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MERCEDES AMG PETRONAS TURBO

ALL THE teams are using new engines in Formula 1 this season, turbocharged direct-injected 1.6-liter V-6s. But innovative packaging of familiar technology is putting the Mercedes AMG Petronas team at the head of the pack.

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The Mercedes AMG Petronas Formula 1 car; four wins for four in 2014, including the Chinese Grand Prix, April 20, 2014.

Formula 1 subtleties are usually arcane, but this innovation and its resulting benefits are easy to understand.

Briefly, it has to do with a rethinking of the turbocharger.

The idea of forced induction, of course, is to cram more air and fuel into combustion chambers, thus making more power.

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The basics of turbocharging. Image from Garrett AiResearch.

A turbocharger performs this forced induction by exploiting energy of the engine’s exhaust. By the way, this exploitation is one reason the 2014 F1 cars are less noisy than their normally aspirated counterparts of recent years.

The turbocharger has two elements: a turbine, which gets its spin from exhaust heat, connected to a compressor that increases the pressure of the engine’s intake charge.

In a traditional turbo, these two elements are in one unit with a short shaft linking them. This packaging is tidy, but its efficiency is hampered by PV = nRT, the ideal gas law.

Pause here for some Physics 101. In the ideal gas law, PV = nRT, P is pressure, V is volume and T is temperature. R is a constant, the ideal gas constant; n is a chemical measure of the particular gas, its amount of substance as characterized in moles.

Don’t ask. Let’s ignore n and R (which probably got me in a whole lot of trouble back in college physics). Instead, think about the relationship of pressure and temperature within a given volume: As the pressure of a gas increases, it gets hotter.

Not only hotter, but less dense, which is counter to the whole idea of cramming air and fuel more densely into the combustion chambers.

It’s a pity the compressed charge gets so hot.

Ideally, a turbo’s turbine should be close to the exhaust, better to exploit heat. But a turbo’s compressor should reside in cooler surroundings, better to enhance charge density.

Which is exactly the idea of the Mercedes AMG Petronas turbocharger. It is split into two separate components: a turbine unit to the rear with a short path from the exhaust ports, and a compressor unit located forward, away from engine heat and with a direct path for cooling air.

The only tradeoff is its lengthened shaft nestled in the engine’s vee between the two units.

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Mercedes AMG Petronas Formula 1 engine, viewed from the right. Its turbine is aft of the engine block at the rear. Its compressor resides under the three-pointed star enclosure. Forward of the block is the car’s hybrid battery pack.

Separating the turbo’s two elements eases plumbing too. Exhaust goes directly aft to the turbine. Forced induction from the turbo’s compressor gets isolated plumbing that goes forward into an intercooler exposed to cool air and then back to the intake ports.

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The intercooler is in the car’s left sidepod. The turbine unit can be seen to the right aft of the engine.

Enhanced efficiency of Mercedes forced induction is said to give perhaps 50 more horsepower, a significant advantage. What’s more, the compressor’s cooler location allows a smaller, lighter intercooler with lower losses in its operation.

Kewl, eh? ds

© Dennis Simanaitis, SimanaitisSays.com, 2014

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This entry was posted on April 20, 2014 by in Driving it Today, Sci-Tech and tagged , , .
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