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RDMG
Dave R
Northern Virginia
(76 posts)

Registered:
04/07/2016 08:29PM

Main British Car:
1979 MGB 4.6L Rover V8

O2 Sensor Locations
Posted by: RDMG
Date: March 30, 2018 08:43AM

I am about to send my RV8 thru-the-wing headers for my MG off to be coated, but I want to weld a bung onto each of them for an O2 sensor first.

The all-knowing internet suggests that ideal placement is approximately 1m from the exhaust ports, and in a vertical or near-vertical position to avoid condensation drips. I canít see how to do that on an LBC. I see a few examples here where a sensor is just below the 4-to-1 collector, horizontally mounted, in the fender well before the header turns to the rear. Iím wondering if a better spot is after the header turns horizontal, near the trans bellhousing?

Does anyone have some thoughts on where the best placement for 02 sensors should be, and hopefully a pic or two?

Many thanks,

Dave


mstemp
Mike Stemp
Calgary, Canada
(189 posts)

Registered:
11/25/2009 07:18AM

Main British Car:
1980 MGB Rover 4.6L

Re: O2 Sensor Locations
Posted by: mstemp
Date: March 30, 2018 09:38AM

What type of FI are you running? If Rover 14CUX follow the MG RV8 location which is after pipe turns horizontal.
If this is just an AFR gauge then itís less critical, mine is a single at the Y and function well.


MGBV8
Carl Floyd
Kingsport, TN
(3431 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: O2 Sensor Locations
Posted by: MGBV8
Date: March 30, 2018 10:36AM

IF using a wide band O2 with heater, it is not critical. After the collector is fine with the bung pointing up.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5564 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: O2 Sensor Locations
Posted by: BlownMGB-V8
Date: March 30, 2018 11:04AM

I always put the bung on the side of the pipe so the sensor can be changed and that's the way the OEM's do it too. Under the car seems just fine. If you get up in the wheelwell with it you have to watch your tire clearance very carefully. The only way I could see condensation being a problem would be if you put it on the bottom of the pipe and then you'd be knocking it off on speed bumps.

Jim


RDMG
Dave R
Northern Virginia
(76 posts)

Registered:
04/07/2016 08:29PM

Main British Car:
1979 MGB 4.6L Rover V8

Re: O2 Sensor Locations
Posted by: RDMG
Date: March 30, 2018 12:17PM

Many thanks!

Iíll be running megasquirt FI with wideband sensors. Looks like Iíll go with a side mount on the horizontal portion of the header, after it exits the wheel well.

Dave


MGBV8
Carl Floyd
Kingsport, TN
(3431 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: O2 Sensor Locations
Posted by: MGBV8
Date: April 02, 2018 05:40PM

Quote:
I always put the bung on the side of the pipe so the sensor can be changed and that's the way the OEM's do it too.

Most probably do, but I found some that are up.

[cdn4.pelicanparts.com]

More info:

[wbo2.com]


mstemp
Mike Stemp
Calgary, Canada
(189 posts)

Registered:
11/25/2009 07:18AM

Main British Car:
1980 MGB Rover 4.6L

Re: O2 Sensor Locations
Posted by: mstemp
Date: April 02, 2018 07:54PM

If you read the gauge manufacturer instructions you will find that they need to be at least 10deg inclined to prevent condensation fouling etc. Not too hard to do in a B. I have 3 sensors in.my car and all are on an angle.
Here is AEMís instructions.

[aemelectronics.com]



MGBV8
Carl Floyd
Kingsport, TN
(3431 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: O2 Sensor Locations
Posted by: MGBV8
Date: April 03, 2018 09:16AM

My second link says the same.


DiDueColpi
Fred Key
West coast - Canada
(1259 posts)

Registered:
05/14/2010 03:06AM

Main British Car:
What if the Hokey Pokey really is what it's all about?

authors avatar
Re: O2 Sensor Locations
Posted by: DiDueColpi
Date: April 04, 2018 02:18AM

Ok, so here's my random ramblings on O2 sensors.
In general O2 sensors should be as close to the engine as possible.
This has nothing to do with response time and everything to do with heat.
Single wire (non heated ) O2 sensors won't operate until they get up to temp. And the only warmth that they have is the exhaust. So the closer they are the better.
Heated ( 3 wire or more) O2 sensors are not as sensitive to placement but will get up to temp faster the closer that they are to the engine.
Orientation matters.
When warming up the engine produces a tremendous amount of condensation and some of that collects on the O2 sensor.
If the sensor is oriented to allow for the collection of this condensate.That moisture stays inside the housing and increases warmup time. It also shortens the sensors lifespan dramatically.
Most sensors, with the exception of the later AFR sensors need a supply of clean air. They use that air as a comparison sample.
This sample is taken from a small filter on the side of the sensor housing or through the wiring harness sheath.
Clean, preferably cool air is required. Oil and coolant contamination is common and will cause all kinds of sensor reading flaws.
Exhaust leaks are clearly not allowed. Even a small crack or incomplete weld will make the sensor reading useless.
Heated sensors can be used anywhere in the system. With a couple of caveat's. They must be located before the Cat. if you have one. And while they could be mounted right on the tail pipe. They must be far enough up the pipe to avoid contamination of the sample from simple reversion. But closer to the engine is still best.
Lastly, the exhaust system needs to be grounded.
For one and three wire sensors in particular it's critical.
And also to reduce the electrical noise in the pipes for an AFR sensor as well.
You would think that this was a non issue but, rubber hangers, organic gaskets and a touch of rust can leave the entire exhaust system without grounding more often than not.

That's all I've got for now kids.
Fred



Edited 1 time(s). Last edit at 04/04/2018 02:34AM by DiDueColpi.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5564 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: O2 Sensor Locations
Posted by: BlownMGB-V8
Date: April 04, 2018 11:58AM

Pretty comprehensive.

Jim


Blown v8
Bryan Phipps

(41 posts)

Registered:
03/10/2013 04:52PM

Main British Car:


Re: O2 Sensor Locations
Posted by: Blown v8
Date: April 08, 2018 12:52PM

If you have the option "to open your headers" how far should the sensor be away from the opening?


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