"Dave Plowman (News)" wrote in message
...
In article ,
Trevor Wilson wrote:
The site Trevor gave in a later post says it can work by either
counting injector pulses or a flow device.

**Correct. It's a bit fiddly, but more accurate actually measuring the
fuel flow. I ended using the pulse counting method myself (I didn't
care much for mucking about with fuel lines), but I did have two fuel
flow meters, which came with the computer. One was plastic, the other a
substantial die-cast affair. Accuracy was pretty impressive, according
to the manufacturer's data.

I must admit to being surprised. Both my cars are injection and both use
the pulse measuring system to calculate MPG and both are very accurate.
Years ago I did have an aftermarket one that measure fuel flow and it
wasn't.

**As I understand it (please note, I am not speaking from any real authority
here) no injector is perfect. Some are clogged a little. Some are clogged a
lot. Some are not clogged at all. Pumps are subject to wear. As a
consequence, the BEST way to measure actual fuel consumption, is to measure
the amount of fuel used, rather than inferring how much fuel SHOULD be going
into the cylinders.

Having said all that: My present car probably uses pulse measurement
techniques and the computer appears to be respectably accurate (though I've
never actually checked it).

Trevor Wilson