I would like to hear your suggestions about this.I have read a few books and spoken to a few people already regarding tuning for cruising conditions and light load (up to 140kpa) and i can find 2 options.
1) Use the best timing for optimum torque and keep the lamda around 1.00-1.04 (same thing that motronic does on our old audis which didnt come with a wideband)
2) As best lamda for economy is said to be around 1.16, tune for that area and possibly reduce the timing slightly to avoid engine 'struggle' or misfire.
So far i have tried:
i) keeping lamda from 1.13 to 1.10 from 30 to 102kpa, then bringing it up to 1.03 to 120kpa and timing from 2000-3000rpm going in those areas from 33 to 38deg roughly. The car did not stuble, knock or misfire. Consuption was worse than stock motronic but decent.
ii) Brought lamda to 1.08-1.03 in same kpa areas and increased timing by a couple of degrees, reaching about 39.50 on 3000rpm(sort of same as my motronic map used to have). I immediatelly noticed that the car had more torque than before when off boost and was more agile. I havent managed to see any significant difference in consuption either way.
iii) same setup in timing but lamda being kept at 1.11 to 1.09 on the above kpa areas. The car although not heard knocking or anything, it felt to be less torquey and on a motorway run, it consumed quite a lot more fuel. I suspect the leaner option wasnt working for the engine.
I havent tried a long journey with the (ii) option yet, but so far, in the city it seems to be ok as far as consuption, around the motronic levels.
In a week or so i will have the 1.1.81 version and i suspect that with the extra mat vs tps table i will be able to avoid increasing my VE map on the cruise areas to avoid playing around with the warm up enrichments, as my EGO is set to keep substracting fuel rather than enrichening, and that overall will have some negative effect on the consumption. In addition, cold weather and cold starts are not helping either i suppose.
It would be interesting to see other people's views regarding tuning those areas in VEMS. What do you opt for client's cars?
I know that aftermarket ECUs are not meant to provide a cruising optimum as they are meant for motorsport, but since vems has become the people's aftermarket ECU and it is being used on lots of everyday cars, it would be nice to be able to take advantage of all it's feauters to be able to beat old motronic technology in maintaining a good consuption level!
thanks