Here is a general question for you gear heads. Help educate me.
What is the motivating factor for engineers to develop a manual 7 speed gearbox?
Is this solely a means to achieve a certain level of fuel economy rating on paper?
Is it actually intended to be used on track?

Back in my youth, my first manual gearbox was a 4 speed on a 68 VW Beetle. I then moved up to a 1981 Datsun B210 hatchback with 5 gears. I guess that was high tech for the times. The rest of my cars during the 80s and 90s were all 5 speeds. I guess that was the de facto standard. At that time, I thought it was the ideal manual gearbox box configuration. I still do. You have gears 1 thru 4 to keep you busy and then you had the 5th gear to “chill” on the long commutes. It was always referred to as the “overdrive gear”. In other words, less on power, more on better fuel economy.

In 2016, my Camaro SS came with 6 gears which I thought was just a novelty. Barely ever used the 6th gear. Fact is that it made the car feel like mush. Now, my 2019 SG has 7 gears. Again, in my almost two years of ownership, I don’t believe I’ve used the 6th or 7th gear more than 2 or 3 times. To be honest, most of the timeI forget that I even have it. Also, the car just doesn’t feel right to me on either 6 or 7. So again, why bother?

At some point I would like to start tracking the car once I get over a little inner ear medical condition (yes, it sucks getting old :<). No doubt I would benefit from some professional training on the basics of tracking a car.
But is the 6th or 7th gear actually used? What am I getting wrong here? Appreciate any input.

 

EPA numbers and Overdrive solutions. That would be my take on the 7 speed. Racing might get into 5th for top speed but I doubt 6th or 7th would get touched.

Elmer

 

Top speed of the car is 5th gear -- 6 and 7 are used purely to meet emissions/fuel economy numbers. This is the same reason we have silly features like 'skip shift' -- Auto makers will do anything to get the EPA ratings up by 1mpg... as it affects their overall MPG for their whole car lineup.

Additionally, if you only gave the car 4 or 5 gears, then you'd have no overdrive gears (bad) -- You'd also have to have really short gearing -- Can you imagine doubling the torque in first gear, or having a really long first gear and a really short second gear? It'd be impossible to put power down. This means that car needs at least 6 gears -- and the 7th gets the MPG option up there (as well as helps with sales and allows R&D testing for other future car models).

 

Yup, 6 and especially 7 are for EPA ratings. I very rarely use 6, and just use 7 to make sure I remember to find it! For most freeway driving 5th is perfect. In fact, on the Spring Mountain course we were on, we were using 3 and 4 only. On a longer track 5 comes into play.

 

You never use 6th or 7th on the highway?

 

I use Eco Mode a fair amount of the time and drive around town in 6th gear a lot of the time. Can pretty much use 5th and 6th gears from 35 mph upward. Even in 6th gear, the Z06 has a lot more kick than most other cars on the road. One thing I found is I can get better gas mileage running Eco Mode in 6th than I can get running Eco Mode or No Eco Mode in 7th at speeds less than 75 mph. The reason is in 7th gear the engine rarely switches to 4 cylinder operation (usually on a downslope). Slight up slopes put it right back into 8 cylinder operation. However, in 6th gear, I can run 70 mph in cruise and the engine will run in 4 cylinder mode until I hit a much greater upslope than it takes to cause a switch in 7th gear. Sure rpm is higher than I would run in 7th at the same speed but I am operating on half the cylinders a greater share of the time so mpg increases. On long trips, I will put the exhaust in Stealth Mode and use 7th gear to reduce engine noise so I can hear the radio. Even in 7th gear, the car has substantial pickup so downshifting isn't required if I need to move around slower traffic.

Bill

 

It also allows the gear ratios to stay closer together and that keeps the engine in its power band when rowing thru the gears. Same thing with the A8 and A10s with keeping the engine in its torque/power band instead of like a 5 speed or even a 6 speed where the engine will drop down more rpms between shifts and therefore does not keep the engine in its power band. Plus the quicker you get to the next gear the engine has to work less and improves fuel economy.

 

I agree that the 7 speed was likely part of the overall effort to improve fuel economy and perhaps even a bit of marketing since '7 speed' is one better than '6 speed'. Porsche was also getting attention in 2012 for their 7-speed in 991 911.

Regardless of its purpose, I've never used 7th gear, or even cylinder deactivation as gas mileage in not important to me in this car.

 

The truth is that I don’t take many long drive trips. Especially during the past 12 months with the pandemic situation. Most of my highway drives are 35-45 minutes sprints with the usual South Florida traffic congestion. My exception was last week, when I took an early morning north bound hour plus drive with mild traffic and realized half way thru the drive that I could have shifted up to 6 and 7. That’s what made be start thinking about how often are these gears actually used.

 

Makes sense. I only use them on the interstate. I shift into 6th around 60-65 mph and 7th around 75 mph when I am cruising along.

 

I find that odd also. I use 7th all the time. Usually when I hit about 70 mph on the highway.

 

Our engines have a tremendous amount or torque. They are quite happy to be in the highest gear on the transmission and get you where you want to go. Just quit screwing with the gas pedal when you are "cruising".


Elmer

 

I think if you look at the ratios, that alone should answer your question. GAS MILEAGE, pure and simple (and, attendant emissions). Absolutely no other need for my C7 to have yet another overdrive beyond what my C5 has.

 

Fuel mileage. It was not to tighten the 1-5 ratio as much as it was to add an additional overdrive (7th) for fuel economy.

 

Seeing your in S FL like me I can report that on both Homestead and Sebring you'll only use 3rd and 4th. You might need 5th on the back stretch of Sebring if you exit the previous corner perfectly. 4th gear is good until about 140 MPH There are places where you'll be temped to go into 2nd but honestly the car has so much torque it pulls out of the hairpins in 3rd with less drama.

I drive in 7th on the highway all the time, can achieve 28 to 33 MPG that way depending on cruising speed.