04 MSM: car has 3 o2 sensors, which is hydra? - Miata Turbo Forum - Boost cars, acquire cats.

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Old 05-01-2013, 03:24 PM   #1
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Default 04 MSM: car has 3 o2 sensors, which is hydra?

Like it says...

I could just try and trace everything, but that might be a problem since it seems the wiring from two of the sensors goes to the same drilled hole in the body that's been filled/sealed with a bunch of silicone goop of some sort.

I'm fairly certain it's not the one post-cat.

Sooo.... o2 housing? Or pre-cat?

Just hoping someone might know off the top of their head.


My next question is: Do i even need any of these o2 sensors? (Besides the Hydra wideband, of course.) I can't fathom why this car has 3 friggin o2 sensors.
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Old 05-01-2013, 03:31 PM   #2
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1 pre cat, one post precat, one post second cat.
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Old 05-01-2013, 03:32 PM   #3
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1 for the hydra, 1 for the gauge, and the original post-cat sensor to make sure the cat is still working? I assume that is what the post-cat one is at least.
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Old 05-01-2013, 03:40 PM   #4
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Quote:
Originally Posted by Braineack View Post
1 pre cat, one post precat, one post second cat.

......

Right... but on a Hydra car do i A) need all 3, and B) which one should be the wideband?

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Originally Posted by thenuge26 View Post
1 for the hydra, 1 for the gauge, and the original post-cat sensor to make sure the cat is still working? I assume that is what the post-cat one is at least.

No gauge. Hydra can't output to a gauge because HERP DERP. One of the 3 is Hydra's wideband (At least i think...), and the other two are stock things that likely aren't doing a damn thing anymore.


Or... there IS an un-used bung on the exhaust, and there's a sensor of some sort in the trunk of the car that was there when i bought it. Maybe that's a something? I don't ******* know. I'd think with a standalone i'd only need 1 sensor, not 3, 4, or 5.
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Old 05-01-2013, 05:40 PM   #5
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Originally Posted by concealer404 View Post
No gauge. Hydra can't output to a gauge because HERP DERP. One of the 3 is Hydra's wideband (At least i think...), and the other two are stock things that likely aren't doing a damn thing anymore.
Did it ever have a gauge? Because if it did, then it would have needed a second wideband. That would at least explain one of the extras.
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Old 05-01-2013, 08:14 PM   #6
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Never had a gauge. I called Jeremy and he said it's the one after the o2 housing in the downpipe, pre-cat.

Seems I gotta pin the plug and run it to the ecu.

Suppose I should have asked him if I can get rid of the others.
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Old 05-02-2013, 02:03 AM   #7
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My understanding is that pre 2.7 its just the front and pre-cat (Wideband) but that the 2.7 uses all 3?
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Old 05-06-2013, 12:29 AM   #8
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I'm also figuring this out as I bought my car already running a Hydra 2.5 and I just "upgraded" to 2.7. Now I find out my wideband is missing!
Concealer: of your two front O2s one should be a 5 wire wideband for the Hydra and one the stock 4 wire narrow band.The after cat O2 does nothing. My guess is that the previous owner left both stock O2s incase they had to switch back for emissions.
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Old 05-06-2013, 05:53 PM   #9
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Originally Posted by cbaylis77 View Post
I'm also figuring this out as I bought my car already running a Hydra 2.5 and I just "upgraded" to 2.7. Now I find out my wideband is missing!
Concealer: of your two front O2s one should be a 5 wire wideband for the Hydra and one the stock 4 wire narrow band.The after cat O2 does nothing. My guess is that the previous owner left both stock O2s incase they had to switch back for emissions.
Yeah, sorry i should have updated.

I called Jeremy and the Hydra wideband is the one after the one in the o2 housing.

I'm pretty sure you're right as to what the previous owner was doing. The stock ECU is still mounted in the car, and he had the MAF hooked up as well when i bought the car, stock injectors in the trunk.
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Old 05-06-2013, 11:46 PM   #10
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It's always fun when you're trying to figure out what the previous owner was doing. Better to have too many sensors than not enough! I never got the Hydra O2 with the car. I thought I could switch my AEM wideband to the Hydra but it's a different plug.
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Old 05-07-2013, 02:57 AM   #11
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Quote:
Originally Posted by cbaylis77 View Post
It's always fun when you're trying to figure out what the previous owner was doing. Better to have too many sensors than not enough! I never got the Hydra O2 with the car. I thought I could switch my AEM wideband to the Hydra but it's a different plug.

I put on the stock WB connector with my WB perhaps its a compatible WB?
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