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post #31 of 69 (permalink) Old 10-05-2004, 07:38 AM
 
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Quote:
Originally Posted by Bruce Colby
Can't get A/F on the Motronic twinspark because there's no O2 Sensor. It seems there wasn't much unleaded fuel in Europe in the mid to late 80's when the 75 TS was in production. Hence, Motronic wo/O2 sensor feedback to control A/F. I assume it's a nonaddaptive 4.x Motronic system. Interesting isn't it? I wonder if the ECU is coded to take O2 sensor input but that it's just not used on the European engines of that time frame. Any thoughts?
I Have never even heard about a 75 TS without a O2 sensor. And I've seen quite a few...
There is a jumper (looks like a relay socket) in the harness near the ECU where you can set the engine up for different octane ratings and the legend goes that if you remove this jumper the engine disregards the O2 sensor and runs the engine as if it was without a cat.
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post #32 of 69 (permalink) Old 10-05-2004, 07:52 AM
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post #33 of 69 (permalink) Old 10-05-2004, 09:05 AM
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Quote:
Originally Posted by 75evo
At WOT, the Motronic will ignore the O2 sensor and will run on a given map in the ECU. But what's important is the A/F given by the wideband O2 sensor.

Did they use a wideband O2 sensor during dyno?

Its useful because then you can figure out where your car is running lean and where it is running rich. Then you can start tweaking the ECU a little.

For max power, I was told, 12.7:1 A/F is good. Actually using a Lambda value is better.
If you mean "Did the dyno have a wideband O2 sensor?", I don't really know. But if it had one, they didn't use it. This wasn't a serious tuning session, it was just a "put your car on the rollers and see what it'll do" type thing. There were about 14 cars processed in 3.5 hrs (about 15 min/car) so it had to be pretty straight forward. I think the Motronic TS results were fairly consistent with the original factory specs so I believe it's running the way they intended. That makes me happy.

My interest in the possibility of hooking up an O2 sensor is primarily academic. If the facility exists to run the engine with adaptive feedback, that would be interesting to try. The 75 shop manual (TS engine supplement, in English), shows both a knock sensor and O2 sensor on the wiring diagram page. The problem is, they are only listed in the key at the bottom of the page; they are not shown in the diagram itself. All of the ECU pin-outs for AFM, TPS, rpm, relays, power, ground, etc., are the same as say a 1990 US spec, Motronic spider. Even one side of the dual ign shares pin-outs with the '90. It's just tempting to extrapolate.

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post #34 of 69 (permalink) Old 10-05-2004, 11:48 AM
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post #35 of 69 (permalink) Old 10-05-2004, 12:25 PM
 
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Well Bruce, it's not adaptive. Just closed loop, good for emissions and fuel economy.
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post #36 of 69 (permalink) Old 10-05-2004, 12:29 PM
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Mats,

Early cars had no lambda. My uncle's TS was an '87 (old style grille, yellow corner lights) and it had no lambda.
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post #37 of 69 (permalink) Old 10-05-2004, 12:35 PM
 
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-87? I thought they were released in -88?
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post #38 of 69 (permalink) Old 10-05-2004, 12:46 PM
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Let me correct that, his was an '89. You could be correct that the first production 75 TS rolled out in '88. Still, his had no close loop control. Actually my dad's '93 164 V6 has no closed loop control either.
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post #39 of 69 (permalink) Old 10-05-2004, 12:49 PM
 
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Different markets... Thats why they have that jumper.
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post #40 of 69 (permalink) Old 10-05-2004, 01:54 PM
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Quote:
Originally Posted by BigSwede
Different markets... Thats why they have that jumper.
Mats,

You make it sound as if I could at least get closed loop control if I install an O2 sensor and eliminate/add the "jumper". Care to comment?

Then there is the knock sensor. Did the closed loop TS's of this vintage have one to help control timing?

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post #41 of 69 (permalink) Old 10-05-2004, 02:03 PM
 
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Probably, unless they changed the harness, but since there is a jumper I'm guessing they didn't.
Add the O2 sensor and add a jumper and you're set.

The knock sensor is probably only there for protection, if you use poor fuel quality the knock sensor lowers the ignition but it's unlikely that it tries to optimize the ignition. Probably the ECU just follow a base map (that you select with the jumper).
That's my guess anyway...
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post #42 of 69 (permalink) Old 10-05-2004, 02:13 PM
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G'Day Bruce,

See my site (in my sig) for the "Alfa 75, Twin Spark 'S' Version with Catalytic Convertor" manual and a description of the plug/jumper.

Wiring diagrams in the manual show the O2 sensor (S10).

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post #43 of 69 (permalink) Old 10-05-2004, 03:58 PM
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Quote:
Originally Posted by Craig
G'Day Bruce,

See my site (in my sig) for the "Alfa 75, Twin Spark 'S' Version with Catalytic Convertor" manual and a description of the plug/jumper.

Wiring diagrams in the manual show the O2 sensor (S10).
G'Day yourself! Seriously, thanks for the link. I've never heard of the "S" version before. This should be interesting. Good, reliable information is always the hardest to find and this looks like both. I'm glad I had a T1 to do the download though.

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post #44 of 69 (permalink) Old 10-05-2004, 08:55 PM
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post #45 of 69 (permalink) Old 10-05-2004, 08:59 PM
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