The Triumph Dolomite Club - Discussion Forum

As the title says, except that I'm actually at the stage of collecting the necessary parts. I have some experience as I already fitted one in my spitfire. Which is the best place on the exhaust pipe to fit the sensor? It should be not close to the manifold but not too far either. Can anyone suggest the ideal location? I would prefer not to remove the exhaust from the manifold side as I have read horror stories of studs shearing off - is it such a huge problem and can anything be done about it? For those already using the gauge - what ratio are you using? 14:1 or slightly richer?

For mounting the AFR sensor, I’m afraid you’ll have to take the downpipe off. You ideally want it placed less than a foot of the collector for the manifold, the closer to the manifold, the better. I am assuming your using the stock exhaust manifold, that means somewhere in the down pipe.

As for AFR, idle should be around 14-15:1 but if you tuned it to run at 14.7: which is what it should be, that it might not idle or run very well/smoothly and to tune the AFR for things such as cruise and acceleration will be an annoying job to be either switching needles on the SUs or fiddling with all the settings a pair of Webers would have

I've had an analogue AEM wideband fitted for about 10 years.
I honestly wouldn't bother. It's dependant on so many more things like RPM, Load, throttle position etc. it makes it still guesswork.
The analogue one does make it difficult to read, but the digital ones you get look so gaudy and hideous, it'll be completely out of place.
The example given about idle at 14 to 15, if my car specifically (a slightly mutilated 1850) idles at those numbers, a blip on the throttle and it'll stumble and die immediately. It's much much happier at around 13.
Also, make sure you clock the sensor so it sits at an angle, the sensors don't like it otherwise, apparently.

Boost All The Dollys wrote: ↑Thu Feb 13, 2025 1:54 pm For mounting the AFR sensor, I’m afraid you’ll have to take the downpipe off. You ideally want it placed less than a foot of the collector for the manifold, the closer to the manifold, the better. I am assuming your using the stock exhaust manifold, that means somewhere in the down pipe.

As for AFR, idle should be around 14-15:1 but if you tuned it to run at 14.7: which is what it should be, that it might not idle or run very well/smoothly and to tune the AFR for things such as cruise and acceleration will be an annoying job to be either switching needles on the SUs or fiddling with all the settings a pair of Webers would have

Thanks for this. I've attached a photo of the exhaust downpipe after the manifold. It looks like it's stainless steel or is it stock? Sprints are very rare where I live and have no idea how the stock downpipe looks like. Regarding idle rpm, I found through trial and error that my spitfire likes it much better at around 12:1 (from the book 14:1). I later confirmed this with Paul Teglerizer's website (https://www.teglerizer.com/triumphstuff/ - the absolute bible on anything spitfire).

ham204v2 wrote: ↑Sat Feb 15, 2025 5:59 pm

Boost All The Dollys wrote: ↑Thu Feb 13, 2025 1:54 pm For mounting the AFR sensor, I’m afraid you’ll have to take the downpipe off. You ideally want it placed less than a foot of the collector for the manifold, the closer to the manifold, the better. I am assuming your using the stock exhaust manifold, that means somewhere in the down pipe.

As for AFR, idle should be around 14-15:1 but if you tuned it to run at 14.7: which is what it should be, that it might not idle or run very well/smoothly and to tune the AFR for things such as cruise and acceleration will be an annoying job to be either switching needles on the SUs or fiddling with all the settings a pair of Webers would have

Thanks for this. I've attached a photo of the exhaust downpipe after the manifold. It looks like it's stainless steel or is it stock? Sprints are very rare where I live and have no idea how the stock downpipe looks like. Regarding idle rpm, I found through trial and error that my spitfire likes it much better at around 12:1 (from the book 14:1). I later confirmed this with Paul Teglerizer's website (https://www.teglerizer.com/triumphstuff/ - the absolute bible on anything spitfire).

I would say that looks like mild steel considering that it’s rusting but I’d give it a magnet check to make sure.

As for position, the topside of that bend would be ideal cos it’s easy to access from the top

As for position, the topside of that bend would be ideal cos it’s easy to access from the top

There are two downpipes, the lower one is barely visible in the photo. Won't the reading be more accurate if the sensor is positioned after the downpipes merge?

ham204v2 wrote: ↑Sun Feb 16, 2025 5:28 pm

As for position, the topside of that bend would be ideal cos it’s easy to access from the top

There are two downpipes, the lower one is barely visible in the photo. Won't the reading be more accurate if the sensor is positioned after the downpipes merge?

Oh, yes, I forgot the sprint had two down pipes. Ideal place for the sensor is between 6-12” from the collector and between 15ᵒ and 75ᵒ from horizontal. Basically, don’t have it perfectly horizontal or vertical as it can build up condensation and hurt the sensor