Technical Intake temp question

[cubic25]

Hey all,

My 2018 Fiat Doblo with the 1.6l Multijet diesel engine, has strange IAT behaviour, and I was wondering if a larger intercooler would help.

I've noticed, using an OBD tool, that at 80-95kmph, the intake air temp sits at around 45 degrees C, regardless of ambient temp.

At 95-105kmph, the IAT rises to 60+ degrees C. Regardless of ambient temp.

Then, at 110kmph, the IAT drops again to 40-45 degrees C. Regardless of ambient temp.

This is despite being in the same gear, so the revs aren't dropping.

Is it strange that the intake temps are hotter at 100 than what they are at 110? Would it be tuned like this for any particular reason?

I only ask because I do a lot of freeway driving and our limit is 100, so my car is spending a lot of time sucking in hot air. Is this detrimental to engine health, or do diesels not mind? Do hotter intake temps help the DPF do burn offs? Would fitting a larger IC do more harm than good?

Thanks for any advice.

EDIT: Just to be clear, I'm not looking for performance gains. Just want the van to last as long as possible.

 

[portland_bill]

I would expect the intake temp to follow the outside air temp, perhaps reducing slightly at higher speeds due to airflow.
However, with a turbo the air heats up as it is compressed by the turbo. I was not aware of any temp control on airflow through the intercooler, but there might be.

Fiat will have spent a lot of time and money testing and tweaking all aspects of how the engine operates. What you are seeing is almost certainly what Fiat would expect. For best longevity and reliability, leave it as standard, and follow the servicing recommendations. Manufacturer knows best.

A larger intercooler will not flow more, that is controlled by engine demand and the standard intercooler is good for the job, not restrictive. Cooling the air more makes it more dense, so effectively more oxygen in the cylinder, but this will have no effect, as the engine will always have excess air, that's how diesels work, and power is dependent on fuel injected. As the air is compressed in the cylinder it creates heat, which ignites the fuel when injected. Putting cooler air in will reduce the temp acheived which could reduce power, use more fuel, increase emissions, increase wear.