Carrera GT

496 horses sounds like a remarkably precise rumor, but it would go a long way to explaining the lap time. 450 hp doesn't explain how just rear steer and PDK puts the GT3 so far ahead of the RS 4.0 in the space of a one minute lap.

BBMGT3

I'm not interested in your Fiat. I'm talking about Porsche 997.2RS vs 991.1 gt3, since you said that on the same tire the older car will "spank" the newer car.

So, after admitting that the new car has a faster shifter, making it... faster.. It has more power, which makes it faster, it has a better chassis, which anyone who has driven a 991 overwhelmingly admits is a more capable machine than the 997 (carreras), making it faster...

It has a weight disadvantage, this is agreed.

How do you know it has a big aero disadvantage? Have you driven the car? Experienced its down-force in fast corners? The entire car was built to be faster than the 997.2RS.... are you saying Porsche released a car that is worse than the model before it?

And the longer wheel base... well if it makes it slower thru slow stuff, doesn't that make it better through fast stuff? Oh right, it has worse aero.

I'm not saying I like it. I really don't.

But you can't possibly be serious.

Carrera GT

This is the rear-steer idea. By steering the **** out, (inverted phase) it effectively shortens the wheelbase. 20cm. Eight inches. I think the 991 is 10cm longer in the wheelbase than the 997.2. I'm not sure about apples to apples 991 GT3 to 997.2 GT3 RS 4.0, but round figures, 10cm longer, but the turning geometry is no 20cm overall shorter.

Hopefully someone with all the numbers can chart 911 wheelbases back to the '69 short wheelbase car and we can see a comparison of at least the 964 to 993 to 996 to 991.

Keep in mind that is a real (not imaginary) reduction in the geometry. It's also variable (depending upon the range of motion of the rear axle steering) which is said to be up to about 1.5 degrees (I assume that's plus or minus a zero position, but it's got to be a lot more complex than just pulling in more toe-in or turning both wheels outboard.) The important factor here is optimizing the rear wheel contact patch relative to the intended "optimal" slip angle.

Here's Preuninger explaining four wheel steer (aka rear-steer.) He's explaining that it's a steering rod and electric motor assembly hanging off the rear suspension (unsprung weight.) I'm not keen on the increases in unsprung weight (which goes directly to the ability of the suspension to keep the tires all four squarely planted and weight distributed consistently.) But I see the logic in removing the "horse and buggy" rear suspension geometry and having all four wheels turned. I think the next step, as I've mentioned in another post (search for Honda, I think) is to have differential steering (at least in the fronts) but eventually in all four. The Porsche system might already have differential control over the rears, which I think might be mandatory to achieve the "radial" objective, meaning each wheel is perpendicular to the radius from the prescribed apex of the turn. All that said, I think rear-steer is the hidden agent that allowed the 991 GT3 to apparently nose ahead of erstwhile "faster" cars (though undiminished in their value, at least in my humble.)

http://www.youtube.com/watch?feature...vlRf3ls#t=857s

zanwar

The rear wheel steering on the 991 should negate any wheelbase advantage of the 997.

Mike in CA

Bookmarking this post for use in eliciting future retraction.....

NJ-GT

How is a system that doesn't work above 31mph helps on any racetrack turn?

I checked all the racetrack's data I have visited in the last few years, and none of them have turns where my minimum speed gets that low, so ,

RWS=FAIL

Nizer

Turns rear wheels opposite direction of fronts below 30; turns same direction as fronts above 50.

Mike in CA

Due respect, consider reading the specs before issuing FAIL statements:

At speeds of up to 31 mph (50 km/h), the system steers the rear wheels into the opposite direction of the front wheels. The 911 GT3 enters the curve faster, which permits more dynamic cornering. The ‘virtual shortening’ of the wheelbase by around 150 millimetres also results in significant improvements in agility and everyday usability; the turning radius is reduced, and manoeuvring and parking become much easier.

At speeds above 50 mph (80 km/h), the system steers the rear wheels parallel to the front wheels. This results in a geometric virtual wheel extension of about 500 millimetres, thereby increasing stability particularly at high speeds. Simultaneously, the side force on the rear axle triggered by the steering input of the driver is built up much faster than with a non-steered rear axle, which leads to a more spontaneous and harmonious initiation of the change in direction.

NJ-GT

Everything is down to tires. The MP4-12C comes with really bad tires (Pirelli Corsa System), these Pirelli are garbage, I had them twice (996 GT3 and Scuderia), they stink. My RE11 (a full street tire) produce better grip than the Corsa System.

Slap a set of Pirelli Trofeo on as stock 996 GT3, and the 7:54 Nurburgring car would be running in the 7:30s.

Put both cars (mp4-12c and wannabe-GT3) on the same tires: hoosiers, slicks, Trofeo, the MP4 will put a smack down on the wannabe-GT3. Wanna bet?

Unless VW has fixed the long gap between the time you pull a flappy paddle, and the time the shift actually happens, this wannabe-GT3 will continue the trend experienced with PDK and DSG.

Shifting happens up and down, not just up, PDK (assuming VW can fix the lag between paddle pull and actual shift that makes the real world shifting slower than advertised), as well as DCT, DSG and the Graziano unit in the MP4, take a lot of time to go down on gears.

I have driven all these DCT/PDK/DSG trannies, and the only time they shift fast, is when you leave them in full auto-mode and during upshift, so shifting happens by itself, but if you go manual mode (and this includes the 458 Italia) the gap between paddle pull and actual shift is noticeable, so the few milliseconds on actual upshift, plus the many more milliseconds (many more because if the lag is perceptible to the driver, we are talking 100+ ms ) does not make for a super fast shift. Going down gears, they sometime feel like they don't want to listen to the input, on how long it takes to shift, especially sections on a racetrack where you go from 5th to 3rd or 4th to 2nd.

The 599GTO, 430Scuderia, 16M paddlers are wired straight to their own TCU, almost zero lag, whether you go up or down, up-shifting time with 60ms interruption but considerably less time spent between paddle pull and actual shift, and same thing happens when downshifting, near zero lag.

Take a read on the 599GTO and 430 Scuderia shifter, these two cars shift nearly as fast as F1 cars.

PDK/DSG/DCT is street technology for comfort cars, nothing fun on them. Drive them on a racetrack compared to a Aventador, 599GTO, 16M, and Scuderia, and make some objective conclusions, instead of drinking marketing material.

Manifold

As frustrated as I am with some aspects of the 991 GT3, I'm not having any trouble believing that it's faster than the 997.2 RS 4.0 (on the same tires). After all, making it faster was clearly one of Porsche's goals, hence PDK-only and RWS.

NJ-GT

Thanks for the marketing quote.

On a racetrack, turns of 31mph do not exist (unless you track on a Karting track with a 3,500 lbs full size car). I can count with one hand the autocrosses where a turn was at or below 31mph. The wannabe-GT3 won't have an advantage over the SWB 997.2 GT3 on slow turns, as RWS would be disabled on the high rotation mode. This gimmick is for parking.

At speeds over 50mph, a longer wheelbase car still has a disadvantage, as it doesn't rotate as quick as a shorter wheelbase car. The real gains will come at much higher speeds, 100 mph and up, where a LWB car is more stable than a SWB car.

So, only on circuits with very high speed turns will this RWS help, now show me those racetracks, and public roads with those speed limits here in U.S.

mike2727

Did you ever drive a tuned/reflashed DSG ?
Day and night difference, no noticable lag not on up or downshifts

Try a Stage 3 DSG from HPA, again it is night and day, and this is a software only tune, so I do not see why this cannot also be the case with the PDK-S

Mike

Hothonda

Do your fingers ever get tired of your posts?

Carrera GT

Your argument about shift times in the Scuderia amounts to "it just does" and you neglect to refute the two points I made which invalidate your "it just does" sentiment.

Tires can make a huge difference and I don't know what's under each car in the comparison. Equally importantly, the magazine numbers are one driver, one day, and the factory claimed time is perhaps Timo Glock, so it's not driver for driver unless the magazine hired some serious hot shoe and really dialed in the driver to the car over a period of time, not just "hey show up on Tuesday, we've got Hockenheim booked for the afternoon."

I agree that there's not a lot of distance spent below 30 or even 50 mph on the tracks I see around California. If anything, I look at the data and try to keep the car out of those speeds at all costs (safer and more valuable on the clock to make time getting speeds up from 60 to 65 mph for half the track than from 130 to 135 mph for a split second on the straights.)

As for rear-steer as such, conceptually, logically, "on paper" I think it's the first generation of something that Porsche will increment and evolve, as is their way. They've been inching towards rear steer with active braking differentials since the 993. Now the diff is electronically actuated, that gives them control over push and pull without so much parasitic loss and traction compromise. Pondering rear-steer, my only dislike at present is having all the junk as unsprung weight on the rear tires. Maybe that's why they finally went to forged wheels. They had to go to 20's to wrap the 410mm PCCB fronts, so I guess they added up all the spreadsheets and found their compromise.

That the 991 GT3 is even within one second (per minute of lap time) of the RS 4.0 is not to be ignored. That it's ahead, on presumably similar spec rubber (though smaller rears) does more than hint at its potential.

I'm not swallowing anything. The proof of the pudding will be in the eating, not the drinking of the kool-ade.

911 Crazy

Want