NikTheGeek · Oct 21, 2012

On my similar age Rover 75 you could press the trip button whilst turning the ignition on to get in the the diagnostics and settings of the on-board computer. There you could adjust the off-set for the fuel calculator if it wasn't accuratley calculating your fuel usage.

Anything like that on the Range Rover?

I only ask because today was my first decent towing session. 100 miles with a double horse box with 2 horses in. Brimed it till the fuel hose clicked and did the same as soon as I got back. On board computer said 16.2, brim to brim check gave me 20.23 using Miles Per Gallon Calculator - Workout your Car's MPG Easily! With MPG Calc

Which I think is pretty good going considering it was 50 miles of winding country roads at 20mph and the autobox was everywhere.

Can I calibrate the onboard computer to make it a bit more accurate?

Nik

Saint.V8 · Oct 21, 2012

Only on the L322 the p38 doesnt have that option

I also use the mpgcalc on iphone too!!!!

wammers · Oct 21, 2012

So you are saying you put in 22.5 litres but the computer is saying you used 28 litres. That is down to the vagrancies of the fuel contents gauge i am afraid. Did you zero computer before you set off? Also depends on the flow of the filler you filled it with mine will click off on some pumps when tank is empty.

NikTheGeek · Oct 21, 2012

You've lost me now

It doesn't tell me (I don't think) how much litres I used, just what my average mpg was. Yes I did reset it before setting off. Trip1, trip2 and the computer. I also used the same nozzle at the same filling station before I set off and when I got back and you could hear the diesel gurgling as it approached the top so it was full.

wammers · Oct 21, 2012

NikTheGeek said:
You've lost me now It doesn't tell me (I don't think) how much litres I used, just what my average mpg was. Yes I did reset it before setting off. Trip1, trip2 and the computer. I also used the same nozzle at the same filling station before I set off and when I got back and you could hear the diesel gurgling as it approached the top so it was full.

The computer takes it's fuel quantity reading from the fuel level sender. The computer measures the miles travelled. It then continuously compares fuel used against miles travelled to give an average usage. So the accuracy of the fuel sender reading controls the accuracy of the computer read out. Simple as that.

wammers · Oct 21, 2012

16.2 MPG is 100 / 16.2 = 6.17 gallons used. 6.17 gallons x 4.55 = 28.08 litres used.

20.23 MPG is 100 / 20.23 = 4.94 gallons used. 4.94 x 4.55 = 22.49 litres used.

So you have a difference of 5.59 litres or 1.22 gallons.

Pikey · Oct 21, 2012

wammers said:
16.2 MPG is 100 / 16.2 = 6.17 gallons used. 6.17 gallons x 4.55 = 28.08 litres used.

20.23 MPG is 100 / 20.23 = 4.94 gallons used. 4.94 x 4.55 = 22.49 litres used.

So you have a difference of 5.59 litres or 1.22 gallons.

wrong see me after class..

100/16.2 = 6.17283950617284

1 gallon [UK] = 4.546 09 litres

= 28.06228395061728

finish the equation and post your answer below...

wammers · Oct 22, 2012

redhand said:
wrong see me after class..

100/16.2 = 6.17283950617284

1 gallon [UK] = 4.546 09 litres

= 28.06228395061728

finish the equation and post your answer below...

Pikey don't be a ****ing pedant. Generally accepted gallon is 4.55 litres round figures used. He probably spilled more on his hands filling it up than the difference in the final figure.

Pikey · Oct 22, 2012

wammers said:
Pikey don't be a ****ing pedant. Generally accepted gallon is 4.55 litres round figures used. He probably spilled more on his hands filling it up than the difference in the final figure.

Have you seen the price of fuel???

gotta acount for evey drop...

wammers · Oct 22, 2012

redhand said:
Have you seen the price of fuel??? gotta acount for evey drop...

Yeah bloody expensive, i remember when some smart bit of stuff came out filled the tank, took your money and brought you the change, all for 5 bob a gallon. If ya got lucky you tapped her up and took her out when she finished her shift. Oh the memories.

Datatek · Oct 22, 2012

I was pretty sure that on the diesel the consumption calculation was done from the injection timing and duration from the EDC not the tank sender?

wammers · Oct 22, 2012

Datatek said:
I was pretty sure that on the diesel the consumption calculation was done from the injection timing and duration from the EDC not the tank sender?

Maybe there are several inputs Keith. Your way would make more sense i agree. I have a dicky sender around half full. It will go from one notch over half to one notch below it in a few miles sometimes. The range then plummets as does the MPG but more gradually. If i wait for it to settle then reset the computer MPG goes back up and range also. Maybe i will get a better idea when i fit a new unit. But door is open to anything at the moment i am not quite sure.

Saint.V8 · Oct 22, 2012

I believe the L322 uses a similar metered method....

As y'all know I run LPG - but the OBC still registers MPG calculations - so I am assuming it mesures the Petrol injector pulses (as the amount of fuel delivery is metered and set but injector opening times), although the injectors aren't actually opening as there is a circuit in place to emulate injectors, the OBC still measures the Engine ECU pulses and works out a theoretical MPG based on that....

I average 15.1mpg brim to frim (check out my fuelly account by clicking the little logo in my sig) but the OBC says 18.whatever - I can only assume that as LPG is less efficent by about 15% or so, that the OBC calc would be my equivalant on petrol....and even as my LPG figure rises and falls due to driving conditions, the % difference between OBC calc and the brim to brim calc is always the same 15% percent or so!!

dave4x4 · Oct 22, 2012

Yes, I agree. I am pretty certain diesels calculate the fuel quantity used by totalising the EDC fuel quantity readings in the mapping chip.

What makes me think that ? I have got several eprom chips with different maps. When I try one in particular that I have got the mpg is a mile out. Like 50 mpg. The numpty who wrote the map didn't know what they were doing.

wammers · Oct 22, 2012

So how do we arrive at the situation Nik has. The injection is very accurate indeed and easy to measure, so why was the fuel computer saying he had used 28 litres of fuel when he had only used 22.5. That is a serious difference, over a gallon in 100 miles. The range to go is most certainly measured from the sender unit readings. With my dicky sender up and down like a brides knighty the MPG can get to low teens. But when the computer is reset go back up to low twenties. If it was being measured from fuel actually injected it would never change no matter what the tank unit did.

Datatek · Oct 22, 2012

I think to get the range it must use the sender for fuel remaining but consumption from the injection would make sense, however maybe it uses both for the average?

Chrisfrain2007 · Oct 22, 2012

On my wifes astra, the instant consumption is metered via injectors etc ( I presume anyway due to the way it behaves, ie high idle, low idle , high load, no load ) the range is calculated by how much is left in the tank against instant consumption, so that goes up and down depending how its driven, if the range rover is the same, would a dicky tank level sender mess with the figures?

dave4x4 · Oct 22, 2012

I wonder if a worn piston in the FIP might explain the symptoms?

The fuel map requests say 48mg diesel/stroke and because the piston in the FIP is slightly worn it injects only 45 or 46mg. Yet it uses the figure of 48mg for the calculation.

Just a thought.

Saint.V8 · Oct 22, 2012

dave4x4 said:
I wonder if a worn piston in the EDC might explain the symptoms?

The fuel map requests say 48mg diesel/stroke and because the piston in the EDC is slightly worn it injects only 45 or 46mg. Yet it uses the figure of 48mg for the calculation.

Just a thought.

:whoosh:

Chrisfrain2007 · Oct 22, 2012

dave4x4 said:
I wonder if a worn piston in the EDC might explain the symptoms?

The fuel map requests say 48mg diesel/stroke and because the piston in the EDC is slightly worn it injects only 45 or 46mg. Yet it uses the figure of 48mg for the calculation.

Just a thought.

You mean in the fuel pump? ?

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