VE table IAT correction

[Tcal]

For example iÃ,´ve setted my VE at idle so that EgoC is near 100% when IAT 25c.  When IAT is cold itÃ,´s leaning like -25 in LCD display.
I know that it isnÃ,´t shown in % but hope you catch my thoughts.

This may not be such an issue in warm weather countries, but like here in Finland for example, when weather is really cold like -30c and summerÃ,´s then like +30 or so.
There comes 60 degrees difference.
And hot engine glowing heat when sitting on traffic lights makes it even more...
IÃ,´ve set that wideband authority pretty wide so it can make enough correction, i know this can make problems too...

Anybody having same kind of issues like iÃ,´m having??

[Denmark]

Yep,

I also had that problem with the AE86 i made, and i did not understand it , becourse itÃ,´s like itÃ,´s the otherway around,

Its getting rich when cold, and lean when hot, were i would think it was the other way around,

I just made ,so the wideband was  able to make the big difference in the fuel trim, .


/Skassa

[BenFenner]

I've seen similar things happening. Never really connected it to the IAT, but when warm, the car will be spot on some times, other times EGO will be doing a lot of work. Probably due to IAT as you've seen.

[gunni]

I thought the VEMS was running constant gas weight calculations because itÃ,´s using the air temp sensor?
Is it using it? or is it useless?

[Tcal]

Yep,

I also had that problem with the AE86 i made, and i did not understand it , becourse itÃ,´s like itÃ,´s the otherway around,

Its getting rich when cold, and lean when hot, were i would think it was the other way around,

I just made ,so the wideband was  able to make the big difference in the fuel trim, .


/Skassa

I did mean that my engine runs too rich when IAT is cold and then EgoC leans it to setted value.

LetÃ,´s take another example.
CLT is hot and IAT shows like 50. Just after start even if that IAT is fast, my idle is not so good until that lambda is heated and starts to do its job.


Hmm, this gets now confusing when thinking this. Not sure anymore is it lean or rich... have to go and check it  ;D

[GintsK]

Problem described is old as standalones. At idle air  flow is low and IAT sensor heat up from radiation of intake parts. Keyword: heat soak
In MT you can find value called fake air density low limit. I do not knew what is mathematics/algorithm used. But it works at low rpms and solve described problem.
My value usually is between 95 and 110.

Because of this phenomenon I highly recommend to use IAT sensors with fast response. Especially on turbo. I usualy use IAT sensor from Audi/VW 1.8T engines:
Bosch 0 280 130 085 = VAG 058 905 379

It prevent from running lean after long idle.

[Tcal]

Okay, thanks for this. I have played with that fake airdensity, but obviously not enough.
Now that i looked from MT it can take a value of 255, and iÃ,´ve just tried it up to 100. :-[

Does it correct that cold "problem" what i described in first message, or is it just for heat soaked IAT?

And yes i have that Bosch 085 sensor installed.

[GintsK]

I have no lot experience of cold weather tuning. Here in Latvia was only few days below -15C during few last years.
Here is something related:
http://www.vems.hu/wiki/index.php?page=MembersPage%2FPhatBob%2FFieldReport

[dnb]

There are 2 problems here:

The first is heatsoak - GintsK correctly states both problem and work-around perfectly.

The second is that the IAT sensor may be miscalibrated such that a small change in resistance results in an overly large change in measured temperature.  It's therefore well worth checking the IAT readings against a calibrated temperature meter for a few different temperatures.  (A heat gun or hair drier works well for this)