Induction kits guide (What do they do?)

"Thanks for reading my introduction to induction"

We find that induction kits are one of the most frequent modifications on car tuning projects so we thought we should provide an introductory guide to explain what they are, what they do and the theory behind them.

What is an induction kit?

Quite simply it is an air filter that cleans the air that goes into the engine. All cars have air filters usually sited in the engine bay hidden in an air box.

They are generally constructed of paper which filters out the particles from the air and prevents these from getting into the engine.

The filter housing or airboxe is designed to reduce the noise of the engine, as people prefer quiter engines (they do apparently but not our readers) so the airbox will have various vanes and angles cut to maximize this noise reduction by introducing sound cancelling turbulence.

Because the air is not flowing freely it will be slower so there is potentially a loss of power caused by all that sound deadening.

To make up for this loss of power the air filter surface area is a lot larger than the intake tubes so manufactures have effectively closed the gap between, noise reduction and performance by slowing up the air but allowing a wider area for it flow through seems to balance out nicely.

Induction kits

When it comes to car tuning noise reduction is generally the last thing on peoples mind and many people actually like the induction roar sound on an engine.

Swapping out the restrictive air box with an open filter helps to improve the flow of air into the engine and fully releases the induction roar, a noise associated with tuners cars the world over.

An induction kit is quite simply an open air filter shaped like a cone, dome or tube.

Downsides/pros and cons of induction kits.

So it would appear that induction kits are a win/win situation. However there are some downsides.

As the filter is sited in the warm engine bay it will suck in warm air which carries less oxygen - not great for power!

Thankfully after a mile or so the air temperature in the engine bay is much reduced and closer to ambient temperatures.

Fitting a cold air feed pipe taking air from outside the engine bay will help to counter this problem.

Engines with induction kits fitted typically see the power gains quite high up the RPM range if at all.

So the figures quoted on the box are generally for very high power turbo vehicles, so a claim of 20bhp will in reality be just 1bhp on smaller engines and then only at the top end of your rev range.

By fitting an induction kit you will often find that your low end power is compromised. In small engines the effect of an induction kit is often a noticeable loss of low end power.

This is fine if you want to use the top end of the RPM range all the time, like you would in a race environment, but on the street this is just not viable.

Fuel usage would be much higher and you will be causing a noise nuisance to your neighbours (as if that bothered you anyway!)

Induction kits flow better than paper elements partly because they do less filtering.

Induction kits are still efficient filters but they are never going to be as effective as an OEM paper filter. But you can get performance panel filters which are a good mid way compromise.

Do induction kits always add power?
NO - typically power gains are toward the top end of the RPM range with many engines suffering a power loss, especially low down the rev range.

Do induction kits add fuel economy?
By sucking in warm engine bay air the engine will use less fuel, so round town you might notice a slight improvement in MPG but the induction roar promotes a heavier driving style which negates this.

Engines can be a little more efficient with induction kits so pull in more air but again this should not be considered a fuel economy mod.

This generally means you get more power from your fuel but if you adjusted your driving style, to use less throttle and settled for your previous power figures, you can get improved mpg with induction kits.

Are all induction kits the same?
No, quality varies considerably. We recommend filters that are using a cotton gauze filtration medium.

Some kits come with high flow air boxes and air intakes designed specifically for a car and these will usually out perform basic filter only kits especially if they have a cold air feed pipe to channel cold air towards them rather than the hot engine bay air.

Are induction kits hard to fit?
Induction kits are extremely easy to fit. You may need to cut a pipe or two but most kits can be fitted in a matter of minutes with just a screwdriver.

Why are they so popular?

They sound great, so there is a massive placebo effect of perceived power increase, and they are one of the cheapest most easy to fit mods around.

If you believe that more noise=more power you'll be happy in your delusion!

Sadly though most setups in average cars see little to no power gain by fitting one unless there is a big restriction in your OEM airbox supply of air.

That said if you are modifying your car an induction kit can have a useful place in your parts list

I fitted an induction kit and I have flat spots?
Wait for a while to allow your ECU to adjust to the new air flow characteristics it can take 100 miles or so for this to kick in. An ECU will auto trim the fuelling based on lambda readings and past performance history.

If after a tank of fuel you still get flat spots then you should check your fuel delivery and the exhaust flow rates.

Running lean can be a problem and some have noted that fitting a sports exhaust will further improve things balancing the flow through the engine.

What is the main benefit of an induction kit?
If you want the induction roar noise then the induction kits are good value.

If you are looking for more power then there are lots of better things to spend your money on.

What do we think of universal induction kits?

Not a lot if i'm honest. Anything universal is little more than "a very generic, we couldn't be bothered to optimise anything" box shifting exercise.

Intake involves flow, and bore sizes, filter shape and positioning are all important and generic universal kits rarely work well in anything.

What about panel filters? Are they better than induction kit?

To answer this we have created a separate article on panel filters.

If you would like to discuss induction kits for your car please join us in our modified car forum.

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7 Responses to “What is an induction kit and what does it do.”

  1. Eric says:

    My intake system causes my powertrain light to come on? Do I need to take it in to be tuned? Also I gave it a minute to run and get used to the new intake and the damn light still comes on after a few miles…

  2. Doug says:

    I would take the air induction kit back .Simply put in a K&N you will not only notice performance but when you get on it it is plenty loud heads will roll it sounds good and no check engine light .Just do not over oil it when you clean it you have to spray it with oil.It is transmission fluid red and all .Good luck mine runs sweet with 164,000 miles.

  3. Jesse says:

    Hello i recently put a open air cone filter on my volvo s60 and i want to know if i will damage the car?

  4. shadowalkr says:

    I have a 99 toyota corolla and i’m considering getting an ram air intake kit but i’m wondering is irt going to cause a conflict with the mass flow sensor

  5. Tudor says:

    Why does an intake that lets your engine breathe more cause power loss at low rpm? I mean, it lets more air in, so why would it lose power?

  6. TorqueCars says:

    It’s partially to do with air speed and partially with the fuelling. A narrow pipe causes air to flow more quickly, when the intake pipe is wide, you admittedly have the ability to flow more air, but at low RPM the air is moving more slowly than it would in a narrower pipe, so you get less air into the cylinders. There is an ideal pipe width for a volume of air, and this also depends on the airs pressure and temperature. This is why you lose power low down in some cars under certain conditions with induction kits. The other thing is that the fuelling needs to match the airflow, if there is too much air the engine will run lean causing a flatspot.

  7. Brian Lowery says:

    I put in an induction air filter (carbon fiber canester with hose set-up) after I installed a stainless 2.25 inch catback exhaust (oval muffler) system. The car (98 honda civic lx 1.6) hesitates when not under full throttle and at idle randomly misfires. If I go full throttle it will go to redline without shifting (yes it is an automatic) until I back-off the throttle to let it shift.
    My question is that it seems to be fuel starved and will the factory system adjust for this in short time…or… am I messing this up somewhere else..thanks

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