jackiebo1 said:
Try giving it a tank of the expensive petrol and run that through the engine. It worked on my old corsa well enough.
If by expensive petrol you mean the higher octane "super" fuels, running an engine on that for a tank will not help, in fact it may even make it worse. On a modern engine the sensors in the exhaust send the fuel-oxygen information back to the ECU which then try's to adjust the mixture to 14.7-1 air to fuel (true Lambda and hence why these are called Lambda sensors). Whilst the ECU is trying to adjust this the economy may be even worse, so when you change the octane and burn rate of the fuel the mixture changes, so when you first fill the tank with the "super" fuel, the engine is in fact out of tune and will try to adjust accordingly.
This is why most people get put off using the super fuels as they dont always get good results immediately then say their car ran rough afterwards when they changed back to the lower octane fuel. Its not the fuel's fault, its the owners! If they had either given the ECU time to adjust and then stuck with it, the results are indeed much better. The other thing that speeds up this process is to reset the ECU just after you have filled with the higher octane fuel giving the ECU a fresh start.
jackiebo1 said:
Also recently manafacturers have taken a hammering for mis advertising MPG rates on their cars, very few cars get what they say in the figures.
The figures quoted in advertisements etc are Government test figures. The economy and emissions testing is a very strict set of tests carried out in the UK at Millbrook Proving Ground (yes, same place as the Aston barrell roll was done in Casino Royale!). The car is taken into quarantine where it stays for a set number of hours at a constant temperature (sorry cant remember the figures!), then it is pushed onto the dyno and Dave the driver has a screen that comes down in front of him and he follow the "duty cycle" that he is asked to drive. He mustn't deviate from this by more than 2% (IIRC) and follows the patter request for speed, acceleration, gear change, braking etc until the end of the cycle. This whole process is repeated 3 times from the start including the quarantine.
The results are analysed from pads that are put into the exhaust extraction and therefore extremely accurate data can be recorded.
What does this give you - well, this is a set of extremely accurate COMPARISON data that allows you to compare between different vehicles. Its these figures that are on the adverts (if you look it should say govt. figures somewhere). What it is NOT, is an indication of what you will get economy wise from a vehicle, that is the most often misunderstood thing from this data.
When the testing is done, it cannot reproduce exact affects of additional weight in the car (and yes, I mean you lol!), wind (no, I dont mean you this time lol!) inclines etc.
What I have described is the tip of the iceberg of the test, there is a huge amount more to it, but you get the gist! Duty cycles can be set for all sorts of testing, i.e. London Taxi Co have a specific one for their tests to replicate the sort of journey's their vehicles would make etc. It is interesting, honestly :-D
