Mercedes' new V6 bi-turbo for AMG

We’ve driven it, it’s fantastic and the numbers prove it’s every bit as quick yet more fuel-efficient than the current V8, but does Mercedes-Benz’s new 3.0-litre bi-turbo V6 have what it takes to power AMG models into the future?

According to the engine’s developer, Adolf Kremer, that answer is a resounding yes. Though just what hardened customers used to the ‘more cylinders equals more power’ philosophy might think is an altogether separate proposition.

Speaking to motoring.com.au at the launch of the E-Class Coupe and Cabriolet in Europe this week, Kremer said that the 245kW/480Nm unit has potential well beyond its current tune.

Obvious sacrifices, such as fuel economy, will have to be made, but with a strong base to work from, increased boost could yield greater output.

But is it a possibility for upcoming AMG models?

“It’s possible,” exclaimed Kremer. “If you don’t look upon the fuel economy, you can rise it up [the power output] significantly -- 245kW is a bit conservative... it could be more.”

In its current form, the new bi-turbo 3.0-litre V6 is around 16 per cent more fuel-efficient than the engine it aims to replace (the 4.6-litre V8). Many of the savings made come via re-profiled camshafts and more precise piezo injectors.

Developed in conjunction with Bosch, the piezo injectors can open five times per firing cycle and are precisely controlled to burn only the exact amount of fuel required according to the throttle position, gear position, engine and road speed.

“We use piezo injectors from Bosch which open only 40µm (0.04mm), and they can do it five times per firing cycle. The third-generation piezo injectors mean we can do so much more with injection timing and camshaft profiles, though it’s important to note that the behaviour of every piezo [injector] is different.”

Kremer went on to explain how the trial and error approach of Mercedes’ rivals gave it a leg-up in refining the ECU calibration required to meet the slight manufacturing discrepancies of each unit. These slight differences in tolerance are then programmed into the ECU to ensure each injector is functioning at its optimal level.

“It’s much easier to work from the programming end backwards. Bosch test every injector [they supply] and whether the opening is 41 or 38 microns [the number] is added to the ECU, that’s how we make sure the amount of fuel used is so very precise.” he said.

The 3.0-litre engine is a reduced capacity iteration of Merc’s current 3.5-litre V6. The engine’s bore and stroke have changed from 92.6 x 86.0mm to 88.0 x 82.1mm. In two-door E-Class models it can accelerate to 100km/h in 5.2 seconds, only 0.1 seconds slower than the V8 and roughly a second faster than the previous E 350.

Besides changes to the capacity and the addition of two turbochargers, Kremer said the only other major alteration was a new cylinder-head on the right-hand side bank.

“Because we changed the crankcase ventilation and the drive of the fuel pump we needed to change the rear of the cylinder-head on one side,” he explained.

“The chain drive for the valve gear is unchanged -- it’s the same as the aspirated engine. We also added stiffer valve springs to withstand the new lift profile (10mm) and increased exhaust gas pressure.”

Merc has said previously it will ditch the E 550 when the all-new E-Class is released in Q3 2015. It’s likely therefore that an even more powerful version of the 3.0-litre bi-turbo V6 will take its place, as well as the place of many other models currently offering 3.5-litre six-cylinder and 4.6-litre eight-cylinder normally aspirated mills.

Watch this space.

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