The short answer is the mechanical diff is good, but e-diff is the better.
Better traction isn’t only for the track either.

 

I didn't read the whole thread, but in practical terms....and oversimplifying...

A mechanical LSD will typically be setup for a given amount of "limited" slip or lock. If the limit/lock is too high, it is great for acceleration, but it will tend to cause a lot of understeer going into a corner, since outside rear wheel can't turn faster than the inside by a sufficient amount. That can be very annoying and slow the car down. If lock is not enough, then you won't have enough grip accelerating out of a corner because one tire would spin before the other.

An electronic LSD can continuously vary the amount of lock, from fully open (great for turn in) to nearly fully locked (great for acceleration out of a corner or drifting).

So eLSD is a big, big performance enhancer. Particularly if there is great computer programming behind it.

 

Could someone explain the advantages to PTM. I tried a search, NO joy.

Thanks.

 

Go to the “Ask Tadge” section of the forum, he explains all the intricacies of PTM.

Readers digest, while in Track mode you have 5 additional sub modes Wet, Dry, Sport 1/2, and Race. The selection tells TC/AHC the expected track friction in advance. Among other benefits it allows you to go full throttle mid corner and PTM manages a seamless exit. It’s a great track combination Z51/elsd/MSRC.

 

I'll be in the minority for sure (maybe the only one LOL) but I didn't care for it in my Z. The mechanical diff always seemed predictable, the e-diff seemed to have a mind of its own sometimes.

 

I have owned Seven C7s......

I can not notice the difference between them even in Spirited Driving!

 

I was under the impression that the ELSD was a big factor in launching the car and the 0-60 time.

 

Absolutely no difference in 60 Ft. times on the Dragstrip.
Here @ 2000 ft and 100 degrees they all ran 11.9 to 12.0 in 1/4 if
Z51 or Std......No Difference that I could see!

 

So a base car with NPP and a Z/51 should be equal 0-60 ?

 

Z51 includes...performance rear axle ratio - ( not yet specified, but probably 3.73 as a guess ). Might explain the better 0 - 60 time (better tires help too), & contribute to the lower top speed, compared with the base ( non Z51 ) car.

Z51 Performance Package, includes (J55) Z51 performance brakes,
(FE3) Z51 performance suspension, (NPP) performance exhaust, (GM7)
performance rear axle ratio, (G96) Electronic Limited Slip Differential
(eLSD), (T0A) Z51 rear spoiler, front splitter, (XFQ) 245/35ZR19 front
and 305/30ZR20 rear, blackwall, high performance tires and (V08)
heavy-duty cooling system

 

Better tires and rear end gearing is the difference from base cars.

 

No it doesn't.

And yes normally agreed but it seems to be doing fine...? At least in the GT350 anyway. A company called Fathouse Fabrications has been sending 800 - 1500 RWHP through many GT350's without a failure or haven't heard of one anyway.

 

The Z51 rear end is a 3.80 vs 3.62.

 

Just got back from Corvettes at Carlisle. Tadge said in a talk that performance data will be coming out in the fall. I later spoke to 2 Corvette engineers in the Corvette tent inquiring about trans & differential ratios & was told they aren't divulging that info just yet.

HOWEVER, at the back of the tent one of Chevy's posters listing bullet points about the Z51 package showed the Z51 Performance Ratio to be 5.17:1 YES, THAT'S RIGHT, IT DISPLAYED CLEAR AS DAY, THE RATIO AT.....5.17:1.

This may explain how the z51 equipped c8 can do 0-60 in less than 3 sec. That's a huge difference from current ratio's.

 

^^^
Reminded of our Nissan Murano SUV with CVT (Continually Variable Transmission.) It had a 5.17:1 ratio dif. Easy to do, just have the transmission go from for that SUV a max (in essence) 1st gear 2.37:1 and top gear was 0.43:1. IF the 5.17:1 is accurate for the C8, expect the "Base C8" might be the same and just have a different 1st gear ratio. It would NOT be like having a "stump puller" 5.17:1 dif in a C7!

Expect one reason they "might do that" is to make the transmission more compact. They can use smaller diameter gears than say the 2.97:1 1st in the C7 Z51 M7 (Base C7 M7 2.66:1.) That requires a 2.97 times large diameter gear mated with as small a gear that is viable on the shaft. In that example, if the C7 Z51 M7 had a 5.17 dif then to have the same 1st gear torque multiplication would only need a 2.07:1 1st gear!

Another reason could be what it says in the GM DCT patent. It states they configure the gearing so that "fewer gear pairs" are needed than would be required in previous, normal design DCT's.

SIDEBAR
Regarding the Nissan Murano CVT, I liked it! Was interesting in that first year of production for the highest hp engine available (which we had) there were issues with belt or pully wear. We never had any as it was my wife's fist FWD SUV and she was driving in the Smokies in heavy rain and when coming down step hills she felt the car wasn't safe. Not sure what the issue was but related to my first FWD, a Dodge Colt when gasoline was hard to get and we lived in Western CT. Recall going down steep hills and on the twisty Saw Mill River Parkway to Tarrytown NY, learned when in snow or worse ice, used the hand break to slow! Also used it when having fun in high speed corners!

But after that experience she was never happy with the Murano, so after 1 year bought her a 4WD Porsche Cayenne and she now drives a 4WD BMW X5 SUV!

Also in that first year they had the CVT literally vary torque continually with no steps. Turned out enough owner's did not like that and wanted to "feel it shifting" like they were used to. They changed the programing and had it change gear ratios in a few steps!