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Comment by jonplackett | Hacker News Reader

Why were Porsche so stubborn about putting the engine at the back anyway, if it’s such a bad idea?

I at least understand why Apple want a no-button mouse.

Having the center of gravity in the back allows for more traction with the back wheels. This then leads to better acceleration since you can pit down more power. This also allows one to accelerate quicker out of corners, again due to more traction. Having g the weight be there over the back wheels also means that the car will tend to oversteer rather than understeer which is preferable when driving quickly. And turn in is quicker, as theres less mass in the front, as long as there's traction of course. The 911 is also one of the most practical car of it's type since it has a large trunk in the front.

Since most of the weight of the car is on the back wheels, do it really need an aileron? I’ve heard ailerons were of discussable usefulness in general already, since they are only useful when turning and problematic in straight line (friction of air, and adding artificial weight, risk of flying), and therefore they needed to be adjusted in live. Is it just for the looks on the Porsche?

Whether or it it is “for the looks” probably depends on which particular model you’re talking about. But adding downforce always adds traction.

It only matters at high speeds. Above 120 miles per hour, they provide stability.

It’s only a bad idea for street cars because it makes them harder to drive. For performance, it’s an excellent idea. It gives you better rear wheel traction, and allows you to connect the engine directly to the rear differential. It also allows you to have a flat floor, which makes the cabin nicer, which I’m sure is something they care about.

They fact that they go very fast, and require more skill to drive at fast speeds means they end up killing more people. Porsche used to make incredible, no-compromise, road-legal track cars, with manual gearboxes and very little driver assist. But they’ve toned that down recently, and you’ll never see it from them again. The Porsche Carrera GT was probably the absolute pinnacle of supercar design. But it was very hard to drive, and got a reputation as one of the most dangerous production cars ever made. Killing quite a few people, including Paul Walker. Nobody will ever make anything like that ever again. A novice could take a Veyron around a track, but they’d probably struggle to drive a Carrera GT out of a car park.

The benefits are primarily from the better weight distribution and engine location in relation to the rear diff. The myth of fwd having superior driveability due to better traction is only real when comparing front engine to front engine, like a civic vs a mustang. With the weight in the rear, it’s the same thing in reverse. Oversteer is far more easy to correct but rwd is uncommon so the average joe may be unfamiliar.

WRT Porsche toning things down, a modern 911 turbo S is WAY faster than the Carrera GT was, and the GT3 / GT3-RS models are literally street legal road cars with minimal assists.

It’s not about how fast they are, it’s about how easy the car is to drive. A GT3 is a road car made with road car parts and road car features (even if you buy the ‘track’ add ons, or whatever they call them). It has ‘Porsche Stability Management’, a powerful driver assist, which among other things, is especially good at controlling oversteer. The Carrera GT doesn’t have that, so controlling oversteer is completely up to the driver. It also had the first production ceramic clutch, which was notoriously difficult to use. The tires and breaks of a Carrera GT also really needed to be at proper temperature to work properly.

I’ve driven both, on the street and around a track. I’m not exaggerating to say the average stick driver would struggle to start a Carrera GT and driver it a hundred feet without making the clutch scream. If you try drive fast in one, whether you drive into a tree or not is completely up to you. In a GR3 however, it’s gonna do a significant amount of that work for you.

FYI the Veyron is NOT rear engined like the 911. It's mid engined, like most super cars.[1]

That's what makes the 911 a weird and unusual car.

1. https://en.wikipedia.org/wiki/Bugatti_Veyron

I don't think it's fair to say they were completely stubborn about it.

Porsche have used rear (e.g. 911), mid (e.g. 959, 917, 956) and front (e.g. 928) engine layouts over time.

The 911 is iconic though and customers like its design so they've persevered with it.

It does give them very unique handling. It's fun to drive an unstable car, and "fun to drive" is one of the main differentiators of sports cars from more mundane options.

I did a silverstone track day a few years ago in a single seater f1 style (but much slower) car with the engine at the back. It was super fun I agree, but also terrifying when I accidentally put it in 1st instead of third at the end if the straight and just instantly spun out. Luckily didn’t hit anyone or anything.

F1 cars in general are mid-engined (like Porsche Le Man cars) rather than rear engined like the 911.

So the engine is behind you but in front of the rear wheels. This is generally thought to be optimal layout for a super car.

Porsche used the mid-engine layout for the 959 for example.

Just to remind that a open wheel car or a single seat f1 style doesn't have the a rear engine like the 911, but is a middle engine car.

In fact, almost every car have a front or middle engine. The 911 is very unique in this rear placement layout.

My first car was a VW Beetle. I didn't know crap about cars, physics, handling, etc. The engine needed work so I had it rebuilt and it had pretty good power (for a Bug). Then one day I was driving fast on winding roads and quickly learned about the flaws of having a rear-engined car. I was lucky to walk away from the crash, though the Bug was totaled. Since then I've always had a fear of driving on winding roads...

First, to nitpick, comparative and superlative forms of unique are nonsense, something is either unique or it isn’t.

It might be pretty rare though, like rear engines cars: hillman imp, Fiat 500, etc and of course vw microbus and beetle which rather brings us back to the 911

> Just to remind that a open wheel car or a single seat f1 style doesn't have the a rear engine like the 911, but is a middle engine car.

yeah, but then with that pedantry applied the Honda S2000, BMW 3 Series, Mazda Miata, and various other cars are technically mid-engine.

FR/MR/RR is basically useless to talk about with regards to performance dynamics; HPDEs and driver coaching has taught me that 9 times out of 10 when someone mentions where their engine is sitting in the car by using FR/MR/RR , what they're really trying to get across is where they felt their center-of-mass was during the drive.

And to that point, a Formula style car might be mid-engine, but most have a suspension and aero adjusted center-of-mass that is as aft, if not worse, than any Porsche out there.

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