The basics are: plus, minus, multiply and divide. Then you have greater than, less than, greater than and equals, less than and equals, equals and not equals. You also have ‘and’ and ‘or’ logic functions.

I am currently calculating instantaneous fuel consumption by:

(‘Fuel Inj Duty'[ratio]*0.643*60)/(‘GPS Speed'[km/h])*100

So the fuel injector duty cycle (per cent opening time of injector) is multiplied by flow in litres per minute (3 injectors @ 214cc/min = 0.643 litres/minute), and then by 60 to get litres per hour. This is divided by speed in km/h to get litres per kilometre. This is then multiplied by 100 to get litres/100km.

That works really well, except when you are stationary where the figure becomes infinite! That in turn isn’t so good if you’re trying to additionally calculate averages, so I am today trialling an additional expression that means the calculation for instantaneous fuel economy works only at speeds above 0.5 km/h.

In addition to these simple expressions, you are have a range of functions: tan, cos, log and so on. Unfortunately, in this list there are not derivatives, integrations, smoothing or filtering – all of which are available in the maths functions in the i2 pro data analysis software from MoTeC. I was very much intending to use derivatives and integration, so that’s a bugger.

]]>The dash has three different modes, dubbed ‘race’, ‘practice’ and ‘warm-up’.

I have made the ‘warm-up’ display show any time coolant temp is less than 80 degrees C.

It displays:

– engine revs

– coolant temp

– air/fuel ratio

– engine oil temp

– GPS speed

– fuel level (because in the other dash modes I don’t show fuel level, just a warning when it is low – so this way I get to see it each time the car is started).

At 80 degree C coolant temp, the dash auto swaps to the main display. This shows a huge range of parameters – I won’t list them all here.

I also have a driver-selectable display suitable for driving for best fuel economy. The main bar graph (normally for engine rpm) then changes to instantaneous fuel economy (calculated from GPS speed and injector pulse width), and the dash in this mode also shows GPS speed, manifold pressure, air/fuel ratio (etc). It also brings up trip fuel economy and average air/fuel ratio (ie an ongoing running average of this parameter).

I also have a special text that displays only in this ‘fuel economy’ mode – ‘Poor Fuel Eco’ that shows when instantaneous fuel economy is more than 3.5 litres/100 for more than 4 seconds AND gear is less than 5 AND equal to or greater than 1 AND throttle position is less than than 50 per cent.

I might also add that today I tried more than a few things that didn’t work….. it’s easy to recount it afterwards when it all works!

Another 4-5 hours*, but lots of fun.

* I know that up above I said it was a full day… it wasn’t, but it felt like it!

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