NefMoto

Hey guys!
So, what intake air temperature do you consider "normal" during winter time (ambient temp around 0C)? How to check for faulty IAT sensor? Right now my iat can change literally by 9C in 10 seconds! Dunno if this is right...

I consistently observe IATs 8 to 11 degC above ambient temperature regardless of the ambient temperature during normal running (i.e. with enough oncoming air flow to avoid heat soak through engine bay air stagnation). I have a Powertec SL-1 cone filter with stainless steel mesh as the filter medium and I also have a large amount of free space in front of it due to the battery being located in the trunk in my car and because I have also removed the remaining pieces of scrap iron that served as a mount for the junction box. I don't know if this makes much of a difference though.

A faulty IAT sensor would throw the following codes:

http://wiki.ross-tech.com/wiki/index.php/16496/P0112/000274
http://wiki.ross-tech.com/wiki/index.php/16497/P0113/000275

I couldn't see one for an intermittent signal.

TTQS

This depends on a lot of factors.  Mainly you're looking at how hot the air temps are under the engine bay.  At some point, especially at idle, the hot engine air pools up under the hood and you're pretty much consuming air that is 25+ deg C regardless of the outside air temp.  Only when you rev the engine, or move the vehicle, the much cooler (in winter) outside air actually finds its way to the intake tract.  

This probably accounts for the sharp drop in temperature when you're revving due to the stark contrast between the cold winter air and the accumulated hot engine bay air.

Agreed. I didn't look at your graph initially as I thought you were asking about normal running temperatures during steady cruise. Obviously, if you increase engine and/or vehicle speed sharply, this will draw a slug of ambient air into the intake tract and IAT will drop noticeably until it equilibrates again with the warmer air in the engine bay. I don't know what the response time of the IAT sensor is, but in the millisecond range I should imagine.

TTQS

so 35C difference between ambient and intake temps during idle is OK?

Because when I was logging outside temp was ~0C and max intake temp I see in log is ~35C...

I think that a difference of 35 degC is quite normal, yes. The engine bay temperature will be stagnant during idle and therefore the difference between ambient will be correspondingly higher. I presume that's idle with a warm or hot engine?

TTQS

Idle with engine temp ~90C :)

BTW: Is there anything I can do to lower intake temps without buying new intercooler?

I think the only realistic options are a cold air feed (i.e. routing ambient air so that it directly impinges on the air filter) and an uprated air/air intercooler such as a FMIC. Forced air cooling systems such as the Kenlowe fan (same principle as with the engine coolant radiator) used to be popular aftermarket upgrades but I think that air/air intercooler design and manufacture is now much better due to CAD and air flow modelling methods and improved materials technology than in the 1970s and 1980s when Kenlowe style fans were all the rage.

http://www.kenlowe.com/fans/consumers/fans02.html

TTQS

Ok thanks, TTQS :)

Also, Water / Methanol injection lowers IAT's nicely.