Lucien’s BMW 335i E92 N55: Stage 3 tuning with a TTH 600 turbo

Lucien’s car is powered by an N55 engine.

In Phase 2, the differences from Phase 1 are immediately apparent: redesigned headlights, tail lightsand wing mirrors. But the most significant change lies under the bonnet, with the arrival of the N55 to replace the N54.

On paper, the N54 retains superior engine potential: its twin-turbo architecture allows it to produce more power than the N55’s single-turbo setup. On the other hand, the N55 introduces a new DKG gearbox, which replaces the old 6-speed automatic. When it comes to sound, the N55 remains the benchmark: it is BMW’s best turbocharged 6-cylinder engine in this respect, prior to the arrival of the F80 generation.

Lucien’s car doesn’t arrive at Shiftech empty-handed. It’s already fitted with several parts: a charge pipe, a Wagner intercooler, a Mosselman oil cooler, a Proweld valve system, a downpipe and a complete Proweld exhaust system with twin silencers and twin flaps.

However, there is no modified intake system, nor a reworked high-pressure pump. First and foremost, the car is put on the dynamometer to check exactly how much power it produces: Lucien himself is unsure of his vehicle’s exact state of preparation.

With the parts already fitted, the car has all the components of a Stage 2 upgrade. Next stop: Shiftech, to take it to the next level: Stage 3.

For this upgrade, the choice falls on a TTH 600 turbocharger, a plug-and-play solution. The manufacturer claims power gains of up to 600 ch on ethanol, under ideal conditions. The target set for this upgrade is more modest: to achieve 520 to 530 ch on unleaded petrol. The plan is clear: remove the old turbo, fit the TTH 600, then carry out an initial mapping session using unleaded petrol.

Morgan, from the Shiftech centre in Tours, is overseeing the entire project. Several components need to be removed to gain access to the turbo: the lower cover, to reach the oil return and supply lines, as well as the windscreen cowl, which is necessary to access the engine cover, the air box and the expansion tank.

Once the old turbocharger has been removed, the comparison with the TTH 600 is striking: externally, the two turbochargers are virtually identical, with the same exhaust manifold, the same exhaust housing and the same compressor housing. The differences lie in the internal components: the compressor wheel, bearing and exhaust wheel are different, with the TTH 600 featuring a larger-diameter exhaust turbine, designed to deliver greater flow and therefore improved performance.

Morgan then reassembles the turbocharger before putting the car on the dynamometer.

During the checks, the Shiftech team discovered that the car had already been remapped, both for the engine and the gearbox. To start afresh on a sound footing, everything was reset to factory settings before carrying out a new Stage 3 remap for the engine and DKG gearbox.

Gearbox mapping is , in fact, mandatory from Stage 3 onwards, and strongly recommended from Stages 1 and 2: it improves gear-change times, clutch performance and the overall reliability of the transmission.

To see the power and torque figures achieved on the test bench, visit Lucien’s YouTube channel.