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4 O2 Sensors - Two Dual EFIEs???
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howiser1 Offline
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Post: #1
4 O2 Sensors - Two Dual EFIEs???
The basic question here is will I need 1 Dual EFIE or 2 Dual EFIE's?

I have a Mazda Tribute V6 2005. It has 4 O2 Sensors.

I'm installing an HHO system and thinking about the EFIE option.

This is directly from the Haynes Manual for my vehicle:
"On the V6 model there are 4 heated O2 sensors, one upstream and one downstream for each cylinder head. There are three catalysts; a smaller "fast-light-off" cat right below each exhaust manifold and another larger downstream catalyst. The O2 sensors are located upstream and downstream in relation to the two smaller catalysts." The "fast-light-off" cat are actually an integral part of the exhaust manifolds.

Thus it the layout is like this for one of the cylinders (note this would be times 2 - 2 cylinder heads for the V6 model)

Engine --> Beginning of Exhaust Manifold --> Upstream O2 Sensor --> "fast light-off" cat --> downstream O2 Sensor --> large conventional 3-way catalytic converter (TWC) or as stated above the "larger downstream catalyst”.

Basically all the documentation on this site says that you need and EFIE for ALL O2 that are upstream of the catalytic converter... well TECHNICALLY all 4 of my sensors are upstream of the conventional catalytic converter.
It's just on my vehicle they have inserted a "fast light-off" cat between which is separating the O2 sensors.

Note that there is nothing (no O2 sensors) after the conventional cat converter.

Confused So do I need TWO dual EFIEs for the upstream and downstream sensors (one on each side)? OR do I just need ONE dual EFIE for just the two upstream O2 sensors? Hmm

I guess a bit more detailed info on your site would help explain this. Maybe a few diagrams of the possible layouts and O2 combinations showing where the EFIE would attached might be a good addition… just a thought.
05-18-2008 08:47 AM
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mike Offline
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RE: 4 O2 Sensors - Two Dual EFIEs???
I'm pretty sure that you're only going to need one Dual EFIE to treat those upstream sensors.

Just as a precaution, I would go ahead and locate your signal wires (which you'll need to do to install the EFIEs anyway), and measure them to ground with the engine running. Let's just make sure that they produce about .3 - .7 volts or so, constantly changing. I recently had a situation where the Lexus wiring diagram called their AFR sensors, heated oxygen sensors. But they read 2.8 volts to ground (AFR sensors). As long as that checks out, you should be good to go with a Dual EFIE.

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05-18-2008 10:28 AM
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howiser1 Offline
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RE: 4 O2 Sensors - Two Dual EFIEs???
HI Mike,

Thanks for getting back to me. I will check out the voltages on those "O2 sensors". I was also reading about these AFRs... and curious if this is what I really have. I'm out of town all week... I'll check back in this weekend.
05-19-2008 11:02 AM
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