With their unique ability to deliver both strong performance and CAFE-pleasing fuel economy, turbocharged engines have established themselves as the foundation of the BMW lineup. If you’re hoping that the normally aspirated engine makes a comeback at BMW, you’re going to be disappointed. It’s just not going to happen.
Fortunately, BMW can turn out some great turbocharged engines. And as good as they are in stock form, those engines also allow tuners to extract more power with relative ease, bringing us cars like the Dinan S3-335i Coupe you see here.
Dinan’s engine software is the core of the S3 package for the 335i, with the remainder of the Dinan components enhancing and supporting the added power. The software upgrade makes more power by increasing turbo boost from the stock 8.8 psi to 14 psi while retuning the fuel mixture, ignition timing and rescaling the full map. The software changes also remove the top speed limiter and remap water pump speeds to keep operating temperatures under control as turbo boost increases. Together, the mods add 60 hp and 73 lb-ft of torque to the N54’s output.
Our test car was equipped with Dinan’s complete Stage 3 (S3) package, which combines the software upgrade with a larger intercooler and oil cooler, a free-flow stainless steel exhaust and a cold air intake to deliver an even more substantial power increase: 108 hp and 140 lb-ft of torque, bringing total output from the stock engine’s 300 hp and 300 lb-ft to the Dinan S3’s 408 hp and 440 lb-ft. That’s nearly as much horsepower and a lot more torque than the current M3’s S65 V8 generates (414 hp, 295 lb-ft), and the torque figure is almost as high as the turbocharged N63 V8 produces in the 550i. No wonder Dinan has sold more than 3,200 of these software upgrades for N54-engined BMWs!
Adding horsepower to a turbocharged engine is relatively easy compared to trying to do so on a normally aspirated engine, but producing reliable power gains and maintaining drivability is much tougher. Increasing turbo boost means increasing heat, making the oil cooler key to reliability in the S3 engine package. The Dinan cooler has twice the capacity of the stock unit, plus ducting that directs more outside air through it. Since the N54’s factory oil cooler has had overheating issues, this product is probably worth checking into even if you have a completely stock BMW with an N54 or N55 engine and plan to drive it hard or take it to track events.
The upgraded coolers are undoubtedly some of the most important of Dinan’s upgrades to the S3-335i, but they’re not the kind of modifications you can admire when the hood is popped open. In the spirit of American hot rodding, it’s sweet to have visual upgrades, as well, and the Dinan cold air intake fits the bill on this car. It’s beautifully made from carbon fiber and looks fantastic under the hood. With tubing that pulls air straight from the grill opening while isolating that cool air from the hotter air under the hood, it also works, reducing intake air temperature by around 40°F compared to the stock intake.
Thorough suspension tuning
To handle the increased stresses that come with more power, Dinan upgraded the suspension components while creating the Dinan S3-335i. As the company does with its engine software packages, Dinan offers its suspension modifications for the 335i in three stages. The S3-335i’s Stage 3 package includes upgraded springs, shocks and struts that are custom-made by Koni to Dinan’s damping rates and bump stop specifications, plus tubular anti-roll bars that measure 26.5mm in diameter up front (same as the solid stock bar) and 15.8mm at the rear (up from 13mm).
Our car also had front camber plates that allow an additional 0.5° of negative camber, as well as stiffer bushings for the rear subframe and front control arms. The use of firmer, higher-quality bushings for the rear subframe is crucial when increasing a car’s grip capabilities, since the stock bushings are designed for the grip levels of the stock car. The stock bushings would be overwhelmed by significant increases in grip, as manifested by excess movement of the rear subframe and the entire rear end of the car.