The Porsche 911 RSR has moved its engine forward of the rear axle. Why? And why was the engine behind the rear axle before now? We explain...
In order to understand why the engine placement that Porsche had been using since the inception of the 911 model in 1964. To put it bluntly, technology, engineering and science have all come a long way in those 52 years since the first 911 rolled off of the assembly floor. The car began with racing intentions from its very beginnings, although with a humble horsepower figure, barely in the triple digits. The now-world-famous air-cooled flat six barely breathed above 120 horsepower, in its first years. This was a fairly good thing for the drivers, though; it was more than enough power to propel the car up to speeds where the limited grip of its now-dated tires could easily spell disaster for any person whose bravery exceeded their talent.
But, from the beginning, the 911's designer, Ferdinand Porsche (in this case, the junior of the two) stubbornly insisted on putting the engine in the back of the car. Why? Why would anyone want to put the engine in a spot where the car becomes more difficult to drive?
There are two reasons, actually. The first one is traction. When a vehicle is stationary and about to set forth into motion, then the weight of the car will shift backwards, pressing the tires into the road. If the engine, and therefore the weight, is already sitting on the rear tires, then the car has an ever-so-slight advantage in traction. That's not the main reason why the 911 was rear-engined, but it's a big bonus to the actual main reason.
The main reason, however? Well, it meant that - once the car had gotten up to speed and was approaching a corner - the rest of the performance, be it corner entry direction changes, or braking, (but hopefully not both at the same time, you maniac with a deathwish! This is a Porsche!) or corner apex slip angle. You see, forgetting what I mentioned about the stationary car thing before, where weight transfer helps to improve traction at stationary-to-low speeds, there comes a point where inertia and momentum far exceed the amount of extra grip supplied by the weight transfer. In other words, with higher speeds, the very same advantage in low speed traction works against you, by hindering cornering performance. That weight makes the car lazy, and it won't turn nor change directions as quickly as it labours under the intense load you place on it.
That huge load placed on the tires overwhelms the tires, and suspension, and the car is no longer even nearly as nimble as it would be without that engine being where it is... At least, it wouldn't be as nimble as that, if it had a normal engine placement over the front wheels, like a C1 Corvette with even narrower tires. Placing the engine over the back wheels, however, meant that the front of the 911 became agile, where the car's front half entered the corner with such vigor that the rear ended up sliding out if you weren't careful. But, in capable hands, this gave the driver an upper hand. The 911 could enter corners faster, brake harder and generally handle better with the same tire size. Why did early 911s take aim at the Corvettes, even though they had very narrow tires? Because of the balance and poise of the rear-engined platform.
Porsche were so proud, that they continued using almost uniquely rear-engined cars ever since. Every subsequent iteration saw a power bump. The later cars became less hellish to drive, too, with further iterations increasing the tire width and the tire grip, until even big rear spoilers were being fitted to keep the car in contact with the ground, while also helping to keep the air cooled flat six engine fresh, supplied with cool air coming from the laminar airflow over the rear window. You know that famous Porsche shape? It was dictated by the necessity to have airflow staying laminar (attached, not turbulent) around the rear window to prevent overheating issues.
Then came the 1990s, when suddenly the 911 was in its final air-cooled iteration. By then, the rear-engined platform and shape had become quintessentially 911, like milk and cheese, or Queen and Purple Rain. The aerodynamic design was open for more crazy airflow trickery, including the first generation of the 911 GT3RS to go from a dual-purpose engine-cooling spoiler to a proper GT wing. After all, there was a radiator in the front bumper now. Which, by the way, if you own a Porsche, don't think that you're safe to hit your front bumper into something without damaging your engine anymore!
Downforce figures began to skyrocket with the new watercooled 911s. They rose and rose and rose, up until the governing bodies of motorsports told them to stop adding downforce to the back of the cars. By 2009, the rear wings on 911 GT3 RSR cars were getting to be massive, in some cases spilling over the sides of the cars, like a square muffin-top.
Then, without much warning, in 2016, IMSA decided to reduce the amount of downforce generated by the wings and diffusers, but only one the back ends of the cars. The front downforce figures could remain unchanged. The engineers saw years and years of work on balancing the aerodynamic balance to suit the rear-engined layout of the car disappear. Cars like the Ferrari 488 with its mid-engined platform suddenly had a large advantage once more against the Porsche. Something had to change.
How do you fix a 52 year old tactic that turned into a curse?
I have a confession to state out in the open: from here on out, the article is essentially an educated guess. I'm 99% sure that the information I am about to explain to you, dear reader, is somewhat accurate. But, I can't give you any details because it is untested and unproven. If you happen to have millions of dollars and want me to develop and test this theory in actual practice, I will gladly do that. But, for the purpose of simply explaining why this change would happen so suddenly and so dramatically, as to be - possibly - the first mid-engined 911 ever.
Let's recall from the earlier paragraph, that only rear downforce was reduced by IMSA. The drivers in the 2016 campaign complained and complained that the car was harder to drive and less stable than the competition, in their Corvettes, BMWs and Ferraris, which weren't rear-engined platforms. Nick Tandy, Earl Bamber and the rest of the Porsche team were struggling to find a setup that helped to overcome the aerodynamic problems they encountered but there was no solution. The previous 911 RSR had been "grandfathered" into IMSA competition and its replacement was already being designed.
The concept of an aerodynamic deficiency was earth-shaking to the Porsche team. Porsche depended on its rear downforce figures as a lifeline. Front downforce wasn't even as important in comparison. You see, downforce is most effective on lighter cars. If you have a 1000 pound car, but 3000 pounds of downforce at 130 miles per hour, then that 1000 pound car, on the right tires, can actually hit around double the gravitational forces (aka g-forces) that act on a 2000 pound car with the same downforce figure. The math doesn't work out that nicely, but, the essential idea is the same.
For a full explanation on why this works this way, check out this video by my friend Kyle: https://www.youtube.com/watch?v=abheF2qkenE&list=PL6R7zR4ZbGkOny_RGsc2V3DULdd2SPwSU&index=11
So, if reducing the weight improves the efficiency of the downforce your chassis creates, what does moving the weight of the chassis do to the aerodynamic balance? If you moved the engine of the 911 RSR forwards, you would have a greater aerodynamic balance towards the rear of the chassis of the car. That enables the designers to negate the problem of the reduction of the aerodynamic downforce of the 2017 911 RSR to comply with IMSA Weathertech Sports Car Championship regulations and homologation. And, according to the rulebook, Porsche were fully able to move their engine a few inches forward. This Porsche 911 RSR they unveiled for 2017 cleverly utilizes the rulebook to reposition their team back in the fight with an equal car compared to its rivals again.
When you apply science and engineering to a problem imposed upon you by the governing body of motorsports. This is what I love about motorsports now. The amount of engineering and so on that goes into these cars which is based in finding the most efficient, most simple way of changing something... It's amazing to see. This is what Melons' Better Driving loves to see.
Great job, Porsche engineers. That was clever. I raise my glass to you!
Andrew Geier is an accomplished automotive enthusiast, with 15 years of automotive experience. At age 22, he created Melons' Better Driving in an effort to make people rethink the automotive world with insightful vision and articles about the future of the automotive culture and all of its subcultures, including motorsports. Seen in the site's background image, examining a road which was torn up by rally cars with his friends, his passion is clearly demonstrated by his excited pose.