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Running colder

Forum Stream Running colder

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2014-09-03 07:20:52

Running colder

Intake Air Temperature (IAT) is one of the values listed in the OBD reader.

I come across many forums on users installing CAI (Cold air intakes) or fancy intakes and filters. Most of the time, their fuel economy are screwed.

My thought path isn’t that far as i am walking nearer to CAI principle simply by wanting to separate the two welded pipes of the breather pipe assembly (Item 3 in the diagram above).

I want to run colder intake air.

My initial belief then was that the intake air which is creating vacuum, is taking in heated fumes from the crankcase, and from the valve cover before receiving into the air box, mixing with engine bay air (which is hotter than the ambient air).

And the breather pipe that is transporting the heated fumes into the air box is joined with the coolant tube. The coolant tube is hot about 88deg.C (190deg.F). Since they are joined, it would mean heat is passed on through conduction.


Assumption: If i can bring down the intake air temperature (IAT) from running condition of 50 deg.C / 122 deg.F (My ambient outside temperature is about 32 deg.C / 89 deg.F) the engine would run better*

*Better was initially defined as more powerful. Anyways that contradicts fuel economy on hindsight.


I was exploring bringing down the IAT via the separation of the breather pipe and coolant pipe in item (3) in the diagram above.

The coolant pipe is conducting heat to the breather pipe.

Then i found an interesting forum reply while researching if anyone has separated the breather tube or the likes of it.

(!) Bringing down air intake temperature by eliminating heat does not result in better fuel economy, because

a colder intake air is a denser air

the ECU would adjust to pump in more fuel (runs richer)

results in poorer fuel economy

better fuel economy is a result of leaner running

it is better to keep intake stock instead of mod to CAI because of how the MAF & MAP sees air using the airbox (resonance box)

Main thread:

The following response i would like to highlight are listed below




Stock is best.

Enjoy reading!