Is there really that big of a difference between MT & AT!?
#32
07-10-2011, 07:48 PM
Not true I own a 2010 Mercedes E Class with paddle shifters and the 7 speed transmission. It will upshift when you hit the redline if you do not shift manually once you've enganged manual mode as opposed to bumping against the rev limiter like the G does. Other than that it operates exactly like the tiptronic.
#34
07-10-2011, 09:13 PM
That's incorrect. The PDK is NOT an automatic. Automatic's are characterized by the presence of a torque converter. There is no torque converter in the SMG, PDK, DCT, DSG gearboxes - they are all clutches just like a 6MT G has. Our M5 feels nothing like an automatic when you drive it - not even close. It might not require you to clutch and in the right mode not require you to tell it when to upshift or downshift, but NEVER does it feel like an automatic.
Otherwise the rest of your post is a good explanation.
#35
07-10-2011, 09:59 PM
That's incorrect. The PDK is NOT an automatic. Automatic's are characterized by the presence of a torque converter. There is no torque converter in the SMG, PDK, DCT, DSG gearboxes - they are all clutches just like a 6MT G has. Our M5 feels nothing like an automatic when you drive it - not even close. It might not require you to clutch and in the right mode not require you to tell it when to upshift or downshift, but NEVER does it feel like an automatic.
That said, a lot has changed recently that has affected the classic "MT vs AT" war (and I'm talking in all cars, not just G's).
"Back in the day" (really, up until about 3-4 years ago) most automatic transmissions had less gears than the manual option offered in the same vehicle (5AT vs 6MT, 4-speed automatic in a Honda Accord vs 5-speed manual, etc.). This extra gear allowed for the manual transmissions to not only be faster but usually have a slight edge on gas mileage when driven nicely (mileage increase is amplified especially when you include the effects of a non-locking torque converter, which I'll discuss later).
However, in newer generation automatics, you usually have an extra gear (or two) than your manual transmission option for the same vehicle (at the very least it's typically the same, though some cheaper "econobox" vehicles still give MT an advantage in gear count). But for example, the new G37, it's a 6MT or 7AT now (auto went from being a gear down to now a gear up), for the new BMW 5 Series, 6MT vs 8AT (I'd put my money on the 8 speed auto being faster, at full acceleration the RPM's hardly drop more than 1200RPM when it shifts). The limiting factor here for the manuals is pretty much no one makes a transmission with more than 6 ratios, and no one really wants to, otherwise that's a lot of shifting you have to do as a driver.
Now, you add to the fact that in older cars, torque converters, by design, always bled power, because they are after all a hydraulic device and the input always had to spin faster than the output. So you always had some power loss, whether cruising (resulting in slightly worse mileage) or when driving the car with performance in mind (slower).
On the other hand, new torque converters can lock, which pretty much negates the two downsides I just previously mentioned. I'm unaware of whether the G35's AT transmission possesses a locking torque converter or not.
Then, finally, we come to driver feel. With the torque converter it's hard to get the car to react perfectly every time, but with a manual transmission the driver controls everything so he can precisely manipulate the car to do what he wants it to do (assuming he has the skills to do so).
Of course, there's always the consideration of whether the AT has a "manual" mode (tiptronic, whatever you want to call it), and how "good" it is at being like a manual. Many automatic cars even in "manual" mode still downshift AND upshift for you when they feel like it. The Infiniti auto is one of the few I've ever encountered that NEVER upshifts for you even if you are slamming into the rev-limiter and never downshifts for you unless you are going too slow for that gear (like 5mph in 5th), and I really like that extra control it gives you. Mercedes automatics DO not do this. Even in "manual" mode it will shift - up or down - whenever it damn well wants, and it really sucks. BMW transmissions will downshift to max gear when you floor it (so you can't do a "5th gear pull") and will upshift at redline (so you can get in a bad situation if you have your back-end kicked out mid corner and you hit redline and it throws it into the next gear).
There's probably a couple things I forgot to touch upon, but those are the "big ticket" things. The new automated manual transmissions like the SMG, DCT, PDK, DSG, etc. combine the advantages of both types of gear boxes.
In the end, it's really driver preference. Most guys that are freaking out about a few tenths will be buying the 6MT anyway.
But to really answer the OP's question. If you have two 100% stock G35 coupes, one 5AT, one 6MT, and assuming the 6MT driver knows how to launch and shift the car, the 6MT will be faster, no questions about it. Unfortunately, there are a lot of guys out there that can't launch or shift their 6MT, and then a 5AT races and beats them, and then we get one of those threads with one of those guys claiming the 5AT is faster and we get a sh!tstorm...
That said, a lot has changed recently that has affected the classic "MT vs AT" war (and I'm talking in all cars, not just G's).
"Back in the day" (really, up until about 3-4 years ago) most automatic transmissions had less gears than the manual option offered in the same vehicle (5AT vs 6MT, 4-speed automatic in a Honda Accord vs 5-speed manual, etc.). This extra gear allowed for the manual transmissions to not only be faster but usually have a slight edge on gas mileage when driven nicely (mileage increase is amplified especially when you include the effects of a non-locking torque converter, which I'll discuss later).
However, in newer generation automatics, you usually have an extra gear (or two) than your manual transmission option for the same vehicle (at the very least it's typically the same, though some cheaper "econobox" vehicles still give MT an advantage in gear count). But for example, the new G37, it's a 6MT or 7AT now (auto went from being a gear down to now a gear up), for the new BMW 5 Series, 6MT vs 8AT (I'd put my money on the 8 speed auto being faster, at full acceleration the RPM's hardly drop more than 1200RPM when it shifts). The limiting factor here for the manuals is pretty much no one makes a transmission with more than 6 ratios, and no one really wants to, otherwise that's a lot of shifting you have to do as a driver.
Now, you add to the fact that in older cars, torque converters, by design, always bled power, because they are after all a hydraulic device and the input always had to spin faster than the output. So you always had some power loss, whether cruising (resulting in slightly worse mileage) or when driving the car with performance in mind (slower).
On the other hand, new torque converters can lock, which pretty much negates the two downsides I just previously mentioned. I'm unaware of whether the G35's AT transmission possesses a locking torque converter or not.
Then, finally, we come to driver feel. With the torque converter it's hard to get the car to react perfectly every time, but with a manual transmission the driver controls everything so he can precisely manipulate the car to do what he wants it to do (assuming he has the skills to do so).
Of course, there's always the consideration of whether the AT has a "manual" mode (tiptronic, whatever you want to call it), and how "good" it is at being like a manual. Many automatic cars even in "manual" mode still downshift AND upshift for you when they feel like it. The Infiniti auto is one of the few I've ever encountered that NEVER upshifts for you even if you are slamming into the rev-limiter and never downshifts for you unless you are going too slow for that gear (like 5mph in 5th), and I really like that extra control it gives you. Mercedes automatics DO not do this. Even in "manual" mode it will shift - up or down - whenever it damn well wants, and it really sucks. BMW transmissions will downshift to max gear when you floor it (so you can't do a "5th gear pull") and will upshift at redline (so you can get in a bad situation if you have your back-end kicked out mid corner and you hit redline and it throws it into the next gear).
There's probably a couple things I forgot to touch upon, but those are the "big ticket" things. The new automated manual transmissions like the SMG, DCT, PDK, DSG, etc. combine the advantages of both types of gear boxes.
In the end, it's really driver preference. Most guys that are freaking out about a few tenths will be buying the 6MT anyway.
But to really answer the OP's question. If you have two 100% stock G35 coupes, one 5AT, one 6MT, and assuming the 6MT driver knows how to launch and shift the car, the 6MT will be faster, no questions about it. Unfortunately, there are a lot of guys out there that can't launch or shift their 6MT, and then a 5AT races and beats them, and then we get one of those threads with one of those guys claiming the 5AT is faster and we get a sh!tstorm...
I completely agree with his statements.
on a note, the newer mercedes will hold gear. The C55 amg will hold gear and not upshift in manual mode.
#38
07-10-2011, 11:47 PM
I'm aware that the PDK uses 2 clutches, but I can still press gas to go and brake to stop without doing anything else myself (shift/clutch pedal). It's taken a manual clutch and automated it so you don't have to do the work. I'd still call it an automatic..
I wouldn't bother getting into semantics with someone if they called the PDK Boxster an auto. It would be like getting an electric can-opener and claiming it's not, that it's a manual can-opener that automatically opens cans for you.
*shrug*
I also know it IS fun to drive a manual car, but I think some people only like the idea of a manual because it inflates their ego.
I wouldn't bother getting into semantics with someone if they called the PDK Boxster an auto. It would be like getting an electric can-opener and claiming it's not, that it's a manual can-opener that automatically opens cans for you.
*shrug*
I also know it IS fun to drive a manual car, but I think some people only like the idea of a manual because it inflates their ego.
#39
07-11-2011, 12:13 AM
#40
07-11-2011, 12:20 AM
#43
07-11-2011, 01:39 AM
#44
07-11-2011, 07:23 AM
#45
07-11-2011, 07:24 AM