Bazillion speed auto trannies.

[me and my metro]

I have a 700r4 in my 84 GMC Diesel pickup with 4.56 gears and 33" tires. This combination works great, the gear splits are perfect for towing or running solo.
I also have a 95 Ford chassis motorhome with a 460 and an E4od and 5.13 gears. The gear splits in the E4od are not ideal. Lock up torque converter timing adds to the problem. One two is fine especially with the 5.13 final. Two three is too big a split at about 1500 rpm, plus immediate torque converter lock after shift. Three four is great, about 1000 rpm. For about $2000. someone makes a valve body and programmer that adds two gears. It uses overdrive in between each gear for a total of 6 gear ratios. If I drove this more often I would consider this.

[Daox]

Originally Posted by spacemanspif

CVT is still governed by the size of the 2 pulleys. If the trans is designed for a 0.75:1 as tallest gear, you're in no better shape than typical 3spd/OD trans from the 80s. If the trans is designed with tallest gear if 0.25:1; well the the computer can pick the most optimal cruising gear.

Actually, the Mitsubishi Mirage's CVT has a 2 speed automatic shifter in it to widen its ratio range. Added complexity? Yep, but it also kicks button the highway. We shall see how they fair over time...

[darcane]

Originally Posted by redpoint5

It actually has an infinite lack of appropriate gears, so 9 is less of a compromise than 6, or 5, or 3.

I don't know why reviewers and other so-called car enthusiasts dislike it when their car seeks optimal gearing for the task at hand.

I've driven a couple CVT cars (Nissans only so far) and found the experience thoroughly unpleasant. The engine seems to have little interest in doing what I want it to do. I found it particularly disconcerting when going down a modest slope and having the engine rev wildly for no apparent reason.

Note that I do not consider your Prius to have a CVT.

[Ecky]

I sometimes wish my 5MT Insight had an extra gear. Not a taller top gear, as anything taller would be mostly unusable in any place that has wind or is not completely flat, and it's already only at 1700RPM at my preferred cruising speed, but 1st, 2nd, and 3rd are very far apart and often force me into suboptimal gears when driving around town.



2250RPM in 1st -> 1150RPM in 2nd (13.5mph)
2250RPM in 2nd -> 1400RPM in 3rd (26.75mph)
2250RPM in 3rd -> 1750RPM in 4th (42.75mph)
2250RPM in 4th -> 1850RPM in 5th (55.5mph)


Luckily, most of my driving is rural and once I'm actually rolling, I'm very rarely below 3rd gear.

~

I can see both sides to this.

More gears = more parasitic loss in an auto, more weight, and a 9 speed would be a nightmare in a MT.

On the other hand, more gears = more options to stay at the perfect RPM/load combo.


I'm inclined to believe that, with how wide the efficiency band is on modern engines, any more than 6-7 gears is getting deeply into diminishing returns, but I can definitely see how a 6 or even 7 speed could be beneficial over 5.

[cRiPpLe_rOoStEr]

It's all because EPA test procedures are more favorable to close-ratio transmissions instead of wide-ratio ones, so in order to keep a high gear spread to retain a decent performance with fewer compromises more gears are added. In regard to SUVs, adding just a crawler gear is perceived as less weight-intensive than resorting to a 2-speed transfer case.

[ksa8907]

One big downside to more gears is that the computer has a hard time deciding which gear to choose when downshifting. I have said it before, but the chrysler 8 speed is particularly appalling in this regard.

I like the 6 speed in my cts. It will be in 4th by 25 mph and 6th with od and tc lockup at 42mph.

From driving a few modern vehicles, i feel they all could benefit from more torque, more converter lockup, and faster shifts.

[Baltothewolf]

Originally Posted by Ecky

I sometimes wish my 5MT Insight had an extra gear. Not a taller top gear, as anything taller would be mostly unusable in any place that has wind or is not completely flat, and it's already only at 1700RPM at my preferred cruising speed, but 1st, 2nd, and 3rd are very far apart and often force me into suboptimal gears when driving around town.



2250RPM in 1st -> 1150RPM in 2nd (13.5mph)
2250RPM in 2nd -> 1400RPM in 3rd (26.75mph)
2250RPM in 3rd -> 1750RPM in 4th (42.75mph)
2250RPM in 4th -> 1850RPM in 5th (55.5mph)


Luckily, most of my driving is rural and once I'm actually rolling, I'm very rarely below 3rd gear.

~

I can see both sides to this.

More gears = more parasitic loss in an auto, more weight, and a 9 speed would be a nightmare in a MT.

On the other hand, more gears = more options to stay at the perfect RPM/load combo.


I'm inclined to believe that, with how wide the efficiency band is on modern engines, any more than 6-7 gears is getting deeply into diminishing returns, but I can definitely see how a 6 or even 7 speed could be beneficial over 5.

That graph looks off to me. My insight will only do 106 in 3rd before the Rev limiter kicks in. That graph is implying 112-115.

[serialk11r]

Originally Posted by Frank Lee

Just go fast enough to pull top gear. Done.

Engines having broad flat torque curves thus having a larger useful rpm range + vast multitudes of ratios is missing the point?

Efficiency band while accelerating? And accelerating lasts how long- a few seconds. Cruising along lasts how long- exponentially longer- could be hours. Put that thing in the efficiency zone when at cruise speed.

Well, reading more responses to this thread, I think I know where the differing viewpoints are coming from.

I live in the SF Bay Area, where traffic moves slowly, and we have lots of lower speed limit roads that are similarly clogged. Having more gears is extremely useful for not getting stuck at a relatively high rpm at a crawl because the next gear is too tall. I've only been in cars with 7 speed automatics so far, but even with 7 gears some of the gaps between the gears feel too big (although usually that is because 2-3-4 are closely spaced for track performance or something...).

On the other hand if you live in the middle of the country where the roads are open and you use the top gear more than you use 1st gear, then I can see why you would find all those gears to be useless.

[jcp123]

Originally Posted by serialk11r

Well, reading more responses to this thread, I think I know where the differing viewpoints are coming from.

I live in the SF Bay Area, where traffic moves slowly, and we have lots of lower speed limit roads that are similarly clogged. Having more gears is extremely useful for not getting stuck at a relatively high rpm at a crawl because the next gear is too tall. I've only been in cars with 7 speed automatics so far, but even with 7 gears some of the gaps between the gears feel too big (although usually that is because 2-3-4 are closely spaced for track performance or something...).

On the other hand if you live in the middle of the country where the roads are open and you use the top gear more than you use 1st gear, then I can see why you would find all those gears to be useless.

Kinda. I grew up I the Bay Area, that is where my Pa had his Passat with 5-speed auto. It seemed wonderfully flexible to me at the time. Though maybe this was a matter of perspective: my parents were coming out of a pair of 3-speed Caravans and I was also comparing it to the four-speed auto my Ma was replacing her Caravan with as well. Still I do not recall wishing for more gear as I did in some cars. Though I had barely acquired my own license at the time, I had fairly good instincts for a 16ish year old. The Passat felt good and right, in some ways it is still a personal benchmark.

I think I come at it more from the Luddite side. 8- and 9-speed trannies really seem like excess, a really expensive marketing tool which in the end means nothing more than a 10hp bump on paper to keep things "competitive". The more is better trope is pretty tired, and cars are no exception.

[Ecky]

Originally Posted by Baltothewolf

That graph looks off to me. My insight will only do 106 in 3rd before the Rev limiter kicks in. That graph is implying 112-115.

I was thinking that myself, but I took the numbers I used in my spreadsheet match both InsightCentral's Encyclopedia and those in California98Civic's thread. The only thing I can think of is that I've used the wrong revs/mile. Tire calculators have given me as high as 932 and as low as 899 rev/mile from 165/65r14.

Here's an updated one using 926, which I think is "spec" for Potenzas: