'87 M6 oxygen sensor - what does it do?

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DennisLJacob
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'87 M6 oxygen sensor - what does it do?

Post by DennisLJacob »

Hello gentlemen, I have a '87 M6 and recently had a Miller MAF conversion and WAR chip installed in the car. The shop who did the install, did not do the "usual" dyno session tune function. What they said they did was hooked up a wide band O2 sensor and Air/Fuel gauge to the car and did test and tune functions while driving the car. But what I'm confused about, besides the bill, was there is only one exhaust O2 port. How did they have the A/F guage hooked up when I assume the 02 sensor would be needed for the ECU to control functions of the motor A/F response? I'd ask the shop owner, but we are not on speaking terms at the moment. What does the O2 sensor do in these cars? Is it just something to monitor the catalytic converter operating status? The shop removed the cat, so a X pipe is installed where the cat used to be. I believe the O2 sensor is installed in the X pipe. Does the ECU/WAR chip use the O2 sensor for A/F control?

I've tried calling Miller and have emailed them, but they haven't replied to my inquiries.
1987 M6, 1998 Dinan SC MZ3 Roadster
baders
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Re: '87 M6 oxygen sensor - what does it do?

Post by baders »

Shop A/F ratio machines have a probe which inserts into the exhaust. The O2 sensor reports to the ECU and as a closed loop, controls engine A/F ratio to about 14.7:1. The throttle position switch tells the ECU to ignore the O2 sensor at full throttle and idle.
1986 635csi LOCUTUS / Arktis Blau Metallic / Pearl Beige / S38B36/ Close ratio dogleg 5sp
2002 E46 M3 / Topaz Blau Metallic / Black Nappa / 6 speed SMG software tuned / Bilstein PSS10 Coilovers / CMP RACP reinforcement
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DennisLJacob
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Re: '87 M6 oxygen sensor - what does it do?

Post by DennisLJacob »

So the car won't run right without the O2 sensor signal going to the ecu - right? So how can the testing being done when using the O2 sensor attached to a A/F gauge? That is how they said they tuned the WAR chip. It seems to me that can't use the same O2 sensor output for both the ecu and the gauge at the same time. So that sounds like a lie to me. Is that how you would understand that?
1987 M6, 1998 Dinan SC MZ3 Roadster
baders
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Re: '87 M6 oxygen sensor - what does it do?

Post by baders »

The car will run OKish without the O2 sensor. You are not clear in what you are saying they did. First question to ask (or research) is if the WAR chip operates in closed (needs the O2 sensor) or open mode (does not need) ? I'm not familiar with Miller chips. The other question is what machine did they use to test the car. As I mentioned above, most shop testers have a probe which goes in the exhaust to measure O2 and therefore A/F ration. Maybe you missed that.
1986 635csi LOCUTUS / Arktis Blau Metallic / Pearl Beige / S38B36/ Close ratio dogleg 5sp
2002 E46 M3 / Topaz Blau Metallic / Black Nappa / 6 speed SMG software tuned / Bilstein PSS10 Coilovers / CMP RACP reinforcement
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DennisLJacob
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Location: Genoa, Nevada

Re: '87 M6 oxygen sensor - what does it do?

Post by DennisLJacob »

The shop owner was rather vague in the work they did. I questioned them about why they didn't do the Miller dyno run tuning? Their reply was they installed a wide bank O2 sensor and hooked up to a gauge inside the car. Then drove around town testing their settings. I think they were either padding the time for labor charges instead of doing what Miller does. To tell you the truth, I suspect that they just installed the "base" software program and then did nothing more. The dyno results were quite a bit less than expected. From Korman Autoworks, they told me a Euro exhaust cam gear, euro headers and K&N air filter with performance chip should give a little over 300 HP. My car with the Miller MAF and WAR chip on top of those items only generated 280 HP. So my car is 20 HP down from expected with no additional performance out of the MAF conversion. That doesn't jive with Miller's dyno results.

The shop owner gave me an email response of "we tuned it for safe performance and not over stressing the engine and components" story. That they could have tuned it for more performance, but decided against it. One of the things that Miller stated was the engine runs smoother and has a smoother idle and on throttle performance. My car, right now vibrates noticeably when at idle. I can feel it in the seat of my pants. So I'm suspect. I'd hope to hear from Miller when I've called and emailed him for information. I need to figure out if I can test or see if the current tune is the default tune from Miller and if it has been modified in any way. Needles to say I'm concerned.

By the way, I've updated my "need professional help" topic to current status. I'd like to hear your thoughts when you get a chance.
1987 M6, 1998 Dinan SC MZ3 Roadster
baders
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Re: '87 M6 oxygen sensor - what does it do?

Post by baders »

Sorry, but if your car hasn't been on the dyno how do you know power output ? I'm just confused. Where are those power output figures coming from ?

I'll check the other thread. Struggling with vision at the moment as just had laser eye surgery :)
1986 635csi LOCUTUS / Arktis Blau Metallic / Pearl Beige / S38B36/ Close ratio dogleg 5sp
2002 E46 M3 / Topaz Blau Metallic / Black Nappa / 6 speed SMG software tuned / Bilstein PSS10 Coilovers / CMP RACP reinforcement
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DennisLJacob
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Location: Genoa, Nevada

Re: '87 M6 oxygen sensor - what does it do?

Post by DennisLJacob »

Sorry to hear about the eye surgery. I had similar done a couple years ago for cataracts. I did the vision correction implants and wish I had not. I went from near sighted to far sighted to the degree that I have to wear reading glasses 24/7. So the implants really didn't change my vision life very much. It just cost a whole bunch of money, that I consider as being wasted.

The shop completed their "drive around town" tuning without my knowledge. I had asked to be at the dyno test/tune session. I thought they were going to do the "tuning" at the dyno location. So when I showed up, all the shop was going to do is a basic run and then leave. The first run was 4th gear which generated 228 RWHP and the second run was 3rd gear which generated 241 RWHP. They did some conversion information that would make the 3rd gear pull crank HP at "about" 280. I'm at 5,000 elevation and tested on a cool morning. It could be they used the wrong crank computations, but I don't have an idea about that. Do you or anyone here know what a correction factor might be? Should I use the 4th gear pull instead of the 3rd gear pull?
1987 M6, 1998 Dinan SC MZ3 Roadster
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