Question About The Ford Ecu Program (stock)

[gtfpv]

g'day i'm just wondering if you could educate me please on the ECU charactoristics.
THE BA MKII FPV 5.4 specs state 15.3 litres per 100kms. my GT done exactly that consistantly according to the display . after many hours. when you reset it it is all over the place but each time it gets over 50 hours it is always the same 15.3 . and when you fill up . distance to empty is 428kms . this was totally stock .
after the addition of a catback, and dual intake, and bmc filter . the computor was reading 14.4 ltrs/100 and distance to empty 478kms . for several fills . but after a few weeks/ months . the economy has returned to the origional 15.3 and 428 . according to the screen readouts .

IS THIS charactoristic in technical terms of the ECU. IF SO wouldnt this mean that without an edit , no matter what mods are added performance will return to stock economy wise atleast

it sounds very hi tech and to consistant to be a coincidence . with my vehicle .
perhaps you could clarify the facts if there are any here . cheers . ?

[ratter]

Hope Chris doesn'nt mind me answering

The advertised fuel economy figures are not actual road figures, but a test figure which is is standard between all manufactures for our aussie cars, depending on driving styles and conditions, some people will see these figures while others will get worse and some will get better.

The computer in your car is constantly monitoring what is happeneing in closed loop operation and tries to keep the car running at a emission friendly lambda of 1 which is an air fuel ratio of 14.63:1 for us older members. Under harder acceleration the computer will go open loop and run from the base fuel table.
It monitors what is happening by using the o2 sensors and looks at what is happening with the Short Term Fuel Trims (stft), the computer is constantly changing the injector duty cycle to keep the closed loop at a lambda of 1, the stft actually shows how much adjustment the computer is making to try to keep lambda 1, Over a period of time the computer remembers how much it has been changing the injector duty cycle via the stft it then makes a larger adjustment via the Long Term Fuel Trims (ltft) to try to keep the stft closer to where they should be.
The ltft is basically a running change the computer has made to it's operating parameters to try to keep emissions clean.

When you reset the computer you loose these ltft and stft so that's why things will change for a while after a reset or battery change.

Now when the computer is editied, depending on how much adjustments are made the car may get the same economy(sometimes better), but if all aspects are tuned correctly, these stft and ltft may not have alter as much to keep things correct, so a reset would may not alter things too much as it was tuned to be closer to correct when editied and best of, your power will stay more consistant.

In your case the addition of the exhaust and intake mods made the car run leaner, which is why the distance to empty showed bettter, but over a period of time the ecu adjusted it self via reading the stft and then the ltft to bring it back to where it thinks it should be.

[ratter]

I hope the above post explains to some, why it is important to have good operating o2 sensors as they are very important to a correctly operating ECU, Not may people are aware they only have a certain operating life and do need to be replaced from time to time, even if no codes are displayed.

[gtfpv]

thanks RATTER . much appreciated and good to read. very interesting .