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Mid restoration of a MKIV Spitfire, this is going to be fairly standard set-up but do fancy fitting an 02 sensor so I can take the guess work about setting up the mixture. On my EFI Herald (Fitted with a Bell SS Manifold) it is positioned at the 2-1 collector beneath the gearbox, but as the Spitfire will have the standard twin SU's would it be an advantage to have sensor points to cover each carb independently or just stick to the one? My thinking is that with two sensors the carbs can be more finely set-up to get identical mixture settings rather than a combined 02 reading, which in theory could have one carb a little rich and one a little weak, but the combined reading OK.

Pic is possible positions for the sensor(s), if going with dual sensor is will probably be easier to fit them by using a 90° elbow (other pic)....may seem like a dumb question, but elbow/extension takes the sensor out of the main flow of exhaust gases, would with impact on the readings?

Darren 

 

 

 

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Hello Darren

                       Will the dual position be to hot?

I am not sure the Elbow would work not in the gas flow

Roger

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Hi Roger,

Think you could be right, depending on what instructions you read, 24" is the minimum distance which would probably push it past the first collector and then exhaust gases are being mixed from the 2 carbs.

Oh well, single sensor it is...

Darren

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JoSo I have welded in the bung for the 02 sensors, so for a carbureted car what is a target AFR at tickover. 

I went for the LD Performance kit in the end. Roger, I think you use this one IIRC... We're you happy with it?

Darren

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On 5/16/2019 at 8:09 PM, Darren Groves said:

but elbow/extension takes the sensor out of the main flow of exhaust gases, would with impact on the readings?

 

On 5/16/2019 at 8:43 PM, rogerguzzi said:

Will the dual position be to hot?

I am not sure the Elbow would work not in the gas flow

you don't want them in direct flow too close to the head and too hot. Innovate recommend a 1" extension if in the headers. Its where i have my two sensors mounted so i can monitor the carbs individually, if you buy the screw in extensions (not expensive) you must get the open right through ones not the CAT cheating ones that are designed for another job entirely, the proper extensions will position the tip just on the edge of the gas flow and they will work correctly. i'll see if i can find a link to the extensions i found.

21 hours ago, Darren Groves said:

, so for a carbureted car what is a target AFR at tickover. 

about as lean as it will tick over nicely at, the engine isn't doing any work at tickover, so as long as your not going stupidly lean there is very little chance of doing and damage, its the AFR's at cruise and under acceleration that you want to concentrate on. i always had idle AFR's in the 14-16 range they will bounce around in that range as there isn't much going on at idle, certainly thats what the direct logs show, i suspect some of the AFR gauge implementations may use some form of damping algorithm so that the display isn't jumping all over the place, the sampling rate that the sensors will support is actually very high, so a lot of what you see is down to the controller software and processor speed.

alan

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