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Old 05-05-2009, 07:28 PM   #1
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Default Cops issue - interference with LC-1

I installed a set of COPS today following the instructions in the Lazzer/Braineak thread. They started and ran fine, but I'm getting interference on my LC-1 now. I have the LC-1 installed with the two grounds coming together into a single wire then grounded at the ECU ground on the intake manifold.
It's reading the correct A/F for a second then bounces between lean and rich then back to correct for a bit then wacks out again.

Anyone ran into a anything like this before?

I have a feeling it has to do with the LC-1 grounding.
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Old 05-05-2009, 07:35 PM   #2
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Definitely an issue with the LC1 ground. Where do you have the coils grounded to?
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Old 05-05-2009, 07:38 PM   #3
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Tried three different grounds, one to the ECU/LC-1 ground, one to the valve cover/body ground, and one time ungrounded. It acted the same way all three times. I put the stock coil back on to test and the interference went away.
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Old 05-06-2009, 01:16 AM   #4
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Maybe you have misfires?
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Old 05-06-2009, 02:01 AM   #5
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It ran smooth without any misfires.
I'm going to re-do the LC-1 grounds tomorrow. I'm willing to bet that's the issue.
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Old 05-06-2009, 10:44 AM   #6
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Quote:
Originally Posted by Fidgitk View Post
It ran smooth without any misfires.
I'm going to re-do the LC-1 grounds tomorrow. I'm willing to bet that's the issue.
I would revert to the stock ignition if you can and see if it goes away to confirm it in fact is the cops and you didnt develop a new problem.

Something makes me doubt its the cops.
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Old 05-06-2009, 11:07 AM   #7
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Quote:
I put the stock coil back on to test and the interference went away.
I believe he's already confirmed the cops are the culprit.

On my setup I have a Link and LC-1. The Link grounds to the on the exhaust side near the back of the engine. I've grounded the heater ground on the LC-1 to the body, and the system ground to the same place the ECU is grounded. No problems with my COPS.

Jay
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Old 05-06-2009, 11:49 AM   #8
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OH MY BAD. I didnt even notice he wrote that.
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Old 05-06-2009, 06:27 PM   #9
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Hmm... well I redid all my grounds and I'm still getting interference.
I'm not sure what else could cause this.
Here is a log of the interference.
Attached Files
File Type: xls datalog200905061606.xls (1.01 MB, 61 views)
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Old 05-06-2009, 06:47 PM   #10
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You should be grounding the system and heater wires separately. Did you do that?
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Old 05-06-2009, 06:53 PM   #11
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According to the LC-1 manual you should ground them together.

From the manual:
Quote:
5. The BLUE and WHITE wires should all be grounded to the same ground source.
Optimally, these (and any other MTS device ground) will be soldered to the same lug, and
connected to a single point. When this isn’t possible, connect each one to a separate lug,
and attach in close proximity. Multiple lugs on the same bolt is not optimal, and can result in
unwanted signal “noise.” When possible, soldering is always better than crimping. Please
see chapter 2.3 for more information on Electrical Grounding Concerns.

2.3 Electrical Grounding Concerns
The electrical environment inside a car provides unique challenges, combining high voltages and
currents, low-voltage signals, convoluted signal paths, and variable conditions (i.e., fans turning
on and off, or starter cranking).
When using precision electronics, it is important for ALL electronics to share a common ground.
Remember that “Ground” is more than just the return path for any circuit- it is also the reference
against which any voltage is measured.
Since it is not always practical to ground every device to the exact same location, here are some
tips on grounding:
1. The BEST grounding scheme is all grounds (i.e., ECU, Gauges, LC1 heater, LC1
system, etc.) SOLDERED into a single lug and bolted to the engine block.
2. The next best is all grounds attached to the same source, as close as possible, but on
separate lugs. This is because even the corrosion between lugs can create ground
offset and noise. Incidentally, this is why many ECUs have separate ground wires for
injectors vs. ECU system ground- separating high voltages and low voltages reduces
noise.
3. Grounding to the engine block is usually better than grounding to the frame.
4. Grounding a gauge to the radio is usually bad- ground offset can vary with volume.
5. Grounding to an ECU housing is generally not optimal- housings are strapped to the
frame for shielding, but not necessarily grounded.
6. One of the WORST things to do is to ground most of your electronics to one place (i.e.
the engine block), but ground one device somewhere else (i.e., the frame). Not only can
this result in ground offsets, it can also create a “path of least resistance” for high
currents THROUGH a low-current device. This can result in melted wires and vaporized
diodes, when, for example, starter currents flow through gauges.
On a side note I figured out the source of the interference. I had my Fan, RPM switch and fan switch grounded to the same lug. I pulled the fan switch ground and now I've got a smooth A/F signal again.
I just need to figure out how to solidly mount the coils now.
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Old 05-19-2009, 02:44 AM   #12
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Well it seems I didn't find the source of my interference. I had taken the coils off until I could properly mount them, and put them back on today.
It turns out that the interference nearly goes away after the car warms up, but comes back after the car cools again. The fan switch ground was just coincedence.
There are other fields that show the interference too, EGT and fuel pressure, but they track nearly the same as AFR with either set of coils. They are unused fields though so I don't know if it means anything.

Here is a Datalog that shows the interference and it smoothing out to almost no interference.

It shows some correlation to the Map field, but I'm not sure if it's just the AFR reacting to the change in Map.

This is getting pretty frustrating.
Attached Files
File Type: xls datalog200905182337.xls (1.43 MB, 74 views)
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Old 05-20-2009, 02:16 AM   #13
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It's NOT ground. It's probably the power.

The LC1 and the COPs are probably sharing a power line.
Add the 10,000 uF capacitor I recommended in the past, for the COPs.
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