Cornering, handling and the 911

[surflvr911sc]

True, the M cars are different animals, but I'd still miss my 911.

[nostatic]

I'm trying to talk my wife into taking her A8 to the track. She evidently has done a few high speed runs down the 110 fwy (below Pasadena...the fun part) at rather high rates of speed. 300hp and quaatro good...

I have to disagree somewhat though. I've driven a few M3 coupes, and they didn't feel as visceral as the 911. The M Coupe was closer, but even that felt more disconnected than my SC.

[snowman]

Yeh, they are still 3 series. Entry level stuff

[dickster]

After having the car down for 3 months for the engine conversion, I felt like I was in a go-cart just driving it down the street at 10 mph. It still feels that way, even at 100+ mph.

thats the difference for me with a 911 - the speed is effortless. i just had a friend drive alongside me on the m/way to check the accuracy of my speedo. it had been reading 80mph, but it felt more like 50-60mph - it checked out ok.

[Jack Olsen]

I mean, think about this, you take a basic 4 door, car, with 5 passengers in it, and its capable of beating a 911, on the race track!! JUST DOWNRIGHT AWESOME! And thats with the AC turned ON.

My car has nice, cool air conditioning. You wanna race your 6 against my 911?

The bigger BMW's are great Autobahn cruisers, but they're not really ideal for a track. Too much weight.

The M3 is a very decent track car, though -- in my opinion.

[djmcmath]

I don't know about Bimmers our Audis, but I do know that every time I drive my P-car, I'm grinning the whole way, no matter where I'm going. I always come back from a drive exhiliarated. Is it the raw driving feel, the "visceral" nature of the car? Is it the weight distribution and suspension design? Beats me. I just enjoy driving the darn thing.


Dan

[goliver]

Talk about tail happy. I had an M6 and it was a pig! My 911 would smoke it in any contest except fall asleep ho hum boredom while driving. If you want comfort and high speed prowess get a 928. I use my S4 for the long drives and the 911 for urban assault missions.

Cheers,

Geoff

[island911]

Originally posted by Matt Holcomb
Another significant factor is an exceptionally low center of gravity.

I'm always amazed that this is lost on so many 911 owners.

If there is one theme of the 911 (pre 89) it is low C.G.

(Anti) swaybars on a sedan are no substitute for a low C.G. (it's a tire loading thang)

[Jdub]

Shrup: Great news! Where are you taking the car to have it aligned?

What I notice most about the Pcar is the need to keep both hands on the steering wheel when negotiating a corner. My car, at least, wants to come back to center (I guess this is understeer?). This is a Momo steering wheel, smaller than the stock SC three-spoker, and I have the advantage of a new suspension and fresh alignment. I love it!

John

[Early_S_Man]

John,

The 'return-to-center feeling' is the direct resultant of the 6°+ caster angle Porsche chose to use on the 911 front suspension. Mercedes also has used 'high-caster' to great effect for 40 years or so ... a little secret GM didn't learn about until the engineering for the 1972 Monte Carlo was being done ... GM bought several Mercedes sedans and set their engineers about dissecting their suspensions to find out why they handled so well, and 'high-caster' was the 'discovery!'

BTW, I was told that corporate secret by an Air Force mechanical engineer, who had as a grad. student, interned at Chevrolet Engineering in '69 - '70. Lots of interesting work went on back then at GM's 'Black Lake' ... the worlds largest skid pad, where Paul van Valkenberg [co-author of Donohue's Unfair Advantage] worked in instrumentation and testing during the Jim Hall Chaparral road racing days!

[djmcmath]

We keep saying "low center of gravity," but I've never actually seen a real comparison. I won't disagree -- logically, the reason it's silly to try and make a car like a Civic fast is because of the vertically mounted engine with a high CoG. Logically, the 911 has an impossibly low CoG -- but how low? How does it compare with other cars?

But then, it occurs to me that there's probably a reason these numbers aren't posted anywhere. It's probably very difficult to determine the actual number. You'd either have to weigh all the components and determine their exact placement in the car, or do some psycho kinematics experiment, or something.

Hmmm,

Dan

[ZCAT3]

Comparing older 911s to newer BMWs is hard to do and not really fair. My E39 M5 would easily take out a stock 80s and earlier 911 at the track if driven by 2 equally competent drivers. It is hard to compete with 400 NA HP, even if the car weighs in at 3600 lbs. The key here is "stock." When you start using a car like Jack's for comparison everything changes. Porsche never introduced a production car like that and certainly had no where near the knowledge to do so 30 years ago.

For example, I just added adjustable sway bars to my 930, and even on the street the difference in handling is very noticeable. The car feels lighter and way more balanced. In fact, it reminds me a lot of my M5.

The older 911s defintely have a connected to the road feel though that no other car I have driven matches.

[Jamie79SC]

Try a Toyota MR2 and you'll get some of the same road reel as an older light 911. A few summers ago, I rented one a year ago and chased a friend in his Gruppe B 3.2 liter 911t . He's a better driver than I am and has an faster car, but we still had a blast.

[no substitute]

This is great stuff, but there is a wrench that can be thrown into the works. Why does the Cayenne seemingly break the conventional rules and handle nearly as well as a 996? Heavy, high c.g. (even in it's hunkered down stance), etc., and this is even with the PSM turned off.

[twin plugged targa]

There are plenty of cars that will out handle a 911, but as someone already mentioned there is a serious danger that the pilot will fall asleep with boredom before the race ends!.
For me a BMW is a car I will drive 'when I am old'

As for the low centre of gravity, I imagine that the engineers use a similar calculation to a maritime calculation for transverse stability where they calculate the centre of gravity GM (or Meta centric height) and then calculate the amount of effort taken to heel the vessel to a certain angle before it becomes unstable.
I would imagine there must be some similar calculation made to figure at what height the bulk mass of weight is (GM) , raising that height and weight upwards increases roll and eventually lifts a wheel or the car slides.
With a vessel we lower the GM to increase stability by ballasting (filling completely)fuel or water tanks.
Likewise with cars we reduce the sprung height increasing the weight below the GM of the car.
If our fuel tanks were baffled this would also help the 'free surface effect' which is basically reducing the 'slop' of fuel in the tank and help reduce body roll!.
I believe race tank cells are honey combed for fire reasons but this would also help stability!.
.... hmmm rambling here, perhaps no one is interested in boat stuff
Ben

[djmcmath]

Ben,
I was actually thinking of the metacenter calculations when I asked the question. Ironic. I haven't taken naval science in quite some time, but it seems to me that the free surface effect of the gas in the tank, or the oil, for that matter, probably contribute only negligibly to handling stability. Neat thought, though. But back to the point, it seems like actually measuring the metacenter with any degree of accuracy would be pretty painful. What do you do, rock the car up on it's side and see where it balances? Can we do that with somebody else's Porsche, but not mine? Hmmm...

Dan

[ttweed]

Originally posted by djmcmath
What do you do, rock the car up on it's side and see where it balances?

Actually, you can measure both longitudinal and lateral CG of any car rather simply with platform scales, a jack, 2' tall blocks, and some trigonometry.

TT

[Randy Webb]

to get the CG, you put the car on a frame and balance it out. I think there is a description in Race Car Vehicle Dynamics or some other tome.

But.... what is the CG??

[Sonic dB]

vis·cer·al ( P ) Pronunciation Key (vsr-l)
adj.
Relating to, situated in, or affecting the viscera.
Perceived in or as if in the viscera; profound: “The scientific approach to life is not really appropriate to states of visceral anguish” (Anthony Burgess).
Instinctive: visceral needs. See Synonyms at instinctive.

[lateapex911]

I think we should define "Handling"

To me, handling is how well behaved the car is during cornering, transient manouvers, as well as combinations of braking, cornering and throttle application, on different surface profiles.

IT is not how many Gs it can pull on a skidpad. (BTW, I'm sure the author was making a point but no 6 series car pulls over a G in a corner without some chassis changes and some serious stick (aka Race rubber))

Nor is it a fast slalom, or a fast road course time. Good handling cars may post good numbers, but they are not, IMHO, the only measure of handling.

911s, at least many of them are not known to be among the top eschelon of the great handling cars. Why? Well, they can bite. There was a statistic, which has now become urban legend, that of all the first year 911 turbos sold in the states, nearly half were sold in CA, and nearly half were wrecked in the first year, backwards into walls, etc.

Now, I know that is a great (bit sad) story, but I doubt the numbers. I do think there is some truth in it. Trailing throttle oversteer was a known 911 issue, and was worsened by the addition of more weight (turbos, etc) high US spec ride height, newfound power, and so on. (not to mention the demograpic profile of the buyer) Cars that snap spin when you jump off the throttle are not driver friendly, and can't be considered among the worlds best handlers. And yes, some TTO is a good thing, if it's kept in check. The Miata and BMWs have a good amount.

The Cayenne may be a safe handler, but I doubt its an enjoyable handler! Too numb, and while its weight and traction may be well managed, it will prove to be a terminal undresteerer at the limit. In my book, thats not a great handler. Not neutral. Another good handling trait, neutrality..

The M3 is one of the best, and has an engine to match the chassis. The M3 is responsive, communacative, balanced, with great transient behavior, as well as high limits. BMW has acheived this through solid engineering, great chassis geometry, good wheel and tire choice, great shock and spring setup, and a good stiff platform.

The 911 starts with a deficit...the rear engine weight bias, with a large mass outside the wheelbase. Porsche has done an awesome job to overcome the physical limitations the package presents (and has also maintained the packages inherent dynamic strenghts, such as high R/F weght transfer which aids braking). But, while it is a great ride with great dynamics, and can be driven around it's weaknesses, it is not a car that is at the top of the list handling wise.