This morning looked like a perfect day to be on the track, and knowing there was event running I tossed my helmet bag into the trunk before heading out to a luncheon. I got to the track at 2:15 and by 2:30 I was entering Turn 2, and staring down 100+ feet to its second apex. There’s a number of pucker-inducing features on this track that make it both feared and oh so satisfying. Today was the day I’ve been looking forward to…and dreading.

Mosport is a very fast and dangerous former Grand Prix track that is used in a number of high profile Race Series. It’s my local track and I’ve racked up a lot of seat time running events here running a track-prepped Supra TT and MR2T. As such, this is the best track for me to evaluate a high performance car on, and also to run it against some of the fastest track day cars you’re likely to find. Today there were several Porsche GT3’s, a pair of new 911 twin turbos, Viper, a rainbow of Corvettes, and a lowly 993 Porsche…that’s it…and my 2010 XKR convertible.

I prefer afternoon sessions because usually there are fewer cars on track, and everyone has had a chance to get their tires and brains up to speed, with any overly enthusiastic participants having either calmed down or been loaded in pieces on a flat bed. Even with only maybe 12 cars running the track it was surprising how often you were passing someone or being passed. With the exception of 3 or 4 full-on race cars, the group was fairly closely matched.

Those of you who saw my track review last fall know I was very pleasantly surprised by the ability of the XKR, but it was on a different track that I had only run a couple of times, and I hadn’t even had the car a full day yet, so I needed today to more fully explore the car’s limits….and they are HUGE! I had ran it then with the full “DSC ON” and noted that it intervened in slower corners, applying brakes, cutting power, or whatever else it does when it senses the tires losing grip. Today I warmed up using that and then switched to “TRAC DSC”. That was a little better, but it was still relentless in its efforts to prevent me from getting on the power exiting the tight corner that leads on to the back straight. Then I turned “DSC OFF”, and it became a whole other animal. The first time through that corner resulted in a pretty impressive power slide, but after that I wasn’t aware of any real sliding or spinning, but the throttle became fully under my control, and available for the maximum acceleration that had been prevented before.

The car consistently passed 140 mph on the straight before braking into a sweeping corner. It felt quite stable at that speed while handling both a slight kink and gentle crest just before the brake zone. The back straight is a good place to pass or be passed. I was able to gain on all but a couple of cars on the straight, with the 510 hp power band easily compensating for the car’s heavier weight. I enjoyed a steady diet of Viper, Vette, 911 TT and a couple of the GT3’s. A couple of other GT3’s had their way with me...but hey, they are basically factory race cars.

The brakes have fantastic clamping force, and really haul the XKR down with relative ease. This track is pretty hard on brakes, with one brutal brake zone that my two track cars simply can not handle without major fading. The XKR’s massive brakes exhibited no fade what-so-ever. Race tires and higher speeds into most corners would put additional load on them, but my sense is these brakes are fully track worthy, with a race pad extending their abilities even more. I was comfortable pushing the car quite hard today, and didn’t leave a whole lot on the table. The street tires were screaming from turn-in to exit on some corners, with the pitch of the squealing being my audible indicator of how close I was to the tire’s limits.

But it’s the XKR’s neutral handling that was responsible for my being able to push the car so hard on the track. This is a car that is easy to drive fast in a straight line (as you all know), but it’s also easy to drive fast around a twisting race track near the limits of tire adhesion much of the time. There’s never a tendency to push or under-steer into or through a corner, or to over-steer through a high-speed sweeper. If you lift the throttle abruptly in some cornering situations you’re sure to be able to induce some over-steer as you shift weight off the rear tires to the front. That’s one technique used by drifters to get the tail out, and stabbing the throttle is another way to do it in the XKR, but that’s part of the advanced driver’s arsenal of driving techniques…not the car imposing it.

The Dunlop SP Maxx tires are really pretty decent. They work fine as a street tire, but they also work awfully well on the track. As a comparison, I’ve found Michelin Pilot Sports in the past to get very “greasy” on the track, losing an awful lot of grip as they over-heat, and showing a lot of wear on the edges. The Dunlop’s didn’t noticeably lose grip, they don’t look any worse for wear, and they were very communicative in the corners, letting me know exactly how they were coping under those demanding loads. The rear tires gained 6 lbs and the front 7 from heating up on the track, reflecting the normal extra load that the front tires experience on the track. The driver’s side tires take the worst beating because of more right turns on the track, and just started to scrub the triangle wear indicator on the tire’s edge, indicating that the tire wasn’t rolling over too much at the normal street tire pressures I had started with.

I had planned to try the paddle shifters on this track outing but I ended up not bothering. The ZF’s programming is so good I think it very unlikely that I could improve on it. It never shifted mid-corner, where the slightest unexpected change in power delivery to the wheels could cause the handling and vehicle control to be affected, and the electronic limited slip differential worked without me ever being aware of its action like I do on the street. I preferred it auto shifting in “Sport Mode”, but the throttle is so responsive, and gobs of power being instantly on tap, that you need to use care with the “loud” pedal. Do not use it as an on and off switch or you’re sure to see the rear of the car pass the front!

I asked a few of the guys that were gathered in the staging area next to the short front straight how the car looked ripping by them and they said just awesome, and commented on the great exhaust note. One of them took a couple of photos for me that I’ll add tomorrow and then the batteries died. One of the Vette owners came over and asked what it was. I don’t think he knew anything about the XKR, but when I mentioned it was 510 hp his face lit up with the sudden understanding of how I had passed him with 440 hp so convincingly. But when you factor in the weight he probably should have been quicker on the straights, and so should my Supra with almost the same power but a 500-600 lb weight advantage. As it turns out the Supra doesn’t accelerate as fast, with the XKR reaching a slightly higher top speed on the long back straight. The advantage would be in the gearing, the lightning quick shifts, and the broader 5L S/C powerband.

Does it need more power from a pulley or ECU tune? Not according to the cars I was dicing it up with today, but when it comes to power it’s not about needs…it’s about wants! For the moment I don’t have either… but I also know better than to say “never”!

But what I do recommend is that you get yourself and your car to a track school to learn to enjoy each other to the fullest...it's simply the most fun you can have in a car with your clothes on

Bruce

 

That's awesome, Bruce!

 

Bruce,

I agree with aahmichael! A great story!

Although I have no interest in tracking my car, your story opened up another aspect of XKR ownership and was informative and a fun read! Looking forward to the pix!

Was any special prep required? Or did you simply check the fluids and tires and go off to the track? Do the pop-up rollover bars suffice for track days, or is a roll bar required? Even though you wore a helmet, can you describe the noise inside the cockpit at 140mph? Were you allowed to run with the top down?

Stuart

 

Bruce,
Thanks for the great write up. It's good to know that the Xkr holds up well at the track!
What tire pressures did u start with? Did u have to let out air between the sessions?

 

Thank-you Bruce for a great story!
I had planned on putting my XKR on the dragstrip, but hadn't considered a a road course. Good to know the cars' limits will exceed mine.

 

Great, thanks for sharing! I found it interesting that you did not use the manual mode on the transmission.

I always wondered how tricky it is to use the paddle shifters in the heat of the moment. It seems I would have trouble finding the paddle shifters when I wanted to shift!

 

I think using the paddles is a matter of practice- if u don't use them on a regular basis, it would be hard to use them at the track. However, if u use them normally it's a lot easier than a manual transmission with heal-toe rev matching with every down shift.

 

Only got a couple of pics before the camera died...not too exciting I'm afraid...

entering pit lane

exiting T10 on to front straight

front straight into T1


Bruce

 

Thanks guys, and I'm glad you're interested. This is a big passion for me, and was a key factor in choosing this car.

Stuart, no prep other than checking fluids and tire pressures, filled the tank, helmet, and driving shoes for pedal feel. Made sure nothing was loose in the interior that could go flying around, and stowed helmet bag and overnight bag in trunk. I think convertibles may have been allowed at all events I've done over the years. Last fall's at another track required the factory pop-up roll bars, and there was no discussion about it at this one. The helmet seems to somewhat amplify the engine and exhaust sounds as it resonates in it I guess, but it doesn't really change it otherwise. Maybe try it on that long drive to work sometime!

Octurbo, I started with factory 33f/36r psi and did not need to bleed off any pressure during the event. I checked track pressure by hot pitting and immediately measuring 40f/42r. I carefully examined the tires and wear indicators just now and think a goal hot pressure for front might have been ideal 1 psi higher at 41, and the rears 1-2 psi lower at 40-41. The particular benefit of less rear pressure would be the slightly more tire flex and a larger contact patch that would increase grip under hard throttle.

AMC, I'd like to try the paddles, but that just wasn't a good time to learn. Had I not been running on fumes when I pitted around 4:30 I'd have stayed out to try them. By then just about everyone was packing up and I'd have had the track practically to myself. I wouldn't expect an advantage because it seems to be shifting as I would, and not when I wouldn't, so it's not a biggy one way or the other. That's the sort of thing you do once you become more familiar with the car's overall handling over the entire track. A experienced track friend with a GTR has done extensive data-logging and found he can't beat full auto with his paddles, and the tranny overheats quickly in that mode as well.

Bruce

 

You had quite fun

Thanks for sharing

 

Haha, I was just driving my girlfriend's 2012 Sonata's car with paddle shifters. It's really quite hard to use them around town, with all of the turning at intersections and such. Unfortunately the stick on the console is backwards (forward for up, pull down for downshift! Bleh!). But the XK has no manual mode on the shifter at all!

I can believe that what you say is true that the automatic sport mode is great, but I'm thinking more for my future uses on the twisties--whether or not the paddle shifting would be good enough for me. I do enjoy heel-toe downshifting, rev matching and doubleclutching (you can never trust the synchros on a Chinese transmission!!!) in my manual Mustang!

 

That's a personal preference, and relates to, or is at least associated with, driver involvement. High performance sports cars have always been stick, and if I had shown up at a track in the past with an auto I'd have been laughed at. But that's all changed, and the full manual in higher end sports cars is quickly going the way of the dinasaur. Paddles replace the clutch for involvement, and I'm sure most enthusiasts appreciates an auto when driving conditions make a manual a pain.

I've experimented with the paddles briefly on the road the odd time, but only got into it on one particularly twisted section of country road where I chose to be laser focused. When the road straightened out I switched back to full auto and it felt good to chill. I remember in '09 when my GTR friend got his and soon after was praising the virtues of his auto with paddles. I thought you'd have to pry the stick out of my cold dead hand, but after my second day with the Jag I was thinking I'm quitting the stick cold turkey.

Try the XK and see what you think...it's got enough excitement you probably won't suffer any withdrawal.

 

Haha, I think my primary use of the paddles would be to hear the sound of engine blipping as it matched the revs. I love that sound!

 

Nice writeup Bruce, enjoyed reading it. You inspired me to play around some more with the DSC and transmission settings on my way to go get lunch yesterday. I had never put the car in sport / manual before... I didn't realize you got a big gear indicator that replaces the clock in between the gauges (or that the indicator turns orange when you get near redline, like a shift light). Pretty cool =]

 

Additional thoughts ...

I'm compelled to expand on comments about the OEM Dunlop Sport Maxx tires. As previously mentioned, there were no nasty surprises as they were undoubtedly pushed well beyond the heat range of a performance street tire, continuing to provide remarkable grip when they would have been expected to turn to mush. That allowed me to push them harder and harder as I explored their limits of adhesion at higher cornering speeds. That's what you expect from an R Compound race tire, and even those go "off" when pushed hard. As an example, a popular Toyo Race tire used for track days and in professional racing achieves it's maximum grip on about the third lap where the tire's heat has become optimal, after that grip starts to fall off. Kumho R Compounds on the front of my Supra survive only two track days because they can't take the heat, where the rears last several.

But their best attributes were their progressive nature, and their ability to provide critical feedback to the driver. Some tires as they are pushed to, and beyond, their limits will suddenly and unexpectedly just stop gripping, and the driver has a big moment to deal with as he loses car control. A tire that progressively loses grip gives the driver the feedback he needs to avoid loss of control, and it loses it's grip slowly. It will allow a controlled slide. If the tire is losing grip due to high cornering loads and aggressive throttle the experienced driver can push beyond it by anticipating it, and dialing in a little corrective steering to counter the throttle-oversteer condition before it even happens.

Turn 3 at Mosport is a hard right-hander that's a little more than 90 degrees. It's tight going in, where you're first hard on the brake, then aggressive steering to turn-in to the apex at right, and then a slow unwinding of the wheel as the corner opens up over a couple of hundred feet to where you've finally crossed back over to the left side of the track. A short straight follows it and a sweeping downhill left that many cars can reach their highest track speed through. The objective is to exit T3 with as much speed as you can, and to do that requires you to feed in as much throttle as you can once you pass the apex. The problem is you're still cornering for a long distance as the corner slowly straighens out, so you can't nail the throttle. But as it does straighten the ever reducing steering angle allows you to increase throttle more and more while pushing the tires as hard as you can... without exceeding their limits!

This corner is an acid test for the character of a tire, and it started giving me critical feedback from the moment I initially and aggressively steered in towards the apex where the tires started to squeal. At the apex they were screaming like a raped chicken, and with every lap I'd give it more and more throttle beyond the apex and along that long exit, until it continued to scream until the car was basically straight and could scream no more. You just can't do that with an R Compound race tire because the soft rubber gives off so little sound. Users may have noticed on the street that rear traction is particularly limited when the tire is cold or cool, but increases significantly as it heats up. That's consistent with its max performance summer only rating, but I can tell you it grips like a champ when pushed on the track. I know some don't like it because it is expensive, and surely isn't the quietest tire on the market either, but it's an incredible match to the performance abilities of the car. I'll still switch to the Pilot Super Sports when the Dunlops are done for a variety of reasons, but sure hope they share some of the same track qualities.

An important part of tracking a car is keeping your body correctly and comfortably positioned in the drivers seat, and that's a difficult task without a proper race seat and harness that's designed specifically to do that. Constant and considerable cornering and braking forces are trying to throw your body about. In right cornering the driver's knee and elbow typically have to be pushed against the door to keep the hips and mid-section from sliding, and against transmission tunnel and console in left cornering. Arms and hands on the wheel become levers to hold your upper body. Those muscles are fighting against forces of about 1 g, and it does get tiring.

After a day at the track you know you've had a real workout, but all that effort has another down side. Your body functions as a giant receptor receiving feedback signals from the car. A "light" grip on the steering wheel can feel the losing of front tire grip as a gravelly feel and/or lessening of force applied to the wheel. A death grip on the wheel used to support your body reduces your sensitivity to that feedback... and to make subtle corrections. Same thing when the rest of your body is straining to hold itself in place. But fortunately the XKR seats are very supportive, and I was rather well held in place without much strain. The 16 way seat is well designed and I use the 3rd memory to save adjustment specific to track use for seat and steering wheel. On track I have the seat lowered to allow sufficient helmet clearance, seat further forward for optimized arm position and steering control, and bolsters set with a sense of purpose. The power seat also allows you to tighten and lock the retractable seat belts against your body. To do that I have to move the seat all the way back, sharply pull on the chest strap to make it lock, and hold it there while pressing memory 3 to move the seat forward against the belt that now keeps it locked. I found all of that does a terrific job, and much better than in my Supra for instance, where the same techniques don't prevent lateral sliding hardly at all.

I got pretty impressive fuel economy on the track as well. I filled up a couple of miles from the track, reset the trip meter, and filled up again after I was done. I couldn't have spent a more enjoyable afternoon in the car, and it cost $84.10 in fuel... 6.22 mpg just never looked so good!

We've all purchased these vehicles for their unique blend of styling, luxury and performance, but other than some spirited country road driving or bursts of acceleration on public roads many owners will never really experience or fully appreciate the very serious performance side of these cars. Most magazine tests and reviews discuss some aspects of performance, but fall rather short, and we tend to equate a car's 0-60 or 1/4 mile time with its overall performance. While real world use may seldom challenge much more than that, it's gratifying to know that our pride and joys can dice it up with other performance icons...and until this track event I couldn't say that with complete certainty.

I hope many owners will make the opportunity to appreciate this cats prowess by participating in driver education events like a car control school or high performance driving school, and maybe even further develop your skills by doing autocross or road courses events. You'll become a safer and more competent driver that's better prepared to handle unexpected emergency situations on the road, and that can make the difference between avoiding an accident, or becoming a statistic. You might choose to develop those skills using another car, and that's fine too, but you'll be able to use them in every car you drive. BMW Car Clubs of America offers everything you need, and you don't have to be a member. They have local chapters probably within reach of just about everyone...http://www.bmwcca.org/chapterfinder.


Bruce

 

Bruce,

Thanks for an excellent in depth analysis. I have a question regarding safety requirements for tracking a convertible. Here in the states most sanctioning bodies require an approved roll bar installed in the vehicle at a minimum. Is this the same requirement in Canada?

Tom

 

Thanks. I'm sure it is, and the factory pop-ups on the XKR qualified at an event I did last fall when they checked. I see convertibles running at BMW and Porsche events everywhere I go in Canada and the US where cars like Boxsters with factory roll hoops are common. I was told the pop-ups were fine so long as they were standard, and would think they are probably required today to even licence the vehicle for street use.

Actual racing events would require a roll cage, 5/6 pt harness and all that but I don't see that applying to driver ed and track day events. Easy enough to check with any events folks are considering doing, and I'd be interested in hearing if anybody is denied.

Bruce

 

Nice write up, Bruce. Sounds like you are REALLY enjoying the capabilities of the XKR and from all that I see in your posts, you are very selective about the events.

I am, however, concerned about the liability of tracking a vert. What is the factory "pop up"? I'm not familiar with the concept.

You know, I hate to sound like a scarecrow but, you absolutely MUST have some roll bars in the car, "pop up" or other that will sufficiently protect you when the car flips over. I know you are careful but, things happen at speeds of 140 MPH... Cars do flip over and it does not take much for that to happen. I actually eye witnessed two flips; the worst was at Thunderhill race track when an AC Cobra replica got sliding sideways following a corner and suddenly it became airborne, did two barrel rolls in the air before landing upside down. The car did not have any roll bar or racing belts and the driver got thrown sideways across the door as the car slammed down and the window bars collapsed. He was killed instantly.

The other incident was nearly identical except it happened right in front of me on a CA freeway when the driver of a Lincoln Navigator hit her brakes in panic when she noticed the slow traffic ahead. The SUV slid sideways, despite the antilock brakes, and lunched into multiple barrel rolls, landing upside down on top of the concrete freeway barrier. Driver, passenger were seriously hurt.

An other time a GT-3 car in my run-group touched doors at Sears Point with a Sport Racer in those famous "S" turns and for an unknown reason the GT car flipped. In the million-to-one odds situation, a piece of fiberglass that broke off the Sport Racer's bodywork, flew through the air, sliced like a razor through the heavy duty window net of the GT-3 and got between the helmet and the racind suit, slicing the exposed neck of the driver. He bled to death before anyone could have helped him.

I've seen the aftermaths of a good number of other flip-overs on the track, inlcuding a Ferrari Daytona that rolled simply from trail-braking into a downhill turn at Laguna Seca.

I think, most people do not realize how easy it is to roll even a lowered car. Once you get sideways and keep sliding, when the leading tires suddenly regain traction the motion energies must be dissipated somewhere, thus the car lunches rather high into the air, doing several rolls before landing.

Enjoy your high speed track days but, be sure that you do not skimp on safety. I'd invest in a good racing suit, as well, as you can never tell when your car will catch on fire from a blown engine, a busted fuel line, oil filter or, who knows what else. The suit will give you a few seconds of time to bail from the burning car.

I'd also add arm restraint straps to prevent your hands/arms to fly all over the place and land under some nasty hard suface in case of a flip.

Albert

 

Albert, the XK/XKR convertibles come standard equipped with two roll hoops that are automatically deployed if the car starts to tip. Your concerns are well-founded, and warning others that bad things can happen on a track is a good thing. I'll address some of those issues related only to "school" events on race tracks, as opposed to car control and auto-crosses that are run in large parking lots.

BMW and PCA Driver High Performance Driver Education (HPDE) events are very well run, and quite safe. Bad stuff can certainly happen, and occasionally does despite the best efforts of organizers, and participants are required to sign a liability waver for that reason. Organizers have track staff (marshalls) positioned all around the track observing the cars as they approach and pass their stations. They are in constant radio communication with all other staff in order to communicate any issue before they become a problem. The marshalls also communicate with each driver through the use of signal flags, and participants are taught the meaning of the flags, and what to do when they are used.

Students attend classroom sessions, and make do exercises in the paddock (parking) area before going out on the track. Beginner and novice students can only go on the track with an instructor in the car, go on the track together as a group, and will sometimes first ride in their instructors car to become a little familiar with the layout. Lead and follow sessions are sometimes done where each student takes a turn following a lead car which drives around the track at a relaxed pace, so students can learn the race line, braking zones, corner turn-in points, apex, track-out points, etc. Instructors coach their students as they drive, keeping speeds safe, and letting the student pick up the pace only as their skill level allows. This level of participation is probably safer than driving on public roads.

As the student's skill level advances through classroom and track training they advance to the intermediate "run group". They still require an instructor in the car, and go out on the track as a group. They use run groups so that only students at the same skill level are on track at one time, and that keeps the vehicle speeds similar to keep the traffic flow safest. This level is very safe.

When the instructor is certain that the student has reached a good proficiency level the student will be "signed off", which means he can go on track with the intermediate run group, but now without an instructor...if you wish. This is where unchecked egos can get some students in trouble. I recall wanting to be recognized as deserving to be signed off, but usually chose instead to have an instructor ride along to benefit from his expertise. So intermediate level can also remain quite safe.

Advance level run group is where you no longer have an instructor, and the cars in this group typically haul *** at a pretty fast pace. Instructors run groups often share the track with the advanced group, and they often are driving very fast dedicated track day or full-on race cars. The slower drivers can get intimidated by the faster cars, and there's much more passing due to the differences in vehicle speeds. This level participation is definitely more dangerous. I was nervous at first, but as my skill level increased, and I became quicker, I flowed well with most of the others, and became very good at watching my mirrors and waving the faster cars by.

All passing on the track requires the car being passed to signal the approaching car that he is prepared to be passed, and he indicates which side he wants to be passed on. An HPDE is not a competition...it's a cooperative, and that's makes all the difference in safety. Those not obeying signal flags and passing signals are ejected from the event following a warning.

When I reached the advanced level I started to do HPDE's at as many new tracks as I could, and drove as far as 17 hours to get there. I knew those events would be run safely, following the same rules and format, and I needed the car in one piece to drive home in. Flat bedding a wreck home can get quite expensive!

The events I choose to do now are not HPDE's, they're private organizer open lapping track days wheretheyrent the track and allow a small number of participants, and only those with a high skill level. Probably half are race cars that use the day for "test and tune" to develop the car and prepare for races, and the others have high-end and fast sports cars that want to run with the other "big dogs", and want full access to the track without waiting for their run group turn as with HPDE's. It's as much a social event for those guys...and my track buddies often work out their schedules to do the same events for that reason. I consider the events I select to be safe, partly because I know many of the drivers, we do it in the spirit of an HPDE, we've done it for a long time and have uniformly high skill levels, we're all out large sums if we prang the things, and we do it for fun...not to win. A passenger might say "let me the hell out of here...you guys are fricking insane"... and I wouldn't even try to convince them otherwise Most events that I do are in cars I've specifically prepared for track use, and they do have roofs!

But I'm not suggesting any of you try to sneak onto a track without proper training, but you can certainly participate and enjoy the experience at the beginner, novice and intermediate levels with reasonable safety...and as with many things, there's always an exception!

I've had more "close calls" on public roads than I have on race tracks over a period of years, and in some ways feel safer on the track. I guess I have more confidence in the judgement of these experienced drivers where the public roads are full of truly dangerous drivers. Mechanical failures on your own car or another track car can be a real hazard at those speeds though so I'll just leave it there.

Bruce

 

Great write and experience. I was wondering how the OEM Dunlops performed. Need to plan a vacation around meeting you at a road course sometime!

Jay