Onboard computer: can you adjust it?

This site contains affiliate links for which LandyZone may be compensated if you make a purchase.
The fuel injected depends on engine RPM. The more RPM that is requested the more fuel is injected that is how the engine is throttled. So the stroke of the pump is variable not constant. I suppose the quantity servo pot could be feeding back info as to stroke at a given speed and therefore amount.
 
Saint.V8 said:
:whoosh:
Click to expand...

I don't even know that the EDC is. So I don't know if I should be worried about a worn piston in it. Ignorance is bliss sometimes.

Anway, the Rover 75 uses the M47 BMW. One would imagine that diesel fuel ecomony measurements are done in a similar way ie at the injectors or at the fuel pump. When accessing the diagnostics, option 20 gives you the fuel economy correction as follows:

From The 75 and ZT Owners Club Forums

20 Correction Factor for OBC Fuel Consumption display
20.0 The Factor is displayed numerically in the form ABCD (Thousands/hundreds/tens/units)
The formula for the Factor = Indicated Consumption x 1000 / Measured Consumption

The indicated consumption should be established by running the system for several hundred miles, preferably a thousand or so without resetting the OBC at any stage. The longer you allow the un-reset system to operate, the more 'accurate' is the indicated consumption. Determine the measured consumption using brim to brim calculations over a similar period.
Now calculate your more accurate factor using the formula above. These digits are what you insert for ABCD.

Press the button to show 20.1 which allows the units (D) to be set.
The display counts down from the current figure and cycles until you press at the required one.
This sets it and the display will advance to 20.2

20.2 This allows the 'tens' (C) to be set as above. When you press the set button, the display advances to 20.3

20.3 This sets the 'hundreds' (B) and then the 'thousands' (A). Each digit is set in succession by a single press.
After setting (A), the display advances to the next function (21.0


That may shed some light on how it works on the M47. Is there not a T4 setting? If the Rover 75 has a correction factor, you would imagine most cars with an onboard computer would.

Anyway, I'll do the same test but not towing, on a nice motorway run and see what, if any, difference it makes. If it helps at all, various members on here suspect I have an in-tank fuel pump issue.

Nik
 
Last edited:
If the FIP piston was worn, it would inject more, but it would be the same amount at full throttle, so if it injected 2mg extra at idle it would be 2mg extra at full throttle, I think?
 
Chrisfrain2007 said:
If the FIP piston was worn, it would inject more, but it would be the same amount at full throttle, so if it injected 2mg extra at idle it would be 2mg extra at full throttle, I think?
Click to expand...

But its irrelevant as wammers says, the pump is variable, so would have to take readings from throttle pot,
 
Chrisfrain2007 said:
If the FIP piston was worn, it would inject more, but it would be the same amount at full throttle, so if it injected 2mg extra at idle it would be 2mg extra at full throttle, I think?
Click to expand...

Don't work that way, if it injected more fuel at idle, the idle speed would rise. It will only inject enough fuel to maintain idle speed as read from the crank sensor. Fuel quantity is controlled by the quantity servo and would be adjusted to suit. There is a separate idle control circuit activated by the idle switch as the throttle pot is at minimum engine speed demand. Fuel injected at anything other than idle depends on throttle speed demand and engine load at that time. Eg if half engine speed is requested on throttle pot but load on engine is high. Fuel pump will attempt to inject fuel to raise the RPM to half engine speed. Map will only allow a certain amount to be injected at that setting, so if load is too high the ECU will signal box to change down. That is why with a chip fitted and more fuel available at any given engine speed or load the box does not change down as often under load.
 
I would think a worn FIP would inject less not more. Due to leakage past the piston in the FIP?
Don't know for sure but the total amount of fuel injected would be overstated for the mpg calculation.:)
 
dave4x4 said:
I would think a worn FIP would inject less not more. Due to leakage past the piston in the FIP?
Don't know for sure but the total amount of fuel injected would be overstated for the mpg calculation.:)
Click to expand...

If the piston or pump internals were worn to such an extent and not injecting the correct amount of fuel to reach the throttle pot % engine speed demand. The ECU would think the engine was under load and via the fuel quantity servo would increase the fuel via piston stroke at that setting to adjust the fuel delivered to attain the requested speed. Within the ECU maps reference for that engine speed of course. But i think there would be major very evident running problems if the pump ever got near that state.
 
Just been on your page 18 mpg I got an auto and I'm way above that you sure you haven't a leak or bad injectors been serviced or are you one of these maniac drivers that doesn't know how to feather the throttle :)
 
defender300td1 said:
Just been on your page 18 mpg I got an auto and I'm way above that you sure you haven't a leak or bad injectors been serviced or are you one of these maniac drivers that doesn't know how to feather the throttle :)
Click to expand...

I've only had the car a few weeks. I've been driving as gently as humanly possible. I can't have a leak as I'd notice it on the drive after its been sat and it doesn't even drip oil. But no idea about the injectors. Anyway, 20mpg towing according to the brim to brim method and I thought that was ok for what was probably a 2 ton trailer. I'm going to do a brim to brim on a motorway run.

I do notice black smoke when I start it - which I've seen other diesels do, but I've never owned a diesel where I've noticed it myself. Black smoke tends to be over-fueling.

It also seems to burn oil. I think. Put it this way, 2 weeks ago, I checked the level and filled it, this weekend it was half way between low and high on the dipstick - in just 2 weeks. Never had that before either...

Nik
 
NikTheGeek said:
I've only had the car a few weeks. I've been driving as gently as humanly possible. I can't have a leak as I'd notice it on the drive after its been sat and it doesn't even drip oil. But no idea about the injectors. Anyway, 20mpg towing according to the brim to brim method and I thought that was ok for what was probably a 2 ton trailer. I'm going to do a brim to brim on a motorway run.

I do notice black smoke when I start it - which I've seen other diesels do, but I've never owned a diesel where I've noticed it myself. Black smoke tends to be over-fueling.

It also seems to burn oil. I think. Put it this way, 2 weeks ago, I checked the level and filled it, this weekend it was half way between low and high on the dipstick - in just 2 weeks. Never had that before either...

Nik
Click to expand...

Smoke on starting might be a couple of duff glow plugs.
20Mpg with a 2 tonne trailer load can't be bad.:)
 
New automatic vehicle fuel consumption urban cycle is 20.3 MPG. 25.8 Mixed urban/extra urban. Consumption depends on topography of your area. If it is just used for short trips around a hilly town, in traffic, stop start, 18 MPG is pretty normal. You ain't going to be getting 25.8 that's for sure.
 
Datatek said:
Smoke on starting might be a couple of duff glow plugs.
20Mpg with a 2 tonne trailer load can't be bad.:)
Click to expand...

Can you point me to some? Don't want to buy duff ones off ebay, Island 4x4 doesn't have them (at least nothing shows up under the P38 section). Britpart does, but others have questioned their quality.

Could you give me a pointer to a source? How many do I need? I know that'll sound really daft and I assume it's 4, but I saw something the other day that said "Number 6 injector" and something else saying "injectors: 5 required". So thought I best ask... :)

Nik
 
see how it goes sign up to fuelly you can let it work it out for you over time better than snap shots.
if there is no patches over night on the floor then i guess its a bit of a burner,make sure its level and cold when checking im sure you know that i have noticed with such a long sump a slight angle can throw it out by miles are you a 10/40 oil man ?? you need 6 its an inline 6 cyclinder engine
 
Last edited:
You must log in or register to reply here.

Similar threads

H
Worth it or can of worms?
Replies
14
Views
2K
Nodge68
Nodge68
dwarfer
L322 in two years of ownership...bought with 121k now 123k
2
Replies
29
Views
3K
Agarange
A
300bhp/ton
Driven: New Defender - On & Off Road. Is it a Pretender?
2
Replies
29
Views
5K
tottot
tottot
Andy Reid
instrument cluster gone blank - but it's working?
2
Replies
27
Views
6K
Saint.V8
Saint.V8
S
For Sale Range Rover P38 Diagnostic machine (can also be unlocked to do others)
Replies
1
Views
3K
biketeacherdave
biketeacherdave
Back
Top