BMW M5 E39 - Proven

A few years ago, we tested all the basic bolt-ons in this E39 BMW M5, which included Evosport pulleys, a full engine-back Supersprint exhaust system and Powerchip/Evosport software. Because there wasn't a good intake system available at the time, we swapped a pair of performance drop-in filters. The car turned into a rocket and registered over 377 wheel-hp on a Dynojet 248C dyno.

Advanced Flow Engineering has recently released its intake system for the M5. Since it's been a while and we'd be testing on a different dyno at Tuning Technologies, we established a new baseline. Additionally, in order to find the intake's true gains, we reinstalled stock filter elements, ordered from Bavarian Autosport-a great source for factory BMW maintenance and aftermarket performance parts, including this AFE intake system.

Baseline
Peak wheel-hp: 358.5 @ 6500 rpm
Peak wheel-trq: 330 lb-ft @ 4650 rpm

Vehicle Data
Transmission: Six-speed manual
Mileage: 37,150
Testing octane: 91

Current Modifications
Powerchip/Evosport software
Evosport pulleys
Supersprint headers
Supersprint 100-cell metallic catalysts
Supersprint crossover pipe
Supersprint cat-back exhaust

Dyno Data
Dyno Type: Dynojet 424x
Temperature: 60 degrees F
Location: Tuning Technologies, Colton, California
Transmission Test Gear: Fourth

Notes
On its initial pull, the ABS system sent out a failure warning, limiting runs to 5000 rpm before the rev limiter kicked in. Prior experience of this vehicle reminded us to pull the two ABS fuses (#17 and #30), which did the trick. Throughout this dyno session, oil and water temperatures were kept to 200 and 190 degrees F respectively, and the air intake temperature to 90 degrees.

AFE Intake System
Peak wheel-hp: 364.2 @ 6500 rpm
Peak wheel-trq: 335 lb-ft @ 4750 rpm
Peak wheel-hp gain: 6.2 @ 5570 rpm
Peak wheel-trq gain: 10.8 lb-ft @ 2600 rpm

Construction
Plastic, steel and aluminum

Pros
Uses the factory cold-air intake ducting, keeping the intake air temperature near ambient
Washable and reusable cotton air filterFactory look
Easy installation
100-percent reversible

Cons
Outside the price tag, none

Parts
MAF to intake manifold dual piping, dual cone filters, silicone couplings, hose clamps, factory airbox adapters and covers, mounting hardware, installation instructions
Tools Flathead screwdriver, 4mm Allen key
Installation Time 30 minutes
MSRP $735.29

Notes
Installation is easy and sufficiently straightforward to not need the instructions. Although the largest gain in torque was low enough in the rev range that it wouldn't be used in a high-speed driving situation, the gains from 4500 to 6000 rpm varied 3 to 7 lb-ft of torque and 3 to 6 wheel-hp. In case anyone was thinking of an aftermarket hood with air ducts, we also tested the AFE intake with the airbox covers removed, providing nothing but air directly from the dyno fan instead of scooping it from below. But this didn't net even one horsepower, proving there are no downsides to leaving the covers on. On the dyno, the intake is noticeably louder with the hood open. On the street, however, the intake can't be heard over the roar of the car's aftermarket engine-back exhaust system.

Conclusion
Initially, we hoped to see a larger gain, given the baseline power. Just a four-percent gain-typical for an intake system on most other cars-should have netted about 14 wheel-hp on this dyno. But since the E39 M5 is equipped with two large boxes from the factory, its restriction is undoubtedly much less than we'd expect from just one airbox. Special thanks to Tuning Technologies for its assistance and to Bavarian Autosport for supplying factory filter elements.