I've been hanging around the forums for some time after trying out the 09' supercharged and NA and a 2010 NA car locally. Its been nearly impossible to find a 2010-11 locally to test drive so I took the opprtunity on a trip to give the car a try.

I drove a 2010 XFR in ultimate black...I sort of knew what to expect after the feeling the difference between the 4.2 and 5.0 in the previous cars. All I can say is wow, I left the lot and attempted to ease onto the throttle, I suppose I was successful...but I didn't know that till later. The throttle mapping is clearly much more aggressive in this car than the 5.0 NA...or maybe its the same and there's just that much more power.

I took a buddy who owns a prior gen M3 that he enjoys very much with me for the drive. Pulling away from one of the lights there was a bit of open road I eased away up to 30 or 40 mph and mashed the gas, it was hilarious, my buddy says 'wooooooh' in the backseat from the accelleration. And I mean wooooh in a good way, the accelleration is a hoot in the car. Even knowing the car was 510 hp it still surprised him!

I remain utterly amazed at how the car changes character - and I love both of them! I'm not sure if its the adaptive suspension or the the adaptive transmission. But the car responds aggressively if treated that way...and is the proverbial ***** cat otherwise. Amazing.

The test drive completely sold the car...I will pick one up later this winter...absolutely a special car.

On the slightly negative side, a couple comments:

I had the sensation that the S mode was a bit too aggressive in the 5.0 NA that I drove, it just felt too eager and too on edge to use for any amount of time. The sensation was exactly the same in the XF, while I'm not after a BMW type adjustment on how aggressive the transmission is...I kinda wish it was milder so it could be of some use away from anything other than a racetrack. I'm left thinking it would almost never be used.

I'll disclaim this comment by stating that I presently drive a Mazdaspeed 3 which is a very very fun car...kinda like hooters...not totally delighfully unrefined by close. Its a very communicative car and only weighs 3200 lbs. The car begs to be pushed everywhere...on breaking, on cornering and on accelleration and I've gotten in the habit of doing so.

So, I pitched the XF into a tight intersection and got onto the gas, I know it wasn't was the larger rwd car wanted...particularily by how much it began to understeer. I only lost a foot or so of line but it really surprised me how long the chassis wanted me to wait to get on the gas....can anyone comment on this? Do you find the car quite understeer prone on lower speed cornering? I suspect a little throttle delivery would help...but I didn't know the car well enough to go there...

Overall the car is amazing and does everything I need it to and several things I want it too.

 

My 10 SC shift mapping is not good with S AND dynamic mode on. With Just S it is quite driveable but only when you are in the mood. The transmission in standard drive is so good and responsive I rarely take it out of that mode.

 

S mode and auto on the public road is tiresome - you don't get the room to use the revs all the way to the auto shift point, in my experience,. That said, I use S mode and the paddles quite a lot - you just change up earlier than S/Auto and later than D/Auto would. Dynamic mode makes the biggest difference in the real world. I use it almost all the time. D/Auto/Dynamic is plenty aggressive enough for the public road.

Someone with a better idea of how vehicle engineering feeds into driving dynamics should chip in here, but my experience from driving an XFR on the R Performance Academy day was that it is quite easy to induce understeer in tight, slower turns. Adding throttle will only increase understeer unless you back off the steering (assuming you have room!). With practice, you find the limit of front end grip and "surf" that edge. Remember that the TC and stability systems are doing an awful lot with these cars. Turn them off completely and you will do away with understeer and replace it with a short and large dose of oversteer - followed by the sound of crumpling metal, assuming limited room! You probably drove the car in normal mode - maybe with dynamic mode engaged. TracDSC is about as far as it is sensible to go and it allows a lot more margin for drift before the systems rein it in.

edited to add: In normal mode, driving with even a little bit of "spirit" you will feel the TC limiting the power you are putting down quite regularly.

 

duh, can't use the forum tools properly - sorry! How do you delete an unnecessary post?

 

The car was in dynamic mode when the understeer occurred, and what you suggested may happen upon applying a bit of throttle did happen....more understeer. I didn't get a chance to really test this out repeatedly...I grew up driving rwd mustangs...I am therefore much more accustomed to oversteering than under...was a new feeling!

Any comments from an R instructor would certainly be welcomed, I'm sure I'll figure it out on my own some time soon though...

 

Darlo - agree with your first paragraph based on my experience with my SC.

 

The physics of four wheel vehicles equipped with pneumatic tires and with front steering mean that rwd and awd cars will understeer in tight corners. This is intuitively easy to understand when you recall how a pneumatic tire works. Cornering forces are developed ONLY when the tire runs at a slip angle. To initiate cornering the front wheels are first turned, the drive forces continue to push the car forward in line with the rear drive wheels causing the front tires to generate slip angle forces and the car turns in but initially understeers. Once the car begins to rotate then slip angles develop at the rear tires also, understeer usually reduces somewhat at this point.

Only if you can then apply enough power to rotate the car more quickly than the rear tires can generate slip angle will the car go neutral or oversteer. Each time you apply additional power the car continues in the direction of the drive forces causing more understeer unless the drive forward also generates additional rotation. With inadequate tires some impressive drift angles are possible where the drive forces are actually pushing the car towards the apex while the front tires no longer generate slip angle forces in the desired direction. Best results occur when all four tires are working equally hard to generate both forward motion and cornering forces. Fast rwd or awd cars will always understeer, oversteer is slow because the front tires are doing nothing useful.

Simply put, the front tires generate a slip angle by being physically turned while the rear tires do not. Only rotation induced by the front tires can allow the rear tires to generate a slip angle and contribute to cornering. Various attempts have been made to develop four wheel steering without much success.

Awd can reduce initial understeer for the same reason as fwd will, the front steered wheels generate slip angle forces plus cornering force from the drive forces aligned with the direction of the wheels. Until the contact patches are overwhelmed by too much drive torque fwd will beat rwd through slow corners every time.

Fwd will corner faster than rwd or awd up to the limit of grip of those front tires because there are no drive forces being wasted pushing the front tires sideways. With an excess of power rwd trumps fwd because, once rotation is induced by the front tires steering then th rotation can be increased by more drive making the rear tires do some cornering work.

Really hot fwd cars can mimic this effect using the scandie flick, unsettling the car to induce rotation on turn in.