Metalgearsolid_x

Hey guys,

I am automotive enthusiast who has slowly started the research for his new car. I tend to research 6 months to 1 year before I purchase my vehicle. I have always wanted a Corvette. The C6 Z06 was (IS still somewhat) my fav corvette model. But I must say, I'm blown away with the C7. So I may ask a few question here and there next few months as I do my research and feedback from current owners are VERY appreciated.

C7 is fitted with E-diff. I currently have V-LSD (viscous lsd in my 370z) and it's okay. It's nothing I'd write a blog about or tell a friend. I absolutely LOVE mechanical diff and their predictability. I should also mention that I autox regularly (and occasional 2-3 times a year HPDE). At least 15+ autocross sessions a year (that's roughly 100+ runs). It's REALLY important for me to know the predictability of e-diff in autox. So how is the new e-diff? if you turn all the nannies off, does e-diff still brakes individual wheels to slow down? Anyone had a chance to autox with the new e-diff? also, how does this new e-diff perform at the track (HPDE EVENT)? Also, what does base model corvette come with, open diff ? isn't that a little scary to control/put down 460+ hp to the ground with open diff?

Synchrorev match in my 370z is fantastic option. It just makes driving the manual so much easier. I'd glad chevy implemented that in the new C7. Just like the 370Z, can the synchrorev (or should I say "rev match in c7) be turned on ALL THE TIME in the corvette? meaning I can turn on and off the car without having to worry or remember to turn on rev match manually? Bc as of right now, all reviews reflect that you must "tap the upshift" by the steering wheel to turn on manually after each (re)start of the vehicle.

Picking the right color is tough. There are plenty of computer generated pictures of c7. But is there a dedicated "real life" C7 color thread? I apologize if I didn't look but I didn't see it.

thanks

TachItUp

The base car still has a mechanical LSD.

From what I understand, the C7 e-LSD does not brake individual wheels, it will just send power to the wheel with the most grip.

JoesC5

First, the eLSD is only available on the Z51 model of the C7.

Second, the eLSD does not control braking of the rear wheels. It is similar to a conventional mechanical posi-traction, but instead of springs pushing against the clutch disc pack , the eLSD has a hydraulic cylinder. The LSD uses signals from various sensors to electronically control the amount of hydraulic pressure(from a self contained hydraulic powerpack) to regulate the distribution of the power applied to each of the rear axles.

acrace

I haven't driven a Z51 yet, but a couple of base vehicles, so I can't comment on eLSD.

But check out the following link, as it has some good basic info on the eLSD and also the suspension layout, which would be of interest if you're an avid autocrosser who likes understanding suspension details:

http://www.edmunds.com/car-reviews/t...alkaround.html

I'd also suggest checking out the Autocrossing & Road Racing subforum (under General Corvette), if your queries are going to be more autocross/track days based.

RickMN

Many of the track-test reviews and competitive comparisons have done road tracks, and slalom course passes. They all have very positive things to say about the C7's ELSD and how it contributes to its drivability, balance, and quickness in those situations.

TTRotary

This is an interesting question for Autox. E-diff is basically a synthetic TorSen differential, so yes, it is designed to really get the power down coming out of a corner, and it is reported to be very effective in real life.

I don't think much info is in yet concerning Autox. I would surmise that the e-diff on the C7 Z51 would help you get very consistent times as long as you are on the stock tires. The settings are calibrated to the tire's available grip at different temps. Now, once you go to another tire, I'm not so sure. I would definitely NOT switch to another street tire. But I would expect a stickier-than-stock tire like the A6 to work well with the setup.

icntdrv55

I admit right up front that I'm not an auto-X'r, but this statement surprises me. I would have thought that the e-diff lockup was controlled via programming that utilizes the signal from the individual rear wheel sensors, and thus, would accommodate and adjust for tire size/stiction changes.

TTRotary

I don't think there is a way to compensate for tire sizes from sensor info. Grip is determined by reading the tire temp. The firmware then computes available grip based on fixed values for that particular tire. This is cool, but the firmware cannot respond to tire changes. This is like the old OBDII speed-density WOT fuel tables.

Tires can have very different grip characteristics in a given temp range from each other. A michelin MPSC runflat will not behave the same way at 140F as a Goodyear SCII even though both are street tires. Track / DOT radials are different still - they are designed to work best at elevated temps and tend to be slippery when operating at street tire temps - they may in fact provide less grip than a street tire under street / canyon carving conditions. Conversely, a street tire will overheat and "go away" at track temps. Autox is a special animal - tires like the A6 have to be able to heat up quickly during the 1mn run and the chemistry is optimized to provide max grip at lower temps than its R6 road race cousin.

In general with a system like this, you want to err on the side of having more grip than the firmware assumes. ANd then there is the question of tire compounds, which are a whole new ballgame. We have new tire chemistries which return 300 UTQG but stick like the 100AA tires of a few years ago. This was unheard-of 36 months ago.

What would be really cool is if one could download the data set for other tires into the e-diff computer. Then you'd have some pretty amazing results.

onthebottom

Great article, thanks!

rcallen484

icntdrv55

I understand at least the basics of what you're saying, but I presumed that the e-diff lock-up was based primarily on the delta of right vs left wheel rotational speed. I was assuming that the vehicle stability and PTM algorithms were brake-based and used data from on-board accelerometers.

Baron7700

I have first hand experience. It works pretty flawlessly, as in, in none of my runs I was upset or surprised with something the car did. I will edit this with some videos I have.

http://forums.corvetteforum.com/c7-t...-and-pics.html

Trackaholic

I have a 350Z and used to do many AutoX and track days (but now mostly track days). My viscous LSD crapped out after maybe 75,000 miles, during an AutoX run. Changed over to a Quaiffe mechanical LSD and have enjoyed it ever since (now have 177,000 miles).

The eLSD on the Z51 is basically a clutch type LSD with a variable clutch force. I've heard good reviews in magazines, but a friend who drove a C7 at Ron Fellows was not very impressed. He thought it inhibited trail braking techniques and would force the Vette to understeer if you were braking late while cornering. I've never driven anything as powerful as a Vette, so maybe trailbraking isn't as necessary as it might be in other cars, although it seems like it would depend on the layout of the specific corner.

I personally believe the eLSD with proper tuning would be a great benefit, and GM typically tunes their sporty cars very well for the track (Cobalt SS, Camaro 1LE, Corvette, are all good examples of this). I am also waiting to hear more from those who have actually driven one on the track, but I suspect it will be a good performer. I do worry somewhat about the added complexity though.

-T

steel_3d

This guy says there are issues with trailbraking:

http://www.viperalley.com/forum/2013...gen-v-zr1.html

Any other references backing this up or refuting it? No magazines have mentioned it, and I'd be somewhat surprised if Jim Mero and the other test drivers wouldn't consider this a problem.

Definitely does not sound pleasant. I trailbrake the c6 a lot to get the front end to set.

The guy in the link above also comments that the revmatch is flaky.

The good news is - most of these things should be fixable in software.

JerriVette

Which car do you think will auto x faster? The 370z or the c7 z51? Same driver....

cbboarder

What this guy doesn't mention is that the rev match can be turned off and on from the paddles behind the steering wheel. Maybe for this event GM "lock in" the rev match.

genv6.2gm

this isn't a 911, how much trail braking do you need? the older cars would make you sh*t when the rear lifted braking into a turn. not saying the older vettes are bad but imho needed much more respect in this area compared to my porsche.

Philr56

Chevy updated the build your own section of the Stingray site. Colors and options will show up:

http://www.chevrolet.com/corvette-st...-zipcode=31768

VIN666

Um, all the e-diff criticism in the linked article sounds like BS to me.
The logic of the controller is to open the diff on turn in, which allows for quick turn in. On corner exit it gradually applies the eLSD to aid with traction out of the turn.
Why the diff would make the car understeer when trail braking is beyond me.
All I know is, that all the GM test drivers seem to love it.
Same with all the credible magazine drivers...

TTRotary

Probably a safety bias built into the firmware. I have not driven a C7 yet, but C5 and C6 do not like to go into corners under any kind of decel, at least not in my experience. They're not 911s, but they also can't brake deep into a turn the way the FD3S RX-7 or even the MKIV Supra could. With the Vettes, you want to complete your braking early and go into your corner with a bit of throttle, basically balancing the car with the throttle. The C6 is better, but the C5Z could get downright spooky under threshold and trailbraking. The C6Z06 Z07 does much better, due mainly to much more available grip. My comments here pertain to lap sessions on street tires.