Ian jones
Well-Known Member
- Posts
- 1,104
- Location
- north east england
Mismatched tyres causing the vcu to operate constantly will affect mpg
may i ask what can cause poor mpg
friction drag .. .. particularly before the engine and oil have reached optimum temps.
( my choice of helper for that .. : ZX1 Home )
dirty crankcase vent system .. resulting in excessive crankcase pressure ( more 'work' for the engine )
inneficient fuel combustion :
dirty injector nozzles .. ( or faulty injectors )
fuel contaminants such as water
( to combat those .. i use .. http://www.landyzone.co.uk/lz/2409712-post6.html )
dirty air filter
faulty MAF that might cause ovefuelling ..
sticking egr valve .. ( where fitted )
faulty air intake temp sensor causing a default of -5c to be used by the ecu ..
faulty coolant temp sensor .. that would Probably effect injector timing in theory
faulty glow plug system ( inneficient combustion on cold start up )
faulty turbo actuating system .. although by how much that would effect mpg i not be sure
i.e. for an 'overboost' the ecu would cut the fuel supply to a safe level ..
for an 'underboost' .. in theory the ecu would see not enough manifold pressure / air-mass to supply desired fuel ..
although would have thought anything that detracts from efficiency could potentialy waste fuel
a faulty coolant thermostat that caused the engine to run too cold would effect mpg
low cylinder compression
~~~~~~~~~~~~~~~
the ecu needs accurate readings of air temp. / coolant temp / air mass / manifold pressure
to compute fuel delivery / injector timing for a particular go-pedal 'demand' ..
if the sensors were to give the wrong readings .. the ecu could supply/inject more fuel than needed for optimum combustion .. therefore wasting fuel ..
and / or .. provide the wrong injector timing .. again wasting combustion energy ..
disclaimer: i don't know the particulars of the td4 engine mapping .. or 'defaults'
but on investigation .. many common rail diesel engines with computerised management systems
have certain things in common to provide best fuel combustion for a given power demand
~~~
obviously many of the above .. if a 'fault' .. would .. or might .. show other symptoms ..
rough idling .. lack of power .. etc etc
~~~~
use of the PTI heater causes the idle rpm to rise .. adding to fuel consumption ..
same for .. if the ecu sees high electric consumption for some other reason ..
i.e. idle rpm raised to compensate for load on the alternator ..
~~~~~~~~~~~~~~
overall condition of the drive train .. clutch / gears / vcu / diffs ..
tyre pressure ..
aerodynamics ..
driving habits ..
what 'ianjones' said regarding the vcu / tyres .. post no. 21 .. makes sense ..
I got an app called 'Road trip' a few months ago & was shocked to discover I was only doing 22 mpg. I can be quite heavy footed & will often use the kick down. I drove the next tank very steady & was pleased to push it up to 26mpg, all based on town driving & short cold trips. I went on a 400+ trip & got 35mpg driving a very steady 60-70mph there. On the way back I got 28mpg driving 70+
No synergy fitted, EGR valve not blocked, TD4 auto
Hope that helps as a comparison
should have added that ..
i can't comment regarding an auto-gearbox .. mine's a manual ..
and the auto's seem to have their particular foibles as to when-to-change-gear
although if i had one .. i'd probably use the manual-sport-shift-option ..
or whatever it is that enables the driver to choose which gear at what rpm ..
( no doubt the operational efficiency of the auto box would effect mpg ..
( i.e. whatever it does to transfer torque /power to the wheels
and ..
i've not a clue regarding my mpg as far as 'multiple short trips / city driving' is concerned
as my weekly driving routes don't involve much of that as a percentage of the total ..
Sorry manual . Has a synergy chip on , on Eco I've a heavy right foot but our lass drives it more and she definitely hasn't . 220 miles to 50 quid think I worked it out right . Mixed driving
50 quid equates to approx 34 litres, or 7.5 gallons. 220 miles from 7.5 gallons is about 28 mpg, not 19.
originaly posted by Nodge68:
So basically you push the lever forward to go up to the next gear but as you aren't going fast enough the ECU ignores the requests.
Welcome To LandyZone, the Land Rover Forums!
Here at LandyZone we have plenty of very knowledgable members so if you have any questions about your Land Rover or just want to connect with other Landy owners, you're in the right place.
Registering is free and easy just click here, we hope to see you on the forums soon!