Dual clutch vs 8l90 tranny
12-18-2018, 01:28 PM
#41
Team Owner
The only way you get smooth shifts and a smooth take off in a DCT is with slipping clutches which produces heat and wear. Below 20 mph presents a big problem and many other situations described else where..
A TC at slow speeds is a fluid coupling which produces heat but no wear. You can't get the same level of smoothness in a DCT but it will cost you if you do.. A properly designed TC in place of the odd gear clutch pack in your DCT would be a cool thing. (Excuse the pun) There are some out there. I wouldn't want one anyway. Why no one has gone the way of the LFA, I don't know.
A TC at slow speeds is a fluid coupling which produces heat but no wear. You can't get the same level of smoothness in a DCT but it will cost you if you do.. A properly designed TC in place of the odd gear clutch pack in your DCT would be a cool thing. (Excuse the pun) There are some out there. I wouldn't want one anyway. Why no one has gone the way of the LFA, I don't know.
Most new DCT's have wet clutches and overheating the clutch discs would be very rare. Even AMG, on some of their high horsepower models use a planetary gear auto transmission but without a torque convertor. Instead, they use a multi-disc wet clutch like used with a conventual manual transmission or a DCT.
What makes you think that a computer controlled clutch slippage in a DCT would generate more heat and wear than your left foot controlled clutch slippage with a manual transmission, like in my Z06?
Last edited by JoesC5; 12-18-2018 at 01:49 PM.
12-18-2018, 01:41 PM
#42
Safety Car
Two of my four cars have conventual manual transmissions with conventual dry clutches and neither has any auxiliary cooling to keep the clutch cool. Yet the other two vehicles I own have planetary gear automatics with torque convertors and both have auxiliary cooling to keep the transmission from overheating.
Most new DCT's have wet clutches and overheating the clutch discs would be very rare. Even AMG, on some of their high horsepower models use a planetary gear auto transmission but without a torque convertor. Instead, they use a multi-disc wet clutch like used with a conventual manual transmission or a DCT.
Most new DCT's have wet clutches and overheating the clutch discs would be very rare. Even AMG, on some of their high horsepower models use a planetary gear auto transmission but without a torque convertor. Instead, they use a multi-disc wet clutch like used with a conventual manual transmission or a DCT.
12-18-2018, 02:08 PM
#43
Le Mans Master
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Has NEVER happened on my Boxster, even when driving at an auto-x or a HPDE. Never. One does not have to "learn" how to drive a DCT. Maybe if you get a poorly programmed one but those of us who have driven the PDK know that most folks saying all this folderall about DCT's have never driven a PDK.
PS. I just went back and looked for your video and can't find it. Could you post the video again or at least what post it was in? Thanks
PS. I just went back and looked for your video and can't find it. Could you post the video again or at least what post it was in? Thanks
Last edited by ByByBMW; 12-18-2018 at 02:20 PM.
12-18-2018, 02:21 PM
#44
Safety Car
Has NEVER happened on my Boxster, even when driving at an auto-x or a HPDE. Never. One does not have to "learn" how to drive a DCT. Maybe if you get a poorly programmed one but those of us who have driven the PDK know that most folks saying all this folderall about DCT's have never driven a PDK.
PS. I just went back and looked for your video and can't find it. Could you post the video again or at least what post it was in? Thanks
PS. I just went back and looked for your video and can't find it. Could you post the video again or at least what post it was in? Thanks
12-18-2018, 02:32 PM
#45
The Consigliere
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Hopefully the ME's DCT will be as robust as Porsche's. Road and Track beat on a Porsche PDK and tried to break it. They failed:
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12-18-2018, 02:45 PM
#46
One of your two cars with conventional manual transmission needs auxiliary cooling, the dreaded "clutch pedal on the floor" in C5s and C6s is the result of slipping the clutch too much in spirited driving. The heat generated causes the fluid in the "over the shaft" clutch actuator to boil...air bubbles don't compress very well.
12-18-2018, 02:49 PM
#47
"The Turbo 400/3L80 from the '60s was adapted to the front wheel drive Cadillac Eldorado/Oldsmobile Tornado by casting a transaxle case to use the guts of the Turbo 400 and incorporate a differential, it was called the Turbo 425."
The differential doesn't have to go in the middle of the transmission...unless there's a law I'm not familiar with.
12-18-2018, 03:14 PM
#48
Melting Slicks
I have 5 vehicles so I don't daily mine but I do in fact own one and yes it can be clunky in slow speed situations, backing up a hill, etc. One can not expect a computer to know exactly what the driver is thinking / about to do all the time so it's going to get the clutch pressure wrong at some point and have to adjust after the fact. This is what makes them not the best in these situations.
Go on ANY forum of a car that has DCT (rennlist, bimmerforums, etc.) and you will find people saying these exact same things. There are certainly people who ignore the symptoms... that's fine... but to say they are as smooth as a regular auto is simply not grounded in reality. Do some looking... "PDK shudder uphill" boom... thread on rennlist with responses saying "that's normal for a DCT"
There is also a reason why Acura makes a DCT that has a Torque Converter. If the problem didn't exist why in the heck would a manufacturer fix it?
12-18-2018, 03:29 PM
#49
Le Mans Master
One of your two cars with conventional manual transmission needs auxiliary cooling, the dreaded "clutch pedal on the floor" in C5s and C6s is the result of slipping the clutch too much in spirited driving. The heat generated causes the fluid in the "over the shaft" clutch actuator to boil...air bubbles don't compress very well.
12-18-2018, 04:03 PM
#50
Team Owner
Air does compress and that's only part of the issue, but that's neither here nor there. I was under the assumption that the pedal to the floor issue was actually due to the exhaust routing by the line rather than the clutch itself. But I've only heard stories, I have no first hand experience so theres that as well.
12-18-2018, 04:29 PM
#51
Team Owner
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12-18-2018, 04:32 PM
#52
Drifting
Thread Starter
Two of my four cars have conventual manual transmissions with conventual dry clutches and neither has any auxiliary cooling to keep the clutch cool. Yet the other two vehicles I own have planetary gear automatics with torque convertors and both have auxiliary cooling to keep the transmission from overheating.
Most new DCT's have wet clutches and overheating the clutch discs would be very rare. Even AMG, on some of their high horsepower models use a planetary gear auto transmission but without a torque convertor. Instead, they use a multi-disc wet clutch like used with a conventual manual transmission or a DCT.
What makes you think that a computer controlled clutch slippage in a DCT would generate more heat and wear than your left foot controlled clutch slippage with a manual transmission, like in my Z06?
Most new DCT's have wet clutches and overheating the clutch discs would be very rare. Even AMG, on some of their high horsepower models use a planetary gear auto transmission but without a torque convertor. Instead, they use a multi-disc wet clutch like used with a conventual manual transmission or a DCT.
What makes you think that a computer controlled clutch slippage in a DCT would generate more heat and wear than your left foot controlled clutch slippage with a manual transmission, like in my Z06?
problem is that there no torque moltiplication
12-18-2018, 04:42 PM
#54
Drifting
Thread Starter
A nice type of tranmsson IMO could be a modern traditional auto like 8l90 or a zf, though equipped with an heavy duty lock up clutch that handles can all the torque so it could be engaged even on high rpm too.
in this trans idea i want to use conv for stop, starting and in case of torque demand, so the transmission would be locked up for more time than a traditional automatic.
Also this clutch would be a performance part not just an item to reduce mpg,
in this trans idea i want to use conv for stop, starting and in case of torque demand, so the transmission would be locked up for more time than a traditional automatic.
Also this clutch would be a performance part not just an item to reduce mpg,
Last edited by Christi@n; 12-19-2018 at 09:50 AM.
12-18-2018, 04:44 PM
#55
Drifting
Thread Starter
converter only can produce torque moltiplication
Anyway is not a problem, but why delete a well tried mechanism with a long story that can such a kind of magic developes torque, to fill in one that can not do it?
Last edited by Christi@n; 12-18-2018 at 04:52 PM.
12-18-2018, 04:46 PM
#56
Race Director
There's more than one way to skin a cat, you obviously didn't read the rest of my post so here it is:
"The Turbo 400/3L80 from the '60s was adapted to the front wheel drive Cadillac Eldorado/Oldsmobile Tornado by casting a transaxle case to use the guts of the Turbo 400 and incorporate a differential, it was called the Turbo 425."
The differential doesn't have to go in the middle of the transmission...unless there's a law I'm not familiar with.
"The Turbo 400/3L80 from the '60s was adapted to the front wheel drive Cadillac Eldorado/Oldsmobile Tornado by casting a transaxle case to use the guts of the Turbo 400 and incorporate a differential, it was called the Turbo 425."
The differential doesn't have to go in the middle of the transmission...unless there's a law I'm not familiar with.
The reason a transaxle has the differential output stubs around the middle of the housing in a mid-engine configuration is for engine placement. If you put the differential at the rear of the transmission then you would have to move the engine forward (or the wheels backwards) 12 to 18 inches. Guess you could put the differential ahead of the transmission but then you would have issues of getting the power past the differential to the transmission and then back to the differential.
12-18-2018, 04:47 PM
#57
Le Mans Master
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i'm asking WHY that is a problem.
Edit: Never mind, saw you edited your other post.
Last edited by ByByBMW; 12-18-2018 at 04:52 PM.
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12-19-2018, 08:51 AM
#59
You can say the "super fine clutch disc particles" cause the problem but in reality, it's heat that causes the clutch fluid to boil. I'm willing to listen to your theory on how "super fine clutch disc particles" can boil clutch fluid.
12-19-2018, 08:58 AM
#60
Drifting
Thread Starter
most likely the right word would be: "just there's no torque multiplication", that's the same here in Italy
(just = the problem is)Last edited by Christi@n; 12-19-2018 at 09:02 AM.
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