Downstream Oxygen Sensors - Results

[mike]

I am seeing more situations where a vehicle's computer is using the downstream (or post catalytic converter) oxygen sensors as part of it's air/fuel calculations.

I recently purchased a Suzuki Grand Vitara that has documentation that says that the downstream sensors are used in the calcs. It's been coming up in a number of threads lately too, where various vehicles are using the data in some way to adjust fuel trim. In some cases, these downstream sensors appear to be negating the effects of the EFIEs being used on the upstream sensors.

This thread is for results of testing modifications to the downstream sensors. If you have results of testing, either positive or negative, on modifying the signal on your downstream sensor(s), please post them here. Please be sure to include the make/model/year of your vehicle.

Please limit any discussions in this thread. Try to start new threads with discussions about a specific member's result, and post a link here to the new thread. That way we'll keep this thread as a summary of vehicle types and the results obtained.

[crazeehorse]

Test Results for 2008 Hyundai Sonata
Downstream 02 senson

4 cylinder - 2.4 cc displacement.
Automatic transmission ( 4 speed )

Test Loop is 17.1 miles. A few hills but mostly level.
Speed was 48 mph by GPS and with cruise control.
ScanGuage II was used for average MPG. Calibration
is good.

Unit is 25 plate cell 2 3/4 x 6.0 in. Encased in pvc shrink wrap.
EFIE is connected to the cells terminals.
NAOH with 1/2 teaspoon per 1300 ml distilled water

Amps Avg MPG

Nov 12 2008 -- EFIE set for 250 mv
20 A 36.1
15 A 35.9
10 A 36.4

Nov 13 2008 -- EFIE set for 190 mv
10 A 37.5
15 A 37.2
20 A 37.1

EFIE set for 160 mv
10 A 37.3
20 A 36.5

EFIE set for 210 mv
10 A 36.9
20 A 36.9

NO HHO/No EFIE 37.9

Nov 14 2008

EFIE set for 230 mv
10 A 36.6
20 A 36.2

NO HHO/No EFIE 37.2

Nov 15 2008
EFIE set
285 mv 16.5 A 36.1
310 mv 25.0 A 36.2
240 mv 28.0 A 36.5
185 mv 28.0 A 37.2
180 mv 28.0 A 38.2

NO HHO/No EFIE 38.2 @ 48 mpg
NO HHO 38.5 @ 58 mpg

Nov 18 2008
EFIE set 185
10 A 34.3 @ 58 mph
No HHO / No EFIE 34.3 @ 58 mph
HHO / No EFIE variable speed 34.3

I tried to set the voltage on the EFIE with the
engine running but it would go all over the place
mostly lower...down to - volts. I set the EFIE
with the engine off but the ignition on.

[mike]

A couple of points:

You can't use a scangauge to tell you what's going on with HHO and EFIE operation. The HHO and the EFIE both fool the scanguage and make it's measurements incorrect.

If you're EFIE is all over the place (measuring from the red and black test ports), that's an indication that you are on the wrong wire. When connected to an oxygen sensor signal wire, it should definitely be a steady reading. Measuring the red or black port to ground, however, should be reading wildly changing voltages in the range of .1 to .9 volts or more. That's the oxygen sensor itself. Note the engine must be running.

I've checked your Sonata, and it doesn't have AFR sensors, which can also cause the wild readings on an EFIE.

If you have trouble getting this issue resolved, please contact support@fuelsaver-mpg.com. He can help you get your EFIE installation debugged.

[alpha-dog]

Although I can't tell you anything about fuel effiecency, what I have noticed on my first trip with quad EFIE's installed is the long term and short term fuel trims. Whenever I take my foot off the gas to coast from about 50~60 mph LTFT will go as low as -17.5 briefly, STFT will go to -24 for maybe a second, very brief. After that they will resume to something richer. My EFIE's are set to ( downstream ) 150mvdc, and ( upstream ) 165mvdc. I feel this may be a good setting, overall LTFT is lean ( - ) but STFT can go a little more rich ( + ) while cruising.
Russ

[mike]

When you take your foot off the gas and coast, your air fuel ratio will go very lean, and this will cause a change to your fuel trim. But it's not really a significant reading because it only happens when you're coasting. You want to see negative fuel trim numbers when you're driving normally.

I suspect you'll need to increase the EFIE settings to both the upstream and downstream EFIEs. But only the mileage will tell the tale.

[01olds]

HI i dont have too much to add here..EFIE subject....at first it seem to make a difference....now after several thousand miles the engine is misfiring ocassional reguardless of driving conditions (wasting lots of gas) so now disconnected EFIE..attempeting to get car running smooth again maybe i had it (EFIE) set too high ....so at this post ....will get car back running smooth then reconnect EFIE...see how it goes oh and to i am experminting with wind defelectors.....well see what results comes from that idea...good luck to ya all don..

[Yodamaker]

Hey guys,

We have installed the extender on the second O2 sensor and it stopped the CEL from coming on. But, we have not overcome the the base mileage of (pre-application) 28mpg on the 05 GMC Canyon pickup with the Vortec 2.8 4 cyl. we will be installing the duel EFIE this wednesday for the pre and the post O2's. Until then, we will be testing out different settings on the EFIE to see if we can get some idea of results.

So far we have tested
195-210mv - 25mpg

We have changed the settings to 175mv this time around and will report tomorrow. This truck gets driven about 100-140miles everyday. so the numbers are usually based after 100 miles of driving. Fill-up to fill-up.

[hygear]

The extenders I installed on the post cats on my 2005 Dodge Ram didn't help at all.Still got a light with any mv setting over 90.I think the Dodge ECM is more sensitive than most.The only remedy seems to be a second efie for the post cats.

[alpha-dog]

One thing I've learned is that all four EFIE's need to have the same offset voltage. With to much disparity between upstream and downstream o2's offset voltage my truck will not act right. It will slow down a lot faster than with the offsets set the same.
I've began setting my offsets with the engine off and key on, then test the offset voltage after driving 10 or so minutes. The offset voltage only changes about 20mvdc.
Russ

[Yodamaker]

alpha-dog Wrote:One thing I've learned is that all four EFIE's need to have the same offset voltage. With to much disparity between upstream and downstream o2's offset voltage my truck will not act right. It will slow down a lot faster than with the offsets set the same.
I've began setting my offsets with the engine off and key on, then test the offset voltage after driving 10 or so minutes. The offset voltage only changes about 20mvdc.
Russ

What settings are you using?