Understand fuel trims - Block 032 VAG COM

[Welly]

Afternoon all.

I had a PM from a user asking about fuel trims on block 032 in VAG COM. What they are, where they are and what they mean.

I thought this was a fair question, and one that many people don't understand, so I did a spot of googling.

I found an incredibly useful post on another Audi/VW forum in the states, that gives a very good (I think) description of what fuel trims are, what they do, and why they do it.

The link isn't specific to the S3 or A3, but is true enoguh anyway.

So here you go, enjoy.

http://scaudi.com/sc/index.php?showtopic=4780

Read the whole lot as there are some useful comments after the OP.

 

[Westy]

Thanks for that mate! I just had a quick scan through it, got lost about 3 words in.

 

[Welly]

Thanks for that mate! I just had a quick scan through it, got lost about 3 words in.

 

[finesse]

Germans!!

 

[Welly]

Germans!!

Yeah, I'm not feeling the love today either I must admit....

 

[finesse]

this is better

http://wiki.ross-tech.com/wiki/index.php/Fuel_Trim_Info

 

[Welly]

this is better

http://wiki.ross-tech.com/wiki/index.php/Fuel_Trim_Info

I saw that, but it's a lot more complicated to read. I thought the other post was site clear and concise.

Thanks none the less.

 

[sportstractor]

uber gut read

 

[badger5]

simples

wots up with you lot

 

[Westy]

simples

wots up with you lot

The problem isn't so much understanding the words written but actually staying awake while reading them

 

[thorsy22]

Was having an argument with my little brother about this kind of thing a little while back, though its on his rover 25 tdi. He was saying by putting bigger injectors he'd get about 40hp more, this all without a remap. Being a diesel is it the same principal as in that thread (so not possible due to ecu adaption) or down to the rover not being as sophisticated as our audi's and just putting the extra fuel in regardless?

Assuming I've understood it all correctly (would like to think I have, but did have the problem of mind wandering pike westle, lol).

 

[sportstractor]

you say an inferior system, but i bet most systems are equally sophiscated. And we only think other wise because we dont have a swish program like vagcom to connect other systems too.

 

[thorsy22]

you say an inferior system, but i bet most systems are equally sophiscated. And we only think other wise because we dont have a swish program like vagcom to connect other systems too.

I never said it was inferior mate.

Like I said it is a completely different car to ours (Rover 25 TDI - diesel being just the first point), just from my understanding of the fuel trim theres no way just putting bigger injectors in can give 40hp without a remap (unless the old injectors are knackered or the wrong injectors have been installed), due to the engine trying to maintain the correct fuel/air ratio as per its map. In this instance the engine management system would detect the mixture as being too rich due to the larger injectors and decrease the injector "on" time to maintain the fuel/air ratio as per the map, please correct me if I'm wrong though.