What's the best correction if "slow in" turns out to be too fast?

A bit scary to not lift the throttle in that situation.

 

if you do lift pray that PSM catches it....

read some of the sections of the books on understeering....and power oversteering....

 

Maintain throttle and try to turn in. if you're way too fast, just drive off straight and then brake when you're in a straight line.

That's my experience, which isn't very much. I hope it helps.

 

This is why Internet coaching does not work. 'Not lifting' does not mean full throttle - it just means enough throttle to prevent too much transfer of mass to the front, with smooth transitions, without jabbing the throttle up or down. Proper driving is all about smoothness and none about slamming... But this must be practiced with competent coaching.

 

Understood, that's what I assumed was meant by not lifting. And I guess we really mean transfer of load, since mass (and center of mass) can't actually shift relative to the car.

By the way, the recent book "Fast Car Physics" is pretty good on this topic:

http://www.amazon.com/Fast-Car-Physi...0351455&sr=8-1

 

Wow, all these posts and no body suggested to drive Flat Out, that is how I drive, Flat Out

 

Gee -- The car isn't even warmed up . My opinion .. pamper the car a little . Get your feet wet before diving in. Baby steps . It's a brand new expensive car .

 

Mass, load, potatoe, potato.

Actually from a Physics perspective there IS transfer of mass, a very small distance, but nonetheless transfer, and that is what makes for a load (down-force) change on either axle. You can eliminate mass transfer with a suspension-less chassis with infinite (or very high) down-force preventing dynamic rotation in any direction, but that is not practical or desirable.

 

The mass does move slightly because of the movement of the suspension, but the large vertical load transfer at each wheel due to hard cornering, acceleration, and braking is due to horizontal inertial effects resulting from the CG of the car being above the road, not due to the car's mass movement at the suspension. With no suspension, the car won't rotate in either direction (as you noted), but there will still be about the same load transfer.

From a design perspective, a key is to keep the CG as low as possible, which is why Porsches sit so low, have aluminum hoods, etc. It also helps to have a wide track, since that reduces load transfer during cornering.

Again, the "Fast Car Physics" book is a really good resource on this stuff. Being an engineer myself, the physics aspect particularly interests me.

 

I agree fully. This is our first Porsche, and I never quite imagined having a car like this (nor this expensive), so we're certainly pampering it.

I'm following the break-in rules, but that can be done while still cornering in a spirited way. And I'm trying to learn the best cornering techniques for this particular car right from the outset, so that I develop the right driving habits, accounting for the rear-engine layout.

 

and if u do lift.......in a spin, both feet in

 

So you guys mean slow down as you come to the turn then flatten the gas peddel as your in the turn??

 

I'm not an expert, having only had limited training, track experience, and reading so far, but let me lay out my understanding so that others can comment.

In a track setting, you'll be braking hard as you approach a corner, trailing off the brakes as you turn in, gently applying increasing throttle starting somewhere around the apex, and full throttle by the time to get to the turn out point where the next straight begins. As noted by others, all of this has to be done smoothly to avoid upsetting the balance of the car. And things get more complicated when you have back to back corners, hills and dips, cambering (superelevation) of the road, etc.

On public roads, where we can't push as hard, since we don't typically approach curves with as much speed as the track, little or no braking may be needed approaching a curve, and my question is about what to do if the speed coming into the curve seems (or is) too high (ie, some braking approaching the curve was needed after all).

My understanding is that if you lift off the throttle, vertical load will shift from the rear to front wheels, which will reduce the lateral grip of the rear wheels, and with the weight of the engine in the back, there's risk of the rear tires slipping, potentially resulting in a spin. So my follow up questions are:

(1) Has the 997 been designed to compensate for having the engine in the rear, thus reducing the risk of spinning?

(2) Because of the rear-engine layout, other than maybe avoiding lifting the throttle, are there any driving techniques which are specific to the 997?

 

Yes. The 997 is very stable. You need to be reckless to spin a 997. But some have done that and would have done it with any other car (short of a FWD).

 

Spinning and loss of control is really about the tires losing adhesion with the pavement and the driver (or PSM) being unable to adequately compensate quickly enough. At speed, on the track, the car should be in a controlled slide in most corners conditions permitting. The deflection between the tire's intended path and the car's actual path is called the slip angle and there is an optimal angle to achieve optimal speed. Also, in many tight corners the quickest way through them is to turn in hard enough and apply enough throttle to induce some oversteer to rotate (slide) the back end around towards the new intended direction. If you can unwind the steering wheel smoothly enough and keep the car well balanced it works out fine. If you don't, a spin or a tank slapper may result. Ross Bentley takes 23 pages to explain these dynamics in his book Speed Secrets so I'll leave it at that. There's a fine line between being reckless and being accomplished.