Adding an O2 sensor?

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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.
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sharx333 wrote:

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.
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.
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jim beam wrote:

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
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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"?
John Horner wrote:

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sharx333 wrote:

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

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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?
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sharx333 wrote:

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.
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jim beam wrote:

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!
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Matt Ion wrote:

ok.
indeed, but this is apparently not the case for the o.p.
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Matt Ion wrote:

...or my '82 & 83 Civics.

'82 is exempt and '83 soon will be!
JT
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Grumpy AuContraire wrote:

Again, depends on your local laws. In BC, if the car came from the manufacturer with a cat, then it must always have a cat. In most of the province, nobody will usually notice or care, but legally it must still be there; in the Vancouver area, where we also have emissions testing, the car won't pass if it originally had a cat that's now missing, regardless of the year.
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Matt Ion wrote:

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?
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sharx333 wrote:

Fair'nuff... it was more of a generic response to Jim's comment that a cat is "not essential".

I'd suspect it's more likely the various parts were left out for cost savings, with no regard for emissions OR mileage.
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Ayon kay Matt Ion:

Oh, no slight meant there, Matt. I was just making it clear that I'm not contemplating anything illegal :)
Anyway, I'm somewhat confused by TeGGer's response over at rec.autos.makers.honda, where he says that the O2 sensor is simply there for emissions. He's a resident guru there and I'm inclined to believe him, but OTOH when someone asks about poor mileage, group posters usually point to the O2 sensor as the culprit. Also, most references on the net say that the sensor is vital for normal running.
Anyone have any idea on how this ECU was tweaked to run without an oxygen sensor? How does running in open loop affect things?
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Open loop makes the fuel-air mix richer than optimal(for emissions) ALL the time,just as it does until the engine warms up to operating temperature.You have to avoid a too-lean condition in -all- operating conditions,to avoid damaging the engine.
Closed loop optimizes the fuel-air mix for the leanest possible mix - without- risking a too-lean condition that could burn a piston or make the motor run too hot.It minimizes the extra hydrocarbons (rich exhaust)that the cat-converter has to burn up,for best emissions.
You have a open-loop at the start because the catalytic has not warmed up yet,nor has the motor.(coolant,plugs)
--
Jim Yanik
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Jim Yanik said:

This makes a lot of sense.. So a sensor retrofit would be useful then?

If only some kind soul would try this... :) But I think the ECU would just throw a CEL. I'll look at the ECU pinouts today, and post back.
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I doubt it would be worth the expense. Considering you would have to change the ECU in addition. That's big bucks. If you're looking for better gas mileage,changing your driving habits would be far more productive,keeping your tires inflated properly.

It's supposed to;it's a failure of the O2 sensor(missing = "open" sensor),and the control loop is no longer closed,emissions not controlled.

Your car should have a *different ECU* if it does not have an O2 sensor. Honda kept the same wiring harness for cost and simplicity,but the ECU would have to have different programming to ignore the missing O2 sensor and not flash the CEL. Since Honda solders in their PROMs,ECUs are different.
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Thanks, jim. You make a good point.
I'm really curious about this "open" vs "closed" loop mode. Are we greatly disadvantaged by always running in open loop? Or are we "lucky" as TeGGer says? Can't an ECU run in closed loop using just MAP, TPS, TA, etc sensors?
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sharx333 wrote:

engine is experiencing. the only way to do that is with a sensor. older sensors only detected what's called "stoichiometry", i.e. when the mix is perfect. newer sensors are "broad band" and detect the range typically sought, i.e. lambda from 0.8 to 1.2. [the former is lean, the latter rich - and peak torque.] either way, a sensor allows the ecu to tune the engine perfectly for its running conditions. closed loop is the way to go.
if you want to retrofit, you could look at this as a science experiment and buy a used ecu online from the states. they're typically in the $30 to $100 range for the standard models.
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sharx333 wrote:

Well, it's worked for over 100 years... your average classic muscle car has virtually nothing in the way of "engine management".
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