Rear Engine versus Mid-Engine Handling
 

It's an old debate: 911 vs 914 -- which handled better? 911 vs Caymen -- Which handles better?

Here's an interesting take on the discussion by Car and Driver (which I haven't subscribed to in decades). I saw a back issue in the service station while getting one of our cars inspected today and noted that they had a video link which I just looked up.

As a 911 driver, I have to admit that they didn't discover anything that I didn't already know. It does seem to me that the "Dark, Rainy night test" was thrown in there so that the Cayman would win something, and provide a springboard for them to say at the end of the written article something to the affect of "and if the Cayman had a little more engine, and a little more tire, the results would be different".

There is a conventional wisdom that rear engined cars are evil handling (thank YOU Ralph Nader!) and people are determined to validate that world view any way that they can.

Sorry, but IMMHO rear engined cars ARE EVIL HANDLING.

It took Porsche many years to come up with a rear suspension geometry that was at least more benign.

And stop blaming Nader, it was PURELY GM's "fold-under" rear suspension that put the EVIL in rear engined cars.

I read the article on that in Car and Driver I think it was last month, and after reading it I came away a little disappointed. Sure the 911 came out on top, but I think the entire advantage came from the tires. And while Car and Driver acknowledged that that tires and engine had an impact, why didn't they just conduct the test with the same set of sticky tires on both cars?

I would like to see another magazine or website redo this test, and to equalize the tires. Then we will see who walks away as the champ, my money is on the Cayman.

Hmmm..

What was the stearing ratio for the Cayman vs the 911...?

I have owned many 911's and many 914's and in my opinion, for what is it worth, the 914 is one of the best handling cars I have ever driven. Nothing beats mid-engine. I had an '01 NSX (mid-engine) and it too was terrific.

My first car was a Corvair, fell in love with Rear engine cars. Porsches beat me up all the time. I knew that one day I would have one. When I got back to the world, I had enough money to buy a 914 outright. That car was so fun to drive. As time went on I moved up to a 911S, 911 SC now a Carrera. Still love them.

I'll answer a question with a question. How many race car builders build rear engine cars?

As a kid growing up in the hills and twisty roads of east Tennessee, my first car was a 62 corvair monza sport coupe, and being a kid and not yet an engineer, I discovered first hand that mass, speed, centrifical force are not good buddies. Indeed they do not play well together. I lost the car on curve, did a 180 and almost wiped out a young family. At the end of it, no one was hurt but we were all shaken. I immediately learned respect for the car and with it, the knowledge that designers don't always get it right. The kid that later bought my car did not fare so well, he too lost it on curve and was wiped out.

I've since owned 2 911s and one 914. The 914 corners like a mad centipede. Flat and predictable and is IMHO a better, all round safer design, but I love the 911s, I'm totally hooked, but I drive them very conservatively. You lose control and there''s hell to pay.

g

Two words: Vic Elford.

13 more: While he could have any Porsche he wanted, his favorite platform was/is....

I thought the same thing. They went through all the trouble of measuring polar moment of inertia but they did not equalize the tires? That makes the quantitative results pretty moot since the Cayman would perform a lot better on sticky tires.

If you're asking about manufacturers of formula cars and sports-racers (like Lola or Dallara), I don't think that it's not really meaningful. With the exception of the FIA prototype rules in the 70's that required "trunk" space, those cars are specifically designed to do one thing only -- get around a race course. There are also other aspects of the design such as aerodynamics which enter into the picture. As such they don't have anything to do with the real world. Porsche 911's were not designed as racecars for the street. They are designed as street cars that can make terribly effective race cars.

In the real world where accommodations for 2 or more people are required, as well as trunk space and head and shoulder room, it's not clear that rear engined isn't the better solution. A lot of handling also depends on the driver and how they use the capabilities of the car. Personally I maintain that the rear engine weight bias and longer polar moment provides opportunities for better managing the traction than a mid-engined car. So it's not necessarily easier to drive, but the ultimate potential may be higher.

The nearest analogy that I can think of is in the world of Martial Arts. Most people would maintain that katana (sword) is a superior weapon to the humble staff. It's lighter and handier, and has an edge for cutting. But the simple staff in the hands of a knowledgeable user will consistently defeat the sword because it has more options for the attack or defense than the sword. They may not be obvious, but they are there.

Getting back to cars -- C and D suggested that with a bigger engine and tires that the Cayman might be faster. It might be interesting to compare the Cayman R to for example a 996 GT3 to see how it fares. In that case the results might be closer, but it's not clear that the 911 still wouldn't win. Looking at the tests in turn...

Acceleration and Braking: Even with the same Power/weight and frontal area, the 911 will exceed the Cayman do to the weight distribution. It's more balanced under braking, and more heavily skewed towards the driving wheels under acceleration. Definitely 911.

Skid-pad. If you gave both cars the same tire foot-print, but allowed the tires to be sized to match the F/R weight distribution of both cars, it's not clear to me that the results wouldn't pretty close between the two of them. Even

The Slalom seems to support what I was saying about how a car is used. The 911's speed varied more through the slalom compared to the Cayman. This is the edge that the 911's weight distribution affords the driver -- they can actively modulate the understeer/oversteer a lot more because of the weight bias and the slower response of the longer polar moment. With a mid-engined car, you've got the balance that you've got -- if you go over the line a little bit it will spin. With the 911 you can dance on both sides of "the line" and still bring it back of you know what you're doing. Even with more power and tires, it's not clear that the Cayman would beat the 911. So I'd say 911.

"Race Course Segment" - more of what I described in the slalom paragraph.

Spin Threshold -- Look at the difference in performance between the two cars -- 10 MPH!!! That's the key! This test would most likely be all 911 no matter what the HP or tire size.

"Dark Rainy Night" - This seemed to be more of a tire test than anything.

So even if "all things were equal" (including the tire footprint), it looks like the Cayman might swing one of the tests it's way -- but the 911 would still win the rest.

Just my $0.02

Any weight overhanging the wheels takes weight off of the opposite end. If you have weight overhanging at both ends then you have a nice even distribution of weight on the tires (like with onverhanging wings) but if you have an engine out the back and nothing in the front then you have less weight on the front tires with the engine in than with it out. You steer with the front wheels remember? Good idea to keep the fuel tank full and put the oil tank up there, but then you spoil the low polar moment of inertia.

Front engined cars are evil handling too.....I'll take rear engined over front engined all day long and twice on Sunday!

Scott

I think the spin out was 85 versus 65 mph. That's 20 mph advantage to the 911.

After reading this a few weeks ago, I'm inclined to agree with you.

An Illustrated History Of Automotive Aerodynamics – In Three Parts | The Truth About Cars
http://images.thetruthaboutcars.com/...05-527x349.jpg
http://images.thetruthaboutcars.com/...tatra87ad1.jpg

Seriously...?

I think the average driver is much more able to cope with front-engine vices (limit understeer, power oversteer) than rear-engine ones (trailing oversteer)... in a front-engine car, you simply lift, and things will most often straighten themselves out. Try that in a 911 :eek:

But perhaps you were kidding...

Regards

d.

If by "swing axle" we mean that deplorable "system" later found on the Bug, then blame the swing axles; at least 98.746% blame there. If one doesn't have a suspension that works well under lateral load, then one has a bad handling (if not potentially lethal with enough power) car from the get go. I'd propose that if they had mounted that potent V8 up front, they'd still have wrapped their cars around something as the swing axle would've "given up" with speed and cornering load.

In my very inexpert opinion (and very modest experience with driving a mid-engined cars), I'd opt for the rear engine. That very low polar-moment of inertia that is a boon in a mid-engine car also is a knife edge when the rear does come around ...it just happens faster than in a rear-engined car. In this way, I find the rear-engined car "safer" in that it is easier to read at the limit. And compared with front engine?...Nah! I just love the dynamics of a good 911!!

Edward

If you put two equal drivers on the track in a 914-6 and a torsion bar 911 with the same Hp/Torque and the same wheels/tires i would not bet against the 914.

Here is the article:

The Mid- vs. Rear-Engine Debate: Porsche Cayman R vs. 911 GT3 - Feature - Car and Driver

I'd like to get my 911 on that platform! (photo, bottom of p. 1)

All cars set up to handle "neutral" will have trailing throttle oversteer. While I suspect the mid engine car may ultimately be faster, the 911 is actually easier to drive at the limit. If you autocross/race a 911 for any length of time and experience the tail stepping out, you'll realize that it steps out in a slow and deliberate way. This is due to the larger polar moment. I'm more afraid of my wifes Boxster on the track than I am of my 72 911 race car. Mid engine cars seem to snap spin (due to less polar moment) and require quicker reactions.

-Andy