95 Civic has no O2 sensor!

Hello,

My 95 Civic ESi (Philippine domestic version) is a "stripped-down"
version of the U.S. EX model, I think. It has a 'PH16' engine (PGM-FI,
16Valve, 1.6Li, SOHC
non-vtec, ECU code P27) but has no oxygen sensor and no cat converter.
This is common knowledge here, and there is a plug where the sensor
should be. My
question is, is this a great disadvantage in terms of mileage? Average
mileage for civics here is 18 to 24 MPG (~8-10km/liter).

Is the ECU always running in open loop mode? Can we somehow buy an O2
sensor and put it in, and if so, will this buy us much MPG-wise?

Thanks so much in advance.

 

wrote in @b28g2000cwb.googlegroups.com:

Would it save you enough to pay for the cost of converting the rest of
your engine management system? Probably not. I can pretty much guarantee
you your ECU does not have the capability of using O2 sensor signals,
and you're surely missing other devices used in conjunction with the
oxygen sensor.

On road-going cars, the primary purpose of O2 sensors and their
associated hardware/software is emissions, not mileage. Any mileage
increase you see (if any), would be a bonus, and would be a side-effect.
Some race cars use oxygen sensors to improve mileage during a race, but
these are using ECUs programmed for mileage. Stock ECUs are programmed
for emissions.

And yes, any car without a feedback system (like yours; like a 1970
Honda 600) is running in what we now call "open loop" mode. "Closed
loop" is the other term used to describe "feedback system". Even cars
with oxygen sensors operate in open loop at times.