ooldguy93

a little history to put my question in perspective :

I've been running W2W and open track events for, almost, 50 years

In a wide variety of vehicles FV to a '66 427 C2

I've owned / raced a C2, C4 LT4 and C5 Z06

Just purchased a '13 Z06 which will be tracked

I've heard about aero lift at the front ( above 150 ) with OEM body

Should I be concerned ?

Any suggestions from actual experience ?

thanks

TrackAire

I guess the first question is how many tracks do your expect to attend where speeds are over the 150 mph mark? I know at the NorCal tracks, you'd have to have a ton of horsepower to hit the number but in SoCal and other tracks that use a Roval type configuration, a C6 Z06 could exceed that number.

Aero is a tough one....the nice thing about the C6 platform is you have so many proven options & vendors that offer splitters, spoilers, wings and extractor hoods to keep the car on the ground. I would probably approach Katech and LG Motorsports first and I'm sure many others here will chime in with proven advice.

StreetSpeed

It's not gonna lift off the ground, but all stock C5s and C6s get a little "floaty" in the front above 120mph in my experience. I just got used to it, until I did all the aero stuff. It's not dangerous, so I say drive the car and see how it feels and if you want to deal with it there are dozens of things to do that are helpful.

blkbrd69

The only time I noticed any aero lift was NASCAR 4 at Daytona on a breezy day at 160mph+. Katech splitter, sideskirts and spoiler got rid of the twitchiness. WC style hood glued it down and fixed cooling issues.

6SPEEDZ

Katech has a full aero report available. It shows the changes from stock to having al of their parts on.

Suns_PSD

The world challenge Hood from one of many manufacturers does wonders at increasing front downforce and cooling, it also looks great too.

0Anthony @ LGMotorsports

The C6 for sure is better than the C5 for lift at the nose, but at speed yes they will. Like the others have said, it isn't going to pull the tires off the ground but it will cause the car to have a high speed push. One of the reasons we say focus on front downforce before throwing a big wing on the car.

harrydirty

Got my c6z to 186 at Mojave Mile and car was stable, did not notice any twitchiness, but then again, this was in a straight line.

ooldguy93

in response to Trackaire ;

" I guess the first question is how many tracks do your expect to attend where speeds are over the 150 mph mark? "

further clarification

the tracks I'm referring to :

Road America - got to 150 on the front straight with a V8 Miata
with aero

COTA - 120 in an n/a Miata

Road Atlanta - 120 in an n/a Miata

Ohio Mile - 140 with a snailed Miata

so only would want to spend ( possibly ) $5k if there is a real
( safety ) need for it

brkntrxn

I have driven both at speed and agree with Anthony, the C5 lifts more than the C6. IF you do anything to the C6, just put a vented hood on it.

With your extensive experience, I would recommend putting some rake in the suspension (say about 5/8" front to rear) and driving it to see how it feels. If it is still too twitchy at speed after that, then simply do the vented hood.


-Kevin

Silver -V-

If you are concerned, the ZR1 front with an extended splitter will keep you stable, but I have not had issues prior to adding that to the car. Even at COTA, the braking zone brings your speeds down so far there is no corner where you develop much aero push with a stock nose. On the long straight, the car gets a bit lite feeling, but once under braking the speeds and front end dive eliminate that issue. Try it first, then add aero as needed.

As an issue, I did have problems with air coming up behind the car and popping tail lights out. Buttoning up the rear end is something to watch if you add a front splitter. We plan on running cameras and tell-tale wind guides at our next session

Bill Dearborn

With my C6Z I typically ran speeds in the 150 to 158 range at the end of the back straight at the Glen. Car felt settled on the track all the way up the straight, steering didn't get light and the car felt like it was planted to the pavement. With the right tires it could go around the carousel turn after the bus stop in the mid 90s. Front end would start to push some there and maybe a little more front down force would have helped.

Bill

Suns_PSD

OT: Bill, can you report back on your C7Z compared to your previous C6Z at the track? Lap times and what not?

Thanks

Mordeth

I am interested in Bill's response as well!!

Bill Dearborn

It gets a little complicated making comparisons as there was an issue with the C6Z that I didn't recognize until the next owner called me about it. There was also an issue with the C7Z when I ran it at the Glen this last summer. The best comparison is probably from VIR.

At the Glen I was able to run the C6Z into the 150 range at the end of the back straight pretty regularly if there were no traffic issues. I could do this on street or R compound tires. My fastest lap there in the C6Z was on a 32 deg day with snow flying. It took several laps to get the tires warm but I turned a 2:08 followed by several 2:10s.

When I came back with the new car this season it was a nice middle of July day on a newly repaved track. My first two sessions I was just getting familiar with the track and didn't push it all that hard but did get close to 150 at the end of the back straight. But, then I started having a severe vibration from all 4 of my tires sliding on the rims and being out of balance. The more I ran the car the slower it got. It felt like I was driving on 4 square wheels and the speeds at the end of the back straight dropped down to the levels I used to see with my 345 HP 97. About 138. There was no overheating problems as the coolant temp was in the mid 220s and the oil temp was in the mid 270s which are far from overheating and I had seen similar temps at VIR with no performance issues. I also forgot to mark the S/F line in my PDR so didn't get lap times. From what I could determine from the video timer the laps were in the 2:14 range but there could be a second or two either way.

I ran the C6Z at VIR for two seasons before I switched to the C7Z06/Z07. Once I learned the track my times there were in the 2:12 to 2:14 range depending on traffic and my speed at the end of the back straight was in the 155 mph range. I had a very bad bump steer issue with the car in the up hill Esses where the back end of the car would step left when I went over the little hump in the second turn of the Esses which happens to be a slight right turn. Any speed much over 100 mph turned into a butt tightener. It turned out the car had been lowered by a previous owner and the rear suspension travel was almost bottomed out. When I hit that bump it would bottom out. I didn't find out until the next owner called me about the rear spring and whether I had lowered the car.

Once I got the C7Z that turn and that bump are just a little thud on the track. It goes right over it with no issues. My speed across that turn is up 15 to 20 mph based on what is happening when I enter the Esses. That drastically reduced my lap times and I have been on a steady progression downward since then. I was running 2:11s then dropped to 2:09 then 2:08 then 2:07 the last time I was there. My speed at the end of the back straight is about the same as the C6Z but I am pulling a heavier load up the hill (almost 300 lbs along with all of the aero drag from the Stage 3 aero package). The last time I was there I was running with an excellent driver in a C6Z and I was able to run him down and pass him. His top speed was just about the same as mine but I was able to gain on him in the turns.

Overall, I think the C7Z is a better track car but the C6Z is a long way from being a turd. They are still competitive. Put both of them on a shorter track like CMP with its tight turns and the C7Z may have an edge due to its really high torque numbers in the lower rpm range. But both might find a C6 GS or C7 GS that would give them trouble. It is low end grunt that gets you off the corners there and one thing the C7s have is PTM mode and the eDiff which really helps in getting that power down as you start to increase throttle in the turn. Of course there are some C6Zs that have PTM as well but not many. None of them have the eDiff.

Bill

Poor-sha

Nice report Bill and I agree. I really could feel the lift in the C6Z compared to the C7Z and it hurt my confidence in high speed sections. I never got comfortable going flat in the kink on the front straight and it always felt floaty over the crest on the back straight.

truth.b

What speeds were you seeing at the kink in your C6Z?

1badtantrum

More feedback:
Should I be concerned ?
Any suggestions from actual experience ?
Alot of blah blah blah but here is my feedback from experience growing with a 2009 C6Z06.
Concerned...depends. Concerned relative to safety...I don't think so. i don't think the amount of lift at that speed is going to be the only consideration in something bad that happens in an inherently dangerous activity.
If your talking about concern relative to minimum lap times, yes be concerned. Aero/downforce make a huge difference in laptimes.

I started with a bone stock 2009 C6Z06 and track at VIR 4-6 times a year. I can say there is noticeable kind of looseness, drift or perhaps this is lift, that I had with my stock aero, C6Z06. With or without wind above 120MPH on the back straight at VIR the front was loose feeling. Felt like the front end was just floating along. The front straight above 120MPH through the kink at start finish was significant crabbing and the same loose feeling. The uphill esses were tough for me to sustain anywhere close to my entry speed. I got my lap times down to 2:13-18 consistantly on Nitto NT05.
I then upgraded to Katech front splitter and rear spoiler with DRM bilsteins. That made a very noticeable difference in feel everywhere on the track and inspired a lot of confidence in handling a firm seated feeling fed back through the steering wheel and seat. Most noticeable difference was the front and back straight at VIR at speed. The uphill esses were much better but it takes a much better driver to maintain 120's-130's through the uphill esses. My times dropped to 2:08-2:12 consistently. Added a rear ACR wing and scrub Hoosiers dropped times with this setup to a fastest of 2:03:xx with constant times of 2:06-2:08. The car may have been a bit unbalanced with the ACR wing but it may have also reduced oversteer...
I added LG coilovers in early spring and dropped my fastest time to just over 2:02. The coilovers made the most noticeable difference to me in the uphill esses where the back and forth transistions are at speed and quick repetitive to get a driver like me to notice. I also notice the ability to take a little more curb to straighten a corner like 5a and the car doesn't even notice...enough about shocks in aero thread. I then added the large LG front splitter up front in the early fall. The larger splitter made a huge difference in downforce and firm planted feedback in almost every section of the track that is 80MPH+. The front straight kink is a very firm feel now so I can take that at 145+ and increasing with confidence where I was previously comfortable with 135. The uphill esses feel incredible. Rounding turn 9 now, data shows speeds of 118+ where I never exceeded 110 without the splitter previously. I should be able to get through turn 9 at 125 this spring. Turn 10 is much faster as a result. The back straight is completely different with a very firm squashed to the ground solid feedback. Also noticeable downforce feel in the whole downhill section "roller coaster and Hogpen". The front splitter change alone this past fall allowed 4 different laps on the same weekend just over 2:00:xx. I was very surprised at the speeds recorded/supported by data (Traqmate and HPTuners).
There is a noticeable degree of steering 'numbness' with the corvette when compared to something like a BMW M3 that I have tracked in the past. The addition of poly/delrin bushings, shocks, tires, etc have significantly improved the feel and feedback.

1badtantrum

It took me so long to write my response, I did not see your response till after. I really like the fact that you use floaty to describe the feeling at VIR at the top of the hill. a little side breeze and you were floating a few feet right or left until you apply the brakes.

Poor-sha

low to mid 140's

LOL. Been there.