I had an interesting experience yesterday when I took my new (to me) 2007 C6 to the track. The track is Pacific Raceways, near Seattle, where I have been a Porsche Club driving instructor for about 12 years, so I have just a few laps there under my belt. The car is stock, save for Toyo R888 R-compound tires that were brand new.

Because I was unused to the car, I left the traction control on. I was overall very happy with how unintrusive the TC nannies were, but a weird thing happened about 3/4 of the way through each session. In the middle of the very technical T5A-5B/T6 complex, the nannies would suddenly awaken. The warning script would come on, and the car would suddenly lose what felt like 50 hp. I would each time reach down and switch the TC off, and all would be back to normal, except the dash light warning me of impending doom would come on.

Anyone have an idea why this was happening? My guess is that as the tires heated up during the session, the difference between the slip angle and the steering input angle became great enough that the nannies became alarmed, but that's just a guess. I have never driven a car on track that had traction control, so this whole "hand of God" thing is new to me.

Thanks

Terry

 

Do you still have your Tire Pressure Monitors (TPMS) in place and are they all working properly?
Sometimes what you've described happens when the computer isn't reading the TPMS.
It almost seems as if Active Handling sensed/thought that the car was just getting too out of shape and simply intervened?
You might've had better results with Competitive Driving mode (two quick pushes of the Traction Control button) but personally, I would've likely just turned (and kept) the Traction Control completely off before even heading onto the track.

 

Hi Terry

with LS1LT1 concerning lack of tire pressure sensors.

It sounds like your track tires are mounted on different wheels, and either they do not have tire pressure sensors, or the sensors haven't been programmed into the TPMS computer in the car properly.

What DIC message did you see???

I bet it was "Service Tire Monitor".

Here's an excerpt from the 2007 Owner's Manual:

Different model years react differently to running with no sensors, but I know the early years (I have an '06 Z06 that I track regularly) are not happy when running with no sensors, and when you get that "Service Tire Monitor" message the Active Handling is VERY intrusive!!!

When that message comes on you are unable to go into Comp Mode with the AH, and if you were in Comp when the message comes up Comp will automatically drop out and the AH will revert to full on and will react very aggressively to not allow high yaw rates or lateral G's - as you experienced.

Where the 2007 Owner's Manual quote above references "about 30 minutes", the 2005 and 2006 manuals have a "60 minute" time period before you get the "Service Tire Monitor" message and the very aggressive Reaction from the AH.

In about 2008 they took any reference to a specific time out of the manual, but I know on my 2009 it's about 20 minutes.

That time period is from each engine start/ignition cycle, so if running with no sensors you'll have about 30 minutes from each startup until you'll get problems - and if you start up in the paddock area, drive out to stage for the start of a session, and sit there for several minutes until the track is clear and your run group gets a green, then you're 10 or more minutes into your 2007 30 minute time period. 20 or less minutes into the session you'd encounter problems with AH.

You say that you had problems "about 3/4 of the way through each session", and that's exactly what you'd expect from the above scenario. One way to extend your time on the track is to warm up the car, then shut down in the staging area, and only restart just before going out onto the track so you get the full 30 minutes before issues arise.

If you're running longer sessions, I'd recommend tire pressure sensors in your track wheels/tires. I like to know if I'm having high/low pressure problems anyway.

Good luck with the problem, but I bet the tire pressure sensors are the culprit.

If you determine that they are, you'll need to make sure you get sensors for a 2005-2009 C6 - they changed the TPMS computer in the car in 2010 and it requires a different sensor. Also, you'll need a TPMS tool to reprogram sensors every time you swap from street wheels/tires to track and back.

BTW, I run HPDE's in Comp Mode. I'm not doing W2W racing and looking for podium finishes or more sponsorships to get a better ride. If you're smooth you will RARELY see an "Active Handling" message blink in the DIC. If you really throw the car around AH will probably activate more frequently and put on an individual brake.

The only place I run that I regularly get a blink in the DIC and might feel a very short brake application when running in Comp is at Daytona when running around the high banking - mostly accelerating out of NASCAR Turn 4 at about 160. It used to occur more before they repaved the track and I might get a quick blink up on the banking when bouncing up and down. But last fall I still got it on the nice smooth track out of T4, although it depended on what line I was running and whether I was turning more for entry onto the front straight from a high line on the banking, or running a lower line around the banking and held a steady sweeper onto the straight.

At any rate, with the AH sensing things every 1/1000th of a second, if it is sensing things that my butt isn't quite feeling, I will gladly accept its help to keep me off the wall at 165+!!!!

Bob

 

Bob and LS1LT1,

Thanks for the info--very interesting stuff. But I am running the stock wheels with, as far as I know, the TPMS's still in place--I had the track tires mounted at Discount Tire and they said nothing about removing the TPMS's.

Since it always happened in the exact same complex of turns, which are high speed left/right/left transitions, followed by a steep uphill climb, I think it was probably a function of slip angles vs. steering inputs at high tire temps. Or, perhaps, due to the fact that the shocks are the original 60K items (new ones are sitting on my garage floor--just didn't have time to install them) maybe that was it?

Now that I have a better feel for the car, I'll start running with the nannies off. I too am not going for lap records or podiums, just out having a blast!

Thanks

Terry

 

I've had the very intrusive AH from a tire pressure sensor problem once - the brakes jerked the car around at turn in, and trying to accelerate out of the turn I had no throttle response until virtually all yaw and lateral G were gone with unwinding of the steering wheel.

So, if you didn't have it that bad then you probably just had normal AH intervention in that section.

Butt....your mention of "about 3/4 of the way through a session" still makes me think that the time period for the "Service Tire Monitor" message due to your sensors not being properly programmed may be part of the problem.

As far as running with all nannies off, I feel absolutely no need to do that in my car - I drive in Comp, not everything off.

My driving style and the tracks I run just don't give me any problems, except for an occasional blink of the DIC as mentioned in my previous post. If you're driving 10/10ths all the time and drifting most corners, then you'll probably get a lot of AH even if running in Comp, and in that case you'd want to turn AH off completely.

So....I'd recommend trying Comp and see if you get DIC messages and feel brakes jerking the car around. If so, then you'll definitely want AH all the way off.

Bob

 

Terry, you don't say the tire sizes you are running but I run R888 also, sizes 255/35r18 up front and 295/30r19 in the rears. Anyway the only time I have had Traction Control interfere is when exceeding @90mph. About the only time that happens is in the straights.

It has been my experience that AH does a real good job of correcting under-steer, not so good over-steer. But from what you described it sounds like it kicked in for over-steer. In an under-steer condition you can feel the ABS working, in over-steer it feels like reduced power.

 

That's exactly what happens in that complex-- the tail comes out a bit when you get on the power.

I think I'll just have to remember to switch off the traction control now that I'm pretty used to the car.

BTW--my previous (14 year) track car was a Porsche 944 with a transplanted 968 motor. It ended up a fully caged, gutted, 2500 lb animal. Since both cars are laid out the same way--front engine/rear transaxle, I felt right at home in the Corvette. It just felt like a bigger, faster version of my 944. Very sweet.

Terry

 

Try comp mode (no traction control but still have Active Handling) first and see if you get the same reaction. Active Handling is less intrusive in Comp Mode as GM opens up the dead band in that setting. The system corrects understeer by applying the inside rear brake and it corrects oversteer by applying the outside front brake.

The slip angle thing is interesting. If I get it right your theory is as the tires get stickier you need to turn the steering wheel less to get the same turn in and lateral G force. The algorithm works by computing yaw rate, G force and steering angle so if you pull more Gs in a turn with less steering input it might interpret an oversteer situation. Although it seems like once you get into an oversteer situation the G Load would reduce.

Bill

 

Terry

Bill is right, put it in comp mode. You are not having a problem with TC but with AH. With just TC off you still have fully intrusive AH. In comp mode you are able to hang it out there a tiny bit before it interferes.

 

Thanks, all. As it is, I'm still trying to figure out how to set the clock in this thing

After 23 years of driving/racing low powered momentum cars (Spec Racer Ford, Spec Miata, 944), I'm loving every one of those 400 hp.

This year, my 18 y-o son starts on the track, following in the footsteps of his 24 y-o sister (who also started when she was 18 and now has 70+ days on track).

I think the Corvette will be perfect for him, first with all the nannies on, then with them off. He started in karts when he was about 8, so he's ready.

 

Hi Terry,

I ran four days last year at PR in my 2008 corvette with the Porsche Club, I had a great time at every event and look forward to a couple of more days this year. The PCA instructors are the best and the PCA does an awesome job with Driver Education.

My suggestion is to talk to Randy Goins and describe your problem. Rand was my last instructor (labor day weekend) of the year, awesome guy and very familiar with the C6 and Pacific Raceways. I'm sure you know Dean too, same deal.

I ran all last year with all of the nannies turned on, I would sometimes get a hit at the exit of turn 2 and more often at the exit of turn 9, just over the bumps and into the main straight. I hated that one because I REALLY didn't want to slow down going into the straight so I learned to stay closer to the center of the track.

I traded the '08 and picked up a new GS, with work the way it has been I have not had opportunity to get out yet this year, I hope to later in the summer.

A question for you, are you running with the stock camber adjusters or have you upgraded to the pfadt version? Reason I ask is one let go on me last year while accelerating out of turn 2, it was a little unsettling to say the least. With the new car I'm contemplating the need to upgrade from stock, it would be good to know if this is a common problem and should be done without further thought or just go with stock as it doesn't happen very often.

Mike

 

Hi Mike,
I know Randy and Dean well, and have been instructing with them for years. Great guys.

Drop by and say hi the next time you are out. I'll also be instructing at the Corvette Marque Club day. My car will be the yellow one, number 00, surrounded by hot chicks (OK, maybe I'm exaggerating on that last part).

The car is all stock at the moment, save for the R-compound tires. it will have new shocks before the next track day, but that's it.

I think I'll jut turn the nannies off. My 18-yo son will be starting out on track this year, but he'll be running with them on.

Thanks

Terry

 

Hi Terry,

If/when I can get to the track this year I will be sure to stop by and say hello.

In regards to the nannies being turned off, last year I did a skills event and did it in
comp mode. I could make the car understeer and oversteer and it felt like the nannies
were not turned on at all, though when on the oval and in heavy rain, it became evident. The point is, with the car in comp mode there seems to be a lot of latitude before active handling will kick in. The point is, when in comp mode, AH is active but not by very much.

The way to turn them all off is to push the traction control button twice and on the second push, hold the button down for a few seconds until a message on the DIC comes up and tells you there is no traction control or active handling. Sorry if I'm being redundant here.

I'm really interested in your reaction to turns 5A, 5B and 6 as I have had a bit of a challenge through there. When I come out of 4 and after the dips just before 5A, the car feels a bit unsettled to me so my approach to 5A is a bit slow. From what I understand in this section, if you mess up 5A it is tough to recover enough to get 5B and 6 correct. With all of the bouncing after turn 4, I'm a bit slow into 5A as it is difficult to get the weight transfer brake prior to 5A and I don't want to jump on the throttle too quickly out of 5A but just squeeze the throttle for 5B and squeeze a lot more for 6. By the time I came out of 6 I'm moving pretty fast towards 7, concentrating too hard to even look at the HUD.

Last year I had a fresh set of Michelin Pilot Sport ZP's, awesome tire but a bit expensive to burn up on the track.

Mike

 

Mike,

The 5A-5B-6-7 series is the most complex I've encountered at the 10 tracks on both coasts I've driven, including VIR, Mid Ohio, Watkins Glen, and Laguna Seca. Don Kitch says it's the toughest in North America, and he would know.

My advice is to get all your slowing and downshifting done on the rise toward 5A. If you walk the track you'll see that the hill into 5A is really steep, so the car will squat down on its suspension and lose a lot of momentum there even without a lot of braking. Smooth brakes as you go up the hill will scrub off the last bit of speed and keep it from getting upset. You then want to just nip the apex of 5A, then very gently guide it through the next set of turns, avoiding any harsh or sudden wheel inputs. Then be very careful and gentle with your wheel inputs as you cross the transition at T7--this is, IMO, the most dangerous part of the track.

Take it slowly at first, then ride through with some of the old geezers who know the track. Be careful and sneak up on it slowly--it's dangerous. But quite a rush when you get it right.

Terry

 

Terry,
The depth and breadth of experience of the PCA instructors never ceases to impress. I can't thank all of you enough for your generosity sharing your experiences. I know I am a much safer driver after training with all of you and look forward to many more sessions. I hope to eventually join your ranks so I too can share what I have learned.

In some ways I'm glad to see I am taking on one of the toughest sections of the track and being cautious about it. A good friend of mine had a serious accident between turns 6 and 7 when a car went off the track and dodged back in front of him as he tried to get around resulting in a T bone accident.

I haven't had opportunity to walk the track yet, though last year I did the next best thing and volunteered to help set cones before the event. It was very illuminating. Aside from the altitude changes, what was interesting to note was the distances the cones were set from the various turn points. Its a sobering indication of how much distance is traveled at speed, something you don't really notice behind the wheel.

What gets me going into 5A are the dips. I must still be a little hard on the brakes at this point and need to modulate a little better. The added braking power of the GS will certainly change the feel of this turn from my last years car. The dips (3) seem to get momentum moving in the wrong direction (up) then trying to brake to get momentum and force moving in the right direction (down and on the right front wheel at turn-in). Once into the turns though, as Randy would say "squeeze, squeeze, squeeze the throttle" while going through 5B and 6, as you say being gentle but accelerating just the same. I know the track is pretty rough through 7 so there isn't the traction available as there is for the newer pavement at turn 2. Last year someone mentioned loose pavement at the entrance to 8, all of this making the track more challenging than it otherwise would be.

I hope to get out again this year for at least a couple of events, I'll ask for you as an instructor.

Thanks again,

Mike