This is a common trope without adequate evidence I've heard from Boxster/Cayman owners when arguing why their car is better than a 911. While I won't deny the 718 platform handles great, so do modern 911s. The 911RSR went mid engined to allow fitting a bigger rear diffuser.

Within reasonable limits, rear weight bias is good. It helps with traction when accelerating a RWD car, and it helps even out braking forces when slowing down. Also, when a vehicle turns (ignoring rear wheel steering for now), it rotates about a point in line with the rear axle. The closer the centre of mass of the car is to the rear axle, the lower the mass moment moment of inertia about the point of rotation (note that moment of inertia is about a point of rotation, and you can use the parallel axis theorem to compute the moment of inertia around a different point on a parallel axis). Having the centre of mass further back (closer to the rear axle) makes it easier for a car to rotate about the axis it turns around.

There's a reason why rear-engine 911s outperform (lap times, acceleration, and braking) mid engined Ferraris/McLarens/Lamborghinis/Corvettes with superior power to weight ratios. Also, do you wonder why the C8 Corvette adoped a 911-like very rear biased weigth distribution, rather than a more balanced weight distribution like the 718? It's because being more rear heavy than a 718 improved performance.

Fundamentally, the benefits of a mid-engine layout are more complicated than just moment of inertia making it easier for a car to rotate. A mid engine layout changes how the car reacts, putting more weight on the front axle, giving more front grip, and changing the dynamics of the car when skidding (where the axis of rotation is no longer in line with the rear axle). Not necessarily better, but different, and perhaps more intuitive. Also, it allows fitting a bigger rear diffuser, as Porsche did on the 911 RSR or 718 GT4.

On a separate note, don't say "polar moment of inertia" as that is something used in calculating torsional stiffness; "moment of inertia" or "mass moment of inertia" are the correct terms here.

 

My SA told me they will produce the GT4 in 2021 and 2022.

 

^ This is a very likely scenario. Since MY22 is legal in NA and possibly all of RoW, I'm betting that we'll see current gen 982 variants in '22. Even if there is a gap in production time line with next gen, we should have seen at least some protos running around. Nada! So, we might have couple of MYs of life left. There was a report about 25th Anniversary to drop; so, there is that.

 

Wizee's explanation was quite scientific, my brain is not smart enough to put it in such words lol! Mine is going to be in much more lament terms, having an RR platform allows the car to trail brake into corners and much later braking as you can load up the front a lot more. Also helps with the acceleration as it provides more traction having the most weight around the rear wheels.

The 911 RSR engine was moved forward to incorporate the rear diffuser as previously stated. And if I remember correctly it was only moved about two inches.

 

Agree, a lot of science up there. I’ll be more simple as well, if the rear engine lay out has some sort of inherent advantage then why does no other competitive manufacturer use it? I would venture to guess there must be some legitimate reasons to avoid this layout or the race track would be full of rear engined competition. Not to mention the sports car market. And for the record, I am certainly not bad mouthing the 911 or it’s handling. In a money is no object world I would have bought a 911 GT3T, not a Spyder.

 

I'm not saying there aren't advantages the the rear engine layout as the two main ones that jump out are traction at launch and trail braking but a mid engine car will have the better handling dynamic overall, with everything else being equal. Porsche has spent 50+ years trying to make the layout work and has moved away from the widow maker nicknames to making the rear engine layout so tame now where people are saying it's moving into gran touring territory.

Formula 1 has spent the last 50+ years with the mid engine layout as well as F2 and F3 even when F1 was allowed to basically do whatever they wanted in developing their cars in the early days. Nobody switched to a rear engine layout. Corvette just recently switched to a mid engine layout when they completely redeveloped their car. ...and Corvette fans are as loyal to their brand as 911 folks are to their brand but they took the leap of faith because they said they weren't able to extract anymore performance gain from the front engine layout. They could have gone rear engine but didn't. As far as I know, the main cars in automotive history that have the rear engine layout are the bug, 911, and VW bus and of course, they're all from the same parent company and the 911 is a directive of the bug from the early days.

Hey, don't get me wrong. I'd take a 911 GT2 RS with all the toppings but I don't have that kind of money so I got the Spyder. The 911 is a great car. It has a great history and it performs very well.......but if say someone were to ever develop an exact equal but in a mid engine layout, the 911 as we know would lose out in race conditions.

 

You keep saying this, but don't actually back it up with physics. If the 911 were handicapped by its rear engine layout, someone would have made a road car that performs better with a similar power to weight ratio.

The rear-biased weight distribution in an RWD car gives:

• Better traction in acceleration
• More even weight distrubution betnween front and rear axles in braking, which helps stopping distances and trail braking
• Centre of mass closer to the axis of rotation, for more agility

Much of the handling deficiencies and "widow maker" tendencies of early 911s were due to the trailing arm rear suspension rather than the weight distribution. While having the centre of mass too far back in the car certainly has its issues, the roughly 40:60 front:rear weight distributions 911s have is pretty much ideal for rear wheel drive cars. That's why Chevy copied the 911's rear heavy weight distribution with the C8; while it's mid engined, the 40:60 front to rear axle weight ratio is identical to the rear-engined 992. Many mid-engined cars (eg. Lotus Elise/Exige and Evora) are more rear heavy than the Porsche 911, yet nobody talks about how they're handicapped by being mid-engined.

People keep parroting that mid-engine is superior "because physics" but they don't actually understand the physics or realize that the 911's weight distribution is near identical to many of its mid-engined competitors.

I'm not saying that the more rear-heavy, the better, but the optimal weight distribution is closer to the 911's 40:60 rather than a BMW M4's 50:50.

 

Obviously rear engine is superior, that's why Porsche's halo cars like the Carrera GT and 918 Spyder were rear engined! Oh wait...

 

It's hard to package a long V12, V10, or even a V8 in a rear engined car without getting a really wonky shape with the engine sticking way too far out back, rear being too tall, and an excessively rear heavy weight distribution. The rear engine layout only really works with flat four, flat six, which nobody else builds other than Subaru, or transverse inline four engines. This is why you rarely see rear engined sports cars from other brands. Instead, they build mid-engine V8 or V10 cars with the same 40:60 weight distribution as a 992 generation 911.

The C8 Corvette, Audi R8, Huracan, Testarossa, and many others have a 40:60 weight distribution. The Lotus Evora has a 39:61 weight distribution. Ferrari 488 has a 41:59 weight distribution. The Carrera GT's 42:58 rear biased weight distrubution is not too different from the 992. The 918 has a 43:57 distribution, but it's all wheel drive, so the weight over the front can be better put to use.

Academic studies have also confirmed the 40:60 weight distribution of a modern 911 is generally optimal for RWD cars, eg. https://link.springer.com/article/10...239-008-0037-2

 

I think this is correct in reference to the RSR, but I recall reading somewhere that Porsche has moved the engine forward with every generation since the 964?

 

This thread is totally off-topic.

I would like to remind everyone that is an engineer: You are not the only one and this is embarrassing.


As for the 718 being the last MY.
I remain uncertain.
I would be quite surprised if the next cayman is electric, unless the lineup takes a short hiatus between generational models.

 

I would add that while the party line for the rsr going mid-engine was for aero reasons, there were many other benefits as well even thought the actual front/rear weight distribution hardly changed. One of the bigger advantages was reducing rear tire wear, by changing where the weight was they could get more out of rear tires. I don't know about the current rsr but in older gens often when cars got hit with BOP adjustments, the cars would need to carry additional weights potentially even ahead of the front axle to balance the rear engine so even more weight at the extremes. With the mid engine layout there's a lot more flexibility for where to carry any additional weights between the wheels. None of these are particularly relevant to street cars sooo.....

 

Thank you for all your feedbacks. I’ve noticed my SA and he will try to find out more later as any info will be unveiled. It wasn’t an official confirmation but more of the words from the management so I’ll keep keep waiting and hoping MY2022 will be available still. However, if not, I don’t mind finding a pre-owned 718 spyder which shouldn’t be difficult.

 

I spoke to my SA in Canada today, and he's been told that MY2021 will, indeed, be the last year for this platform (at least in Canada), and this includes the RS which will make a limited 2021 run.

 

SA's do not know. Porsche will release it when they have decided.

Everybody thinks that SA's have some special classified clearance to give them unreleased info. This is simply not true. SA's are just as in the dark as everyone else. SA's mostly work for a low base salary and get commissions. I highly doubt Porsche Corporate would release that info. to SA's