heavychevy

Correct.

The HACK

Guys guys guys...Bench racers, get ready for some MATH.

M7 gear x rear end multipliers:

1st gear: 2.29 x 3.42 = 7.83
2nd gear: 1.61 x 3.42 = 5.51
3rd gear: 1.21 x 3.42 = 4.14
4th gear: 1.00 x 3.42 = 3.42
5th gear: 0.82 x 3.42 = 2.80
6th gear: 0.68 x 3.42 = 2.33

A8 gear x rear end multiplier:

1st gear: 4.56 x 2.73 = 12.45
2nd gear: 2.97 x 2.73 = 8.11
3rd gear: 2.08 x 2.73 = 5.68
4th gear: 1.69 x 2.73 = 4.61
5th gear: 1.27 x 2.73 = 3.47
6th gear: 1.00 x 2.73 = 2.73

7th (for manual and auto) and 8th (for auto) are excluded in the calculation because, well, on the race-track you will NEVER use those two gears. As you can see...1st all the way through to 6th, the auto has the gear multiplication advantage in this application. Given the same engine output, minus the small 5% power loss for torque converter on top of clutched manual, you're still looking at a distinct advantage for the AUTOMATIC gearing on the ZR1. Based on Poor-sha's 70-161mph spread, that's 3rd, 4th, and 5th gear, where the automatic enjoys a 37%, 34%, and 24% multiplication advantage in power to the WHEELS.

The A8 is simply FASTER guys. In fact, you'd have to constantly drive 1 gear lower in the manual to keep the same gearing ratio.

heavychevy

What are the multipliers for the Z06? Surely the auto has the advantage there too.

The HACK

I think the 8 speed auto has advantages across ALL models. That's the "game changer" right there. Used to be, across the industry, the autos can't hang with manuals because the manuals has less driveline loss AND better gearing ratio, as the typical autos have 1 less gear than manuals and to make decent efficiency the last 2 gears are overdrives.

But with the A8 all of a sudden auto has leap frogged manuals.

Z06 gearing same as ZR1.

I grabbed the specs for the Grand Sport, and the M7 and A8 multiplier gaps for track use isn't nearly as big for the Grand Sport/Z51 variant.

M7:
2.97 x 3.42 = 10.16
2.07 x 3.42 = 7.08
1.43 x 3.42 = 4.89
1 x 3.42 = 3.42
0.71 x 3.42 = 2.43
0.57 x 3.42 = 1.95

A8:
4.56 x 2.73 = 12.45
2.97 x 2.73 = 8.11
2.08 x 2.73 = 5.68
1.69 x 2.73 = 4.61
1.27 x 2.73 = 3.47
1 x 2.73 = 2.73

For MOST tracks, you're in either 3rd or 4th. The Grand Sport A8 enjoys a 16% and 35% higher multiplier. Even with the typical 5% higher driveline loss of the torque converter, 4th gear in the auto will still provide more power to the ground.

Here's the C6 Grand Sport's gearing ratio comparison, M6 vs A6:

M6:
2.97 x 3.42 = 10.16
2.07 x 3.42 = 7.08
1.43 x 3.42 = 4.89
1 x 3.42 = 3.42
0.71 x 3.42 = 2.43
0.57 x 3.42 = 1.95

A6:
4.03 x 2.73 = 10.99
2.36 x 2.73 = 6.45
1.52 x 2.73 = 4.16
1.15 x 2.73 = 3.14
0.85 x 2.73 = 2.33
0.67 x 2.73 = 1.82

As you can see, in the C6 (at least with cars that can be optioned with either auto or manual) gears 2-6 the manual enjoys a small advantage AND a ~5% advantage in less drivetrain loss. Going back 15 years where the manuals has more gears than autos:

C5 M6 vs A4:

2.66 x 3.42 = 9.10
1.78 x 3.42 = 6.09
1.30 x 3.42 = 4.45
1 x 3.42 = 3.42
0.74 x 3.42 = 2.53
0.5 x 3.42 = 1.71

A4:
3.06 x 2.73 = 8.35
1.63 x 2.73 = 4.44
1 x 2.73 = 2.73
0.70 x 2.73 = 1.90

The manual enjoys a multiplier advantage once the torque converter is locked up, in each and every gear, with a taller final overdrive gear for better freeway fuel economy too.

Guys, the reign of manuals is over. With 8 speed and 10 speed autos on the way, there's really no way the manuals can compete with autos, in both efficiency and performance. They can still space out the first 2 gears in a way where you hit 62mph before 2nd peters out, and gear 3-4-5 much more aggressively for track/performance applications, and still have 6-7-8 being overdriven aggressively for fuel economy.

On the Grand Sport, it's still justifiable to get an M7 because 1) manual with the tranny cooler runs a much lower risk of overheating and 2) 3rd gear, where you're spending the bulk of your time coming out of corners, is nearly a wash compared to the auto. But you're going to have to justify spending more time in 3rd to translate to the same lap time as if you were driving an auto.

In the Z06 and ZR1? If overheating is not a concern, in a 2-3 hot lap type environment? A8 is FASTER.

Poor-sha

Gear ratios are the same from ZR1 to Z06.

heavychevy

To me, that nullifies gearing as the reason. The A8 in the Z06 did not achieve higher speeds than the manual. Look at the videos I posted. Tommy Milner exits turn 7 (before the back straight) faster than Vinnie and ends up slower on the back straight by several Mph. There is something else at play. Eric manages to exit turn 7 several (~5) mph faster actually and ends up 9 mph up. He doesn't mention upgraded tires on the video but I don't know him personally to ask.

But this throws meadowz06 theory out the window. Cuz pro driver isn't a good enough explanation.

Dave Schotz

Hack, I agree with you 'from a dead stop'. However, on the Road Course, and assuming you're in the 50+ MPH range for slower corners... the A8 would be in 3rd gear, the M7 in 2nd gear... and thus the 'acceleration' would be equal, if not advantage Manual due to weight and drivetrain benefits.

So it's not as simple as '7 ratios vs. 8'... when it comes to road racing... it's the gears you're in... and 1st gear means nothing... and it seems in the A8... 2nd gear may mean nothing as well.

Best Regards,
Dave

The HACK

Sigh. Again, bench racing at its FINEST.

Time of the day, ambient condition, hell rotation of the earth can ALL have significant impact on lap time, terminal velocity, and a slew of other measurable. Comparing time as driven by different drivers on different days of cars in various guises of modification is USELESS. I can only tell you what the fact says. That A8 autos have better gearing ratios now, and should have a decided multiplication factor advantage on track. That's a fact.

Here's what *I* can tell you. I've driven Auto Club Speedway hundreds of times. All the way back when it's called California Speedway. This ONE TIME, for whatever reason, it was unseasonably cool for California, and my terminal velocity before having to slow down at the end of the LONG, long NASCAR front straight was 145mph in my BMW MZ4 Coupe. The ambient high that day was in the 60s (I know, right? 60 degree high in So Cal might as well have hell frozen over). I have never, to this day, hit close to 140mph again in my MZ4 Coupe, because ambient in So Cal for my typical Auto Club Speedway track day has been in the mid 80s to high 90s, occasionally crossing over 100 degrees.

HERE is another factor to consider. Last time I was at Buttonwillow Raceway for a 2 day event, I set my highest terminal velocity coming out of the Esses before Sunset at 118mph on the first hot session of the day at around 10:00am. But my FASTEST lap (traffic not withstanding) came on day 2 in the early afternoon, with my highest terminal velocity before Sunset being at 115mph. Why? Because it was in early March, and the conditions in the morning, while favorable to HP and speed, was unfavorable to my tires, which like a little more heat to come to life (because scrubs). So while on day 2 the early afternoon laps had slower terminal speed at the longest section of the straights, it had more grip in the turns and I shaved nearly 1.5 seconds off of my lap time despite being, on average, 3-5 mph slower on the straights.

Go figure.

If you're going to use Driver X vs Driver Y on track Z on different days, in different cars as the "empirical evidence" for something...Don't bother. Hell, I am Driver X vs Driver X on Track Z in same car, and on any given day, if the temperature swing is in the right range, it could have dramatically DIFFERENT results. Like a couple of seconds different results.

There are two things in this discussion that can not be disputed. Math, and engineering. Engineering on the A8 is superior to the M7, for the same reason why manuals have been superior to autos for ages. More gear means more ways you can stay in the meat of the power band. That, is the truth. And math doesn't lie. The gear ratios in each and every gear in the A8 is favorable to the M7, meaning the longer you stay in the same gear near the same RPM, the A8 will ALWAYS out accelerate the M7. That, is the OTHER truth*.

Those two facts leads me to believe that Chevy doles out the auto to journals to test simply because the A8 is and will be faster around the track. Is it more fun to drive? No. Is it BETTER? That depends on your definition of better. Is it faster? That is indisputable.

* P.S.: This is where I am going to tell you that gearing is irrelevant on track. That despite the obvious multiplier advantages in the auto, that the speed and lap differentials between the auto and manual doesn't aways manifest itself in lap times.

Since your speed through a turn is dictated by the available grip, if you have two cars of the same weight, power, and tires, but different gear ratios, they'll both go through the turn at the same speed. On the front, since you're already moving and in gear coming out of a turn, launch and first 2 gear multipliers are irrelevant, the speed down the straight and terminal velocity should be SIMILAR. That's why despite the obvious advantages in gearing, C7 M7 and A8 0-60 times and 1/4 mile speeds are very close. They're not 20-30% different as the gear multipliers would seem to suggest. Why?



This is a graph comparing a 5 speed and 6 speed's speed vs. RPM. Take 80 MPH, for example. the 5 speed is at 7,000 RPM in 2nd gear, while the 6 speed is at 5,500 RPM in 3rd. If we're to consider ONLY the section between 80-85mph, the 5 speed would actually accelerate from 80-85mph faster than the 6 speed would because it's putting down more power at a higher multiplier. But if you take the AREA under the graph between 50mph to 100mph, the 5 and 6 speed would actually yield very similar results. 50-100mph is basically where a car would spend the bulk of its time on track, by the way. So the difference(s) in speed and lap time would actually be fairly similar between these two gearboxes on a typical track.

But they wouldn't be the same. The 6 speed will be faster between a straight if the straight is preceded by a 30mph turn, and terminates at a 110mph straight. where as the 5 speed would actually have gearing advantages in short kinks between 40-55mph. The gives and takes of gearing will likely mostly even out by the end of a lap, depending on how many long straights there are vs. short kinks.

So while Poor-sha and Mero might have both started at 70mph, but at ~160mph Poor-sha would have wound through the gears from the upper 2/3rd of 2nd, through 3, 4, and had JUST shifted into 5th in the lower half of the rev band, while Mero would have topped out of 2nd on the exit, or have shifted/stayed in 3rd near meat of his power band, all the way through 4th and 5th as he FULLY WOUND OUT 3 full gears worth of acceleration**. Having executed 1 less shift and having the meat of his RPM/Speed/Gear shift for all three gears vs. half of 2nd, and just barely getting into 5th, there would have been slightly more area under the curve for the A8 Mero was driving.

Or it could have just been that 30-40 degrees of ambient temp difference.

** I'm basing this off of the chart Poor-sha posted, not on any video. Based on the speeds in the data provided, those would be the gear(s) I would be in for each of the vehicles chosen. Now, had Poor-sha been in 3rd rather than 2nd coming out at 70mph? His disadvantage would even be bigger.

IF you're still reading at this point, shame on you. You shouldn't waste your time on my ranting. Anyone still reading now have no life. BUT. The fact that the A8 has more gears, has more gears available for more different type of gearing opportunities, and can shift faster than humanly possible? That's why the A8 is the faster gear box for Z06 and ZR1. That fact can not and will not be in dispute.

Can an M7 be more fun to drive? Heck yeah. Can the M7 be faster? Sure, depends on the driver and track I suppose. Is the M7 better? If you ask me, YES. Is it faster?

NO.

End of discussion.

The HACK

So, um, my response regarding bench racing isn't directed at you. I was typing out my response as YOU were typing yours. And if you manage to read through my OTHER response, it would seem we both agree.

The reason why I posted the ratios is it's a simple, distilled way to visualize WHY the A8, technically, is the faster transmission. If you want more explanation from me (not the best, but it'll have to do) why the A8 will still BE faster for the 70-160 straight, see the graph posted in the post above as to why having close ratio gearboxes (and more gears) may still be advantageous.

And remember, in the M7 (yes I did the calculation) it'll be a 2-3-4-5 shift to get to 160+, while in the A8 it's a 3-4-5 shift to get there. One fewer shift, more meat under the graph.

Okay now END of discussion.

The HACK

Okay, I guess discussion NOT over.

I love bench racing as much as anyone. And I'll tell you this little story. A few weeks ago, I went to a Cadillac Truth + Dare event, where they set up an AX course timed with laser grid. They give YOU the participant one single shot at setting a quick lap. No practice, no second chances. You hop in, you do what you can.

Before I went out, I had a discussion with the pro running the tent, and asked what is the average time around the course. "25-26 seconds is what we're seeing, of course, our pros do it a little faster." He said with a sheepish grin.

I went out there and laid down a 23.xx on my one and ONLY run in the ATS-V. Not to pat myself on my back, but I walked out of the car BEAMING.

As I sat there with my head as big as the tent, watching the rest of the yahoos pull 26-28 second laps, I hear tire screeching and the sound of someone who's wringing the bejeezus out of a car. The driver pulls in and out steps a middle aged lady. I look over at the timing grid, and holy sh*t she just ripped a 22 second FLAT.

My jaw hit the floor. She beat me by more than a second. This is unheard of. I'm used to going to these type of events and setting practically the fast time of the day, almost all the time. I ran over to my buddy who was working the event, and ask who was it that just obliterated my ego, and he smiled and said "that's Linda Pobst."

Pobst? As in ex-wife of Randy? As in accomplished racer in her own right?

"Yep." he said. Then I sat there and watched 3 people get in that same ATS-V, and she went out and beat her last lap by another 1/2 second and did a 21.xx.

My buddy, who works at the Porsche Experience Center in Torrance when he's not on a paying gig like the Cadillac events, sees that I'm dejected, smiles and said to me, "Hack, don't worry about it. First, it's freakin' Linda Pobst. Second, we've been here for a whole week. She's driven that same layout over and over and over for days. I know you, YOU know you. You're probably not going to beat Linda Pobst, but I'm almost CERTAIN that if you spend as much time as we have driving this same course, you can probably do low 22 seconds."

Anyway, at this point you're probably going, "cool story BRO. What's your point?" My point is, I run around with people who are pro and semi pro racers. I have another friend who was rookie of the year and earned multiple podiums in Speed World Challenge before that series went defunct/sold/name changed, and we were having some beer after an event one time, and as we're discussing his racing career and my lack of one, he told me this golden nugget. He said "Hack, the only difference between YOU and ME as drivers, is I have the money and time to race on the track all the time. And I don't mean to say this to put you down, but I've seen you drive. You've got all the skills to go fast. But you're not as fast because you're not on the track every single weekend like I am. So don't beat yourself up for not being a 'pro' like me. If you want to go faster? Buy a race car and go racing. I guarantee you you'll go faster."

So again, what's my point? My point is I hang out with cool dudes. No really, I do. But don't think there aren't people on this forum that can go out and run down PROFESSIONAL race car drivers. The difference between pros and amateurs are simply time, resources, and money. Any one of us who's done this for decades, who has churned thousands of laps at local tracks, can do what the pros do if we spend as much time on the track as they do.

We just can't afford to do it (or can, but choose not to for a variety of reasons. What those reasons are? I have no idea. If I have the money and time to go racing, I'd be doing that instead of typing on a keyboard on a Corvette forum).

3 Z06ZR1

The A8 has the 60ft advantage from the 30 percent lower first gear. So goes the standing start to A8.
Rolling 3 honk type start with expert driver in the M7 and the lower drive train losses wins the roll race!

heavychevy

Correct, he did not factor drive train loss in his calculation.

And calculations are only good in theory. How many times have F1 teams showed up with new modifications that on paper and even in simulation were much faster only to have them fall flat. I've seen plenty of dudes switch gear ratios in Corvettes only to find out it's not faster or even slower. Gear multiplication is not a all encompassing benefit.

And besides, there is proof to the contrary. I'll take video evidence over a bunch of graphs and equations all day. At the end of the day it's the clock that tells you what is faster.

Darion

When does the Best Drivers Car hit stands?

PC

Dave Schotz

Hack, good replies, all good! So far only mag to test 'manual/auto' was Motor Trend with the GT3... and it was .3 on big willow. And the manual car had the iron brakes and sofa seats instead of buckets and Ceramic brakes.

I'd love to see an A8/M7 same driver same track... I think it could go either way, but no denying the A8 at the stoplight.

Best Regards,
Dave

skank

Laguna Seca ALERT !!! There's potentially something very special happening Saturday at Laguna Seca. The Historics is going on and Monterey Classic Car week is going on right now. The big hitters from Team Corvette production side and racing side are going to be there on Thursday, Friday, and Saturday. Normally they are at Carlisle but many top people are here for the week. Sound the sirens !!

CorvettoBrando

Can't wait to hear what is CERV'd up at Laguna Seca. Keep us posted!

Corvette_Nut

Remember When This Happened? I Have A Feeling....






Save The Wave,
Corvette_Nut

​​​​​​

Z06Norway

When A8 is being used, isn't torque converter locked up and the 5% loss isn't there anymore ?

Warp Factor

Most of the time, under high power demands. But there are also situations where the torque converter doesn't lock up immediately, to maintain traction upon shifts.

The HACK

I will have to have transmission experts answer that one, but I always assume that the 5% loss isn't due to the TC not locking up. When the torque converter is spinning the fluid coupling the loss is even GREATER. I had always assumed that the automatic w/ TC looses more power than manuals because the torque converter carries more rotational mass (due to the fluid and the ancillary metal required for the presence of a torque converter) AND the planetary gears for all gears all spinning at the same time. There's a lot more mass to spin up in a torque converter based, planetary gear automatic no matter what, so you tack on 5% more loss in drive train parasitic loss with autos than you do manuals regardless of the lock-up?