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Cold Air Intake (CAI) Tutorial

Want more power?

I’ve had a bug in my head to do this ever since Pete in Australia posted his cold air intake modification years ago. Mine is really no different. Just better documented ;-). Want more power, more efficiency? Don’t mind getting your hands dirty? Don’t mind checking on your work every month or two? Have $25?


Then this mod is for you. You’ll need

  • 1 plastic funnel, $5
  • 1-2 yards of 3-inch diameter dryer ducting tube, $10
  • High heat duct tape, $5
  • Duct tape, $3
  • Lock ties, $2


Before we start, I’d like to warn you about something. This mod does one big no-no, and that is exposing the engine to a greater risk of ingesting pollutants like dust, water, sand, grit or other debris. Volvo engineers have been working for decades to keep this stuff away from the engine, and by doing this you’re removing a big safeguard they designed: the position of the air intake.

To judge the degree of risk, a proper test of several (dozens? hundreds?) of 5-cyl turbo Volvos would be in order. Of course this has not and will not ever happen, so you must decide for yourself how much the extra power/efficiency is worth to you. SO FAR, my engine is fine.

If you absolutely must not take any chances with your Volvo, don’t perform this modification. Put in a K&N filter and call it a day.

Cold Air Intake Procedure

Remove stock pieces

Remove the plastic air piping that begins at the grill and ends at the airbox. No tools are necessary – these parts simply pull apart. Put these somewhere for safe keeping.


Move the battery tray fastener

I found the black plastic battery tray part that holds down the battery to jut out just far enough to make routing the ducting down the front of the battery impossible. So I removed it. I believe gravity holds the battery down with sufficient force. If I went to the track, I’d find another way to hold the battery down, but in regular driving I don’t think it’s necessary.

Route the air duct

Route your new cold air intake ducting from the airbox down the front of the battery and behind the front air dam. Do this carefully, and do it before you work on fastening either end. The duct metal (tin? aluminum?) tears easily so be careful. I tried to find anything other than this dryer ducting, but both Home Depot and Ace Hardware could not produce anything better at the diameter I needed. I wanted what Pete used, but couldn’t find it.


Front spoiler

This is where you want to pull the ducting down from above and find a good place to place your intake. I have a 850 R spoiler on my 850 T5 for a reason I’ve never known. These R spoilers have wonderful ducts seemingly made for this very purpose, the only thing I needed to do was pop out the plastic grille set in the duct. If you have fog light holes but no fog lights, I suspect these would be as good or even better for your cold air intake.

The funnel’s purpose is to — wait for it — funnel air into the ducting. And it provides a nice transition to meet the opening in the front spoiler.

Despite the photos, I had not taped the ducting to the funnel (already cut) before routing the ducting down there. So now that it’s down there, do that. I just went around and around until it felt solid, and in the months since my work, it’s still ok. To secure the funnel to the spoiler, I used lock-ties. I made three small holes in the lip of the funnel, and lock-tied those to the helpfully-placed anchors that held the duct’s grille. The photo above does not show the lock-ties because I snapped it before I added them.


Airbox attachment

Pull the ducting up to the airbox and discover… it doesn’t fit over the airbox connector. They are the exact same size: 3 inches. Ugh. I just taped (heat tape) mine on, then put a clamp over the resulting tape job. Messy? Yes. Effective? Yes also.  I used the heat tape here just in case the temperature got really hot inside the engine bay. Nobody wants to scrape melted or tacky duct tape residue off airbox connectors if/when it comes time to take the cold air intake off.

Thoughts on my Cold Air Intake

So far it’s been six months, and it’s been fine. Rain, snow have not been a problem, but at the same time I’m constantly conscious of what’s down there, and in the first snowfall this winter, for instance, I checked the intake a few times to look for clogging/freezing. I like that the ducting material is weak and I can defeat it simply by poking a hole in it — anywhere — with a car key or even my finger.


Dryer ducting

The dryer ducting wasn’t the ideal material, but having less patience than perfectionism, I went with it. Since then, it’s proved to be ok — even better than ok. First, it’s accordion-style construction makes it easy to lengthen/shorten while you’re working with it. Second, it’s easy to puncture in case you find yourself in a flood, fjording a small river, etc, wherever sucking in water would be a Very High Probability. Third, it’s incredibly light. If that weren’t enough, it’s proven to be durable. In six months of use, there are no holes, even in the area where it rubs other piping.

Sucking in water

Because air is 784 times less dense than water, I wasn’t concerned about taking water into the engine. The routing of the ducting goes nearly straight up for a foot or two, so the energy required to pull water up that I felt would be far greater than the ability of the engine. Plus, the water would have to be taking up all or most of the diameter of the 3-inch ducting for a significant length of of it, otherwise it would drain down and the much-easier-to-pull air would simply be drawn in. HOWEVER, during very heavy rainstorm where a few intersections here in Denver were flooded in August, I disconnected the top of the airbox so that air would be pulled from the engine bay and not this cold air intake system. I’m not brave enough to risk my 850’s engine on my amateur knowledge of physics.

Like I mentioned above, besides the temporary measure of unlatching the airbox top, another method of ensuring water didn’t get sucked into the engine would have been to puncture the ducting somewhere along its length. That would have the effect of requiring even more suction/water to cause damage. One idea here is to puncture the tubing, but put a piece of tape over the puncture for everyday use, and simply peel the tape back if you felt you might encounter water or snow.

Periodic Checks

I check the air filter (K&N) every month and so far the debris it’s collected is sand and grit — same stuff as with the stock air intake, only more of it. I have a photo coming that shows the debris.

So how much power does it add?

You’re going to hate me here, but my answer is “I don’t know”. I don’t have any way of measuring it, either by acceleration (never been to the track) or fuel economy (I don’t drive the same routes because I work from home every day). It felt faster when I took her for some runs after I added it. Five percent? It’s hard to say. Some/all of it may be psychological, but it’s hard to imagine it’s not helping to some small degree at least.

My first thought when I got her on the highway was the slight increase in power is more evident on at high RPM in a highway environment (Ram air effect?), but there is a touch more low-end grunt, which is badly needed on the large-turbo first-generation FWD/AWD Volvos.

What I wouldn’t do

  • Lend the car to a friend for more than an hour or two
  • Sell the car without putting the stock air intake back on
  • Sell the car without notifying potential buyers I had run this system
  • Run it in potential high-water situations
  • “Set and forget” it… I’m always aware of the low position and potentially greater airflow of the intake


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Discuss this Cold Air Intake Tutorial. I’ve added some updated photos there.

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