The engine will produce more power, e.g. be more responsive, but at the expense of more emissions and less fuel economy, and possibly damaging the CAT.
By connecting a properly functioning O2 sensor with a Porsche OEM chip, you should notice an improvement in fuel economy (a minimum of 5-10% mpg).

The 3.2L engine idles better at 13.8 to 14.2AFR and connecting the stock O2 sensor causes the AFR to swing up down in a saw tooth pattern between 14.5 and 15.0. The O2 sensor circuit from the 1980s was not like it is in today's modern cars that use WideBand O2 sensors.
Then keep in mind that the Euro engine had no cat converter and it had no O2 sensor, why did the factory decide not to use an O2 in the Euro? If indeed the O2 was desirable for performance or MPG why was it not used? The reason is it was only being used in the Cat Converter engines to protect the Cat.
If you do not have a Cat Converter you should not be running the stock O2 sensor. But you MUST be certain the AFRs (fuel mixture) is properly working and in perfect order.
You can easily monitor and dial in your AFR by installing a simple modern day WideBand O2 gauge in the cockpit.
The AEM 31-1440 gauge is a fantastic gauge for the money, it uses the modern day LSU 4.9 sensor that needs NO free air calibration.

Here's your target AFRs for the 3.2L without a Cat Converter.
All readings done fully warm:
- At idle you need to target 13.8 to 14.4AFR, use the mixture CO screw on the AFM to do this.
- 3000RPM in 4th gear steady state driving on flat road you should land in the 14.4 to 14.8 AFR range.
- WOT at 3000RPM 4th gear you need to always be below 13.0AFR. Stock chip will be in the high 11s to low 12s

I just gave you info needed to check proper mixture for any 3.2L without a cat :)

Enjoy.

With the stock O2 unplugged the O2 signal line that goes to the DME will read exactly 0.5vdc, you need to verify this to be certain it's correct. If stock O2 is left unplugged and the line remains at 0.5vdc then the program code in the DME that controls mixture based on O2 signal is simply parked in do-nothing mode :) I'm 100% certain of this because I disassembled the entire program code in these DMEs when I rewrote the entire Air fuel model of the code for my MAF system.
Also important to note is that the O2 signal is ignored completely if engine load exceeds 70% and/or RPM is above 4000RPM. This is baked into the program code. You can actually observe this if you free rev parked to 4500RPM you will notice the O2 closed loop behavior stops.

Good luck in assuming the optimal AFRs are maintained without the O2 sensor! Who really wants to have to install WB O2 gauge?

How does the euro engine run without any O2 sensor? As I mentioned you need to be certain Air Fuel Ratios are properly setup. You can use a CO meter or a WBO2 to do this. Actually, this needs to be done even in the US engine with a O2 sensor.

Basically, if you have a US Engine with no cat converter and you unplug the O2 sensor the O2 signal line to the DME pin 24 is pulled to 0.5v internally and this simply puts the DME code in open-loop mode much like the Euro.

OK, then drive with a WBO2 gauge and carry a screwdriver so you can tweak the AFM internal spring so the engine's always at about Lambda of 1.0.

This comment has no value, do Euro car drivers go around with a screw driver? And actually it's a 3mm allen key used to make CO adjustments.

I know this Engine inside out and I'm just trying to help the guy out. If after he dials everything in he can then decide to use or not use the stock O2 sensor. You can't expect the stock O2 closed loop to work if you have no idea what the base mixture is.

So, should we verify base mixture or NOT? CO meters are not readily available but WBO2 gauges are and they are not expensive and far better than the 80s tech CO meter.

Only at idle! Remember, once the RPM increases and the flap moves, the volume of air thru the bypass adjuster becomes relatively insignificant.

This is true, the CO screw effects idle more than off idle but I gave him the target ranges that should be expected. I've tested many 3.2L stock setups and I know what AFR to expect at what conditions like PT, WOT and tip-in. The values I shared are what should be expected in a properly setup 3.2 in open-loop.

Tested signal line voltage on the car side, that being the "prong" that connects to the 02 sensor's signal wire. Ignition is ON and engine OFF. Per Sal, there should be 0.5 v there.

Setting:

Each vertical square = 0.5 v.
0 volts is at the yellow pointer level---pointer at far left of display screen.

http://forums.pelicanparts.com/uploa...1716934481.jpg

That's good. Now hookup the O2 sensor and display the signal on the scope with the engine idling.
With your setup now, the horizontal trace should display the positive O2 voltage (~.80V) up one square and stay there for 4 squares to the right.
Then the trace should move close to ground (~.20V) for 4 squares. This will then be a 50% duty cycle, basically a square waveform.
You will need to decrease the horizontal time base (now .1ms) for 4 squares up and then 4 squares down near zero volts, for a total of 8 squares for one O2 cycle.
The scope probe ground needs to be connected to shield of the O2 sensor to avoid signal noise (random ignition RF signal pickup).

Already did that Dave. Look at post #74, second vid. V setting is 0.1 so squares are small. Duty cycle is at 50% and am very close to the high of 0.8 and low of 0.2.

Yes, but you really need to change the vertical (lower voltage, .02 & not .10) & horizontal (shorter time base .01 & not .10) scales so you can better analyze the O2 signal.
The vertical signal change should be about 4 squares up/down (now much less than one), and the horizontal should be about four squares for a complete O2 cycle and about 2-3 cycles per sweep.
You really can't tell much from the waveform (~ .40V to .60V) the way it's displayed now. Changing the settings will provide for a better analysis of the O2 waveform, besides it changes too fast now.

Wave form is interesting but where the meat of this is in the top right column of info. Vmax, Vmin, Vavr. Move the decimal over 1 point to the right given the "0.1v" setting* and the maximum voltage flutters between .8 and .7. Minimum flutters between .3 and .2 and sometimes .1. The average is steady at .5. If I'm reading this right and if Steve Wong is right as I suspect he is, those numbers suggest the AFR being in order... at least at idle. I have yet to see what happens when the engine is at speed. Am going to get to that.

* Setting the scope at 0.1v was done to fit the wild wave form displayed by the soldered Ox sensor onto the screen. The voltage setting when testing new Ox sensor was left as is in order for the tests to be "apples to apples."
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Actually, the values provided below would typically be of little use, given the limited overall data:

http://forums.pelicanparts.com/uploa...1717007977.jpg

The Vmax - Vmin is only .10V, which typically should be ~ .50V. So a much larger display, e.g. post #72 (Idle), of the O2 signal is preferred when using a scope to evaluate an O2 sensor.

That's not the scope video image for the Ox sensor test Dave. It's the still photo taken when testing the prong on the car side that connects to the Ox sensor's female connection. I tested that per Sal for a target of .5v with the ignition ON, engine OFF. The voltage is .52 - . 42. I suspect that were these readings not acceptable, Sal would have said so.
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Both videos look basically the same, and of little value with a signal image so small.
So you don't have a video of the O2 connected to DME ECM? If that's the case, you haven't fully tested your O2 system, right?

You're right Dave... that test has not been done. How would you wire the scope to the connected system and what's your target voltage?

...I'm wondering if there would be some effect on the system by installing a scope connection.
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No effect. The scope input impedance is high enough to not interfere with such circuit.
As already mentioned, your target voltage with the O2 sensor disconnected is nearly 0.5 V between ECM pin 24 and ground. This is a steady "bias" voltage set by fixed resistors inside ECM and you don't need a scope to measure it. Just use a conventional multimeter with ignition on and engine not running.

As for the dynamic test with engine running, you need to probe the O2 signal while it is connected to the ECM, so that means being able to connect the scope probe to the running system, wherever a connection is accessible (don't know where, as my car is Euro and has no O2 sensor circuit).
As Dave suggested, change your vertical scale and your horizontal scale (time base) so as to display a good signal whose shape can be interpreted and peak values can be read onscreen instead of relying on values displayed on the right, as these are not always accurate with this type of scope.

I'll have a go at that after completing the city MPG test with the Ox sensor disconnected.

To "probe" the circuit, will wrap the scope wire around the male connector on the car side and pushing the female side of the connector onto it.

With no idea what your background in Porsche electronics is Gilles, I must ask if you're absolutely certain this test will not fry my ECU/DME or the Ox sensor?