Perfecting the E46 M3
We've written about E46 M3 projects before, but most of those projects were hard core track oriented. What we have here instead is a perfect street set-up for the M3: more power, more sound and better handling. Our time honored philosophy of balanced performance was followed to produce a car that is better in every regard than stock without any one aspect overshadowing another.
Power
The S54 engine that comes in an E46 M3 is already tuned to achieve the maximum amount of power, so great gains cannot be made without resorting to super or turbo charging. But there are some simple modifications that can help unleash a few extra horses-- especially at the mid to upper end of the RPM chart.
The first thing we look at when we want to extract some more power out of a stock normally aspirated engine is improving the flow of air into and out of the engine. We used an aFe brand stage 1 airbox to open up the engine's intake. The aFe stage 1 kit is a solid piece made of materials befitting the M3 engine compartment. We like the stage 1 kit over the stage 2 because of its better fit and finish and the separate lid that keeps the engine's heat from seeping into the intake (instead of using the hood as the heat shield). aFe quotes a 10 horsepower gain with this unit.
Here is the stock airbox:
This is a picture of the aFe unit installed without the heat shield; note the large cone air filter:
The final installation with the (silver) heat shield:
Now that we have improved the inhaling end of the engine, we need to open up the exhaling portion-- the exhaust in other words. There are many brands of exhaust systems on the market for the E46 M3 including Borla, Corsa, Rogue Engineering, Eisenmann and Supersprint. We are partial to the systems from Supersprint because we know they have the capabilities to do proper engineering and testing. Supersprint tends to be the most expensive, but we have never been disappointed with the results.
Increased air flow and proper back pressure are not the only aspects of an exhaust system one needs to consider; sound is important. Since this customer plans on using this M3 as a daily driver, the sound level needs to be within acceptable range-- not too loud around town and no headache inducing drone on the highway. Supersprint has several versions available, and for this application we chose their "performance" model over the higher flow, but much louder “race" version.
The S54 engine has a unique "raspy" sound to it-- some people love it, others not so much. We have tested all sorts of rasp reducing mid-pipes, but none of them get rid of it completely, and most end up impeding air flow (robbing some potential horsepower).
The Supersprint performance muffler does a great job reducing the rasp and lowering the frequency of the sound emanating from the tailpipes as well as increasing the airflow for better power. Overall, a hard package to beat (check the video at the bottom of the blog).
Here's a picture of the muffler installed. It is smaller and slightly lighter (about 15 lbs) than the OEM unit, though not as light as the race version muffler from Supersprint. Also note the larger diameter tailpipes in polished stainless steel that add a bit of visual flair without going overboard.
In order to use the increased air flow through the engine, and find a few extra horses, we used Powerchip to reprogram the ECU. Powerchip, based in Australia, is one of the biggest and most reputable engine tuners in the market today. We like their programs because they are robust and work across the entire rev range, not just the upper end. The stock S54 engine in the M3 is rated at 333 hp and 262 lb-ft torque. Powerchip is able to increase that to at least 342 hp and 269 lb-ft.
The fourth power adding modification doesn't technically add power, but it frees some up. "Under-driving" some of the auxiliary components strapped to the engine such as the water pump, power steering pump and alternator frees up power to the rear wheels. In other words, power that would have normally been used to drive these pulleys can now go to the rear wheels. We used pulleys made by Turner Motorsport, which quotes a gain of 10 hp at the wheels.
Handling
To better harness the new power, we installed a coil-over suspension kit by TC Kline Racing. TC Kline makes several types of suspension systems for BMW including everything from a mild upgrade to total race ready. For this project we decided on their rebound adjustable kit with 400 lbs springs at all four corners and adjustable camber/caster plates for the front. All of TC Kline's kits have been engineered to work as a system-- the spring rate is matched to the dampers to provide the perfect amount of feedback and control without being overly harsh. The kit we installed provides improved ride and handling characteristics across the performance envelope that can easily be adjusted (ride height and damper rebound) to suit conditions. Typically our customers find that the ride has actually improved over stock configuration.
Here is a picture of the front struts with a close-up of the camber/caster plates:
The suspension is height adjustable. The red ring is the spring perch which can be raised and lowered by screwing it up or down on the threaded body of the damper. We always coat the threads with anti-seize compound so that the perch doesn't stick in the future.
The front strut assemble installed (note we use factory reinforcement plates at the top to avoid strut tower failures):
The system is designed to fit the rear suspension hard on hard without rubber pads. But, since this car will be driven mostly on the street, we custom fit the OEM spring pads. By going through the extra effort of cutting these pads to fit, we are able to substantially reduce the chance for any noises coming from the movement of the rear springs. For a race car set-up we skip this step since we want less variability in suspension movement.
We install the height adjusting spring perch at the top of the spring for easier access:
The rear suspension installed:
We consider the modifications made to this E46 M3 perfect for daily driving. We've added some noticeable power throughout the rev range with particular emphasis on mid range torque and improved throttle response. We coupled the added power to an improved, adjustable suspension system that eliminates some of the inherent understeer and improves overall ride and handling.
