All new boxer beef powers 911 update

Talk about hiding your light under a bushel! Petrol direct fuel-injection might be the headline of Porsche's new 'Second Generation' 997 model 911, but the full story behind the new sportscar's engine room runs much deeper. Indeed, rather than just an induction and fuel system change, the 997 series two's boxer sixes are, for all intents and purposes, all-new.

More compact, mounted lower and sharing virtually no parts with the engines they replace, the new 3.6 and 3.8-litre engines that power the new Carrera and Carrera S models achieve the holy grail of today's powertrain engineers -- more power, more torque and yet lower fuel consumption and reduced emissions.

Coupled with the new PDK seven-speed dual-clutch automated manual gearbox, Porsche's development engineers say the new powerplants have achieved fuel economy improvements of up to 13.2 per cent compared to corresponding series one 997 models.

In addition to meeting or exceeding Euro V emission requirements (not due in force in Europe until September 2009), both engines have received power and torque upgrades to the tune of up to 22kW and 20Nm.

The new engines have revised bore and stroke dimensions and are redlined at 7500rpm -- an extra 200 revs compared to the previous version. That said, power and torque peaks have both moved downward a touch on both the 3.6-litre Carrera and 3.8-litre Carrera S power plants.

The previous 96 x 80.2mm (bore and stroke) 3598cc Carrera powerplant pumped out 239kW at 6600rpm and 370Nm at 4600. The latest series two 3614cc powerplant (97 x 81.5mm) produces 254kW at 6500rpm and 390Nm at 4400 revs.

In the case of the new Carrera S powerplant the differences are even more marked. Significantly more oversquare, slightly smaller series two 3800cc engine (down 24cc) has a 5.3mm shorter stroke and 3mm bigger bore than the engine it replaces. Final bore and stroke dimensions are 102 x 77.5mm.

Its peak power figure of 283kW is up 22kW over the previous generation engine, with torque 15Nm up to 420Nm. Both peak figures at the same revs as the cooking-model Carrera powerplant.

Porsche has gone so far as to have changed the design of the most basic components of the engine -- for example removing the ladder frame style bearing supports for the crank and camshafts. There's a new cam drive design (still chain but without the intermediate shaft) and the inlet and exhaust systems are also new.

This simpler architecture means less parts (around 40 per cent says Porsche!) without compromising strength or durability. Says Porsche's boxer engine development team leader Thomas Wasserbach, the new powerplant is 22 per cent more rigid than the series it replaces.

Rotating mass has been reduced and overall mass is down around 5kg, Porsche claims. This is despite all the direct fuel-injection (DFI) hardware including an all stainless steel fuel system -- required so the new engine is 'safe' with all fuel types (including high ethanol content blends).

Both variants of the new powerplant also feature an electrically-powered 'on demand' oil pump. The 'heart' of Porsche's 'integrated dry sump' oiling system, the electric pump frees up 3hp and contributes around 2 per cent of the fuel economy improvement the new engines boast.

Powertrain development these days is a game of many small gains, it seems.

In addition to the use of detailed changes like the use of low friction coatings on components such as piston rings and tappet buckets, the new engines also boast maintenance enhancing features such as a new two-stage air filter with a service life that has been extended from 60,000 to 90,000km.

Though Porsche is not giving away details on the rest of the new generation boxers, the latest 911 models herald a step change for the revered boxer six. As is the normal practice, the full range of 911 variants using the new engine architecture and its DFI fuelling will be rolled out over the next few years. This will include turbocharged versions and a variety of capacities, including smaller displacement naturally-aspirated engines for the Boxster and Cayman ranges.

First to debut will be the all-wheel-drive Carrera 4 models in around six weeks. These will be followed by Boxster and Cayman models featuring DFI and the option of PDK sequential gearboxes. It's expected the mid-engined Porsches will be unveiled at the Paris motor show in early October.

Porsche insiders say the 911 models' increased performance in its latest series will allow top-spec versions of both the mid-engined models to step up to higher levels of horsepower, which in turn will free up space at the very entry-level of the Porsche sportscar range. In the medium term therefore, don't bet against the return of 2.5-litre 180kW (approx) starter cars wearing both Boxster and Cayman badges.

Porsche's flagship 911 models, the Turbo and the various GT variants are at least 12 months away.

Under current FIA GT rules direct fuel-injection is outlawed. As such it's not clear whether Porsche's GT3 homologation model will adopt the same architecture as the series production models.

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