Intake Air Temperature Sensor (G42) questation

[valjo]

Hi!

some quite strange thing happened to me today. I drive with mine s2 (aby) and i get CAT light (for ecu error). I have also noticed that boost went almost to 1.5!!! (relativ, car is homefried).
well i stopped and checked why i got CAT light and i found that i have disconnected Intake Air Temperature Sensor (G42).
I connected it back, error dissapired but i was back to 1.3 boost.
i know that g42 is important for boost level, but does anyone know what happend if it is disconnected ? does ecu take some deafoult values for g42?
outside temperature was about 5-6c

[Pirvu Eugen]

if the sensor fails the timing is retarded and a 40 degrees temp value is used for boost control.
i think you have to erase all errors in the ecu.
hope this helps
Eugen

[S2central.net]

Heres some info on the IAT (G42) - in addition to whats currently at S2central.net - I really need to update the Motronic data on there sometime...

http://www.sjmautotechnik.com/trouble_shooting/20vairt.html

Suggest you check some resistance values across the sensor with the graph shown.

The weird thing about ABY is that boost pressure is actually decreased with lower IAT so that the engine performance is consistent regardless of weather... Note the factory boost info on this page... AFAIK when the air temperature is above the maximum value shown THEN it reduces boost pressure to reduce detonation.

http://s2central.net/motronic_boost.html

I've never really considered changing this behaviour on the homefries, but I guess I could with a tweak of temperature compensation map. I kind of understand Audi's counter-intuitive logic for this, but it just seems wrong at the same time !!!

The COLD air temps seen by Valjo recently could explain the lower boost values he has been seeing (assuming the MAF has been declared healthy).

Paul

[S2central.net]

Of course - you could just disconnect G42 in the winter for that extra zip with nice cold air in the meantime

[Pirvu Eugen]

I think Audi implemented this boost drop with lower temp for the car to pull the same in all conditions, from Africa to North Pole. At 3B is big diference in how the car is pulling in summer versus winter!
Dont implement this in Chips, let them be FAST with lower temps!

[Pirvu Eugen]

You answerd before!!!!

[valjo]

Of course - you could just disconnect G42 in the winter for that extra zip with nice cold air in the meantime

huh will that damage engine somehow?

i checked my intake temperature sensor and it is fine!
Paul after fixing some small vacuum and boost leak (according to your great post http://www.s2forum.com/forum/showthr...ght=vacuum+aby)
car runs like rocket, i dont get any errors anymore boost is still 1.3 but i am almost sure that that is because weather is colder those days.

i am still waiting for brand new rs2 maf from vagparts becasue from old one i get quite low outputs :mischeif:

[Pirvu Eugen]

I am verrrrryyyyy curious to know how will be the readings from the new MAF.
I have MRC generic chip for the 3B engine and i have 1.3 bar. I think is ok. The engine runs fine.
Pls. tell us the readings from the new MAF!
Thanks!
Eugen

[valjo]

Pls. tell us the readings from the new MAF!
Thanks!
Eugen

i will, as fast i will get it and test it

[Pirvu Eugen]

[lini]

I'll continue here because there is a tight conection. Valjo says tha he got the fault of a lean mixture under lo idle due to two leakages on a vacuum hoses. With th normal ECU without remap the faul was not there. Where is the catch? Can somebody explain if tuner makes any changes for the values where error codes apear? I'm interested especialy at the lambda factor. And the next question is what is the problem in running lean in lo idle since the owerheating of the components is not present. If you run lean at higher rpm then you have a problem but at ofboost driving normaly nothing can happen.

[S2central.net]

Valjo's car did not develop adaptation faults immediately with the modified ECU - that work was done many months ago. My suspicion is that the months of higher boost driving has further weakened these already old / frayed connections.

I retain ALL of the factory diagnostics and safety routines.

Lean running can cause problems at high boost of course - if the air system is leak free and the fuel system is healthy then the mixture on my chips is just fine - actually some safety margin in there. Some users have verified this for themselves with AFR equipment of their own or at dyno runs.

An accurate AFR guage is a good idea alright - fuel components can degrade slowly over time and its otherwise hard to tell when its got bad enough to cause a problem.

Paul

[valjo]

well i have to say that i am sure that mine problems has notting to do with homefries, the problems was 2 hidden boost/vacuum leaks.
it was quite hard to find those 2 leaks, that is why it took so much time!!!

[lini]

@S2central.net: please dont take as an insolt or atack I'm trying to learn things before my projectis far enough so I dont discover a warm water again. What is better than to learn on other's problems...

[valjo]

I am verrrrryyyyy curious to know how will be the readings from the new MAF.
I have MRC generic chip for the 3B engine and i have 1.3 bar. I think is ok. The engine runs fine.
Pls. tell us the readings from the new MAF!
Thanks!
Eugen

hi!
i just measured mine new maf, i post outputs there: http://www.s2forum.com/forum/showthr...d=1#post271753