Looks like ford may be offering a 10 speed trans in the mustang soon.
This got me thinking that at what point does a (insert # of speeds here) speed trans really just become a CVT?
Looks like ford may be offering a 10 speed trans in the mustang soon.
This got me thinking that at what point does a (insert # of speeds here) speed trans really just become a CVT?
I don't think they will ever provide the linear feel a CVT has. I've got a Chrysler 200 rental right now with the ZF 9-speed auto; a CVT would be much more useful, honestly. Seems like for all the gears this thing has, it's always in the wrong one and trying to find a different one. The main idea seems to be that if you're cruising along at a given speed, it upshifts 4-5 times until the engine is basically idling down the road. The problem is the herky-jerky process it goes through trying to find an appropriate gear when you need to accelerate...a CVT would just give me the acceleration.
Five gears is adequate for nearly everything I've ever driven. Any 6 speeds I have owned, I inevitably come up with a 1-3-4 pattern or something for city driving. My Ser SpecV, highway driving was 1-3-5-6.
All I ask is for there to be a pretty big spread between 4 and 5.
I thought the whole reason 3 and 4 speed autos lasted so long was that they didn't need that many gears due to the way autos work. This mess with 9 and 10 speed autos seems like another advertising buzzword fest.
I like CVT's, as long as they are properly programmed and reliable. Kudos Subi.
As autos go the 7 speed in my wife's Merc is great. It does not hunt for gears and the up and down shifts are very smooth. If it helps the almost 6000lbs monster get mid 20s on the highway I am all for many geared autos.
FWIW, everyone has 10 speeds coming.
When you get one, you should do your best to record it- you may be surprised.
CVTs can only handle a limited amount of power (for example I think the Impreza is the most powerful car with a CVT?), that's why these seemingly ridiculous 9&10-speed transmissions are being made, they're the closest thing that will handle the power.
GameboyRMH wrote: CVTs can only handle a limited amount of power (for example I think the Impreza is the most powerful car with a CVT?)
There are many hybrids far more powerful than the Impreza that have CVTs.
These go to eleven.
ProDarwin wrote:GameboyRMH wrote: CVTs can only handle a limited amount of power (for example I think the Impreza is the most powerful car with a CVT?)There are many hybrids far more powerful than the Impreza that have CVTs.
Most of the hybrid "CVTs" aren't mechanical CVTs. They're just a couple of electric motors that act as a trans.
ProDarwin wrote:GameboyRMH wrote: CVTs can only handle a limited amount of power (for example I think the Impreza is the most powerful car with a CVT?)There are many hybrids far more powerful than the Impreza that have CVTs.
Is this like the whole SRT-4 is not a Neon/Caliber thing? The WRX is the most powerful car I can think of with a CVT.
So all the gears are just to keep the engine tighter in the peak efficiency range? Makes sense I guess. I don't have anything newer than the 80's with an auto but it is interesting to see the technology changing.
MCarp22 wrote:ProDarwin wrote:Is this like the whole SRT-4 is not a Neon/Caliber thing? The WRX is the most powerful car I can think of with a CVT.GameboyRMH wrote: CVTs can only handle a limited amount of power (for example I think the Impreza is the most powerful car with a CVT?)There are many hybrids far more powerful than the Impreza that have CVTs.
I didn't know the WRX had one, I thought he meant the Impreza which is a whopping 148hp.
ProDarwin wrote:MCarp22 wrote:I didn't know the WRX had one, I thought he meant the Impreza which is a whopping 148hp.ProDarwin wrote:Is this like the whole SRT-4 is not a Neon/Caliber thing? The WRX is the most powerful car I can think of with a CVT.GameboyRMH wrote: CVTs can only handle a limited amount of power (for example I think the Impreza is the most powerful car with a CVT?)There are many hybrids far more powerful than the Impreza that have CVTs.
Current Maxima? 300HP.
Yeah, pretty sure EVERY v6/cvt nissan is more powerful than a stock WRX.
And it's true that the hybrid 'cvt's are not comparable as far as durability because they don't have anything that can 'slip' like a clutch pack or belt.
What i've seen with CVTs in the past and which may still be true now is that they don't have a low enough gear reduction at the bottom of their range to make a small engine feel powerful from a stop. Compare that to, for example, a giant Ram pickup with a 3.6L v6 and 8spd trans that will burn the ~70lb tires off through first gear.
CVTs may eventually get around that through the use of an additional gearset, effectively having a 'high' and 'low' range. The difficulty comes in programming the thing to quickly and smoothly shift between the two as it requires the CVT to make a big ratio jump in a small time period without feeling a total loss of power in the interim. My old (10+ year old design) Lexus GS450h has such a 2-spd CVT (although it achieves it's cvt function differently from non-hybrids) and the 'shift' is acceptable but not great.
dean1484 wrote: Looks like ford may be offering a 10 speed trans in the mustang soon. 10 speed trans in mustang This got me thinking that at what point does a (insert # of speeds here) speed trans really just become a CVT?
Hell, a Powerglide with a proper torque converter is just a CVT except in name. The drag guys set them up with a loose converter and the engine rides the stall speed on the launch and after the shift. Sounds like crap but goes like hell.
Chadeux wrote: I thought the whole reason 3 and 4 speed autos lasted so long was that they didn't need that many gears due to the way autos work. This mess with 9 and 10 speed autos seems like another advertising buzzword fest.
Chevy had to work very hard on the 6 speed auto to make it get fuel economy as good as the old 4 speed, in the Corvette. Mainly because European market feeds off of buzzwords and more gears = higher tech. The 4 speed got great fuel economy because it was a more efficient transmission, less geartrain losses, and the engine itself had a broad and fat BSFC table that probably would have been fine with a single gear.
https://youtu.be/Ko9kzyqW-l8?t=1m29s
In reply to Vigo:
Most modern Nissan CVTs do have what they call the "aux gearbox". Basically a 2 speed planetary gearbox to allow a wider range of ratios. Started in 2013 for Sentra/altima/pathfinder, 2015 Maxima and murano. Don't recall if the versa does or not. Pretty sure the juke does not.
Rufledt wrote: So all the gears are just to keep the engine tighter in the peak efficiency range? Makes sense I guess. I don't have anything newer than the 80's with an auto but it is interesting to see the technology changing.
Driving a 2015 Grand Cherokee with the possibility of replacing our 2000 Grand Cherokee - the most obvious true advancement is in the transmission. Night and day. I'm ignoring all the shiny beepy colorful stuff in the interior and concentrating on what makes a vehicle here.
I have to say I had a 15 charger sxt as a rental with an 8 speed and I never felt like it was hunting for gears, I actually really liked the car and on a long road trip it managed 33 mpg which considering its a hefty girl and it had 4 people and their luggage I was impressed.
My BMW X1 has the ZF 8 speed and its great. One of the first auto transmissions that seems to know where I want to be. I've been very happy with it. I get the idea that programming has a lot to do with it since the same transmission is complained about in other vehicles especially a lot of Chrysler stuff.
I found the CVT I experienced in a Versa rental to be maddening. It was downright auful. Now I learn they took that mess and spread it to their other cars?
Knurled wrote: Hell, a Powerglide with a proper torque converter is just a CVT except in name. The drag guys set them up with a loose converter and the engine rides the stall speed on the launch and after the shift. Sounds like crap but goes like hell.
Except that setup pours out gobs of excess energy via heat (TC slip). I would say it functions similar to a CVT in that the input speed stays constant and output speed increases, but thats where the similarities end.
A standard planetary set can give you 3 speeds, with one of them being 1:1. If you get creative with how you drive them, you end up with an overdrive, too, so 4 speeds, with one being 1:1. if you put two such units together, you'd end up with 4 x 4 speeds, or 16 gears, though two of them would be 1:1 so in reality it would be a 15 speed box. Or, use a 4 speed, overdrive-capable planetary setup with a 3 speed, non OD and you'd have 12 gears, with two 1:1, so 11 speeds.
Two 3 speed autos would net you 8 total ratios (9 minus the extra 1:1) but no overdrive, which would require a fairly tall final drive ratio. But cruising efficiency in top gear would be better, since geartrain losses at 1:1 ratio are minimal.
Not sure why we haven't seen such beasts yet.
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