IAT readings vs. actual outside air temps.
09-12-2005, 11:08 PM
#1
IAT readings vs. actual outside air temps. I was wondering how much hotter is the IAT reading than the actual air that is really going into the lid. I was thinking the radiator being directly under the lid must heat up that sensor and air around it alot. anyone actually compared real outside temps to the IAT reading?
09-13-2005, 10:13 AM
#3
Moderator
iTrader: (11)
Join Date: Mar 2002
Location: East Central Florida
Posts: 12,605
Likes: 0
Received 6 Likes
on
6 Posts
That chart seems to pertain to post-IAT warming of
the intake charge. However the IAT sensor's fidelity
is another matter. I have observed huge heat soak
in one configuration, my Blackwing lid with the IAT
mounted in the back corner registered huge offsets
from ambient (Walgreen's time/temperature sign)
after idle / parking and took minutes to come into
line. The combination of sensor and close-coupled
lid thermal mass, and a heat-exposed location, and
low, eddy-only airflow made for poor dynamic response
in the IAT. Many minutes for the heat-soaked IAT
to return to near-ambient readings.
Any thermal mass and cooling path will have an
associated thermal time-constant. Some are worse
than others.
Using the IAT in the 85mm MAF throat things are
much better now. A lid with the IAT in the neck, not
some low-flow backwater position, is better too.
the intake charge. However the IAT sensor's fidelity
is another matter. I have observed huge heat soak
in one configuration, my Blackwing lid with the IAT
mounted in the back corner registered huge offsets
from ambient (Walgreen's time/temperature sign)
after idle / parking and took minutes to come into
line. The combination of sensor and close-coupled
lid thermal mass, and a heat-exposed location, and
low, eddy-only airflow made for poor dynamic response
in the IAT. Many minutes for the heat-soaked IAT
to return to near-ambient readings.
Any thermal mass and cooling path will have an
associated thermal time-constant. Some are worse
than others.
Using the IAT in the 85mm MAF throat things are
much better now. A lid with the IAT in the neck, not
some low-flow backwater position, is better too.
09-13-2005, 11:50 AM
#6
TECH Enthusiast
iTrader: (3)
Join Date: May 2003
Location: Greenville, SC
Posts: 550
Likes: 0
Received 0 Likes
on
0 Posts
More to the point, it might be interesting to compare IAT readings over time and at various speeds while outside air temperature remains constant.
For example, after cruising at - say 60 mph, come to a stop and idle and watch the IAT values rise until they peak, then do several quick blast up to 120 or so (on a closed course of course) and watch how long it takes the IAT to come down.
For example, after cruising at - say 60 mph, come to a stop and idle and watch the IAT values rise until they peak, then do several quick blast up to 120 or so (on a closed course of course) and watch how long it takes the IAT to come down.
