Truth on Cold Air Intakes

[Willie 66]

Hey all,

I would really like to start a "scientific" thread sharing real benefits and drawbacks of cold air intakes. Giving real data from dynos would be a great treat, especially if there are before and after runs. If you decide to share, please give good details on your particular application to help out the guys and gals who may be considering purchasing a CAI.

Here's my vehicle:
I have a 2002 GMC Sierra 1500, Extended Cab, 2WD with the 5.3L. Approximately 160,000 miles. Rear end gears are 3.73's. I have 18" aftermarket rims with ever-so-slightly oversize tires. The only performance parts I put on prior to the CAI was a true-dual cat-back exhaust setup: Flowmaster 40's, no crossover, dumped under the truck. I've owned the truck since October 2010 and have never once touched 17 mpg, even on the highway (I got 16.9 once on a straight run down the interstate). I live in southeast Texas to give y'all an idea of climate.

Here's my experience:
I purchased the CAI hoping to make good on the promise of horsepower and mileage gains. I figured out that with 1.5 mpg gains, I could financially "break even" within a year, given how many miles I put on the truck annually, how much the CAI cost, and the price of gas. As far as power goes, I was hoping for a cost-effective gain in torque for towing and highway passing power.

I purchased the AEM Brute Force intake mostly because I like the look over other options. The dry filter was also a plus. I figured all the CAI's on the market are pretty much the same anyway: same size tubes, shapes, materials, cone filters. I could have got all crazy with it and did the ram air tube down to the air dam and wrapped the tube with insulation, but there was no way I could justify the extra cost.

I waited about a tank or two of gas to really test the truck since I knew the computer would need to do some adjusting. Being the car nut that I am, I really pay attention to the way my truck acts and reacts to my inputs. Since I installed the CAI about 3 months ago, I felt a noticeable drop in torque particularly between 2000-3000 RPM. This sucks, because this is both highway cruising speed and a happy spot for towing; however, once the engine revs above 3000 RPM, it has a noticeable gain in power. The CAI made the engine really punchy when downshifting to 2nd at about 60 mph. Both of these situations (bad low end, good high end) are reflected in the handy-dandy dyno sheet which came in the box with the intake. The dyno sheet showed the torque and power curves of a GM 6.0L before and after the CAI - There was a drop in power in the low range, and a rise in power in the high range. Not the same engine as mine, but comparable enough.

There has been absolutely no gain in mileage. No change in driving style. Perhaps we can attribute this to the low gears and the fact that yes, this is a pickup with a really high drag coefficient... Still, I expected to see mileage increase to at least 17.

Here's the TL;DR summary: CAI was bad for low end torque, good for high RPM horsepower, and yielded no gain in mileage. Side note: the added rumble is BOSS. Truck sounds great.

Like stated above, if anyone has real before and after data that could add to the discussion, that would be fantastic.