Honda Car Forum

Pursuant to a recent thread on the number of oxygen sensors in the 1986 or
1988 Honda Pelude, I asked my mechanic about this.

It seems the reason the '88 Prelude had two O2 sensors right beside each
other had to to do with control over emissions. It's well known that OBD-II
systems have two sensors, one before the cat and one after, but pre-OBD-II
engines like the '88 Prelude's have two sensors for entirely different
reasons.

OBD-II cars use the second sensor primarily as a cat efficiency tell-tale.
When a second sensor was used in cars like the pre-OBD-II '88 Prelude, it
meant the engine management system had divided the exhaust into two
streams, each with just two cylinders, and was monitoring each stream
separately. The two INNER cylinders were monitored by one sensor, and the
two OUTER cylinders were surveilled by the other sensor.

Two sensors meant that Honda was able to monitor and adjust mixture and
emissions twice as efficiently as it would have been able to with just one
sensor covering the exhaust streams from all four cylinders at once. My guy
could not remember offhand whether Honda did this just for the carbed
versions of the Prelude or both carb and FI models.

Furthermore, he tells me that the very latest cars are beginning to do this
two-cylinder splitting again, but this time each pair has its own catalytic
converter and pair of oxygen sensors. For example, some Ford V8s have FOUR
catalytic converters and EIGHT oxygen sensors. Can you imagine owning one
of these once the warranty runs out?

I'll stick to my '91, thanks.


--
TeGGeR®

The Unofficial Honda/Acura FAQ
www.tegger.com/hondafaq/

"TeGGeR®" <tegger@tegger.c0m> wrote in message
news:Xns981CE5F5CE93Ategger@207.14.116.130...
> Pursuant to a recent thread on the number of oxygen sensors in the 1986 or
> 1988 Honda Pelude, I asked my mechanic about this.
>
> It seems the reason the '88 Prelude had two O2 sensors right beside each
> other had to to do with control over emissions. It's well known that
> OBD-II
> systems have two sensors, one before the cat and one after, but pre-OBD-II
> engines like the '88 Prelude's have two sensors for entirely different
> reasons.
>
> OBD-II cars use the second sensor primarily as a cat efficiency tell-tale.
> When a second sensor was used in cars like the pre-OBD-II '88 Prelude, it
> meant the engine management system had divided the exhaust into two
> streams, each with just two cylinders, and was monitoring each stream
> separately. The two INNER cylinders were monitored by one sensor, and the
> two OUTER cylinders were surveilled by the other sensor.
>
> Two sensors meant that Honda was able to monitor and adjust mixture and
> emissions twice as efficiently as it would have been able to with just one
> sensor covering the exhaust streams from all four cylinders at once. My
> guy
> could not remember offhand whether Honda did this just for the carbed
> versions of the Prelude or both carb and FI models.

Great report. Thanks TeGGeR.

>
> Furthermore, he tells me that the very latest cars are beginning to do
> this
> two-cylinder splitting again, but this time each pair has its own
> catalytic
> converter and pair of oxygen sensors. For example, some Ford V8s have FOUR
> catalytic converters and EIGHT oxygen sensors. Can you imagine owning one
> of these once the warranty runs out?

No kidding.

>
> I'll stick to my '91, thanks.

And me wit me '00

"TeGGeR®" <tegger@tegger.c0m> wrote
> Two sensors meant that Honda was able to monitor and
> adjust mixture and
> emissions twice as efficiently as it would have been able
> to with just one
> sensor covering the exhaust streams from all four
> cylinders at once.
snip for brevity
>
> I'll stick to my '91, thanks.

I dunno. Might be that the improvement in fuel mileage (via
more precise engine controls over each cylinder's air/fuel
charge etc.) makes the extra sensors worth it.

In article <Xns981CE5F5CE93Ategger@207.14.116.130>,
"TeGGeR®" <tegger@tegger.c0m> wrote:

> Pursuant to a recent thread on the number of oxygen sensors in the 1986 or
> 1988 Honda Pelude, I asked my mechanic about this.
>
> It seems the reason the '88 Prelude had two O2 sensors right beside each
> other had to to do with control over emissions. It's well known that OBD-II
> systems have two sensors, one before the cat and one after, but pre-OBD-II
> engines like the '88 Prelude's have two sensors for entirely different
> reasons.
>
> OBD-II cars use the second sensor primarily as a cat efficiency tell-tale.
> When a second sensor was used in cars like the pre-OBD-II '88 Prelude, it
> meant the engine management system had divided the exhaust into two
> streams, each with just two cylinders, and was monitoring each stream
> separately. The two INNER cylinders were monitored by one sensor, and the
> two OUTER cylinders were surveilled by the other sensor.
>
> Two sensors meant that Honda was able to monitor and adjust mixture and
> emissions twice as efficiently as it would have been able to with just one
> sensor covering the exhaust streams from all four cylinders at once. My guy
> could not remember offhand whether Honda did this just for the carbed
> versions of the Prelude or both carb and FI models.
>
> Furthermore, he tells me that the very latest cars are beginning to do this
> two-cylinder splitting again, but this time each pair has its own catalytic
> converter and pair of oxygen sensors. For example, some Ford V8s have FOUR
> catalytic converters and EIGHT oxygen sensors. Can you imagine owning one
> of these once the warranty runs out?
>
> I'll stick to my '91, thanks.

Some older cars may have two sensors that operate at two ranges. Newer
sensors combine multiple ranges in one package.

I couldn't care less what Ford does. Even a Kia will be more advanced
soon. Doesn't Honda tune the individual cylinders using the crankshaft
position sensor? Or maybe not any more? My 05 HAH engine has run like
an old beater from day one. It's not silky smooth like the 97 Civic HX
that I had.

Nasty wrote:
> "TeGGeR®" <tegger@tegger.c0m> wrote in message
> news:Xns981CE5F5CE93Ategger@207.14.116.130...
>
>>Pursuant to a recent thread on the number of oxygen sensors in the 1986 or
>>1988 Honda Pelude, I asked my mechanic about this.
>>
>>It seems the reason the '88 Prelude had two O2 sensors right beside each
>>other had to to do with control over emissions. It's well known that
>>OBD-II
>>systems have two sensors, one before the cat and one after, but pre-OBD-II
>>engines like the '88 Prelude's have two sensors for entirely different
>>reasons.
>>
>>OBD-II cars use the second sensor primarily as a cat efficiency tell-tale.
>>When a second sensor was used in cars like the pre-OBD-II '88 Prelude, it
>>meant the engine management system had divided the exhaust into two
>>streams, each with just two cylinders, and was monitoring each stream
>>separately. The two INNER cylinders were monitored by one sensor, and the
>>two OUTER cylinders were surveilled by the other sensor.
>>
>>Two sensors meant that Honda was able to monitor and adjust mixture and
>>emissions twice as efficiently as it would have been able to with just one
>>sensor covering the exhaust streams from all four cylinders at once. My
>>guy
>>could not remember offhand whether Honda did this just for the carbed
>>versions of the Prelude or both carb and FI models.
>
>
> Great report. Thanks TeGGeR.
>
>
>>Furthermore, he tells me that the very latest cars are beginning to do
>>this
>>two-cylinder splitting again, but this time each pair has its own
>>catalytic
>>converter and pair of oxygen sensors. For example, some Ford V8s have FOUR
>>catalytic converters and EIGHT oxygen sensors. Can you imagine owning one
>>of these once the warranty runs out?
>
>
> No kidding.
>
>
>>I'll stick to my '91, thanks.
>
>
> And me wit me '00

I love my '87

Kevin McMurtrie wrote:
> In article <Xns981CE5F5CE93Ategger@207.14.116.130>,
> "TeGGeR®" <tegger@tegger.c0m> wrote:
>
>> Pursuant to a recent thread on the number of oxygen sensors in the 1986 or
>> 1988 Honda Pelude, I asked my mechanic about this.
>>
>> It seems the reason the '88 Prelude had two O2 sensors right beside each
>> other had to to do with control over emissions. It's well known that OBD-II
>> systems have two sensors, one before the cat and one after, but pre-OBD-II
>> engines like the '88 Prelude's have two sensors for entirely different
>> reasons.
>>
>> OBD-II cars use the second sensor primarily as a cat efficiency tell-tale.
>> When a second sensor was used in cars like the pre-OBD-II '88 Prelude, it
>> meant the engine management system had divided the exhaust into two
>> streams, each with just two cylinders, and was monitoring each stream
>> separately. The two INNER cylinders were monitored by one sensor, and the
>> two OUTER cylinders were surveilled by the other sensor.
>>
>> Two sensors meant that Honda was able to monitor and adjust mixture and
>> emissions twice as efficiently as it would have been able to with just one
>> sensor covering the exhaust streams from all four cylinders at once. My guy
>> could not remember offhand whether Honda did this just for the carbed
>> versions of the Prelude or both carb and FI models.
>>
>> Furthermore, he tells me that the very latest cars are beginning to do this
>> two-cylinder splitting again, but this time each pair has its own catalytic
>> converter and pair of oxygen sensors. For example, some Ford V8s have FOUR
>> catalytic converters and EIGHT oxygen sensors. Can you imagine owning one
>> of these once the warranty runs out?
>>
>> I'll stick to my '91, thanks.
>
> Some older cars may have two sensors that operate at two ranges. Newer
> sensors combine multiple ranges in one package.
>
> I couldn't care less what Ford does. Even a Kia will be more advanced
> soon.

no kidding!

> Doesn't Honda tune the individual cylinders using the crankshaft
> position sensor?

yes - it measures crank rotation velocity resulting from each ignition
stroke.

> Or maybe not any more? My 05 HAH engine has run like
> an old beater from day one. It's not silky smooth like the 97 Civic HX
> that I had.

that's because fix or repair daily always were/will continue to be the
cheapest pieces of garbage on the planet. and when i say "cheap", i
mean they leave no corner left uncut in their relentless pursuit of cost
cutting. if another manufacturer uses 4 screws to hold something down,
they'll use 3. cast iron crank shafts? no problem! smaller bearings?
you betcha! low-yield crumple zones /behind/ the engine to cause more
frequent accident write-offs? and who'll rather pay a few g's to lobby
for red rear turn signal lenses rather than incur about $3 per vehicle?
screw the danger in modern high density high speed traffic! hmmm, i
wonder who that might be...

Elle wrote:
>
> "TeGGeR®" <tegger@tegger.c0m> wrote
> > Two sensors meant that Honda was able to monitor and
> > adjust mixture and
> > emissions twice as efficiently as it would have been able
> > to with just one
> > sensor covering the exhaust streams from all four
> > cylinders at once.
> snip for brevity
> >
> > I'll stick to my '91, thanks.
>
> I dunno. Might be that the improvement in fuel mileage (via
> more precise engine controls over each cylinder's air/fuel
> charge etc.) makes the extra sensors worth it.



I'll stick with my '83. Now getting 36 mpg in mixed driving and it
seems to run better every time I drive it...

JT

(The A/C is next on the list to do)

jim beam wrote:

> that's because fix or repair daily always were/will continue to be the
> cheapest pieces of garbage on the planet. and when i say "cheap", i
> mean they leave no corner left uncut in their relentless pursuit of cost
> cutting. if another manufacturer uses 4 screws to hold something down,
> they'll use 3. cast iron crank shafts? no problem! smaller bearings?
> you betcha! low-yield crumple zones /behind/ the engine to cause more
> frequent accident write-offs? and who'll rather pay a few g's to lobby
> for red rear turn signal lenses rather than incur about $3 per vehicle?
> screw the danger in modern high density high speed traffic! hmmm, i
> wonder who that might be...

Well at least you're not bitter..!

Matt Ion wrote:
> jim beam wrote:
>
>> that's because fix or repair daily always were/will continue to be the
>> cheapest pieces of garbage on the planet. and when i say "cheap", i
>> mean they leave no corner left uncut in their relentless pursuit of
>> cost cutting. if another manufacturer uses 4 screws to hold something
>> down, they'll use 3. cast iron crank shafts? no problem! smaller
>> bearings? you betcha! low-yield crumple zones /behind/ the engine to
>> cause more frequent accident write-offs? and who'll rather pay a few
>> g's to lobby for red rear turn signal lenses rather than incur about
>> $3 per vehicle? screw the danger in modern high density high speed
>> traffic! hmmm, i wonder who that might be...
>
> Well at least you're not bitter..!

just wait, one day, i'll say what i /really/ think!

"Elle" <honda.lioness@nospam.earthlink.net> wrote in
news:fydDg.6992$xp2.2203@newsread1.news.pas.earthl ink.net:

> "TeGGeR®" <tegger@tegger.c0m> wrote
>> Two sensors meant that Honda was able to monitor and
>> adjust mixture and
>> emissions twice as efficiently as it would have been able
>> to with just one
>> sensor covering the exhaust streams from all four
>> cylinders at once.
> snip for brevity
>>
>> I'll stick to my '91, thanks.
>
> I dunno. Might be that the improvement in fuel mileage (via
> more precise engine controls over each cylinder's air/fuel
> charge etc.) makes the extra sensors worth it.
>
>


Until they require replacement, at which point your fuel savings dollars
are more then negated. There is such a thing as false economy.

--
TeGGeR®

The Unofficial Honda/Acura FAQ
www.tegger.com/hondafaq/