Many intake manufacturers supply cold air feeds with their induction kits (for example here & here). Some people make their own. But does a cold air feed make more power? Or is it placebo “marketing”?

Let’s find out!

Short Version

Generally speaking there are two types of intake system (which have the air filter in the engine bay).

One type is a sealed system eg the stock air box and intakes like the Pipercross Viper.

The other type has a cone filter which is exposed to the heat of the engine bay eg K&N 57i

Intakes with sealed air filter housings

For sealed systems a cold air feed is a must. Because the air filter housing is sealed a cold air feed allows us to draw 100% of the air from the outside of the car.

Intakes with exposed air filters

For systems which have the cone filter exposed in the engine bay, a cold air feed does very little. It is better than nothing but using heatshields to isolate the air filter from the heat of the engine bay will lower intake temps more.

Cold Air Feed Testing

I’m going to do four back-to-back tests with different intake setups to see if cold air feeds do anything at all.

At the end of the testing we should know

• How a cold air feed affects the performance of performance induction kits ie exposed cone filters.
• How a stock cold air feed affects the performance of the stock airbox.
• If there is a difference in performance between town driving and driving on the open road.
• If cold air feeds make more power in general
• How cold air feeds should be used

Testing Process

I’ll test four different intake setups using the same measurement procedure.

The Setups

Test One

Stock air box, stock air feed.

Test Two

Stock air box, no air feed

Test Three

Induction kit ie exposed cone filter in engine in stock air box location. No cold air feed.

Test Four

Exposed cone filter in stock air box location with cold air feed (stock cold air feed)

The Conditions & Measurements

• Let the engine idle until intake temps stabilise, record the temperature.
• Measure intake temps 10 seconds after movement
• Measure intake temps 30 seconds after movement
• Measure stable cruise intake temps
• Measure ambient temp for each test

Consistency

For consistency and to get comparable numbers, tests will be carried out on the same road with the same manner of driving

The Results

Stock air box with stock cold air feed

Lowest idle temps. Fastest change of intake temperature temps when car started moving. The stock air box with stock cold air feed reacted faster than all other setups. This characteristic is especially suited to cars driven in stop-start traffic.

Best set up with lowest temps generally.

Stock air box with no feed

High idle temps, very slow temp change, high cruise temps.

Cone filter with no feed

High idle temp. Temps reduced quickly but not as quick as stock air box with feed

Cone filter with stock feed

Idle temp surprisingly low. Temp change appears slower than without feed.

Conclusions

• Generally temps closer to ambient with feed than without.
• In stop-start traffic it looks beneficial to have filter in sealed enclosure using cold air feed.
• A cold air feed probably drops temps slightly in all conditions versus no feed.
• Best use of cold air feed is when it is feeding a sealed enclosure. And with pipe taking air high above road surface so it is not ingesting hot air which as been heated by the road surface.

Is A Cold Air Feed Worth The Effort?

It depends how much work is required.

If you are using the stock intake piping which is already present, I don’t see any reason not to use it.

With regards to constructing vents and routing hoses I think the effect is probably not worth it if you are using an exposed filter. In this case I think it would probably be better to focus efforts on heat shielding.

If you are using a sealed intake system, a cold air feed is a must.

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