eilig

Had my first full-day driving experience of the 997S today. Have a question regarding handling.

There is a right hander curve that I've taken thousands of times in my Corvettes, and I love flying through it. Today I drove the 997S through it for the first time, and something strange happened.

I generally just carry speed through it, so I'm not on either the brakes or the gas. As I'm approaching the apex, I'm getting more and more understeer, so I'm dialing in more and more steering input, gradually. The understeer continues until all of a sudden it "catches" and the front end whips to the right. This came without any throttle or brake input, and very gradual steering input. It really caught me off guard, and I have to say, I don't like it. I've never experienced anything like that with a Vette.

So my questions:

1) Has this ever happened to any of you?
2) Is it related to the variable ration steering?
3) Does it have to do with the rear engine?
4) Is there something wrong with my car?

It didn't cause any trouble, as I didn't have lots of speed. But it really shocked me, so I want to understand what the heck is up.

Thanks in advance for any input that anyone may have...

MJones

Coasting thru a corner

1) Has this ever happened to any of you?
Not to me

2) Is it related to the variable ration steering?
No

3) Does it have to do with the rear engine?
The handling characteristics of the Porsche may be different than what you are use to

4) Is there something wrong with my car?
Have you checked your tire pressures?

Happy motoring

eilig

Maybe I described it incorrectly -- not a corner, but a turn, with about the same radius as you would experience on a cloverleaf at an Interstate exit.

I wasn't on the brakes or gas because I had already braked before entering the turn... and I didn't want to get on the gas yet, because generally it seems getting on the gas mid-turn only brings more understeer in a car without the weight of an engine up front.

Good question regarding tire pressure -- I will check that first thing tomorrow morning.

Thanks...

djantlive

911 is set up w tons of understeer to prevent fish tailing due to rear engine weight. when you get too much understeer, add a little throttle to push it instead of keep dialing more of understeer.

Rear engine is about as different as a vette as driving characteristic can be. To a front engine driver, the rear engine takes some time in getting used to. Better doing this in a parking lot or a road w lots of run off. Discover the limits and practice perfection

Chris C.

Sounds like an issue caused by the classic 911 weight balance challenge. The 997 will handle very differently from your Corvette, with nearly 70 pct of weight in the back. Find a instructor experienced with 911s, and have him/her ride with you. Read up on polar moments of inertia in a good driving book.

In general, slower-in, steady throttle and fast out. You don't want to be in a "no throttle or brake" situation with all of the weight being managed 'passively' by the suspension, you need to steer with the throttle. This also means learning when you've turned in enough and waiting for the nose to take it's set.

The 997 is a great car to learn about 911s on, but it's so good it will require great sensitivity on your part to feel the small weight shifts that make all of the difference. A ride in a 911/964 or even 993 will shed more light on this.

Oh, and an alignment check is never a bad idea

Have fun!

BRUCE

I have found that if I feel understeer when I am on the throttle steering toward the apex, a LITTLE less throttle will magically get the nose to tuck in. I think this is because of the rear engine car, and the way a late model 911 suspension is set up by Porsche to be more understeer. While accelerating the weight is even more transferred to the rear, creating less traction at the front. Bringing a little more weight to the front by modulating off the throttle will help get the front tires to bite and turn in.
Eilig, Maybe you were a little on the throttle and let off, creating the unexpected turn.
I try to remember what I have been told. Slow into the corner, gentle throttle toward the apex, adjusting throttle depending on the cars reactions to the turn, then smooth peddle down as you come out of the turn.

donkeyman

I haven't driven the 997 but on my 996 I found that left foot braking deep into the turn until the apex made the car handle very nicely and eliminated almost all the understeer.

But check the tyre pressures first.

eilig

Thanks guys. I'm going to go practice a bit right now (after checking tire pressures of course.)

My only previous experience driving rear engine was 360 Modena, and I never experienced anything like this in that car either. But it has such a wide track, both front and rear, that maybe it's an entirely different beast as well.

Obviously I'm going through a bit of a learning curve here... (If you'll excuse the ugliness of that pun!)

AeroSmith

Precisely. That's the way they teach it at the Porsche Driving Experience.

Light trail braking (after the initial hard braking in a straight line)will help bring you into the apex. Follow that by gently rolling in the throttle while straightening the wheel and that pulls you out.

MJones

Chiming in again.
Pretty hard to diagnose without knowing the details of this particular corner, ie) is it flat, uphill, downhill or a combo of both.
One thing in your statement that is a classic rookie mistake with regards to understeer: the car is not turning, so I'll dial in more steering....and nothing happens...finally the car slows down a bit and bite regains.

Do yourself a favor and sign-up for PDE...you will learn alot about vehicle dynamics and the limits of a Porsche

eilig

I will defnitely have to do the PDE.

Drove the same stretch of road again today and took that curve again, this time paying really close to all characteristics. Didn't realize that this curve does actually have an elevation change -- slight uphill. Also realized that yesterday when the understeer occurred, more than likely I was on the gas (at least to some degree), due to this elevation change. And I also suspect I may have missed the apex yesterday, and that's why it sort of snuck up on me like it did.

So today, I went to a favorite cloverleaf where there's rarely any traffic, and a wide, paved shoulder, put it in sport mode, and did several passes. This was really good practice. I think I understand the handling much better now. Once I get the hang of it, I can see already this baby is going to outperform the Vettes. I got a couple of the passes just right, and couldn't believe the speed I saw when I briefly looked at the speedo.

Gonna be fun trying to bring my ability level up to that of the car!

vtach88

What a great thread.... for a newbie like me....
A bit tired of the "break in" discussions.....

I've noticed the same thing as the original poster - and I've also noted that it is worse if there are any expansion joints in the overpass - as that induces a horrible oscillating bounce to the front end...

saveur2

I drive a 996 turbo, and I know exactly what you're talking about/experiencing.

Couple of pointers: don't "coast" into a turn. You should be either feathering the throttle, or lightly tapping the brake. On turns that I feel the nose is pushing out, I just tap the brake gently to transfer weight to the front and it usually bites. Unless you have aftermarket suspension, or an aggressive alignment, I wouldn't suggest getting more gas, as you'll just end up pushing more. There's a lot of grip available in these back tires....

I had the oscillation before too, but that was before with the stock suspension. After switching to coilovers, the damping has taken the wierd pogo effect out. It just bobs once, then moves on.

have fun!

Likemystoppie?

I had a very similar experience with the 997 carrera I tested 2 weeks ago.


So my NEXT question is.....Are these cars that DAMN sensitive to tire pressure?


edit: and how come you guys didn't tell me the same informative dialog you've shared with this person?

eilig

Thanks for the insight guys. This gives me lots of stuff to practice during my upcoming drives. One more question:

Let's say I'm in a curve with lots of speed, and I'm feathering the throttle, and I start getting major understeer. So I get off the throttle, and start applying pressure to the brakes to try and get the front end to "bite" and get rid of that understeer. Do I have to worry about the back end coming around on me when I apply the brakes?

Whenever I have the thought of getting on the brakes mid-turn, especially when I'm carry quite a bit of speed through there, I have flashbacks to a time when I did exactly the same thing driving a Viper GTS (piece of junk!) mid-turn. I got on the brakes, and that back end kicked out so fast that I almost lost it and spun. I did manage to get it straight again, but not without some serious wrestling, and going off-road into the desert (I was driving a rental out near Vegas at the time).

So, let's say I'm mid-corner, and as a worst case scenario, say I missed the apex and I'm getting big time understeer. Do I have to worry about the rear of the 997S kicking out suddenly if I get on the brakes?

Thanks for allowing me the benefit of learning from your experience!!