Adding an O2 sensor?

Hello,

My 95 Civic ESi (Philippine domestic version) is similar to the U.S. EX
version, I think. It has a PH16 engine (PGM-FI, 16Valve, 1.6Li, SOHC
non-vtec, ECU code P27) but has no oxygen sensor. 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.

 

really? can you post a pic? it's hard to imagine the point of running
fuel injection absent the sensor because without it, the ecu doesn't
know for sure how much gas to inject.

presumably, but you may need to do extensive wiring mods. it could save
you significantly in gas.

double check on this "common knowledge" thing - i've never seen any
electronic fuel injection system that doesn't have a sensor - without
it, the ecu is "blind". check both sides of the cat as well as in the
manifold. it would be amazing if one wasn't there somewhere.

 

Interesting. Early fuel injection systems sold in the US were indeed
open loop designs, such as the Bosch D-Jetronic which was installed on
many late 1960s and early 1970s era Volkswagens and Volvos. Closed loop
came into general use about the same time as three way catalytic
converters did. Late 1970s and onward.

I suppose that it is possible that car makers built open loop versions
for countries without emissions regulations much later than the 1980s,
but I have no idea how it was done or if it is possible to easily
convert such systems to closed loop operations.

John

 

Hello again and thanks for the replies. I've posted photos at this
link, if you're interested:

http://hondaswap.com/ecus-electronics-tuning/car-has-no-o2-sensor-can-i-73624/#post698583

I think this version (ESi, Philippines) is a "stripped-down" version,
if you will, of the EG 4-door coupe (92-95) with a D16Z6 engine, minus
the VTEC. I've been using the service manual for some time now, and all
other parts match. The manual doesn't say anything about other O2
sensors though.

This may have been done to make it more affordable, even though at the
time this was the top-of-the-line model here. Also, the emission laws
here aren't as strict as in the U.S., and back in the early '90's they
were even less so.

Am I missing something here?? Are our civics "crippled"?

 

it certainly looks that way! john raises the good point about
pre-catalyst injection systems not having sensors [i'd forgotten that -
it's /so/ long since i've seen one!] and you've posted the pics. but it
still amazes me. the cost of a sensor, in bulk, to a manufacturer has
got to be less than $50. it's astonishing that honda would elect not to
use one - maybe there was a legal reason.

getting back to your original question, you can almost certainly
retrofit, but there will obviously be wiring involved and it would
probably require acquisition of a new ecu. interesting project though!
and you may as well go for the vtec while you're at it!

 

you're absolutely right.

 

Corvettes used to have a MECHANICAL fuel injection option(totally open-
loop),long before EFI came to be.

 

Anyone remember the Lucas mechanical FI system? Wonderful when it worked
properly, a pig when it didn't, which was most of the time, being made by
Lucas ...

And some Peugeot 404's had a mechanical FI system too.

sd

 

Does it have a converter?

Al

 

Look at any old diesel engine, particularly those on tractors and heavy
equipment... mechanical FI there as well.

 

Now that you mentioned it, it's also "common knowledge" here that this
ESi doesn't have a catalytic converter! I'll have to go check.. where
might it be located?

 

it's a huge bump in the exhaust, round about where the passenger seat
is. but if you don't have an oxygen sensor, you won't have a cat.

regarding retrofit, it's not essential to have the cat. - the important
bit is the sensor.

 

Fuel could also be an issue. In places where tetra ethyl lead continued
to be used as an additive there would be an O2 sensor contamination
issue. TEL was outlawed in the US many years ago, but much of the rest
of the world continued to use it as an octane improver.

That would explain the lack of O2 sensors in countries where the use of
TEL continued.

John

 

That could be it! Unleaded fuel was introduced here in 1994, while the
EG line was from 1992-95. Is it true that leaded fuel could damage the
O2 sensor?

If this is the reason, and not cost-cutting, then could I simply, as
jim says, "retrofit" a sensor? (Taking care to use only unleaded fuel,
of course).

The ECU is a P27 (OBD-1 EG JDM Civic 1600 sohc VTEC) which I think is
the same as the one used in the EX US version. However this model has
no VTEC, and no O2 sensor. Could they have left the ECU "as is"?
Wouldn't Honda have used a different ECU code if it's not the same one?
I'm just hoping that it is, since it means I could just plug a new
sensor in.

I'm not after the VTEC, just want to save on gas.

 

Absolutely. Leaded fuels also deteriorate spark plugs, but they are
readily changed. In the days when leaded fuel was the norm in the US,
typical spark plug change intervals were 12-15k miles. Now with
unleaded fuel and slightly better spark plugs the norm is 100k miles.

TEL leaves nasty deposits when it burns. These rapidly build up on
oxygen sensors and ruin it. They also build up in exhaust systems and
on exhaust valves. Oddly enough, the build-up on exhaust valves acts as
a sort of solid lubricant. When the conversion to unleaded happened in
the US, some older cars had very rapid exhaust valve seat wear due to
the lack of TEL's valve lubricating side effect. Other than for exhaust
valves, everything else about TEL fuel is a downside for the motor!

You would need someone who really knows the Honda fuel injection system
in detail to answer that. Perhaps you can get your hands on a parts
manual for your version and the US version and try to compare what is
different from one to the other. Maybe it is as simple as connecting an
O2 sensor, maybe not. The US version is certainly capable of running
open loop in the case of a failed O2 sensor.

Do you have any friends in Honda's engineering department ??????

John

 

I believe the ECU would be a different model than a US OBD-I ECU,as a US
ECU will set a code and light the check engine light if the O2 sensor
fails. "not present" counts as "failed".(open)
The Euro ECU's program would have to know to ignore the missing sensor,thus
a different ECU. ECU programming is fixed in PROM,thus a different PROM,and
a different ECU p/n.

 

Tell that to my '87 Accords, all of which have had cats and no O2 sensors.

Or my old '80 Mazda GLC, for that matter.

The cat IS essential if your local emissions laws require it!

 

indeed, but this is apparently not the case for the o.p.

 

....or my '82 & 83 Civics.

'82 is exempt and '83 soon will be!

JT

 

Actually the emissions laws here *don't* require it. Even today I
haven't seen any cars that have Cats. But regarding retrofit, TeGGer
over at rec.autos.makers.honda says:

"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.
.. . .
You should count yourself lucky to live in a jurisdiction with more
reasonable emissions laws and thus a simpler vehicle. Honda OEM oxygen
sensors and cats are priced in the hundreds of dollars."



I respect TeGGer's responses, but do you guys think he's right on this
one? What if our cars here in the Philippines are programmed for
mileage, instead of emissions as TeGGer says?