Its too early to be sure of changes, will give it a week..the drive is considerably better and the acceleration smooth, previously the acceleration wasnt so smooth..previosly i could literally see the fuel dial going down real-time while driving but now the consumption has improved..i can only tell by how much after a week of driving..the guy asked me to bring the car back for inspection after 500 km for readjustments if needed
regarding the process, its called an AFR scan(air to fuel ratio)..so what was happening is that my car had an AFR of 12.2 before where the standard is 14.7. So basically it was consuming fuel that was too rich, thus the low mileage. If the AFR is high it means the fuel mixture is lean which results in engine not getting enough fuel to run properly. the factory setting is at 14.7 which needs to be adjusted after every 50,000 km as it can change over a period of time. Atta (the mechanic) first analysed readings from the car's exhaust and the car computer. he then changed fuel ration electronically to see if ECU is working correctly, which it was i.e.e the afr was changing when fuel settings were being changed. After this, he tuned the fuel sensor manually with a screw driver ( a tool exists to do it properly but he didnt have it) at different RPMs to bring the average from 12.2 to 14.7. All this took 15 minutes. I cant be sure if this is the exact way to correct AFR but it does work. The engine needs to get used to the new AFR which is why a week (or 500km) is a good time to measure consumption.
The whole process is documented in the form of a diagnostic report given to me at the end of the job. The diagnostic also revealed no problems with MAF, coolant temperature, others so we ruled them first to be sure it was the AFR that needed adjusting. Hope that helps