Lambda sensor position & thread size.

[jenand40]

Can anyone tell me if the standard Rover EFI Lambda sensor is wide band or narrow band and also the thread size. Thought it was a 12mm thread but tried a 12mm nut and it does not fit. Also it appears that there are only two sizes of boss available on EBay, 18mm or 12mm.
Once I know the correct thread could I just get a nut and weld onto the exhaust pipe?

Generally how far back from the engine is the best position for them in the exhaust. Due to the space available mine would be fitted a good metre from the heads.

No cats fitted to car, just understand that it is better to have them fitted for economy reasons.

[stevieturbo]

First off, exactly what vehicle, what year, what engine ?

You can be certain it will be narrowband

M18x1.5 is generally the standard for lambda sensors across all vehicles, although there are some rare exceptions to this.

No idea what your vehicle uses...as dont know what your vehicle is....if it even uses them at all.

[minorv8]

Yes, you can buy a nut and weld it to the exhaust. Or a weldable bung.

Note that the M18x1,5 is a fine thread so you need to specify that if you buy a nut.

[jenand40]

Engine is a Rover v8 3.9 litre, with standard lambda sensors.

Engine runs okay without the lambda's, just thought that it is better to run with them, as I have them, for economy.

Just been to the local nut & bolt store and they are unable to tell me what thread they are!

[stevieturbo]

Engine is a Rover v8 3.9 litre, with standard lambda sensors.

Engine runs okay without the lambda's, just thought that it is better to run with them, as I have them, for economy.

Just been to the local nut & bolt store and they are unable to tell me what thread they are!

Once again I suspect the 3.9 was fitted to more than one vehicle.

But if it had lambda sensors fitted as standard....they are no longer fitted because ?

Again, vehicle, year ?

And standard M18 weld bosses are readily available, if indeed that is what you need.

http://www.ebay.co.uk/itm/Lambda-boss-N ... 3a83b0e1ca

[DaveEFI]

Generally, narrowband sensors are fitted to keep the mixture close to 14.7:1 as that's where a cat. works correctly. Go outside this, and the cat may be damaged/have a shorter life.

With no cat. you can run at a much weaker mixture (on a light load) for maximum economy. Perhaps 15.5:1.

However, just what a system designed for cats and lambda sensors does without them is anybody's guess.

[stevieturbo]

Generally, narrowband sensors are fitted to keep the mixture close to 14.7:1 as that's where a cat. works correctly. Go outside this, and the cat may be damaged/have a shorter life.

With no cat. you can run at a much weaker mixture (on a light load) for maximum economy. Perhaps 15.5:1.

However, just what a system designed for cats and lambda sensors does without them is anybody's guess.

It runs open loop, same as them all.

Sometimes slightly richer than normal, sometimes very close to stioch anyway.

Whether the cat itself is fitted or not wont really matter too much.

[SimpleSimon]

Generally, narrowband sensors are fitted to keep the mixture close to 14.7:1 as that's where a cat. works correctly. Go outside this, and the cat may be damaged/have a shorter life.

With no cat. you can run at a much weaker mixture (on a light load) for maximum economy. Perhaps 15.5:1.

However, just what a system designed for cats and lambda sensors does without them is anybody's guess.

It runs open loop, same as them all.

Sometimes slightly richer than normal, sometimes very close to stioch anyway.

Whether the cat itself is fitted or not wont really matter too much.

If its on the Cat map tune resistor then its only open loop above around 3300 RPM anything below its on CL, and the Hotwire o2 probes are 12 x 1.25 its a Jap sizing Nissan used the same size probes many moons ago IIRC

[stevieturbo]

Generally, narrowband sensors are fitted to keep the mixture close to 14.7:1 as that's where a cat. works correctly. Go outside this, and the cat may be damaged/have a shorter life.

With no cat. you can run at a much weaker mixture (on a light load) for maximum economy. Perhaps 15.5:1.

However, just what a system designed for cats and lambda sensors does without them is anybody's guess.

It runs open loop, same as them all.

Sometimes slightly richer than normal, sometimes very close to stioch anyway.

Whether the cat itself is fitted or not wont really matter too much.

If its on the Cat map tune resistor then its only open loop above around 3300 RPM anything below its on CL, and the Hotwire o2 probes are 12 x 1.25 its a Jap sizing Nissan used the same size probes many moons ago IIRC

If there are no lambda sensors fitted, it can never be closed loop.

[SimpleSimon]

It runs open loop, same as them all.

Sometimes slightly richer than normal, sometimes very close to stioch anyway.

Whether the cat itself is fitted or not wont really matter too much.

If its on the Cat map tune resistor then its only open loop above around 3300 RPM anything below its on CL, and the Hotwire o2 probes are 12 x 1.25 its a Jap sizing Nissan used the same size probes many moons ago IIRC

If there are no lambda sensors fitted, it can never be closed loop.

Sorry Stevie I should have read that correctly

[minorv8]

Just been to the local nut & bolt store and they are unable to tell me what thread they are!

That´s a nice one ! Two basic things to measure: outside diameter and thread pitch. That gives you the rough idea in most cases, anyone who has been selling bolts and nuts learns that in a matter of hours. Maybe your dealer did not know that this applies to metric bolts too ?

[richardpope50]

Just wondering if they sell thread gauges. Probably do.