Hi ! Thanx for this vid since I’m struggling with vcds on this stft and ltft stuff on my 2001 Audi TT. Short story, lambda control ( actual ) shows around 0.992 on the log. This mean a little too rich right ? But sometime I have the default code « System too lean ». Drive me nuts. And the LTFT shows -3,1% ( group 32 adaptation partial ). I think I’m not reading correctly the infos :/. I have check for possible air leak with a smoke machine, but seems all is fine. And one more thing, fuel consumption seems to high ( 10l/100km ). I must confess that I drive a lot in town.
Actual Lambda and short term fuel are different things, the point of short term fuel trim is to give the lambda (AFR) the most range. The 02 sensor is constantly switching between 0.1 & 0.9. This is all the movement the o2 sensor has so the STFT comes in to make sure the o2 is within stoichiometric range. Hope that makes sense. You need to look at both STFT and LTFT and subtract to add the two together... e.g your STFT is 30 and your LTFT is -30 then your actual fuel trim is 0.
Also about the Lambda that is at 0.992, it is basically on spec. It will always have some minor fluctuations. To give you an Idea, my cars Lambda drops down to 0.750 on WOT (wide open throttle) in my case for a stock car it is very rich from factory. But it helps with cooling the engine on high rpm's. So seeing your 0.992 it is basically as close to perfect as it gets 🤣👌 and then a lean engine code means that somewhere unaccounted air is entering the engine. A couple of years ago my cars PCV Diaphragm had a crack, I did not know much about logging back then but I knew the car was basically as good as it can get, small vibration at Idle but the rest of the cruising or accelerating was tops. Also I am unsure if your car has a cold start, if it does and it shakes on the cold start it means something is wrong, why I say so i that your fuel system is on a Open loop during cold starts, this means that your car doesn't work with feedback at that time, meaning if your ECU says it must run 0.9 it fuels for 0.9, if the actual goes to 0.8 or 1 then your car does not adjust because its "open loop". Only when cold start drops off then your car will move to a closed loop fuel system and do adjustments to get everything in spe which will smooth your vibrations
Hi ! Thanx for all the answers. Could it be possible that I send you a log file? It include Rpm, temp, lambda, block 032, 033. Of course, if you have time for that. No worry ;) One thing I have noticed : I have the same vcds version than yours. But there is no stft/ltft items on the data log list. I guess it depend on the year/model of the car. Anyway, your vids about vcds on Audi are very usefull.
Hey man, yea you can def send me the logs, my facebook link is in the description :) and yea it unfortunately changes from car to car in some occasions :(
Thank you!
It is a pleasure 🙏🙌 Hope I could help :)
Hi ! Thanx for this vid since I’m struggling with vcds on this stft and ltft stuff on my 2001 Audi TT. Short story, lambda control ( actual ) shows around 0.992 on the log.
This mean a little too rich right ? But sometime I have the default code « System too lean ». Drive me nuts. And the LTFT shows -3,1% ( group 32 adaptation partial ). I think I’m not reading correctly the infos :/. I have check for possible air leak with a smoke machine, but seems all is fine. And one more thing, fuel consumption seems to high ( 10l/100km ). I must confess that I drive a lot in town.
Actual Lambda and short term fuel are different things, the point of short term fuel trim is to give the lambda (AFR) the most range. The 02 sensor is constantly switching between 0.1 & 0.9. This is all the movement the o2 sensor has so the STFT comes in to make sure the o2 is within stoichiometric range. Hope that makes sense. You need to look at both STFT and LTFT and subtract to add the two together... e.g your STFT is 30 and your LTFT is -30 then your actual fuel trim is 0.
Also about the Lambda that is at 0.992, it is basically on spec. It will always have some minor fluctuations. To give you an Idea, my cars Lambda drops down to 0.750 on WOT (wide open throttle) in my case for a stock car it is very rich from factory. But it helps with cooling the engine on high rpm's.
So seeing your 0.992 it is basically as close to perfect as it gets 🤣👌 and then a lean engine code means that somewhere unaccounted air is entering the engine. A couple of years ago my cars PCV Diaphragm had a crack, I did not know much about logging back then but I knew the car was basically as good as it can get, small vibration at Idle but the rest of the cruising or accelerating was tops.
Also I am unsure if your car has a cold start, if it does and it shakes on the cold start it means something is wrong, why I say so i that your fuel system is on a Open loop during cold starts, this means that your car doesn't work with feedback at that time, meaning if your ECU says it must run 0.9 it fuels for 0.9, if the actual goes to 0.8 or 1 then your car does not adjust because its "open loop". Only when cold start drops off then your car will move to a closed loop fuel system and do adjustments to get everything in spe which will smooth your vibrations
Hi ! Thanx for all the answers. Could it be possible that I send you a log file? It include Rpm, temp, lambda, block 032, 033. Of course, if you have time for that. No worry ;)
One thing I have noticed : I have the same vcds version than yours. But there is no stft/ltft items on the data log list. I guess it depend on the year/model of the car.
Anyway, your vids about vcds on Audi are very usefull.
Hey man, yea you can def send me the logs, my facebook link is in the description :) and yea it unfortunately changes from car to car in some occasions :(
Great ! I’m gonna check FB ! 🎉