questions

[Cinnabar325is]

Hopefully okay to post in this forum, I figured with the question regarding the gauge wiring, maybe the General Tech forum was better than the Tuning Forum.

I'm installing the LC-1 and DB Gauge in my '89 325is that is running the original Motronic 1.3 ECU. For now.

Two basic questions:

1) I found this courtesy of blueapplesoda:

Wiring scheme is
Pin 1 - Sensor Ground (Grey) -> LC-1 White (sensor ground), one end of button, black pigtail of LED
Pin 2 - O2 Signal (Black) -> LC-1 Yellow (output 1, default narrowband output)
Pin 3 - Heater Ground (White) -> LC-1 Blue (system ground)
Pin 4 - 12v From o2 relay (White) -> LC-1 Red

You will be left with a Black calibration wire, the red pigtail of the LED, and the other end of the momentary button. Connect the three (crimp/solder), and insulate it and stuff it away.

So, is it okay to to eliminate the narrowband 02 sensor entirely and run the Motronic ECU from the wideband 02 if I wire it as shown above?

Or will I run into a host of issues? I've read opinions saying yes and no. It would be nice not to have to weld in a second bung and add all that extra wiring.

I understand also that I'd have to alter some of the output settings to make the Motronic ECU happy... could anyone elaborate?



2) When wiring up the DB Gauge, I would like to know where to tie in the red (12v power, ignition switched), black (ground), and yellow (display dimming) wires that will give me the cleanest and best quality installation. Final gauge placement is undecided, but likely in the center of the dash/console area. So where should I best tie in to switched 12v power and a dimming source?

Messing with and adding wiring always makes me nervous, I'd like this to be neat and clean!

Thanks!

[nando]

I would suggest jumping pin 85 of the o2 relay to pin 85 of the fuel pump relay, so you dont have to worry about the heater control shutting down your controller.

There are lots of dimming and supply sources in the radio area, you can use one of those vamp clamps to tap into the wires.

The default narrowband output of the lc1 should work as is, its on wideband outputs to aftermarket ecus that you have to change the default settings.

[Cynical 1]

only issues i have had with the LC-1 is a CEL for the o2 heater - only if you run the ecu off of the LC's sensor in narrow band mode.

you can put a resistor in place to trick the ecu to think the heater is working, but i found it easier and better in the long run to just add a second o2 bung and keep the stock o2 as well...

and the innovate site has all the install/wiring instructions on it.

[Cinnabar325is]

only issues i have had with the LC-1 is a CEL for the o2 heater - only if you run the ecu off of the LC's sensor in narrow band mode.

you can put a resistor in place to trick the ecu to think the heater is working, but i found it easier and better in the long run to just add a second o2 bung and keep the stock o2 as well...

and the innovate site has all the install/wiring instructions on it.

The 02 heater would still be working with LC-1, I guess the Motronic ECU would just think it was not?

Where would this resistor be added and what resistance is required? Again, I'm not great with electronics, sorry for the simple questions. You'll have to dumb it down for me.

I really like the cleanliness of using just one O2 and then I can use the factory O2 12v power and ground for the LC1 instead of adding a bunch of extra wiring.

[nando]

I really doubt motronic is smart enough to tell that the o2 heater is disconnected, and you are still drawing a current by powering the lc1.

Actually, given how it is wired im pretty certain there is no way foe it to tell.

[Cinnabar325is]

I would suggest jumping pin 85 of the o2 relay to pin 85 of the fuel pump relay, so you dont have to worry about the heater control shutting down your controller.

There are lots of dimming and supply sources in the radio area, you can use one of those vamp clamps to tap into the wires.

The default narrowband output of the lc1 should work as is, its on wideband outputs to aftermarket ecus that you have to change the default settings.

Thanks for the help!

I'm assuming you mean the heater control for the 02 sensor? Could you explain why that might shut down the LC-1?

If I understand it right, pin 85 is the coil ground for both relays, correct? What's the best way to jump them? I am no electrical guru! But trying to learn.

Vamp clamps? Like a Scotch lock I assume?

[Cinnabar325is]

UPDATE: The car is up and running on the LC-1 and wideband 02 sensor. So the ECU is being signaled by the wideband, no more narrowband sensor. Everything seems/seemed to be working properly, included the gauge until I took it out for a drive.

Here's what I'm seeing: at normal cruising, with light throttle in 4th or 5th gear, it's reading anywhere between 16-17 AFR. Pretty lean. Letting off completely, it jumps to 22.4 as it should.

Now, if I get on the gas, anything more than half-throttle, the AFR pegs at one number anywhere between 7.4 and 9.1. And then the CEL comes on.

When I left off the gas and coast, it stays pegged between 7.4 and 9.1 for a few seconds, and finally jumps to 22.4 The CEL stays on.

If I then ease back into the throttle to cruise again, it goes back to reading between 16-17 AFR. And the CEL goes off.

Now, I've done nothing with the LM Programmer and the laptop yet. Nando, you mentioned this in a thread I found:

as far as using it with Motronic - the reason it doesn't work out of the box is because the warmup and error output voltages are set to a stupid value by default. you'll want to reprogram the narrowband outputs, use ~.45v for the error & warmup states.

I'd also do this even if you're using it with a standalone ECU, only you'd be setting the wideband error & warmup states to a stoich value.

what happens by default is the controller outputs a full-rich state while the sensor is warming up (which takes 10-15 seconds). During this time the ECU is seeing this full-rich value and is trying to correct for it. That makes the engine run like shit.

I have no idea why they default it to rich, the safer way would be to default the reading as lean, or even better, stoich so a cold/bad sensor doesn't have any effect at all.

Is this something I should definitely go ahead and change? Any other settings I should alter?

Lastly, is what I'm seeing related in any way to what was mentioned about the heater control shutting down the LC-1? I have not jumped 85 pins on the fuel pump and 02 relays.

Thanks.

[nando]

ah. yeah that's probably a good idea to do. I forgot the narrowband setup does that too.

it's resetting because you didn't make the pin 85 connection, yes. you want to sever the connection to the DME and connect it to the fuel pump instead. then the O2 relay will be on at the same time as the FP relay. The O2 heater isn't neccesarily on all the time which is why the LC1 resets when you hook it up stock.

[Cinnabar325is]

ah. yeah that's probably a good idea to do. I forgot the narrowband setup does that too.

it's resetting because you didn't make the pin 85 connection, yes. you want to sever the connection to the DME and connect it to the fuel pump instead. then the O2 relay will be on at the same time as the FP relay. The O2 heater isn't neccesarily on all the time which is why the LC1 resets when you hook it up stock.

Ok, so under normal circumstances, the DME grounds the O2 85 pin when the car starts and that flips the relay to power the 02 heater correct?

When you say sever, should I actually be cutting the wire for the 85 pin at the 02 relay? Or will adding the jumper in addition be enough?

What's the neatest/cleanest way to jump the 85 pins?

[nando]

I would cut it at the O2 relay and connect the O2 relay to the FP relay instead. the remaining wire you can just leave, all the DME is doing is grounding that pin.

[Cinnabar325is]

Okay, I cut the wire to the 85 pin on the 02 relay and then jumped that pin to the 85 pin on the fuel pump relay.

I also went into LM Programmer and changed the warm-up and error values closer to stoich for both analog outputs.

My next question is why does my DB gauge read ~2 AFR points higher than the laptop with LogWorks3 running?

If the laptop says 16 AFR for example, the gauge will read 18.

And also, either my car is running extremely lean or the LC-1 isn't reading right. I have yet to see anything less than 16.

[nando]

Gage calibration?

What does logworks read at warm idle?

[Cinnabar325is]

Best that I know, there is no gauge specific calibration. I just spent a good 40 minutes driving the car around the countryside here and the gauge still reads about 2 AFR points higher than what the laptop shows. I'm betting that the laptop is accurate based on the numbers I'm seeing. Need to get the gauge figured out though...

Some other things I noted:

-Right at the start of the drive, I had what seemed to be a massive fuel cut while at half throttle, jarred the car very hard and the check engine light came on permanently. I've never had that happen before and it didn't happen during the rest of the drive. CEL is still on, but I didn't check the code.

-Warm idle is anywhere from 15 to 16 AFR, sometimes dipping into the high 14s. It fluctuates quickly over large ranges (I have the reference rate for the LC-1 changed from instantaneous to 1/12 of a second, should I slow it more?)

-WOT AFR seems to vary based on the the gear. It was a bit leaner and variable in 1st and 2nd. It even out and richened in 3rd, 4th, and 5th... I was seeing mostly 13.6 to 14.0 in the upper gears.

-At partial throttle, it is pretty similar to the idle AFR, just a hair on the lean side of things.

Any thoughts?

P.S. - Now my fuel pump seems to stay on for a few seconds after I shut the car off, never did that before. Maybe related to the pin 85 relay jumper?

[Cinnabar325is]

Some updates:

Checked the CEL code, it's a 1221 which relates to a bad 02 connection. If I clear it, it doesn't seem like it will come back.

I did a bunch of research on the different readings between the DB Gauge and the laptop running LogWorks. I believe the problem is a ground offset, since the LC-1 is grounded through the ECU, but the gauge is ground to the factory ground point just left of the steering column.

Is there any way to can ground the gauge so it doesn't have an offset with the ECU's ground?

According to Innovate, I should be able to adjust the Analog Output 2 (which feeds the gauge) to circumvent this issue. For example, if the gauge is reading 2 points higher than the laptop, I can lower the gauge AFR range two points to compensate (i.e.- instead of 0V=7.35AFR it would become 0V=5.35AFR).

However, the LM Programmer will not let me adjust the values to anything less than 7.35. So that doesn't help!

[Cinnabar325is]

UPDATE: I'd thought it would be nice to complete the story for anyone dealing with this in the future.

The bottom line is that I chose to run the power, ground, and signal for the LC-1 through the stock 02 harness for the cleanest installation possible. And when I tested the pins at the end of the stock harness, the meter showed 12v power and decent ground.

In the end, it seems the ground provided by the stock harness is not good enough for the sensitive LC-1.

I rewired things, so that the 12v power and signal from the LC-1 are still fed through the stock 02 harness, but the LC-1 is ground directly to the G-103 (I think that's the right number) on the passenger strut tower.

That cured my issue with the DB gauge reading differently than LogWorks3 on the laptop. Everything seems to be working very nicely now except it occasionally makes the CEL come on. I'll have to dig into that more.