If you work hard to upset the balance of a neutral car you should be able to get it to both understerr and oversteer... but generally a neutral handling car should exhibit progressive breakaway of both the front and rear end...thats what defines neutral. If the car favored either power on oversteer, off throttle oversteer or lift throttle oversteer that would be a car that is more oversteering than neutral. If it exhibits power on, Off throttle or lift throttle understeer or pushing its more of an undesteering car. But neutral is neutral no?

 

Spot on. Not all mid engine cars are completely neutral, but if you do find one like a Lotus or a Cayman then much less experience is needed to push the car safely or rather in comfort while next to a cliff without a guardrail. The limits can be approached rather consistently, because the car itself will often smooth over bad driving techniques. First energy is dissipated throughout chassis vice in one corner of it. Secondly most neutrally balanced cars by definition have power delivery that matches the car itself, so snap power applications are somewhat negated (thus why most car reviewers are so fond of the N/A motors for the open winding road driving applications).

 

Bad drivers will be bad drivers no matter where the engine is located.

 

The RME C8 will handle profoundly better than any Corvette that has preceded it. GM and virtually any automotive authority has promised us such. Call
me doubting Thomas. I’ll wait to “see” it with my own eyes and feel it with my own ***. Right now I’m inclined to think theres a high likelyhood the FME platform will retain a fair number folks who prefer it. I was thinking about this today as I was rowing throw the gears in my M7 ZR1 ZTK on a twisty northern Wis country road.

 

The C7 FE Corvette has beaten many exotic ME cars with DCT that cost 4 times as much on the track. Not sure if the C8 will handle "profoundly" better. Going ME does not suddenly make it magically profoundly better. Just ask any of the ME exotics that the C7 FE has beaten on the track.

 

It better be “profoundly” better. Can’t see them releasing a car without better track times.
Deck seems stacked against them being better though.
The PS4S tires aren’t close to Cups, and the car is much heavier.

 

People here are confusing two different concepts.

One is the natural tendency of a given car to oversteer, understeer or be nearly neutral as the limits are slowly approached.

I can guarantee you that the C8, as most modern cars, will come dialed in from the factory with a slight understeer, as this is safer for most drivers, in most situations.

However, this is of little to no importance is situations, on track or street, as loss of control happens. Almost no loss of control happens in a smooth approach and exceeding of the limits. Loss of control happens on transient conditions (changes in surface traction, undulations, etc) or transient input (throttle out of a turn, brake into a turn, etc). This can upset neutral cars, understeering cars and oversteering cars. Hondas and Minis spin out regularly on track just like 911s, for example.

On this transients, what matters is how progressively or abruptly a car initiates rotation, and how easy or hard it is for the driver to recognize the start of undesirable rotation.

So, lets look at a few things that matter on those factors.

1 - C8 has a longer wheelbase than almost all ME cars - all things being equal that will slowdown rotation.

2 - C8 seems to have a lot of mass at the rear of the car. That super heavy DCT behind the engine is almost as heavy as the engine itself. The C8 likely has a weight distribution closer to the modern 911 than the Cayman. In fact, it is MORE rear biased than the modern AWD 911s. That will tend to be more snappy in rotation. It was obvious that GM was seriously worried about the amount of weight in the back of the C8 - that is why they have a very expensive carbon fiber rear crash bar.

3 - GM's PTM (and the C8 will probably be even better) does a phenomenal job helping prevent power induced spin outs, particularly in Sport 1 and sport 2. So if you keep it on, you can at least remove that as a reason for snap loss of control. If you don't order PTM, 2 clicks on the traction control will bring on competitive driving mode which is almost as good as Sport 1.

4 - It will be much harder for a driver in a C8 to recognize the start of rotation than the C7 driver by feeling the motion (seat of the pants), simply because your body, being closer to the C.G., will not move as much. Rather use the feeling of the "lightening of the steering" to recognize start of rotation. If the wheel gets light, you are already rotating - quick hands NOW.

That is my 2c. The C8 will be more modern 911ish than Caymanish.

 

Really nice thoughts.

Its the only reason i ordered mag ride on my 1lt track build. I want to get ptm.

The stability control on porsches are otherworldly in how you never even feel them working. Theres no blinking light on the dash, no abrupt throttle cut, no weird braking noticed on a single wheel or tugs at the wheel. Its completely transparent. So different than when tracking an amg and a different world than my camaro ss.

Im really really hoping they get it right with the c8 ptm. It can make or break a car for me

 

On the street the PTM is a lot more abrupt than on the track, at least based on my observations. On the track I just give more gas and notice it's not accelerating harder. And same for me. It's a lot bigger of a deal than I expected. I actually like it in race mode. It saves some tires and if it steps in, it's a good thing. I also like Race 2 on tracks with walls and/or tracks I haven't driven much. I'm definitely slower, but it lets me enjoy my car more. It's an expensive street car and a good safety feature.
My racecars I run with everything completely shut off, but this is a street car. I'd be a lot more upset if I hit a wall with it.

 

Modern electronics and staggered tires solve this issue. If a 911 can be driven safely with a back pack on, a Corvette can be driven with a full stomach....

 

Depends on what mode you are in. If you put it in Track->Sport1 or Track->Sport2 it is decent, so long as you don't back off the throttle as the car rotates.

Are you sure you are on PTM on the street? If you don't go to Track, double click, you are not on PTM.

I think the Z mode is the best thing that GM has done. It is currently such a pain to go in to Track-SportX every time before driving that I don't bother. If you are in Track the car reverts to Tour on the next start up.

So I leave mine in Sport (that stays on across re-starts) and simply hit traction control button twice to put it in competitive mode (not as good as PTM SportX, but better than nothing). I can't be bothered with so many button presses on start up.

With the C8, it will be heaven. Start up, hit Z button go. I'll probably leave my Z button as: Track->Sport 1, Sport Steering, Track exhaust, Tour Suspension, Sport brakes. For the street. Unless I can program this into MyMode. In which case, I'll make Z button a track button as: Track->Sport 2, Sport Steering, Track exhaust, Track Suspension, Track brakes.

 

This is true, but most of it is not the superiority of the PASM system vs PTM. The issue is that Porsche cars in general (Turbo, Turbo S, GT2 excluded) have a lot less torque than the GM performance vehicles (SS 1LE, ZL1, GS, Z06, etc). Therefore it is harder to snap upset say a 911 GT3 or a 718 GT4 than a Corvette or Camaro. A Z06 has twice as much mid-range torque as a GT3 to manage. A Grand Sport has 50% more.

When you dip your foot on the skinny pedal of a Z06 the PTM has a lot more variability to manage vs PASM. PTM is actually quite good.

If you go drive a Ford Product (e.g. GT350) you would cry and give up if you have to keep the traction control on on track. The only thing you can do with the Ford or Dodge products is turn everything off. Same goes for AMG. BMW's is tolerable at best, but still annoying.

 

Sorry I meant street modes.

PTM 2, and ESPECIALLY PTM 1 seriously inhibit the ability to get the car to rotate. They cut too much throttle. 2 isn't nearly as bad as PTM, but you're not going to throttle steer in PTM 1 at all.

I dont really want PTM 1 or 2 on the street. I don't throttle steer on the street. I'd rather have more SC on the street.

 

OK, that is what I thought. I think it is a terminology issue.

Tour-Sport-Track, etc are driving modes. You can also change the stability control and traction control in those modes. But that is NOT PTM.

PTM is entered by putting the car in Track mode, then double clicking on the traction control mode. Then you can choose the PTM algorithm (Wed, Dry, Sport 1, Sport 2, Race).

You should try Sport 1. Sport 1 has stability control still on and a much more relaxed traction control. It is good enough to let you spin the tires are launch and even do some light throttle steering out of corners, but will minimize the chances of a loss of control. I think it is quite a good mode for street spirited driving. The only issue is how annoying it is to press all those buttons on start up. The MyMode/Zmode will be welcome additions.



Funny story: I was taking a student for hot laps on a track. We were chatting and I was about to pull into the track and I still did not have PTM set up. So as I was pulling out of pits I quickly put it on track, hit the traction control twice and (this was on Camaro 1LE) hit the button four times down to put it into race. Note that once you are on PTM on 1LE there is no indication of what mode you are in (they all show traction control/stability control off). I started driving, got to first corner felt like the engine had an electrical failure, after several seconds (felt like an eternity) engine worked again, next corner same thing. Took me one more corner to figure it out. I miscounted, so I had one extra click, which put the car from Race to Wet. Boy that PTM did not measure action traction at all. It just completely cut power as if we were on a near zero traction track. I had never used PTM on anything less than Sport 1, so I was completely un-prepared.

So yes. ZMode will solve that problem also. The display is so slow, that I simply count clicks and go. So Zmode will prevent starting on wrong mode. It is crazy that one misclick bring you from the loosest mode (Race) to the most restrictive (Wet) PTM set up. Live and learn.

ZMode for the win.

 

Yeah, I know how they work. On the street I just leave it in sport. I'm not trying to slip and slide.

I've used sport 1 extensively on the track (spring mountain). I developed a lot of bad habits, actually. Sport 1 is pretty restrictive on the track.

 

I have alot of experience in Mid-Engine cars as I've owned a couple of Lotus Elises since 2004. I can understand the legitimate concerns about ME vs FE. I've also driven, AutoXed, and tracked C5, C6, and C7 vettes. Firstly, to set the record straight on the Lotus Elise and oversteer as mentioned previously. Yes, they spin. This characteristic is designed in by Lotus. Firstly, the car pushes in a corner like a bread truck. Lotus was so rightfully terrified about Litigious Americans, they made sure it would plow. The front wheels on the base model are 5.5" wide and the tires are 175 series! The sport version had 195s on 6" wheels. Secondly, there is minimum front camber available, about -0.5 degree limiting front grip. All this adds up to a plow. Spinning could happen from "push-to-oversteer" condition. This is where the car pushes so the driver puts in a bit more steering until the rear unloads in a rush.

The sport version had wider tires, same camber, but god-awful shocks with too much rebound that bound up the car until halfway through a corner and then let go causing a spin. The car did not have a tendency to spin on the road, even aggressive canyon carving. I've accidentally drifted an S2000 out of a parking lot. All of the Elise/Exige issues, with modified steering arms and Dampers.(Both available from www.blackwatchracing.com) fix this issue and the car is incredibly easy and fun to drive.

I mentioned the above, not to inject British awesomeness into a Corvette forum, but to set the stage for the C8. Firstly, I slightly disagree with the previous poster about the C8 being more like 911 than a Cayman. I think it will be more like the Cayman, but not completely. The Cayman is 44/56 F/R vs 40/60 for the Vette. The 911 is like 64% rear, but more importantly a bunch of that weigh hangs cantilevered behind the rear wheels. 911s are fantastic, but you do feel that booty at the limit.

These cars will have Eccentric adjustments for the control arms, so Front camber shouldn't be a problem. GM will also likely have better shock settings out of the gate than Lotus. The big advantage is stability control. The Lotus doesn't have it. Much of the poor driving can be corrected to prevent folks from destroying their cars from lift-throttle oversteer. My hope is that GM relies on stability control vs poor factory dynamics to protect people from themselves. If the shocks are not over-damped and if the chassis is more neutral at the limit, it will help reduce over-driving conditions like push-to-oversteer.

The advantages of ME have been mentioned previously, but the big ones relate to the control of acceleration and rotation. The FE is more benign under corner entry, but as we saw with the pacecar in detroit, High HP FE is tough to manage under corner exit i.e. acceleration. The stability control was being asked to control too much torque on a bumpy track. Mark Reuss was probably embarrassed, but in reality, it was too much power under too slick conditions(i.e.bumps) not enough static grip. The weight over the rear helps tremendously putting power down out of the corner. It reduces the load on the computers and allows more control.

On the rotation front, we will have to see, but the car hopefully has lower polar moment meaning more weight centered in the middle as opposed to out on the ends. This means the car will rotate faster, BUT easier to control. Contrary to what many say, I find it easier to recognize rotation in ME vs FE. We will see.

Bottomline, I think the concerns are not going to be an issue. With various levels of traction control to protect the beginner and adjust-ability in the suspension, I believe we'll be able to setup the car well for track-work but be well-protected from all but the stupidest actions on the street.

 

Is a long time NASA instructor... you have it 100% wrong. Backing off the gas is the worst thing you can do if you encounter oversteer in a RWD car. However, most stock vehicles are setup to understeer and that's what most will encounter if they fudge up on a public road. I guarantee the ME car will be tuned for mild understeer as well.

 

Who has it wrong? Which post? I don't think I mentioned it in mine, if I did, I will correct it! You are mostly correct about oversteer. Specifically, if it is throttle induced oversteer, i.e. spinning the tires vs sliding, EASING out of the gas can help, but the car will still be accelerating. Steady state oversteer, where the rear is sliding sideways but the tires are not lit up, you definitely do NOT want to get out of the gas......

 

I was referring to the OP, not you

 

You'll encounter it in any car. Weight goes forward, front grips harder, rear grips less.

You really notice it most (not that it's the most pronounced, but you notice it most) on FWD cars. It's like the front is tucking in on itself or something. I made the mistake of slightly letting up in a huge compression zone of the N-ring in a FWD car. Scared the crap out of myself.

I just can't do FWD. I went in an upgraded to an M4.