Cayenne Hybrid explained

The hybrid Porsche Panamera will reach Australia some time next year, says Porsche Cars Australia MD, Michael Winkler. But it won't be the first Porsche hybrid in Australian hands. That honour goes to the Cayenne Hybrid, which has just been launched by the importer this week.

PCA has reduced its forecast for the petrol/electric SUV from 15 per cent to just 5 per cent of sales. Nonetheless, it's an important variant for Porsche and it signals the German prestige marque's future intentions.

While Wendelin Wiedeking, former Chairman of the board at Porsche was reported to have said that the company would never build a diesel -- and it now does -- there was never any such proscription against hybrids. And Porsche is very committed to hybrids.

This week, the Carsales Network drove the hybrid variant of the Cayenne (keep your eyes peeled for our launch review in coming days). In brief, it drives like a Cayenne V6 with slightly 'sudden' brakes. Otherwise though, the hybrid elements are not especially conspicuous -- not in the way that they can be in the Toyota Prius, for example.

There's a reason for that. Porsche has settled on a parallel hybrid system for the Cayenne, versus the power split system the Prius uses. The company claims that parallel systems are lighter and provide a freewheeling mode, which Porsche calls 'sailing' -- something not available in a power-split system.

As a bonus, Porsche claims that the parallel system can work without the "rubber band" effect common to CVT systems used in power-split vehicles like the Prius. Relatively, the Cayenne accelerates in a conventional, linear fashion.

Yet the Cayenne manages to offer the same sort of features as the Prius. It can drive two or three kilometres on electric power alone (up to 60km/h), it will recover spent energy during braking and practically everything that would normally be powered by hydraulics is electric in the hybrid SUV.

The nett result is a vehicle with all the practicality of an offroad-capable wagon weighing 2240kg; one capable of reaching a top speed of 242km/h and accelerating to 100km/h from a standing start in 6.5 seconds -- but boasting combined-cycle fuel consumption of 8.2L/100km and CO2 emissions of 193g/km.

Out here for the launch of the new Cayenne range, Porsche's Project Manager for the Cayenne Powertrain Product Line, Stefan Fegg, took Aussie journalists through the ins and outs of the hybrid variant.

"Brand new, on the market, our new Cayenne S Hybrid -- with a system power of 279kW and 580Nm and a fuel consumption of 8.2 litres [per 100km]," he began.

"The base of the car is a 3.0-litre V6 supercharged engine, but it's not a conventional engine. The only belt-driven component is the supercharger. We plugged in electrified power steering, electrified air conditioner and electrified vacuum pump for the brake assistance.

"The electrical energy comes from a nickel-metal Hydride battery, which is fixed under the floor of the luggage [compartment] -- with all the power electronics and the high-voltage lines, and a special hybrid engine management [system] that has double the [data processing capability] of conventional engine management...

"The main part of the hybrid is the hybrid module, consisting of a separating clutch -- which connects or separates the combustion engine from the electric [motor] -- and the electric [motor] itself. It's an internal-rotor synchronous motor that delivers 34kW and 300Nm.

"The electric motor is also used as the starter for the combustion engine and as the generator for the electrical power supply. We fixed the hybrid module in line, between the engine and the transmission. That's the opposite of the Toyota system. In the Toyota system, the hybrid module is a separate part on the side of the powertrain. We fixed it in one line and it's called the parallel full hybrid system. If you use the 'e' power button, you can [run] the electric drive up to a speed of 60km/h.

"The next function is 'boosting', [in which] the electric motor supports the combustion engine in case of maximum acceleration -- and then you have a system output of 279kW and 580Nm.

"The next function is 'sailing'. Sailing means if you lift the accelerator pedal, the separating clutch opens and the hybrid manager switches the combustion engine off. The car is rolling, nearly unresistingly -- just with the roll resistance of the tyres and the air resistance...

"The next function is 'recuperation'. While you're braking, the energy flow comes from the [wheels] to the hybrid module and fills the battery with energy. If you're braking harder, the [hydraulic] braking system of the car [complements the regenerative braking].

"The last function is the 'shift in load point'. That means during normal driving conditions, the hybrid manager sets the combustion engine to the point of best efficiency and the excess energy flows to the battery.

"In all Cayenne models, we have a new Tiptronic S eight-speed gearbox, with two overdrive gears -- the 7th and 8th gears -- to reduce fuel consumption. We have automatic start/stop function in the transmission and we have included the thermal management [system] for the transmission, to reduce internal friction.

"Also, with the new Tiptronic S, we have reduced the time for the gearchanges up to 50 per cent."

The new Aisin-supplied transmission is an important factor in the efficiency of the hybrid model. According to PCA Training Manager, Paul Watson, the new transmission comes with an electric oil pump, which continues operating even when the combustion engine isn't. In a conventional car, the internal-combustion engine drives the oil pump for the transmission, but with the IC engine in the Cayenne Hybrid frequently stopped while the car is in motion, the manufacturer needed to keep the transmission's internals lubricated.

An electric pump was the obvious solution. Without it, "drainback is quite severe," says Watson.

Watson also illustrated the lengths to which Porsche has gone in improving the efficiency of the new Cayenne range -- not just the Hybrid variant, but across the board. His example was the counterbalances in the crankshaft of the V8 engines. These are now thinner than before, but bulge out further, thus providing the same mechanical effect as the heavier counterbalances of the previous engine, through centrifugal force.

As National Training Manager, Watson also oversees Porsche technicians learning about the new Cayenne models, including the Hybrid variant. He says that the training of staff in the technical side of the vehicle is not the issue, it's familiarising them with the occupational health and safety issues related to working on the hybrid Cayenne.

With both AC and DC current flowing through the car and a voltage of up to 288 Volts, the Cayenne can be dangerous to the uninitiated, but as long as the appropriate forms are completed and anyone working on the car knows the state of play, it's not a problem. That's why the hybrid batter pack is isolated in the event of a crash, however.

According to the PCA exec, the safety regs for vehicle technicians have been developed by Porsche in Germany for its dealer networks all around the world. Most countries, including Australia, don't have OH&S regulations specifically covering the service of hybrid vehicles, but Watson says that it's less dangerous working on the Cayenne Hybrid than it is working around the home.

At the end of the day though, it's about commonsense as much as abiding by regulations. On that point, Watson says: "After all, you wouldn't stick a knife in a 240-Volt outlet at home, would you?"

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