Originally Posted by
Clean 2.0 nova
There are a few inputs but none of them are too complex. If you have an engine that was produced to have the option of a trip computer then things are more straight forward. I would imagine this is all C20LET's C20XE's and virtually every other more modern vauxhall engine produced since.
There are a few things a trip computer tells you, but it is instantaneous and average consumption which is most desired. For this the trip computer needs to know 3 bits of info:
A - Speed, 31 pulses per wheel revolution to be exact. I've used my astra digi dashes 15 impulse transducer. The transducer turns twice per wheel revolution so I end up with 30 pulses per wheel revolution in reality - close enough for me. Blu/Red wire.
B - Instantaneous fuel consumption from ECU. I've personally not looked into this signal but it could be something as simple as the same signal to an injector, i.e. the longer the pulse the more fuel is used. Please be aware the ECU (and ultimately trip computer) only knows how much fuel is being administered by the time the injectors are on. Obviously if you run non-standard coloured injectors or are running a higher pressure on your fuel rail then these values will be incorrect. Blk/Brn wire.
C - Fuel in tank. This I assume is for the longer term average consumption rather than just relying on the injector method above. The only thing is a nova fuel tank holds less than a calibra, as such the trip computer will think you are using more fuel. A simple Circuit board can be made to correct the value to the trip computer think the tank is say 3/4 full whereas in reality it is full. Blu/Blk wire.
Other information like clock and stop watch utilise no inputs of course. 'Range' is calculated from the consumption figures already covered. The Air temperature is merely a two wire thermistor connected to Blu and Blu/wht wires. Place this under a wheel arch to stop the engine heat affecting it too much.
Calibration:
There are quite a few hidden setup screens when you put the Trip comp. into diagnostic mode (connecting Brn/Red and Brn/Wht wires together) that I don't fully understand as yet. These are to do with calibration of the fuel tank and some other factors. Each Trip computer is programmed for a particular engine type eg C20LET and wheel size. There is a bloke on the interweb somewhere that can re-program the wheel size and engine type via a tech 2.
In reality I just plugged and played, yes I don't get dead accurate fuel consumption figures but once I know how far the figures are out I can just subtract the offset from what its telling me. If you want it spot on then making up a tank circuit board as already covered should make it pretty accurate.
Hope this gives someone enough info to have a stab - or have I just put everyone off doing the mod?
Iain
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