tilac999

I understand cat converters are not necessary but why not 02 sensors? Isn't feedback of air/fuel mixture a good thing to for power/effeciency/stochio?

GlenL

Because they don't?

Only a very few CIS systems incorporated an oxygen sensor. The 928s with CIS aren't among them.

Mongo

L-Jet and LH cars have a preset fuel map from the factory that has been dialed in for ideal stoichiometry. However, the computer is highly dependent on MAF signal and voltage. If the slightest bit of voltage were to decline due to age of the MAF, it will cause running issues. However, I found that Euro LH coded cars run a bit richer at WOT than a US LH car when the O2 sensor is ignored when hammering the go-pedal.

tilac999

Not on CIS. Why not on a later, sophisticated LH system like my '85?

tilac999

Interesting. Thanks.

danglerb

Euro LH cars have a pot to set I think CO or CO2. The Euro brains don't even have the circuit to read an O2 sensor if you wanted to add one, you have to switch to a US brain.

I don't have a clue on the WHY Porsche did it that way, but my guess is that it wasn't technical, maybe something about perception of any kind of smog control as "bad".

tilac999

So in theory you could fine tune it with a tail pipe sniffer?

danglerb

Not some much fine tune as set the idle characteristics, since wot runs out of the tables and I think ignores both pot and O2 sensor. Real tuning, SharkTuning, is measure with a wideband o2 and burn new chips.

Hilton

The "euro" LH and EZ-K ecu's are identical to the US ones, including the chips. The difference is the coding plug tells the ecu to use a different fuel map and inputs to govern idle speed and base mixture.

I've switched a couple of my S4's between using O2 sensors and not using them - the harness plug exists, and the only change needed is to swap coding plugs, plug in the O2 sensor, and unplug the 3-pin connector on the potentiometer.

The addition of the O2 sensor only changes idle and low-load cruising mixtures, to meet local emissions regulations - under high load conditions or wide throttle all 928's run open loop and use the same fuel map.

tilac999

Mine has added-on wires from the ecu leading to where the 02 would be. Maybe the importer did the mod to pass emissons at one time. My part-throttle, low load cruise seems lean but I have no idea how I would check that.

Hilton

Ah your '85 is an earlier version of LH - 2.2, used from 84-86 on 928's.

My post above was re: LH 2.3 (928's from 87-95). Pretty sure you don't have an O2-loop capable ecu, instead you're supposed to adjust the MAF to a known value which determines mixture for the cats.

Landseer

Jadz928's former 84 Euro has a wideband sensor installed. And some modifications to the ECU to allow it to be sharktunable. Maybe he will weigh-in to explain it.

tv

Search - this has all been discussed many times in detail. Different boards, different chips, different clock speeds. No O2 for euro's.

Landseer

Here's a thread that might be interesting to you.


https://rennlist.com/forums/928-foru...5-86-5-us.html

tv

https://rennlist.com/forums/4737979-post3.html

https://rennlist.com/forums/3369822-post6.html

https://rennlist.com/forums/928-foru...rs-beware.html




keywords - O2 sensor, LH brain, open loop, federalization, euro, impedance, brain,