P plate training ...not

Where are these bowsers? I've never ever been able to put more litres in
than what the tank holds. Never even been able to equal the tank capacity...

 

But, but , but Nev's car says 16.23 l/100 kms (or something). This suggests
an accuracy of 0.01%. Actual accuracy is probably 10% but all those
significant digits look so neat.

Theo
The Compuguestimator on the Norge says I use 5.6 l.100 kms. Reality at the
pump suggests 5.1.

 

Yup. Pretty much sums it up.

What amuses me, is that you seem to deliberately be confusing
measuring with calculating an estimate. If someone else tried that
obfuscation you'd be up in arms !

The *measured* parameters for the EFI are things like the exhaust gas
mix (via o2 sensor), duration of injector opening, quantity of air
flowing through the throttle bodies(MAF) or the postion of the
butterfly in the throttle (TPS), engine temp etc.

The measure inputs are then used to calculate other things based on
assumptions.

There are lots of assumptions made during the programming of an EFI
computer, there's also differences in the granularity of the
measurments and hence how well it can interpolate (finite steps in
measurement need to be translated into smooth changes in quantity of
fuel, ignition timing etc).

When you make assumptions about a variable (rather than measuring it),
it is inherently more likely to be inaccurate than measuring it. Yes,
there's also error in measurement, and yes potentially the
relationship *could* be the other way around, but it's not very
likely.

Fuel flow in Nev's car is a calculated estimate, not measured (to the
best of my knowledge), the calculation is accurate enough for domestic
use, but it includes assumptions about the values of some parameters,
it is therefore not, by definition, a *measurement* of the fuel flow,
but a reasonably good estimate.

Please note, I've already said all this once. Please try reading it
this time.

yes and you still seem to think that domestic use requires scientific
levels of accuracy, the world ain't a lab, get over it.

Nev's car does stick it's metaphorical finger in the air - it doesn't
KNOW how much fuel has flowed through it (ie no flow measured). It
DOES know that it held the injectors open for N milliseconds X times
over the last 5 minutes, and *IF* it's assumption that it's fuel rail
pressure is Y PSI is correct then it has flowed Z ml of petrol. Of
course that also assumes the temp of the fuel and all sorts of other
trivial assumptions that would make minor differences to the
calculated result. Doesn't matter though because for the purposes it's
being used the estimate's going to be close enough.

And just for the record, same goes for the "weather station" temp
measurement in a domestic situation is mostly for the purposes of
considering your physical well being, so the thermometer saying 21 vs
22c doesn't really matter much, I know it means jeans and a tshirt.

Nothing, it's not at all special, it's just a way of adding fuel to an
internal combustion engine, that's nothing special. It does it a bit
more accurately nowadays than the old analogue based carbies, but
there was a fair while there when it didn't. It's no more special;
than any other computer controlled system - why do you think it's
special ?

Better EFI programming, smaller steps between measurement intervals,
more powerful CPUs able to interpolate faster and more often per
second, ability to manage a greater amount of data over a longer
period to calculate more effectively given a wider range of paramerts.
The ability to monitor the gas mix in the exhaust in a fairly
primitive way to be able to then say "oh no lean off the mixture, it's
too rich" (feedback loop on the result)

Also, outside of the efi piece - better engine design - cylinder head
design has come a long way in the last 15 years.

JL

 

It was my point. Did you miss the point I made that the four digits looks
very cute but the accuracy was more likely less than 2 significant digits?

I'm sure Holden can display more digits for you without impacting on the
accuracy.

Theo

 

No one said it was.

indeed very good, you were paying attention after all

<puzzled look> yes Hammo, I've said that twice now, but thats not a
measurement, thats a calculation based on the things that are measured
and the assumptions made.

Only in the sense that you're repeating back to me what I already said
like you're telling me something

JL

 

You used style and Hammo in the same sentence.

Theo

 

Thanks for clarifying what you were trying to say, Andew. I think I
understand your argument. You are wrong, though.

-----sharks

 

There's also a feedback loop from O2 sensor and knock sensor where
fitted which moves around in the tables according to the feedback (if
the o2 says it's a bit rich, knock n milliseconds off the injector
times), if knock sensor says it's knocking retard injector and
ignition timing etc

JL

 

<doubtful look> maybe the F1 teams do this, but too bloody expensive
for a run of the mill road car.

JL

 

Olive.

Theo

 

Damn, damn.

Theo

 

Several assumptions there. 1 that it's easy 2. that they would get
some additional benefit from measuring it, 3. that it would be cost
effective to do so.

It doesn't cost a lot to get the programmer to put in a display output
that calculates a couple of parameters you were going to store anyway.


JL

 

But what should I run in my Boxer?

-----sharks

 

That's gotten a lot better too, with wideband O2 sensors rather than the
old narrowband ones.

Also, knock sensors allow the computer to lean the mix right out and
just rich it up a smidge any time it starts knocking.

-----sharks

 

Eh? I thought we'd already established that there was no waste, or, if
there was, it was only measurable at a theoretical level.

Nev..
'04 CBR1100XX

 

No no no.. I have never quoted any figures produced by the trip computer
for calculated fuel economy/usage/whatever. Where I did throw some
l/100km figures into the discussion (in reply to Boxer's comments) they
were measured at the pump, not quoted from the trip computer.

Nev..
'04 CBR1100XX

 

Pffttt

 

You're talking about fog lights, I'm talking about driving lights. Driving
lights are long distance lights to illuminate the road further ahead then
your high beams do. It is illegal to have them wired in such a way that they
can be on when the high beams are not. Fog lights are designed to be
short-range lights to spread a wide low beam with lots of side lighting.

Theo

 

You run in boxers ?

 

No, I don't think so, and I this is why the focus on the need for a "fuel
flow measure" to be utter bollocks. Clem claims it to be obfuscation.

Hammo