Mixture detection

[julians]

Does anyone know if there is a cheap and chearful product available that allows you to measure/set your fuel mixture correctly. If there is, where can I get one from and how much is it.

 

[Peter Carmichael]

The standard lambda sensor is underrated in this respect. It is a switch, rather than a proportional sender so it tells you where stoich (14.7:1) is. If you are talking about mapped injection, you can then scale up the fuelling proportionally to hit a target air:fuel ratio, say 12:1 for more power or just to give a little margin.

 

This is true for steady state and then you have to consider acceleration fuelling. Loading the engine up appropriately to actually observe many load locations is difficult without the rolling road that you can peg at different speeds. I tried a scheme of testing by which I used speed (and hence Road Load Equation - thanks Tony - or mostly wind resistance) to set different load conditions. You run in each gear at fixed rpm and have a look at how much margin you have to lambda. In the end this only really gave me load sites 0, 1, 2 and 3 out of 16 so it wasn't much use.

 

There is nothing cheap that can tell you exactly what the air:fuel ratio is dynamically and accurately.

[allen]

Have not used one in years, but how about a colourtune? Are they still available?

 

Regards

 

allen

[Tony Martyr]

Cheap and cheerfull usually means horrid and inaccurate when refered to measuring devices. Air fuel ratio and mass fuel flow are very difficult to measure accurately. Think of it - you need to not only know the volume of air entrained but its oxygen content also the liquid fuel temperatures etc.

It is easier for practical control purposes to measure the effect rather than the mass flow and ratio. As Peter says the lambda sensor is used for that purpose in conjuntion with the other effect - the power at the wheels.

[oilyhands]

The colourtune is great for helping set the fueling at idle, it has the disadvantage that you have to be peering right over it preferably in a drakened room to see the combustion colour, it is probably not up to the job of wide throttle openings and high RPM, certainly its heat dissipation characteristics at those temperatures and speeds will be unlike any spark plug.

 

As PC says the best instrument is a HEGO sensor and a cheapo LED read out box, provided it is calibrated for that sensor.

 

Oily