In a previous post the subject of the Mk7 IAT sensor and how the readings can be deceiving was presented.
A related topic is the occasionally asked question, “my IATs with the stock intercooler cruising around are XX degrees above ambient , do I need an aftermarket intercooler?”
Cruising around refers to the condition where the IAT sensor can be misleading.
In the chart below the air temperature inside the throttle body charge pipe, between the IC outlet and throttle body, is shown by the orange line during some routine driving. A few full-throttle pulls are added to the mix in the middle of the drive.
For the majority of the 33 minute drive the air temperature exiting the stock IC is around 2-3 degrees above the ambient air temperature.
The next chart includes the reading from the IAT sensor, indicated by the red line.
During the early potion of the drive the IAT steadily rises even though the temperature leaving the intercooler remains constant.
By the second half of the drive, the IAT is between 16-18 degrees above ambient, despite the temperature leaving the intercooler only 2-3 degrees above ambient.
Using the cruising IAT reading to judge the need for an aftermarket intercooler is not recommended due to the sensor not accurately reporting the temperature exiting the intercooler.
7 thoughts on “Stock IC Cruising IAT”
Crazy! So basically, the concerns with heat soak etc. on the stock IC are a bit overblown due to erroneous readings?
I think it depends on the situation. At full boost for a couple of repeat pulls, like is shown in the middle of the chart, the stock IC does heat up more rapidly than an aftermarket IC. During routine driving, like the rest of the time on the charts, the stock IC stays near the outside temperature.
The main objective of the post was to point out that cruising IAT can be quite different from the air temperature leaving the intercooler, and seeing high IATs while cruising shouldn’t lead someone to conclude they need to replace a stock IC.
Any thoughts on why the sensor reads high and a possible fix.
My guess is that it is caused by the location. It is off to the side from where air is entering the intake manifold, and the sensor is not too far from the wall of the intake manifold.
Thank you Jeff. Hopefully the boffins at VW know it reads high and suitable compensation is built into the ECU.
Hi Jeff, I’m glad you discovered this! In your view, does this at all change the discussion around the stock IC’s suitability in Stage 1, 2 and IS38 applications?
I think how well the stock IC performs is very dependent on the conditions it is subjected to. For a stage 1/2 or IS38 turbo daily driver that may only need to accelerate to merge or pass a car, I think the stock IC will be adequate. The more demanding the load on the IC becomes that is where the limits of the stock IC start to become evident and an aftermarket product has attributes that better suit the conditions.
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