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Henry Yorke

Diy Air Fuel Ratio Gauge

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Henry Yorke

I have always fancied an AFM gauge on my Skip so I know what is going on in the engine, but was trying to avoid having the universal gauges all down my pillar like a set of Punto lexus lights!

 

Anyway I have found this and it seems quite simple:

http://www.redline.lt/magazine/spec-featur...e/article/17/1/

 

This would mean i could mount the LED's somewhere out of the wat, maybe in the dash by the clocks etc? Does anyone know if it will work with a standard 205 lambda sensor or do I need a wideband one?

 

(I found that site looking at a 507bhp Alfa 155 Q4!)

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jim21070

I love the term "welding" when soldering is meant. I just had a mental picture of someone attacking a poor little LED with a MIG :D

 

I digress. A normal Lambda Probe has a very non-linear response and is not really suitable for a light display IMHO. As Lambda 1.0 is approached there is a very rapid drop in voltage to almost zero but past this point there is very lttle change. Going back just past Lambda 1.0 the voltage will then really shoot up so the effect you'll see is a very rapid change of lights as you move towards 1.0 but as you drift past it, very little further change will be seen. In a closed-loop ECU this is just the job but it's not useful for eyeballing.

 

A wideband would be much better. the response is much more linear both sides of Lambda 1.0.

 

A possible source of one might be an otherwise broken Gunson Gastester.

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Rippthrough

And you were doing your technical explanation at the pub meet too! :blush:

 

A narrowband sensor outputs a high voltage just below stoich, and a low voltage just after stoich, so it can only tell you when you are about right for emissions. A wideband can give a linear voltage output from about 6:1 up to around 30:1.

So when you measure the voltage that voltage only corresponds to one exact ratio - which is what you need.

 

I may go to Cadwell on the 3rd Dec to spectate, so maybe we can get it up on some axle stands in the paddock then and run it with the wideband in? I still haven't tidied the wiring up since last time :)

 

-Phillip

Edited by Rippthrough

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