r15suk

My car has a CAT bypass and the O2 sensor has been removed. Originally it was chipped and had to run on 98 Octane, but the previous owner found that the chip didn't make much if any difference (except that it needed 98 octane) so he had it removed.

He said the place that removed it then had to modify/reprogram the DME to deal with the fact that the O2 sensor was removed. Does this sound right?

Cheers
Simon

Makmov

Hard telling absolutely for sure but it sounds like a story.

Shamus964

Possibly/probably not a story - Porsche shipped 964's with one of three country-specific fuel schedules, one of which assumed that no O2 sensor would be present. The DME control unit can be jumpered to allow for mapping to the "ROW without an O2 sensor" mapping.

More info here including pics of the jumper...
https://rennlist.com/forums/964-foru...=row+o2+sensor

Makmov

I guess that is very possible, I was just presuming an PNA car.

PNine64

Why didn't they just put an o2 sensor back in?

Makmov

Maybe it has a bypass without a portal.

PNine64

Ah...that would make sense. He can have one of mine. Strangely it came with two??

Makmov

I don't know for sure.

In any event, you should run a O2 sensor, and it can be a benificial data point.

r15suk

I believe that this is the case, yes. I was wondering how you could modify the DME but it appears that its possible with a jumper then.

Thanks for the responses :-)

cheers
Simon

Seight

My car has had a cat bypass for about the last 5 years. About 4 years ago my O2 sensor was playing up and had basically failed. JZ Machtech removed the faulty sensor and plugged the hole in the bypass. They then installed a new chip that they mapped to my engine running without a cat (my car is 1990 so doesn't need a cat for MOT). They told me that there was no point running an O2 sensor if you don't need to, and it wasn't much more expensive to have the mapped chip than to replace and fit the sensor.
The engine has run sweetly ever since with no issues. It is optimized to run on 98 octane but runs perfectly well on 95 octane. In fact it's not really a noticeable difference between the two.

r15suk

Thanks for the info. It may have been JZ who did the work on my car so it seems to make sense.

cheers
Simon