Our goal for this test was to fit a new intake and full exhaust system to try and hit the magical 100hp per liter at the wheels. This would mean our 3.2L engine would give us 320whp and join an exclusive club. Currently, only a handful of normally aspirated cars with six cylinders or more can claim such a feat, including the Porsche 911 GT3 RS, Ferrari F430 Scuderia and 458 Italia. Of course, the Ferraris have larger displacement, making their 100whp/l even more impressive, but you get the picture - it's an exclusive club.
The subject for our challenge would be an E46 BMW M3. Our chosen car was previously seen in EC 7/12 when we tested upgrades on two identical 3.2-liter M3 SMG to see how they'd compare. As it turns out, they were significantly different...
We returned to european auto source (EAS) to test the stronger of the two, having removed the GruppeM intake but retained the Evolve software from that previous article.
To start, we needed a new baseline. After several runs on the EAS dynamometer we saw 303whp and 246 lb-ft of torque, bringing us close to where we left off one year ago.
Our first test would be a Macht Schnell cold-air intake kit. Unlike more expensive conical systems, the Macht Schnell unit houses a K&N drop-in filter but swaps out the 90° accordion elbow for a silicone boot to smooth airflow. At only $170 and a 10min install, any gain would be cost-effective.
On the dyno, we were pleasantly surprised to see 308whp and 248 lb-ft of torque, with peak gains of 6whp at 7800rpm and 4 lb-ft at 6400rpm.
This was a good start, but it would have been interesting to test the silicone boot with the GruppeM intake to see if we could get further gains. That's for another day maybe...
Next was the cat-back exhaust system. For around $2k, Corsa has sections two and three (section one is the piping off the cats), including two rear mufflers and an H-pipe to eliminate the rasp the E46 M3 is notorious for.
Made in the USA, the Corsa exhaust is 50-state legal and won't affect emissions. The mandrel-bent piping is 304 stainless, and the mufflers feature Corsa's patented "reflective sound cancellation" (RSC) technology, which not only provide a free-flow design but also eliminates cabin resonance. Additionally, there's a 20 lb weight savings over stock, and you can buy the system through Turner Motorsport.
Taking just 60min to fit at EAS, everything lined up perfectly. On the dyno, we recorded 311whp and 247 lb-ft, with a peak gain of 6whp and 4 lb-ft of torque at 7300rpm.
The new sound is intoxicating. It's not loud, just deep and commands respect. We didn't detect any interior drone and the car remains quiet under normal conditions. Hammer it, though, and there's a new roar out back that brings a smile to your face.
With a street-legal 310whp, we couldn't stop there. Our goal was 320whp and we needed to reach it. Fortunately, EAS had several sets of Macht Schnell headers on the shelf, which eliminate the cats for "racing purposes".
The Macht Schnell headers are a direct replacement for the two-piece factory parts and fit all S54-powered cars. They're supplied with 3/8" laser-cut flanges for a perfect fit, and a 2500°F matte black thermal coating to prevent warping. They have an additional O2 sensor bung to allow for wideband tuning, while gaskets and fasteners are included. Although the factory headers only weigh 18 lb, the MS parts were 5 lb lighter.
The installation was straightforward, with EAS taking about 4 hours to complete.
On the dyno, the headers bumped the output to 318whp - so close to our goal - while peak torque remained at 247 lb-ft. The biggest gains were 11whp and 8 lb-ft at 6800rpm.
With the elimination of the cats, the exhaust note was noticeably gruffer, although only slightly louder when cruising, yet civil enough for the car's 65 year-old owner. At full throttle it wails like an opera singer, making your spine tingle.
At this stage we were agonizingly close to our goal and decided that new software was needed to alter the air-fuel ratio - in our case, down from 13.3:1.
Unfortunately, Evolve was unavailable on our dyno day because we hadn't planned for this contingency. So we turned to ESS Tuning for rapid assistance.
The Norwegian company is synonymous with BMW supercharging and had several software files for us to choose from. In fact, we were warned it might take several attempts to find the right file but by the second download we hit 323whp and 250 lb-ft of torque. That was enough for us and we and called it a day.
Our peak gains were 6whp and 4 lb-ft at 8000rpm, and we noticed the air-fuel ratio had dropped a full point to a cooler, engine-saving 12:1.
We had surpassed our 100whp/l goal using California's 91-octane pump gas at a cost of almost $4300.
Looking back at last year's test, this particular car started at an astonishing 289whp. And with just fluids, spark plugs, intake, software and exhaust, it improved by 34whp. That alone is an impressive number when you consider the high state of tune the E46 M3 has from the factory. It's also only 30whp short of the E9X M3 4.0L V8, so this 3.2L six-cylinder rocks!
Our tests have opened my eyes to a car that's now affordable and has plenty of tuning potential, so I just picked up a 2002 M3 six-speed myself!