BMW 325i/328i Tuning Guide

$1000-2000
Once you have an intake, pulleys and software, the next upgrade is a cat-back exhaust. Companies like Active, B&B, Dinan, evosport, Rogue, Supersprint, TMS and UUC Motorwerks all have one, and prices range from $550-1299. The least expensive is sold by UUC, the most expensive by Dinan.

Installation is usually a simple 1-2 hour task. You'll get a handful of horsepower, the car will benefit from a more aggressive sound and there could be a 10-20 lb weight reduction over the stock system.

For $1438 you can treat your stock 328i to 188whp with a performance package from Active. Its CAI, third-generation cat-back exhaust and software have been tuned in-house on its Mustang Dyno. For the 325i, the same upgrades should get you similar power but cost $1314. These prices could drop since Active is hoping to lower the price of its software, so call them first.

$2000-3000
Dinan's normally-aspirated upgrades for these two engines will net a claimed 220bhp at the flywheel, which we estimate to be around 195whp. The upgrades include Dinan's software, CAI, exhaust and larger throttle body for $2286.

Eurosport's cam kit for the OBD2 328i features its M50 manifold conversion kit, Evo2 intake system, Conforti software and cams from the '96-99 M3 3.2 for $2146 (manifold sold separately).

The company recommends you source the manifold but can supply a new one for an extra $497. The larger manifold sacrifices mid-range torque - a loss of 10-15 lb/ft from 3200-4200rpm - but the trade off is superb at the top end. While the stock car peaks at 181 lb/ft at 4000rpm and immediately starts to fall off, the kit helps sustain 185-190 lb/ft from 4300-5800rpm. The end result is a peak gain of 40 lb/ft and 45whp at 6000rpm, equating to 205whp total.

Eurosport also tested the kit with a factory M3 exhaust (you can find used ones) and got 209whp - now you're in E36 M3 territory!

$3000-4000
Active has supercharger systems for both the 325i and 328i that are currently on sale for $3995. Breathing through a factory exhaust, you can expect 250whp at 8psi, and over 255whp if you throw in Active's Gen3 cat-back exhaust for an extra $690.

The supercharger is a Rotrex C30-94 and the kit includes mandrel-bent tubing, high temp hoses, high-flow injectors, front-mount intercooler, oil cooler, bypass valve, hardware, software and an illustrated manual. If you're wondering about reliability, AA reports it's sold over 600 of these kits already.

$4000-5000
VF-Engineering sells a centrifugal supercharger for both engines. Using a Vortech V2 SQ SC polished supercharger regulated to 6psi, the kit also features OEM BMW idler pulleys, CNC brackets, OEM high-flow injectors, Bosch bypass valve and GIAC software. The kit retails for $4500 and will net you 235-250whp. The 328i gets the lesser horsepower but more torque; 220 lb/ft at 5200rpm, compared to 212 lb/ft at 6200rpm for the 325i.

Over $5000
Dinan has a centrifugal supercharger for $6500. Although the company doesn't quote whp numbers for the kits, they've quoted 255-258bhp which we've converted to an estimated 225-230whp, with 200 lb/ft to the wheels. While the price is the same for manual 325i and 328i, automatics cost about $500 less.

Active is considered the pioneers of E36 turbocharging. Even though it has discontinued its turbo kit for the 325i on the website, it sells them to customers who demand one.

The AA stage 1.5 kit uses its stage 2 intercooler and features a Mitsubishi TD06-H turbo with a 120mm housing to suit the engine displacement. There's no reduction in compression, so the head doesn't have to be removed. At 9psi, the $7995 kit is good for around 295whp at 6250rpm, with 275 lb/ft at 5000rpm - a good turbo kit will get you a fat torque curve. In this case we're talking a minimum 250 lb/ft from 4000rpm to redline. Add a boost controller, larger injectors and some race fuel, and this kit should be good for 350whp.

For the 328i only, Eurosport offers its twin-screw supercharger. The stage 2 system uses the 1.7 liter Opcon Autorotor and Laminova intercooler core that are integrated into the CAD-designed manifold. Boost is regulated to 9psi, and air is cooled by a water-to-air intercooler with front-mounted heat exchanger. For $8495, stage 2 delivers 320whp. With a set of M3 cams and an M3 cat-back exhaust, the company saw 333whp at 6800rpm with over 270 lb/ft available from 4000-6200rpm. For those interested in saving money, Eurosport also offers a non-intercooled stage 1 twin-screw setup with undisclosed power ratings.