GT3 vs GT4 at RD Atlanta, The Lost Article 2015

GT3-GT4 Test Drives, Road Atlanta, Craig Watkins 11-18-15, v6

I’ve been to Road Atlanta a couple of dozen times over the past 14 years, for races and tests when I worked for Flying Lizard Motorsports, so I know the track well – but I really only knew it from an engineer’s perspective, having looked at this particular map maybe a thousand times and having pages and pages of notes from session debriefs listening, in detail, to each turns’ nuances – the ones that typically caused the most trouble – or really, cost us the most time.  The apex of turn 3, the uphill and slightly off-camber turn 5, the importance of getting through turns 6 & 7 cleanly, then the potentially high consequence downhill turn 12 – though they rarely brought this turn up, if the car was good elsewhere it would be good through there; flat even, with sticker tires.

In April of this year I rented a 2.0 liter ’68 911 from Michael Eberhardt for the Walter Mitty historic race there.  That was the first time I had actually driven a car there at pace, hearing the voices of Jörg, “the Patrick’s”, Marc, Johannes et al in my head of how they got the cars through the turns. But in a low powered short wheelbase 911 the track was a hoot to drive but light-years from an RSR pulling up to two G’s lateral in some turns.

In early October Pete emailed me asking me to fly to Atlanta, drive, and report on, the new 991 GT3RS and GT4.  At least I wouldn’t be starting from scratch driving new cars on a track I’d never been on before.

The Porsche people kept apologizing for the wet weather the night before at the dinner they’d arranged for us – it was due to be wet the next day as well.  It didn’t really bother me, rain or shine the cars will be great to drive, in some ways their behavior in the wet might be more interesting than in the dry.

Sure enough when we arrived at the track at 08:30 it was raining.  In the large tent they’d set up they gave us the overview of the day, that Donahue and Haywood would do a lead and follow, David in a 991 turbo and Hurley in a GT4.  There were three GT3’s and four GT4’s. At first I thought it was going to be sort of a silly dog and pony show affair, figuring they would just poke around the track keeping us all corralled behind them to keep us from flying off the course and wrecking the cars. But they broke us into groups and when my time came, the first car I’d drive would be the GT3, which I was thrilled about – to see how it had evolved and differed over the twelve years from my own GT3 (996).  The driving compartment is much different, there’s a lot more going on with all of the modern controls, switches, digital displays and center mounted flat screen monitor; my 996 is very spars by comparison.  The telescoping wheel is nice for me so I can sit properly to the pedals but not be too far away from the steering wheel.  I ran over all the basic controls quickly – we didn’t have much time – radio off, door handles, door locks location etc in case I had to get out of the car quickly, basic stuff like that.  Then, how to start off with a PDK, having never driven one in a street car, only on the RSR’s, and they started off with a clutch pedal – or did in the 997 years, I don’t know about the 991’s.

David rolled away in the turbo and the two other GT3’s followed. There weren’t three pedals so I figured you just slipped it into D and rolled on the throttle – so that’s what I did. The PDK was shifting itself right away as we got to pit-out and blended onto the track at the end of turn 1. For sure, I had to get my situational awareness zeroed in to what I was doing, that is, I needed to get the wiper controls figured out, where the basic settings were for the traction control – was it on or off – and so on, while not bashing into the car in front of me – but fortunately they were rolling right along while I dropped back to get my bearings. The pack of GT4’s started half a lap behind us.

I know it takes me a few laps to get the most basic feel for a car and the track, how the brakes feel, steering input reaction, power delivery, overall stability – where to turn, where to brake, where it was particularly slippery and so on. Each lap I’d pick up the pace, especially exiting 5 and 7, I wanted to feel how much grip, or power down, the car had leaving those turns – I didn’t especially want to loop the car, especially in the first session – I had the thought of Pete killing me for being “that guy.” And, the brake point for turn 6 and especially 10A at the end of the back straight, it’s very fast there.

By the third or fourth lap I was starting to push the car more and more, getting a feel for how it broke away and how controllable it was when it did. Coming out of 5 I’d pour a little more on the throttle each time but kept away from the painted exit berms, those looked dangerous to me and I could hear Jörg or Patrick in my head saying how slippery they can be when wet. By the top of the hill at the exit of 5 I’d be flat with the throttle while I very carefully unwound the steering along with my senses pegged waiting for the back of the car to start to move around or step-out – but it never did – it accelerated hard and in total control shifting itself up as it did to about 9k - 9k blows an air cooled 911 engine to pieces (too much reciprocating valve train weight). One thing that started to stand out to me early on exiting 7 was the anti-squat characteristics, it transferred its weight to the rear at a rate that didn’t upset the car with oversteer or understeer, it wiggled a little but it seemed normal to me, remember the track was wet. As it turned out we would do 9–10 laps per session so in that first one I was able to settle-in, get the basic lines memorized and get a beginning baseline feel for the car.

At the end of the session they asked if we had any questions, I didn’t have any yet, I needed more time in the car. The next session was with the GT4. Everything I’d read was that it is a very special car – people were excited that Porsche built this car. At least this time I had a better idea of where the controls were, how to get comfortable quickly with my seating position, and, back to a manual 6 speed.

By turn 5 of the out-lap I had the car stepping out and that was not what I was trying to do or expecting with less power. It did the same in exiting turn 6 and 7 but even more and I thought; this car’s crazy - are the tires over inflated or what? It was the first time I’d driven a Cayman and was expecting a different, more planted or a more even breakaway feel (front and rear). I remembered Johannes telling me when he drove the Ferrari’s that when a mid-engined car steps out it’s harder to bring it back (low polar moment etc), but I didn’t think it would happen as soon as it did. Its power was good, not as strong as the GT3 for sure but felt very good for that car – in the dry it would be a very different car. All of its controls were just right, clutch pedal weight, steering effort, good gear selecting linkage and gear ratio splits. Like the GT3, the brakes were terrific, ABS and all and its stability at speed was also very good – but the GT3 I was told makes well over 300Kg of downforce – that’s real downforce.

When the session ended I stopped the car, got out and sat in the tent thinking either I’m not driving this car correctly or the car is just strange to drive in these conditions. I’d had a big step-out exiting turn 7 and I asked Hurley about it. He said you have to be very very smooth with the steering and throttle to get the most out of the car. I thought I had been but maybe not.

Back in the GT3 for Round 2. This outing I understood and trusted the PDK, it’s downshift blipping, shift points and how the car pulls and acts with throttle, where the control levers were (wipers, defrost). And for sure, anytime I take a 5-minute break from any first outing, in any car, at any track, I always feel much more at-ease with the car and where I’m going the next time out. I was the third car behind David. On the out-lap David pretty much took off at a fast pace and I kept telling myself to hold off and get to know the car. I started using the large curb at apex of turn 3, that I remember distinctly Jörg saying; “Craig, I can stay off the curb, yes, no problem, but I won’t be fast.” For sure it is faster putting the center of the car over the curb, and, it’s much easier setting up for the Esses – the back of the car has a tick more time to make its weight transfer because the radius is less abrupt. And every time I put the right-side wheels up on the curbing I’d straighten the wheel a little bit waiting for the rear to lose traction and step out – but it never did.

Then it dawned on me too that the car wasn’t being tossed into the air by the curbing the way I expected – and it dawned on me the damping must have some regression to it – it was so smooth over the curbing and other bumps but still felt stiff and responsive when making direction changes, I wondered how great it must feel in the dry.

I kept picking up the pace and got to the point where I could come out of turn 7, slowly return to center-steer while putting the throttle to the floor and leave it there all the way to the slight dogleg to the right heading for the downhill and the braking zone for 10A – I didn’t bother looking at the dash for road speed or engine speed, I knew that was being taken care of, I knew I was going plenty fast and that wasn’t the point anyway. I was very mindful of the back possibly stepping out at that speed, and being wet. Then I re-remembered Andreas Preuninger (who prefers to be called Andy) explaining that the car produced 300+Kg of downforce and I could feel that because the car was completely planted and stable. So my next milestone was to find the braking point. I went a little deeper each lap thinking each time I was braking too early when I turned in. Then, on one lap I broke a little bit too late and missed the turn-in point and I went a little wide, expecting the car to do a big brody at a minimum, but spinning the car felt more likely. I was in the ABS for sure while the auto blipper was active and shifting down as it should – and it never gave the feeling it was contributing to the cars oversteer – the oversteer came from me being late for the brake point and late for turn-in and forcing the car to turn left. The car moved around a lot and I was as fast as I could be with the steering wheel to keep wheel angle into the slide while going back to a little throttle waiting for that sickening feeling you get when you know you’ve lost the car – but it didn’t spin, it was unbelievable to me.

The next lap was the checkered and as we all rolled to a stop I sat in the car listening to the rain on the roof and thinking about why the car was so good in that turn I’d botched. It dawned on me that the differential was different in its behavior than the 911’s I’d driven before, my own mostly. The conventional Porsche clutch-style diffs I’d had for years, the same that’s in the GT4, requires acceleration or deceleration torque to keep the diff active (forcing the inside wheel to make more of a contribution to total axle grip – so it follows more closely the speed of the outside wheel and isn’t coasting); so the pins acting on the ramps internally will push the diff ramps apart, through the diff clutches and net a reactive torque to the wheels.

I got out of the car and they had a big lunch ready for us. I sat and ate largely by myself making notes on paper. When I noticed Andy was free I walked over and asked him; are the dampers digressive? Yes. What is the lock percentage of the diff? Zero to one hundred percent he said. Will it go to 100% lock on decel? (That was sort of a stupid question). Yes, both accel and decel, it’s electronically controlled. We talked a bit longer than this, but those were my main questions.

Typical examples of damping graphs. The velocity is actually the rate which the damper is compressed or extended (often called bump and rebound).

So that was what had saved me in 10A. Actually, it was a combination of things: excellent ABS, a locking diff, rear suspension kinematics (including dynamic toe changes), wheelbase, stability control, wide rear rims and very good all-season tires (more on the pros and cons of these another time). I’d done my best, realizing I was probably going to lose the car but was fast enough and gentle enough with the controls to minimize the chances – but I’ve spun enough 911’s in my life to know all the signs were there to spin this one – but it hadn’t.

After lunch, I drove the GT4 again. I like the manual gearbox, its ratios and positive feel – but started to see the high value of the PDK, how much easier the car is to drive – and if you’re looking for absolutely minimum lap times, it’s the only way to go – you can drive it almost like a fool and it will still do everything correctly, upshifts, downshifts, and the speed of the shifts. I remembered how good the paddle shifting upgrade had been in the RSR’s when we first started using it in 2010 I think it was – the drivers didn’t get out of the car soaking wet and steam coming off their heads in cool weather as they had before, so their average pace was higher and the car was less fatiguing to drive, by a large percentage.

The track was no drier than it had been before, maybe wetter. I was the first car behind Hurley this time and I let him gap me. Since I was getting a handle on the track I used the same line I’d used on with the GT3, hopping the curb in turn 3 and staying away from the exit curbing in turn 5 and 12. It felt similar to how it had felt in the first session, the rear moved around a bit more and the car didn’t feel as robotic as the GT3, I mean, even in the wet that car is so good, so predictable. The GT4 did also but to a lesser degree and required a different driving style because of the manual gearbox – blipping the throttle with the side of my foot on downshifts and setting the car up a little differently for corner entry. I was still too abrupt with my inputs, a bad habit from the years of off-road racing where you have to nudge the car into a little oversteer to get it to turn – it’s a habit I’ve had a hard time breaking. For this session I concentrated on brake points, brake behavior (excellent), not looking at the tach for shift points – becoming more familiar with the power curve and sound of the engine – and just concentrated on driving it more smoothly and letting myself understand the cars’ own feel. And, dealing with some of the near whiteout conditions – sometimes that part wasn’t much fun, especially on the run from 7 to 10 and down through 12.

Back into the GT3. This time I knew the track, knew the behavior, knew the controls, knew the sounds. For the entire session I just concentrated on a holding a good consistent pace, clean lines, drift it where it was safe and forget all the rest. Nine laps later I felt I understood the car pretty well, the diff for sure, the digressive damping (Or is it a blow off valve?), the roll (weight transfer), its breakaway characteristics. And that I was really happy for because the harder I drove it, the more the 911 feel came out in the car, distant for sure from the old days but it’s there, and sensational for sure – you just concentrate on driving the car and it will do what you ask. But like any car it has it has a limit - no car can skew physics - and not even this car can save an idiot or careless person. And how could it, right?

By now we were one session away from our departure time and they were offering those who wanted one last session. I was happily game and hopped into the GT4. This time I told myself I’d really concentrate on driving the car as smoothly as I could – stop with the faster initial steering input and progressive with the throttle. Just before we rolled I jumped out of the car and ran up the car Hurley was in, l leaned in and said, very very smooth with the controls, right? He nodded. So that’s what I did, that is, concentrated on the line and being super smooth with all inputs – and the car was then really nice to drive. Going into turn 7 especially I was very smooth with the wheel, just a light touch of the apex and rolled the throttle to the floor but kept it in third gear instead of second, no oversteer, and my top speed was better by 4-5 mph at the crest of the hill before the braking point. Later, talking to our editor Pete he asked me how I liked the autoblip in the GT4 when in sport mode – I told him I never used it – he didn’t seem very happy about that…

But for sure you brake very hard for turn 10A (I tried to just get into the ABS, just a little bit each time – it’s easy to be abusive of ABS) and downshifting the old fashion way, rolling my braking foot over to the throttle and blipping it that way – the car was also excellent, zero sensation that it would induce oversteer. But as I said before, driving the car lap after lap with a manual gearbox, especially a syncomesh gearbox, you are busier in the car, using the autoblip would remove a percentage of that, make the car easier to drive at pace (in the braking zones I mean).

I personally love manual gearboxes, I feel more connected to the car. But PDK is the future and has so many advantages; besides downshifting automatically for you you can go back to throttle more aggressively, for example in turn 1, it upshifts perfectly mid-corner, no problem. You can do that with a manual gearbox too, but you have to be quick with it and ready for some oversteer, and there’s no way you can do it as quickly. If you will track a car or looking for maximum acceleration or minimum lap times (not to mention its beautiful sound) and ease of effort, PDK is the choice. It feels literally perfect.

For me personally, I like the 911 – its behavior, even at this advanced level – is so familiar to me and comfortable. Maybe sometime I’ll get a chance to drive them both again in dry conditions, back to back, if so, maybe I’ll feel differently. But this test wasn’t about which was faster, or about better per se, it was about driving and understanding the behavior of each – it was not a shoot out. Since I race an older 911 and drive 911’s almost daily, I’m used to their feel and behavior; their behavior is second nature to me. The Cayman, in these conditions, wasn’t as settling but I drove it only 30 laps and under very marginal conditions – that isn’t enough time to get to know a car well. But by the end of the last session I’d grown to like the car, to understand the car. It was a good way to end the day and a valuable learning experience for me. I kept thinking how good both cars would be in the dry in turn 12.