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      08-13-2010, 09:39 PM   #45
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Originally Posted by RPM90 View Post
I don't want to debate the issue, but clutch slippage and it's use is part of driving a manual. And, knowing how to use it is part of the interaction.
Using it correctly is a good thing. Best example is proper launch from standstill. Perhaps you don't like the term "slip"? We can use modulate.
However, proper modulation sometimes requires a proper amount of clutch slip.
Well I can admit that 90% of the clutch modulation I do is because of an imperfect rev match. So I missed a little and have to keep it smooth the second best way. That's a little less fun than nailing it perfectly, but still fun.
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      08-13-2010, 11:02 PM   #46
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Originally Posted by maxnix View Post
Probably true!

You know, it is funny, no one in this discussion has objected to drive by wire, but many have thrown up their hands at the concept of clutch by wire.
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      08-14-2010, 08:21 AM   #47
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Quote:
Originally Posted by maxnix View Post
Clutch slippage is not a technique, but bad clutch friction vs power management.
I'm new here, and certainly don't want to start out by making enemies, but that is not true in any meaningful sense at all.

I think you personally are better served by not driving a manual transmission.
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      08-14-2010, 09:38 AM   #48
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I'm new here, and certainly don't want to start out by making enemies, but that is not true in any meaningful sense at all.

I think you personally are better served by not driving a manual transmission.
i wouldn't worry about maxnix. he is full of skewed ideas and mis-information about manual transmissions. just the other day he got owned trying to say that downshifting is bad for your car
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      08-14-2010, 10:16 AM   #49
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Originally Posted by maxnix View Post
What I actually said is downshifting to brake a car is not the wisest use for an engine. Brakes are designed for that and are cheaper to maintain.

A verrrry radical idea to non-engineer types, I am certain!

Wait around and someone will exalt the no-front brakes design of the early 20th century cars because downshifting is superior. Today's engineers just don't understand anything!

Lots of commonly held misconceptions on internet boards, like brake dust is bad. Like you would rather have rotor dust? Duh!
if you go back and re-read the thread, you were clearly explained why that is not true in great detail.
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      08-14-2010, 10:27 AM   #50
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Originally Posted by maxnix View Post
I suggest you do that! Maybe this time you will get it! Good luck!

Have you heard about lifetime sealed automatic transmissions?
originally posted by bradleyland

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Everything is worn in reverse. However, if you've been inside the mechanics of a car, you know that nothing in the driveline is built to operate in one direction. The gears, differential, etc are far more sensitive to shock (in either direction) than they are constant pressure. You could run your gearbox for 200k miles in either direction (forward or backward) under constant design-load pressure and it wouldn't wear out.

Let's talk about the kinetic energy part of your view, because it's a really good thing to understand. Brakes slow your car through friction. Friction generates heat. The heat is dissipated as radiant energy and and convective heat transfer. Much of this is dissipated in to the air, as well as soaking in to wheels and suspension parts attached to the wheel carriers. The problem is, air is a bad conductor of heat, so this process is relatively inefficient. When your brakes fail to brake any more, it is because the heat soak is so pervasive that no more heat energy can be absorbed.

Under compression braking, a different type of kinetic dissipation occurs. Your engine is a reciprocating assembly. It is engineered to:

* go round and round without wearing out
* convert heat energy created in the combustion chamber in to kinetic (motion) energy
* direct the force created from the energy-to-motion transfer in the most efficient means possible
* dissipate wasted energy through the exhaust and a water-to-air heat exchanger (radiator)
* BONUS FOR TURBO: harness wasted heat energy from the exhaust to boost output

The wear surfaces on rods, pistons, cranks, crank journals, etc are all cylindrical. They wear in a somewhat oblong pattern due to the forces involved with a piston that cycles back-and-forth a thousands of times a second, and in a well lubricated environment, they wear very little. This pattern doesn't change significantly whether you're accelerating or decelerating. I'm not talking out my ass here. I've held these parts in my hand and inspected them for wear while (sometimes) replacing them.

When you use compression braking, the kinetic energy from your forward momentum is transfered to heat energy by compressing air in the combustion chamber. Modern engine control systems do not inject fuel under decelerating conditions, so there is no ignition occurring in the cylinders. Your engine is (literally) perfectly designed to manage this type of energy, and it does so in a far more efficient manner than your brakes. As a matter of fact, your brakes are the least efficient mechanism on your car. Their sole purpose is to waste energy every time they are used.

Assuming that compression braking is "bad" for your car in a way that normal operation is not is based on an incomplete understanding of the systems that make up your driveline. Your engine, gearbox, and rear-axle assembly are all perfectly capable of operating for hundreds of thousands of miles in either direction. There is no reason avoid engine braking, provided you can do it smoothly. It is not a free lunch, but it is arguably a less expensive lunch than using your quick-wearing brakes.

1 thing i'll add-

i've driven a n55 dct, and i'm currently driving a step 328i loaner vehicle.....these transmissions downshift by themselves, without me even touching the brakes. how can downshifting be bad for a car's engine or transmission when BMW factory automatics downshift on their own?

maxnix-
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      08-14-2010, 10:42 AM   #51
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Quote:
Originally Posted by maxnix View Post
Probably true!

You know, it is funny, no one in this discussion has objected to drive by wire, but many have thrown up their hands at the concept of clutch by wire.
That's because drive-by-wire doesn't take away the gas pedal.
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      08-14-2010, 12:24 PM   #52
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I like manual, but DCT wins!

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80% of those on this board that move from manual to DCT will be back to manual within 3 to 4 years.

I've got its VAG counterpart, and have been using it as my DD for 3 years now. It's a great transmission and has been a real joy to use in that time period. I really don't have anything bad to say about it.

But like any video game you use every day the thrill eventually gets driven away (pun intended). If anything because it is in fact too good.

If I didn't have the manny tranny einser to play with on the weekends I would probably go

The gearbox is the best I've ever experienced in any BMW of the past 20 years, and finding the desired gear is not a struggle as it used to be.

But even with that benefit it still offers extreme challenges.

And in the end I prefer challenging myself rather than some computer, even if it beats me 99% of the time. Because that 1 time I beat it it will be nirvana and pure sweetness.

So go ahead and stray from the path if you feel compelled, but once the thrill is gone I'm guessing like the Prodigal Son you'll be back.............. in 3 years................maybe 4 years..............TOPS!

I think people are more enamoured by the perception of direct control over the manual transmission, whilst DCT proves manual transmission is inefficient when operated by a human being.

BMW has turned shifting gears into pure subjective entertainment value. I'd rather take the performance edge of DCT over the subjective entertainment value of the manual transmission.
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      08-14-2010, 02:08 PM   #53
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agree with original post comment

After 3 months in 11 DCT 135i, I am truly on the fence still! Went back and forth in the ordering of this car between MT and DCT and now agree that in 3-4 years time I may be back to MT. Also in agreement with many of the posts here, there is no right answer. On the track you cannot ask for anything better than DCT and in your daily commute if the 1 is your daily driver you will enjoy the DCT and its ability to let you "play when you want" and simply "commute" as most do in their daily drivers taking phone calls etc...... BUT when all is said and done if you forget the above and enjoy the interactions that ONLY a MT can offer you will have moments of regret. For me those moments of regret are few and far between as I love the DCT 95% of the time, but when I am at the track and most of my track mates have MT cars I do feel like a "sell out" and possibly losing touch with the driving experience basics, but then I think of Ferrari who do NOT offer MT anymore. For the poster who feels Ferrari still offer MT in some of its models go re-check your facts.....you are wrong........and also dont forget BMW originally did not offer MT in the M5......

Last edited by msos; 08-14-2010 at 02:14 PM.
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      08-14-2010, 05:42 PM   #54
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The automated downshifts with DCT take place at a lower road, hence engine, speed for the gear involved. Typically on my M3 it will go from whatever to 3 then 2 then 1 at a stop. There's negligible compression braking as a result and thus no issue.

By the way, dual-clutch forever. I'll never go back to a manual and I've driven plenty for many years, BMW, Porsche, Honda (the S2000 is sweet), etc. The M-DCT anyway is very good, I don't need to futz around with another pedal, foot, and a sometimes balky/notchy lever to feel "involved".
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      08-14-2010, 07:19 PM   #55
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Agree with your predicition. No one substituation of manual will work for manual lovers. We just need to shift something and feel it.
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      08-16-2010, 12:37 AM   #56
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Quote:
Originally Posted by maxnix View Post
Oh, but I do! And I always try to minimize slippage. With decent coordination, one can dump the clutch while simultaneously applying power and get down the road quite quickly!

So, every time you take off from a stop at a light or a stop sign, you 'dump' the clutch while applying power? And, you think that's good for your clutch every time you move from a stop?
Well, I don't. Proper throttle and clutch modulation, which DOES include proper clutch slip, will get you moving smoothly and in a controlled manner.

Using your method we'd have to burn out on every stop and deal with even MORE friction wear on the clutch due to having to use a lot of HP while we DUMP the clutch to get moving.
Do you think the stock clutch clamping force is that great that it still won't slip a bit even on a clutch dump?
If so, then rethink it.

Last edited by RPM90; 08-16-2010 at 12:47 AM.
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      08-16-2010, 12:46 AM   #57
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Quote:
Originally Posted by maxnix View Post
Clutch slippage is not a technique, but bad clutch friction vs power management.

How do clutches wear? It is not when they are fully engaged, it is not when they are fully disengaged, it is when there is too much power for the clamping friction. Very similar to brake pads which only wear when there is a mismatch between clamping force and rotational power.
With brakes you have to apply brakes and wear them over time. That's what they are made/designed to do. You don't give full force on the brake pedal on every stop, if you do you're doing it wrong.
A properly driven clutch will still wear over time. But, most of it's wear occurs during take off where you have to modulate the slip, and during hard, high hp shifts where the clutch still slips a bit between shifts, as it gets bite and grabs.

The DCT does this too. It has to so that it can accommodate a driver who takes off slowly form a stop vs a driver who wants to launch it at every start.

I'm not talking about poor clutch control where one rides the clutch while moving or shifting through every gear.

Last edited by RPM90; 08-16-2010 at 01:11 AM.
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      08-16-2010, 12:52 AM   #58
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Quote:
Originally Posted by maxnix View Post
Ummmmm......let's see. Maybe the same way that lifetime sealed automatic transmissions are better than periodic mechanical ATF exchanges and filter replacements?


Anyway, moving on, one can certainly slip their clutch all they want, but it will not last as long as the one driven with less slippage. Very simple to comprehend that, I hope.
Good, cause that is what I initially said, and you countered by saying that was wrong.
Ok, so finally you acknowledge that controlled slippage is a good thing, and allows proper veh icle operation.
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      08-16-2010, 01:07 AM   #59
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Quote:
Originally Posted by fancyfl1ght View Post
I think people are more enamoured by the perception of direct control over the manual transmission, whilst DCT proves manual transmission is inefficient when operated by a human being.

BMW has turned shifting gears into pure subjective entertainment value. I'd rather take the performance edge of DCT over the subjective entertainment value of the manual transmission.
Hmmm...so I'm just perceiving that I actually have direct control of shifting the lever and engaging/disengaging the clutch while driving a manual?
I didn't realize that I was just perceiving it. I thought I was actually performing the gear changes.

So then, does the DCT give you an enhanced perception of direct control over your shifts? Moving a switch up/down, or tapping a lever, asking the computer to do the gear change is more real and more directly in control of the shifting process?

Yes, a manual trans does give "entertainment value".
I agree that indeed the "manual" cars are very entertaining and FUN.
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      08-16-2010, 01:28 AM   #60
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Quote:
Originally Posted by RPM90 View Post
Hmmm...so I'm just perceiving that I actually have direct control of shifting the lever and engaging/disengaging the clutch while driving a manual?
I didn't realize that I was just perceiving it. I thought I was actually performing the gear changes.

So then, does the DCT give you an enhanced perception of direct control over your shifts? Moving a switch up/down, or tapping a lever, asking the computer to do the gear change is more real and more directly in control of the shifting process?

Yes, a manual trans does give "entertainment value".
I agree that indeed the "manual" cars are very entertaining and FUN.
When I read his post the first thing I thought was that he sounds like someone who doesn't know how to drive a manual.
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      08-17-2010, 12:46 AM   #61
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Quote:
Originally Posted by radiantm3 View Post
When I read his post the first thing I thought was that he sounds like someone who doesn't know how to drive a manual.
Most MTers don't know how to shift.
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      08-17-2010, 10:06 AM   #62
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Quote:
Originally Posted by msos View Post
but then I think of Ferrari who do NOT offer MT anymore. For the poster who feels Ferrari still offer MT in some of its models go re-check your facts.....you are wrong........and also dont forget BMW originally did not offer MT in the M5......
I did check my facts, and I'm sorry, but you are wrong. It is true that the new 458 Italia doesn't offer a traditional manual, but a 6MT is available on the 599 GTB and California. The links below show the technical specifications directly on Ferrari's website. Under the Transmission and Gearbox section for the 599, it clearly states, "Manual or F1; 6-gears+Reverse". For the California, the Gearbox section lists "F1, dual clutch 7 gears + Reverse" or "Manual 6 gears + Reverse".

599 GTB
http://www.ferrari.com/English/GT_Sp...cal_Sheet.aspx

California
http://www.ferrari.com/English/GT_Sp...cal_Sheet.aspx

The M5 you are referring to is the E60, but the previous M5's (E28, E34, E39) were all traditional manual transmissions.
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      08-17-2010, 10:21 AM   #63
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Perhaps I was not being clear

Quote:
Originally Posted by RPM90 View Post
Hmmm...so I'm just perceiving that I actually have direct control of shifting the lever and engaging/disengaging the clutch while driving a manual?
I didn't realize that I was just perceiving it. I thought I was actually performing the gear changes.

So then, does the DCT give you an enhanced perception of direct control over your shifts? Moving a switch up/down, or tapping a lever, asking the computer to do the gear change is more real and more directly in control of the shifting process?

Yes, a manual trans does give "entertainment value".
I agree that indeed the "manual" cars are very entertaining and FUN.
A human being makes manual gear changes based on speed, rpms, clutch resistance and a gear shifter. This is a very analog method based on feel.

Sure there is great feel to a manual transmission. It would be a greater stretch to believe that the great feel of a manual transmission is necessarily efficient.

DCT has proven that it will out think and out play a human being.

Does DCT have a similar feel of a manual? No way. That is the sacrifice and the decision point people need to make.

I chose efficiency over feel. Others may differ.
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      08-17-2010, 01:07 PM   #64
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Quote:
Originally Posted by fancyfl1ght View Post
A human being makes manual gear changes based on speed, rpms, clutch resistance and a gear shifter. This is a very analog method based on feel.

Sure there is great feel to a manual transmission. It would be a greater stretch to believe that the great feel of a manual transmission is necessarily efficient.

DCT has proven that it will out think and out play a human being.

Does DCT have a similar feel of a manual? No way. That is the sacrifice and the decision point people need to make.

I chose efficiency over feel. Others may differ.
I've been reading a lot over on M3Post and I've noticed a whole lot of threads on people not understanding what DCT is doing in certain situations or acting like expected. That alone would drive me nuts. The DCT computer is programmed to react a certain way in various conditions but it doesn't read the driver's mind. It might be fast, but I'd rather the transmission do what I want it to do over ignoring my request and doing something else because it thinks it's more efficient or safer.
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      08-17-2010, 01:20 PM   #65
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Quote:
Originally Posted by fancyfl1ght View Post
A human being makes manual gear changes based on speed, rpms, clutch resistance and a gear shifter. This is a very analog method based on feel.

Sure there is great feel to a manual transmission. It would be a greater stretch to believe that the great feel of a manual transmission is necessarily efficient.

DCT has proven that it will out think and out play a human being.

Does DCT have a similar feel of a manual? No way. That is the sacrifice and the decision point people need to make.

I chose efficiency over feel. Others may differ.
i bet you choose big mac over spaghetti, too, because it's efficient, right?
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      08-17-2010, 01:21 PM   #66
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Quote:
Originally Posted by radiantm3 View Post
I've been reading a lot over on M3Post and I've noticed a whole lot of threads on people not understanding what DCT is doing in certain situations or acting like expected. That alone would drive me nuts. The DCT computer is programmed to react a certain way in various conditions but it doesn't read the driver's mind. It might be fast, but I'd rather the transmission do what I want it to do over ignoring my request and doing something else because it thinks it's more efficient or safer.
Back in the university days I designed a brainwave analyzer that would warn if you're falling asleep as a fourth year design project.

Maybe you wanna take it for a spin and update the software to read your mind?

haha
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