Profile of finished car shows...
Profile of finished car shows OEM side skirts, DTM front lip and painted bumpers, which give car a more contemporary appearance. Low-profile rubber and 17" wheels help too.
It's show time - the final installment of eurotuner's Project M325i buildup. This month we're covering the final tweaks to our '93 325is coupe - engine mods, a few exterior and interior touches, dyno runs and the long-awaited showdown with our challenger, a '95 M3.
As loyal readers know, the notion behind Project M325i was to take select tuner parts and transform a stock E36 into an M3 beater, but at a fraction of the cost of buying BMW's hot rod. With Bob Tunnell of Bimmer Haus Performance (Broomfield, CO) serving as our tuning guide, we previously upgraded the suspension - H&R springs and sway bars, Koni shocks, M3 bushings and bits - plus shifting, exhaust, wheels, tires and lighting. Now it's time to squeeze a few more horsepower from that sweet inline-six, as well as make the car's exterior a bit more, shall we say, project-car-like.
After all engine work, there...
After all engine work, there was little to show for intake, exhaust, pulleys and chip, but power gains would be significant.
Motor UpgradesThe six-cylinder in our car is the M50, featuring 24 valves, chain-driven dual overhead camshafts, hydraulic lifters and seven main bearings. Compression is 10:1 with a bore/stroke of 84x75mm. Fuel injection and ignition management is controlled by a Bosch Motronic 3.1 DME system with OBD1 diagnostics. Horse-power is rated by the factory at 189 (SAE net) at 5,900rpm; torque is 181 lb-ft at 4,700rpm. Like all BMW sixes, the M50 delivers power with a seamless, vibration-free smoothness.
In 1993, BMW introduced its first variable-valve timing system to the M50, dubbed VANOS (M50 TU). This system altered the valve timing of the intake camshaft, resulting in a smoother idle and increased torque at low- and mid-speed revs; peak horsepower remained the same.
Since the BMW straight-six is a near perfect combination of smoothness, torque and power, Tunnell suggested only three modifications: a cold-air intake, perform-ance chip and underdrive pulleys. Enter Jim Conforti. Conforti, as Bimmerheads know, is the recognized Motronic guru. His reprogramming wizardry has extracted power gains from many powerplants, including the M50.
Conforti makes a nice cold-air...
Conforti makes a nice cold-air intake system, complete with preformed airbox and hood seal, carbon fiber inlet tube and large foam ITG air filter. All components fit well.
We sourced a Conforti performance chip and cold-air box from Eurosport High Performance in Salt Lake City. The company's Josh MacMurray confirmed a chip is the easiest and most cost-effective way to boost power. For the '93-95 M50 VANOS engine, Conforti/Eurosport advertise a 22hp boost at 6,000rpm and a 20 lb-ft torque increase at 4,000rpm (that's flywheel, not wheel, horsepower). The chip also bumps the rev limit to 7,000rpm.
Next we added Conforti's gorgeous cold-air intake - replete with carbon-fiber pipe and huge ITG foam filter - which would add even more horsepower plus a grin-inducing roar from the engine at full-throttle. We also installed a set of UUC underdrive pulleys, good for a few more ponies and quicker engine response.
The protagonists, a project...
The protagonists, a project M325i parked alongside a '95 M3, before setting out to do battle on the track.
We then headed off to Dyno-Pro in Denver to compare horsepower and torque between the 325i and the '95 M3. The bone-stock M3 produced 212whp and 209 lb-ft of torque (or 254hp and 250 lb-ft at the flywheel), while our M325i project car delivered 179whp and 170 lb-ft of torque (216hp and 205 lb-ft at the flywheel).
Impressively, the M325i picked up 27hp over stock, right on Conforti's estimates. However, there's no denying the advantage of the M3's additional 500cc of displace-ment. But the question remained: Would the M3's power advantage translate into quicker lap times?
Before we headed out to Second Creek Raceway for track comparisons, we took time to add a bit of visual appeal to our stealthy 325is coupe. The knee-jerk upgrade would be an OEM M3 front bumper and skirts, but we opted for OEM side skirts from a '96-'99 E36, plus a DTM front lip spoiler and M-Style rear diffuser from Bavarian Autosport. We also painted the lower, grey sections of the bumpers in body color. These changes upgraded our '93 E36 to post-'96 visual spec. The striking 17" AT Italia Type 5 Sport wheels and lowered ride height had already added to the car's more aggres-sive persona.
 Bavarian Autosport rear diffuser...  Bavarian Autosport rear diffuser is perfect replacement for stock panel. It's also near-clone of OEM M3 diffuser, and accents M3 tips nicely. |  DTM-style front spoiler from...  DTM-style front spoiler from Bavarian Autosport gives a more aggressive look to E36 front end. |  '93 E36s are controlled by...  '93 E36s are controlled by OBD1 diagnostic and engine management systems, which require an actual chip replacement from Shark/Conforti. '96 and later use OBD2 with programmable flash memory. |
 Conforti CAI in place with...  Conforti CAI in place with heat shroud fitted to prevent air in hot engine bay mixing with cold air drawn in. | | |