Massively incorrect AFRs (LC-1 & parellel MS1) - Miata Turbo Forum - Boost cars, acquire cats.

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Old 09-19-2009, 04:14 PM   #1
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Default Massively incorrect AFRs (LC-1 & parellel MS1)

Rich and I were playing with my car again today but unfortunately we couldn't tune it as the AFRs were totally wrong.

The car idled fine and would drive slightly boggy, but AFRs would be off the scale at idle i.e 7:1 so removing some fuel from the VE table brought it to a more realistic AFR of around 12:1 for a few seconds before the AFR reading would randomly swing to 22:1 where it would stay!?!

We checked the LC-1 LM programmer and programmed the 0-5v output for AFRs of 10:1-20:1 (for more resolution) and selected the same scaling in Tunerstudio and also did an LC-1 red-button reset after pumping air through the engine/exhaust but it all made no difference. AFRs were still locked at reading 7:1 or 22:1 even though we set the LC-1 scaling for 10:1 - 20:1 thus not covering those figures?

It's left us stumped, so I reluctantly wired fueling back to the OEM ECU until I can figure out why my LC-1 figures are out. I'm going to do a full LC-1 re-calibration and also check that the LC-1 grounds are connected to the same ground as the MS1.

The LC-1 gave good looking and beliveable results when installed in the car a few weeks ago with idle figures of 13-16:1?

Has anyone ever had an issue like this or can anyone shed any light onto the situation at all?
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Old 09-20-2009, 12:11 AM   #2
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have you tried to calibrate it?
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Old 09-20-2009, 12:24 AM   #3
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your grounds are fuckd up somewhere and i would not run all my grounds to the same spot as the MS that is bad if i remember my install manual. MS can still run the fuel its not like it reads of the lc1 to do what it does it uses the tables you already have saved in your msq.
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Old 09-20-2009, 05:25 AM   #4
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I'm going to do a full reset of the sensor and free-air calibration with the sensor removed from the exhaust. I was incredibly careful to make sure all my grounds were perfect, I even seperated the LC-1 heater ground (the noisey ground) and soldered the other two directly to the loom of the ECU (3 ECU pinouts are ground on mine)

It was working fine not long ago so I can't understand it's sudden irratic behaviour.

I'll also compare results from Logworks to that of Megatune and Tunerstudio.

I don't think it's good practice to try and tune the fueling on the MS without a real AFR figure.
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