Say the name Hartge or Alpina to a BMW fan and you’ll get instant nods of understanding and respect. While Dinan doesn’t get the pistonhead props afforded these German uber-tuners, they’re rightfully considered America’s foremost BMW tuner. Steve Dinan’s mob has been modifying BMW cars since 1979. His Morgan Hill California-based company offers upgrades for Bimmer engines, suspensions, brakes and wheels. Like the Germans, Dinan also sells “Signature Vehicles” and creates special Factory Works programs. We concern ourselves here with an ECU upgrade and a cold air intake.
Until the introduction of the sublime twin-turbo 335i, BMW prided itself on the fact that it relied on naturally aspirated engines to reach vaunted performance levels. Increasing performance of turbo-charged engines by modifying their Electronic Control Units (ECU) can lead to fairly dramatic performance upgrades on the order of fifty plus horsepower and foot pounds of torque. I tested Dinan’s ECU upgrade on a naturally aspirated inline six to see if similar gains could be found.
As stated in my previous review of the APR ECU upgrade for an Audi A4, ECU tuning is a difficult task. A tuner must examine thousands of lines of code to find areas where changes in parameters can add to performance. They also have to balance potential gains against potential engine damage.
BMW rates the 3.2-liter inline six in my '00 M Roadster at 240 horsepower. In its original state, the engine is relatively detuned; the same engine with variable timing and separate throttle bodies (as sold in Europe) produces over 300hp. This should mean lots of head room for Dinan to wring-out some extra power– without fear of dreaded engine “issues.”
The Dinan software is sold in various stages, partially tied to other Dinan products. I tested the Stage II software with the Dinan Cold Air Intake (CAI). In addition to increasing horsepower and torque, the software has two additional benefits. First, it removes the 155mph speed limiter, which is only in place to honor a German car manufacturers “gentleman’s agreement” between Audi, VW, Mercedes and BMW (originally made to forestall autobahn limits mooted by the Green Party). Second, the rather low redline limiter is lifted from 7000 to 7400 rpm.
Dealer installation is required; the software is transferred via an installer’s computer directly to the Bimmer via the BMW’s data port. (The leading competitor is the Conforti Shark Injector, which is user-installed via the OBD-II port, saving a trip to the dealer.)
The Cold Air Intake system can be fitted by both friends and foe (dealer). The CAI replaces the [allegedly] more restrictive factory air box with a long carbon fiber tube and a large cone-shaped air filter. In theory, moving the air intake away from engine heat improves performance. In practice, cold air simply allows the engine to produce more power. Unfortunately, many systems that advertise gains do so without merit, and car websites are rife with claims that CAI systems actually decrease horsepower.
Dinan’s website claims that their CAI system adds 12 hp and 11 lb-ft of torque. They also claim a gain of 10 hp and 10 ft.-lbs. of torque for their software. However, they caveat the CAI claims by stating that “a Stage 2 version of Dinan's Engine Software is available for optimum performance from the High Flow Cold Air Intake System as well.” Take it from a lawyer: it isn’t clear if Dinan’s claiming a combined gain or a cumulative gain for the two systems.
Measuring engine improvements requires both objective dyno-based tests and a subjective seat of the pants test. I went to a local BMW tuner, Road 'n Race. to check my installation's gains on their Mustang dynometer. Dynos measure wheel horsepower, not the crank horsepower manufacturers advertise. Therefore a correction factor must be applied. Also, the two most common dynos produce different results and are not directly comparable. To measure current performance of the M Roadster, I used a 17.5 percent correction factor.
On my best run, the car produced 208 peak hp, or 244 hp. That's four more than factory. Torque was up five foot-lbs over stock. While a large fan was used to simulate air movement, some power is lost compared to real road driving.
On the open road, the car felt slightly faster than stock, with better pedal feel during acceleration. These improvements were, at best, slight. The redline limiter was definitely raised, but since peak power is produced earlier, the benefit was limited.
The Dinan CAI sells for $649.00 and the Stage II software is $299.00. Add in a dealer charge for installation and you’re looking at over a grand for a very small gain. Therefore, except for bragging rights the Dinan name entails, I would not recommend this upgrade, though the CAI does look good in the Bimmer’s engine bay.