theseal

direct, same driver comparisons on the same weekend, with pretty consistent conditions, in 3 different corvettes.

Car 1) bone stock 13k mile 04 c5 z06 just purchased, with stock pads, new RE760 340 tread wear grocery getter tires. the only thing not stock is the front end alignment. stock ride height even.

Car 2) 585 rwhp c6 z06, sub 3000 pounds, with bushings, c5z gearing, stoptech brakes with DSUNO pads, some electronic magic, and 335/18 michelin ps2's all the way around that were pretty well baked. (probably 6 full track days on them and some street driving). this car has been tested and tuned to try to get it to handle, with a number of different setups. Lots of springs, bars, shocks, ride heights, etc. currently it seems that this is the best handling setup yet.

Car 3) stock but stripped 1992 6 speed car with ballast to make NASA TTC weight, bone stock LT1 air intake all the way out the exhaust, except light flywheel, carbotech pads, 245/18 hoosier R7's. the car was aligned and a 4 point roll bar and racing seat put in. stock springs and bars, cheap shocks, (like cheaper than koni singles). this is a fledgling effort, first track day.

bottom line, recorded lap times:
Car 1) 1.45.97
Car 2) 1.42.74
Car 3) 1.46.1*

* owner of car 3 wanted driver 2 to take one and only one lap in Car 3, and instructed driver not to beat 1.46. owner of car ended up turning 1.43.9 himself so that's getting closer to the c4's actual current capability.

MSR H CW is the track.

top speeds on 'straights':

Car 1) 106/116/125/123
Car 2) 115/126/139/134
Car 3) TBD but much slower

what's really interesting, and the real reason for the post is the following:

split times show that despite Car 2 (c6) getting 9/10/14/11 miles per hour increased terminal speeds on the straights, those advantages only yielded .2, .45, 1.25, and 1.11 second advantages against the C5 (Car 1), respectively.

In other words, the total straightaway split times gained from '220+ additional pure rear wheel horsepower on the track was only 3.44 seconds. And actually, it was much less. Braking zones were too hard to split time separately, but the c6z was pulling 1.1-1.2 g's braking compared to the c5z usually .9-1 at best.

So actually the real conclusion is that 220+ additional horsepower, plus radically better brakes all together only gained 3.44 seconds on an otherwise very similar car.

Another interesting data point is lateral grip versus 'corner split times'.

the c5 on 265/295 full tread RE760's generally hovered around 1 g; spiking to 1.1.

the c6z, lighter and on 335's all the way around, had identical g numbers. (As I said, the michelins were pretty well toast at this point, as on 1 year old hoosier A6's the car pulled 1.5-6 all day long, and peaked 1.7).

I dont have c4 data yet but will update.

So despite having almost identical peak and average cornering G forces, the c5z was consistently faster in the 'pure cornering' splits. Faster to the tune of .95 seconds in the aggregate - a very significant result given that the c5 is heavier, soggier, with less brakes, power, much smaller tires, and about equal actual grip.

subjectively, the c5z was extremely easy to drive, work hard into corners on the brakes, and come out working the rear tires to the limit until the car straightened out and the car was floored.

the c4 felt much the same; very neutral, predictable at any point, and at any slip angle... though the extremely soggy brake pedal was not confidence inspiring and took some getting used to. i expect that will get fixed as the car is developed. the driving position was also set up for much taller people so vision and pedal/steering reach were issues.

the c6z was white-knuckle ugly, unable to work hard consistently into corners, and with a feeling of knife-edge unpredictability far beyond what the horsepower should have caused. the combination of crazy power and dead tires accounts for a lot of that, but there is still something up with C6Z's that does not lend itself to confidence at the limit.

And that's where you see it in the data; the c4 and c5z are able to really work the whole edge of the friction circle at FULL grip, with any slip angle/yaw angle, with full confidence. The c6z is always leaving the corners of that friction circle a little off of full g's - either under or over the limit of the rear tires.

Still looking for setup answers on this issue.

Bottom line, all three are very fast, very fun, and will pucker up the passenger seat cushion BIG TIME.

the c6z may have been the fastest, but i promise you, BOTH seat cushions experienced a little suction at times in that SOB!

Bang for the buck award: c4 by a mile. this is a $7-9k total effort, plus the time to strip the car.

smartest guy in the room award; track work is still all about the handling and tires... as far as lap times go, power is just the sprinkles stuck in the chocolate on the ice cream cone.

White knuckle award, a car that can hit 140 mph on street tires at MSRH, and never get over a g of grip is no joke baby!

Question of the day? How much time would a set of new hoosiers make up?

troyguitar

over old street tires on a high hp car? A LOT

I kind of wish I'd read more about C4's before buying my C5 to be honest. I let the "common wisdom" that C5's are infinitely better keep me from even looking into the possibility of a C4. Instead of a $50k+ TT3 car that I can't afford to take to the track more than once or twice a year I could have built a $15k TTB car and run it 10+ times a year... hindsight as always brings much clarity.

ratt_finkel

Comparing 3 different cars with 3 different setups and 3 different drivers is like, well, comparing round red fruit to round orange fruit

Sorry, but doesn't really say much. Thanks for the read though

Rob31

C4s a very under rated . Good driver in a new c7 oem tires ran a 1:21.4 compareable driver on used A-6 L98 TPI C4 (me) ran a 1:21.9 I have since ran a 1:20 .8 on those same tires .Im less than .8 off the AM record

theseal

All the same driver except for the asterisk c4 time. Sorry if that was not clear.

rfn026

Most of us run track events. We're not racing.

You can have as much fun in an old C4 as you can in a C6. The small block C4 is just as strong as anything you'll find in the early C5 Corvettes.

People are spending a bunch of money to run track days. What's the point? You can't even win a plastic trophy at a track day.

Just buy a car you can afford and drive around. It's supposed to be about fun.

Richard Newton

96CollectorSport

If anything I think this proves how important set-up is. If they were throwing that many parts at the C6Z it seems like they were doing a lot of guessing on the set-up of that car. A well set-up car should give you confidence not scare the crap out of you.
If you don't know what you are doing then your probably better off leaving it stock.
Also just because the C6Z had StopTech's on it doesn't mean the braking is better - actual braking force is less than the stock system with an off the shelf ST kit. They are "better" because from start of the session to end of the session they are more consistent than stock stuff - the stock brakes are good for 2 or 3 ***** out laps before they start to fade.

The track prowess of the C5Z has been well represented by the old NASA TTA cars that had to use stock suspension and ran some really quick times .

Fresh A6's compared to worn out PS2's could be worth as much as 5 seconds, especially in a high hp car like the Z.

ratt_finkel

My apologies.

theseal

i have a little more data trickling in from some videos... looks like that old c4 on 245 R7's was consistently worth 6-7 miles per hour at the apexes over either the other setups.... its all about the tires!

Its not this simple, but if you averaged 6 mph increase the whole course, that would be 7.2 seconds!

As far as c6z setups go, it was worse when stock in every aspect... they just dont agree with me and i can't really pin down all the reasons.

c4's and c5's fit like a glove.

FASTFATBOY

Is the #3 car the Vorshlag TTC effort?

Phoenix1911

I'd have to agree, the below movie (not me) shows the prowess of not only a great driver but a well setup car (alignment & balance). I've been on the track in my C6 Z06 with Greg (C5 pilot in the video) and he scoots around me in his almost stock C5 like I'm on my cool down lap.


Yes, that is a helicopter at ~1:20, and yes that is a Switzer tuned GTR giving it the beans

Racingswh

Sorry for the off topic but I have to ask. How does the neck restraint system he has connected work when there are no harnesses in that car?

FASTFATBOY

No cage or window net either

Racingswh

Yep. I didn't want to be overly critical but it's just a pile of street cars going W2W. I have never seen an event like that before.

Phoenix1911

You are correct, while there are fully prepped & trailered race cars, half the field drive home in their vehicles after. It is contract passing, and a "Gentlemen's Series" run at Calabogie Motorsports Park. Mostly instructors and A group runners that participate in local HPDEs. It's not full w2w, ie., dive bombing into the corners.

To come back on topic. Basically a stock C5 showing how capable a well tweaked setup can be, as opposed to shoving gobs of money into a C6 Z06 (not to say the same couldn't be done to the C6 version), but.... mo' money, mo problems, mo upset wife, etc.

mesospeedy

So this is making me nervous, is a C5 (all things being equal) really quicker through the corners and easier to drive at the limit than a C6? I've got an '11 GS that I hope to finally get on track this summer (previous job kept me too busy on weekends to get in track time). I tried to talk myself in to a C5Z before I bought the GS, mainly because I knew the LS6 was very solid, and it would have been a noticeable difference in price. But I like the C6 wide body style and interior so much better than the C5s, and I found a great deal on mine, I just couldn't resist. So did I choose the lesser chassis? Or will a good alignment and corner balance and a little seat time be enough to make the C6 work to it's potential? Just for reference, I have some track experience, but non in this car (previously tracked 98Z28)

JerryTX

Same weekend, C6Z06 in the ST1 race group was able to run 1.38 (#480). There is no reason to think if the C6Z06 in your test wore new Hoosiers 335 square that it wouldn't pick up 4 to 5 seconds. A base C6, what I run, is just as competent as any gen vette we are talking about, setups being equal. Our cars, with a good track setup, are essentially neutral handling. Add crappy tires and at the limit, the car is willing to let either end go at any moment, no surprise there. My .02.

FASTFATBOY

At NOLA I am on average 5 seconds a lap quicker on BFG R1's over Nitto NT-05's.

I would say a NEW set of slicks is good for 5 seconds, I don't see why not.

I am impressed with the C4, car's fast.

theseal

dont over think it, you'll be fine. first of all the base c6 doesnt seem to have nearly the same issues as the z06. further, i am talking about 1:42 on baked old street tires at 1 g and a razor's edge, when the lap record for a prepped TT1 car with monster hoosiers and aero in a tricked up viper is less than 5 seconds ahead of that.

if you have a c6z, you have to be very careful right at the edge of rear traction on braking and cornering... whereas the c5z seems to comfortably carry any slip angle you want in the rear in any situation. that's about what it boils down to.

Bill Dearborn

The difference that I notice between the C5Z and the C6Z is the C6Z is more nervous powering out of a corner especially if the corner is bumpy. At the Glen there were corners where I could just roll on the throttle of the C5Z to wide open and it would just drift nicely to the track out point and rocket down the straight. With the C6Z there were some corners where I could do that but there were others where I had to restrain my throttle input until there was less steering angle in the car. The toe of the boot was especially nasty due to the bumpy concrete exiting the apex of the turn. C5Z didn't even notice them while the C6Z would power oversteer you right into the inside guardrail if you got on the throttle before the rear tires were off the concrete.

I suspect the C6Z rear spring is too stiff and that there isn't enough suspension movement. The DRM tuned shocks helped but didn't eliminate the issue.

Bill