Porsche 911 992.2
The unusual powertrain designed for the new GTS T-Hybrid takes our thinking in new directions, including reflecting on jet engines.
When the 992 version of the Porsche 911 was announced in 2018, we all knew there was something sinister afoot. The instrument panel was now digital except for an analogue tachometer, it had a new PDK automatic transmission with extra room for something else to fit in there and no manual transmission was announced at that time. The Porsche world shook to its core. Was the beacon of performance automobiles getting ready for hybridization? Or was the unthinkable going to happen, were they getting ready to go fully electric?
With over sixty years of steady development, every successive version of the Porsche 911 risked driving the brand’s emotionally fragile fans to cardiac arrest. Despite the periodic drama provoked by every improvement over the years, we fans have managed to carry on and Porsche’s brain trust continues to forge ahead producing 911s. Let us review some particularly traumatic innovations of the past that were predicted to spell the end of the Porsche brand.
- 1968: The Sportsmatic Transmission, a semi-automatic gearbox meant for the US market, did away with the clutch peddle. In a Car & Driver article from that same year the distraught reviewers expressed their distain succinctly, “We don’t like it.”
- 1978: The front-engine 928, the planned replacement for the 911, was unveiled. Engine located in the front and quirky futuristic design far ahead of its time was a lot to swallow. Spoiler Alert: the 911 survived, the 928 did not.
- 1988: All wheel drive was introduced in the 964 version of the 911. We all relished the thrills associated with the 911 being little tail happy. Was driving all four wheels going to ruin the Porsche experience? It did not.
- 1997: the air-cooled engine, found in every 356 and 911 since day-one, was replaced by a liquid-cooled version of the flat six with the introduction of the 996. There are still air-cooled aficionados who do not consider post-1996 cars real 911s.
- 1997: The 996’s infamous fried-egg headlights replaced the circular ones and to put it mildly, were not a hit with everyone. Circular units were revived with the 997 variant.
- 2008: PDK (i.e.: automatic) transmission was fitted as an option and the following year offered as a variant in the model lineup. Paddles on a 911 steering wheel. Good Lord. PDK equipped 911s now dominate 911 sales but have yet to completely eliminate the traditional stick-shift.
With this and a long list of other changes, the 911 has continued to survive as the reference sports car and has retained a passionate following throughout its evolution. There are benefits to being a 911 fanatic but every time new technology is introduced, there is also trauma. I suppose this is the inevitable outcome of a car that was unique when it was launched and underwent minimal visual changes over the next sixty years. A brand new 911 is still unmistakably related to the original, even in the eyes of people who have little interest in cars. Contrary to car models that experience regular redesigns, we are dealing here with a car where minor changes are viewed as paradigm shifts. Reshaped taillights, door-handle modifications, slight texture revisions to the Porsche emblem are all discussed at length and in minute detail by the diehards. Whether we admit it or not we Porschephiles harbor the paradoxical feelings of wanting the car to keep up with the times while also wanting nothing to change.
Porsche leadership has always been keenly aware of this paradox and they more than anyone, know that successfully melding tradition with novelty is why the model has dominated for so long. Adding to this complexity, they are constantly faced with the Herculean task of satisfying a long-term customer base while introducing new members to the club. You don’t attract new buyers without keeping up with technology and adding popular features. Using a gentle touch, Porsche manages to evolve gradually, hold on to its identity and maintain the essence of what made the car unique in the first place.
The 992.2 is a perfect example of this balancing act. With its May 28th 2024 release, Porsche introduced two variants. It unveiled a base 911 Carrera with no groundbreaking changes other than slight performance and cosmetic modifications. These cosmetic elements include two enlarged front-radiator nostrils featuring vertical valances instead of horizontal ones, a slightly reshaped rear-engine grill, different headlight and taillight details, a digital tachometer replacing the analogue one and horror of horror, the iconic faux ignition-key has been replaced by a push button. Although trivial to the untrained eye, these changes will keep The Porsche community talking for some time.
Also on display that day was the new 911 Carrera GTS T-Hybrid, including the above mentioned cosmetic changes and more importantly, equipped with hybrid technology that everyone had been speculating about. We were all expecting a performance and soul sapping Prius-like system designed to save fuel. We have been naive so many times before in our assumptions, whenever we thought Porsche was about to compromise its high-performance car standards. This is a manufacturer that has never dialed down performance, instead it always emphasizes driver experience and when required to comply with new regulations, does so while also improving performance, or at the very least maintaining existing levels.
What Porsche did here was enhance performance using the type of hybrid systems employed in F1 and endurance racing while ensuring compliance with emissions regulations. In fact, the Porsche 919 racing car is equipped with a very similar setup. In the 992.2 GTS, Porsche did not simply bolt on an electric motor, it made a significant number of other changes. It started by fitting one large turbocharger instead of using two. It did that to reduce weight because it also attached an electric motor to the turbo, giving it a head start when spinning at lower revolutions. They went on to increase engine displacement from 3 litres to 3.6 litres. They finally added an electric motor to the additional transmission housing space they had created in 2018 for that purpose. A second battery was placed in the engine compartment. The engine management system controls and coordinates all these systems and also deploys regeneration to the new battery when both electric motors are not contributing to the car’s power. These measures have taken the 992.2 GTS’s output to 532hp from 473hp in the 992.1 with little change in fuel consumption.
The increase in displacement is a surprising twist. The addition of electrification usually results in smaller gas engines, not larger ones. Also different here is that I don’t know of a production car that uses both drive-train and turbocharger electric motors. If saving fuel is not the goal, there seem to be easier ways to add horsepower, so why go to these lengths? It turns out Porsche wanted to raise horsepower and responsiveness while ensuring it met increasingly stringent emissions standards. In order to achieve this end, the engine must operate at Lambda 1, engineer-speak for the factor that gauges whether the fuel/air mixture in an engine and exhaust scrubbing devices produce clean emissions. (See sidebar for a more detailed explanation of Lambda 1.)
What this elaborate arrangement boils down to is this, Porsche is looking for ways to keep the high-performance internal-combustion engine alive. What they are exploring here is how to use hybrid technology to increase power while meeting escalating emission standards. At the time of writing this article, reviewers are beginning to test drive the new GTS. First impressions are that you would not know it’s a hybrid and it drives like a car with a normally aspirated engine, meaning there is no noticeable turbo lag. I suppose Porsche is not really going hybrid; it is using electric motors to enhance the experience of the high-performance gas-powered car while producing emissions at Lambda 1.
A traditional high-performance engine can’t achieve Lambda 1 throughout all of its power band using traditional technology. The 992.2 generation GTS is effectively beta-testing many newly developed components and systems that all have to work together. The car is incredibly complex and I cover here just some of the many changes under the hood. Only time will tell whether these multiple components will endure over time in real-world conditions.
Sidebar: More on Lambda 1
Lambda 1 is the measure of the ideal air/fuel mixture that achieves optimal stoichiometric effectiveness. The formula considers both performance and harmful emissions and “1” is ideal. A Lambda number less than one denotes a rich mixture and a number greater than one indicates a lean mixture. Engine designers seek to achieve Lambda 1 throughout the power range. Lambda 1 can easily be achieved in modestly powered engines by using existing technology. High performance engines on the other hand, fail to do so at peak power, which is usually when running high in their rev ranges. Two properties of combustion work against these engines under those demanding conditions:
- Turbocharging allows for leaner mixtures at high power outputs. Lean mixtures under these loads tend to overheat the internals of the engine. The easiest and most effective way to cool down combustion is to add more fuel to the mixture, as rich mixtures burn much cooler than lean ones. In addition to the unwanted increase in fuel consumption, a rich mixture produces more harmful particulates that are released to the atmosphere.
- Even if exotic, extreme heat-resistant materials are used in engine assembly to keep the mixture lean, there is another problem. Fuels burning very hot create chemical conditions that release harmful nitrogen oxide gas (NOx) into the atmosphere. To the lay person, including the author, this characteristic appears counterintuitive. You would think that the leaner the burn the better the emissions.
The dilemma engine makers face is whatever they do to cool down their high-performance engines at high output levels, they are creating unacceptable levels of emissions. If they let them burn too hot, an additional component NOx is added to the list of harmful emissions produced.
Not surprisingly, this is a problem in the field of aviation as well. It turns out that jetliner engine designers are also aiming for Lambda 1.
When General Electric designed its Next Generation GEnx jet engines, it focused a considerable amount of its research budget on increasing combustion compression-ratios while moderating combustion temperatures. Designing optimally shaped fuel-injection devices and air/fuel mixture chambers for these purposes has proven so complex that 3D printing technology has been employed to manufacture these parts made of equally complex metal alloys. GE partnered with NASA for this project and the team has been working on these injectors since the mid-1990s. The current GE design has managed to reduce NOx levels by 60% from the levels produced by its previous injectors.
Back to cars and piston power plants. Porsche achieved Lambda 1 throughout the power range of its gas engine by combining the attributes of a higher displacement engine, a single electric-assisted turbocharger and electric motor connected to the transmission. The synergy created by the teaming of these power sources has resulted in increased power with less heat in the combustion chambers while producing acceptable emissions even at high power-output levels.