It can’t be done: DCT cars can be shifted way faster than stirring a stick.
I was watching a video, and pardon my memory, but it was saying they work great in racing type situations, where throttle action is very definite, but not very well at all in various traffic situations, where throttle action is confused by the weird situations that arise, leaving your gearbox in the wrong “bank” , and a delay to find the right gear.
Also I think it mentioned they are averse to steep uphill reversing, and that early Ford DCT were designed so that heat was not adequately dispersed…leading to them frying very prematurely
I would need to review the video again to check all those facts, and its that horrible Aussie toad of an auto engineer/jouno dude, so I dont want to
Good old Kirby, trash-talking out of his fundament. Sometimes he does it deliberately to prompt debate, which is fine IMO. Sometimes I assume he does it because he forgot a relevant detail, which is also fine. I’ve done both. But sometimes it’s best to remember that pointing at someone’s alleged stupidity without getting your own ducks in a row is, well, stupid.
The V12 flywheel is, give or take, the same size and mass as the stock 3.4, 3.8 and 4.2 XK. If it was stupid heavy for a 5.3 it was presumably certifiably insane for the XK120. You remember the XK120 Kirby, pretty much the fastest mass-produced car of its era and race winner straight off the showroom floor. What were those Jag engineers drinking?
A flywheel is a kinetic energy store. Steam age technology and in spinning wheels and mills before steam. Clutchless engines and dog clutch engines still have flywheels and single cylinder 4-strokes can’t run without them to power three of the four strokes. So, clearly it is not only silly to say that heat soak is the only rationale for flywheel mass, there are plenty of times when it is not even a minor reason, since there’s no friction heat involved.
Gee, “an all-steel flywheel”? Why mention that unless it was possible to have something else. Did Ford ever use anything else? Cast iron maybe? No postwar Jag ever did. Sounds kinda special. Just like every XK and V12 uses.
Would you duct tape a clutch to the the crank flange?
So you weren’t involved?
Err, isn’t that the flywheel rim Kirbs? The most efficient design and the best way of getting the chosen flywheel effect with least mass?
I guess not. You’re the engineer, not me.
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i was totaly amazed about a yr ago , when daugter rented a 2019 Ford MUSTANG , 4cylinder turbo ,10speed automatic !
have a much better respect for the newer multi speed automatic transmissions now!
I took a trip last year in an Expedition with a 10-speed automatic. It was kinda ok on level ground, but once you got into hilly, windy roads, it was simply awful! It was CONSTANTLY shifting - up and down and up and down, sometimes doing 2-3 changes in rapid succession.
Regards,
Ray L.
Did it need… an intermediate speed hold?
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All other things being equal, given equal motive force, in this case engine torque, the flywheel with the lowest polar moment of inertia (MOI) will accelerate quickest. This does not necessarily mean the lightest. Where the weight is located relative to the axis of rotation is more important than the actual weight. A flywheel is a kinetic energy storage system. The energy stored is proportional to the product of the square of the angular velocity and proportional to its polar Moment of Inertia (MOI). The MOI in turn increases in proportion to the square of the radius of the mass from the center of rotation. Consider two flywheels of identical weight, but different diameters. Say flywheel A is 6" in diameter and flywheel B is 12" in diameter. The MOI of flywheel B is 4 times greater than that of flywheel A, so it will take 4 times the applied torque to achieve the same angular acceleration. Once turning, given the same angular rotational speed, flywheel B will conversely store 4 times more kinetic energy than flywheel A, so it will greatly resist changes in engine speed. This is desirable in a street car, where this resistance to change prevents stalling. On a race car, you prefer very little MOI so that you can make very rapid changes in angular velocity to accelerate and decelerate the gearbox to make gear changes, particularly on downshifts. Back in the 1970’s one of the first modifications I made to my 1968 L30/M20 Camaro was to swap out the heavy, stock iron flywheel for the nodular iron, lightweight, low MOI part from an L88 427 Corvette, which was specifically designed for road racing. It was transformative, it was easily the biggest bang for the buck I ever spent on the car. I didn’t come up with this modification on my own research. I had a good friend, Clarence, who was a well respected engine builder for short track late model stock cars and the late, great, SCCA Trans Am series. He also had worked as an engine builder in the K&K racing shop under legendary NASCAR crew chief Harry Hyde (Robert Duval played Harry in Days of Thunder). Clarence knew the dark, secret, corners of the Chrysler and GM Performance Parts catalogs like few others.
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We rented a convertible Mustang like that in Hawaii. The transmission performed well and there was enough power for probably 98% of the driving population. A shame there was no place to really see what it would do.
I’ve driven race cars with very small diameter, multi disc racing clutches. They work like a light switch, either full off or full on. The discs are generally sintered metal with very little tolerance to heat. Slipping the clutch to get rolling is a big no-no. They are easily overcooked. Once the engine is started you really need to rev up, dump the clutch and spin the tires to get rolling. It’s a real challenge to get the car out of the paddock to the grid, dodging paddock spectators, golf carts, etc.
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I’ve only driven a couple when renting cars on a trip. Agreed, they work great when hammered. They bugged me, though, when driving gently – seems like they just couldn’t make up their minds what gear to be in. One particular rental car had an option where you could manually select a gear and it’d stay there for a while, and that was better, but eventually we’d come to a stop and it’d go back to what it was doing.
Apparently. Pretty much every word of that response was wrong.
My wifes cars goes better the harder you hammer the throttle, up to ridiculous levels…the more you try and drive “defensively” or in “fuel saving” manner it feels sluggish and no better than my 4 speed. I know this is how an auto transmission is designed, but its kind of counter-productive for fuel economy and even safety.
I notice she seemed to have “learned” this without me even mentioning it, and drives much faster than she did as a lass, I get flung around in the passenger seat
My FIL generally got a new car about every 10 years, and it was usually some low-end Chevy. He put about 20K miles on a Citation in the dozen years he had it. And riding somewhere with him driving was a session in patience, as he drove sooooo slowly you always felt we were blocking traffic.
Then he got a Cobalt. Still fitting in his standard formula, but the Cobalt came with 16" wheels whereas the Citation and Cavalier he had owned had perhaps 13" or maybe 14" wheels. I dunno if it was the wheel size, but with that Cobalt he suddenly took off like a bat out of hell. Now it was scary riding with him, darting in and out of traffic and zipping around corners.
Talk is cheap Kirby. Prove it.
I don’t believe a word I wrote, as opposed to quoted, is ‘wrong’. But I do genuinely enjoy learning by being corrected, so please support your statement, even if it’s only by dragging up some weird exception to a common view. I’ve got a soft spot for weird exceptions…
There were rhetorical questions and opinionated statements and a partial ‘summary’, but you can’t say I mistakenly wrote X when I should have written Y. Or can you?
Yours (not very) expectantly
Pete
Ray says, “…t into hilly, windy roads, it was simply awful! It was CONSTANTLY shifting - up and down and up and down, sometimes doing 2-3 changes in rapid succession…”
Thanks Ray, I was afraid of that, and having not had an opportunity to drive one of those, I was hesitant.
Generally speaking, see me waving my hands, the new auto trannies are as economic as the stick and more convenient… BUT no matter how you slice it, you drive a car with a stick, you ride in a car with an automatic transmission. And don’t even get me started about the automatics shifting gears in the middle of a tight, high speed turn…
LLoyd
Don't you just hate those who live in the US for ten years and never bother to learn the language?
I think no one should graduate from grade school without learning either Cherokee, Apache, Ute or Arapaho.
LLoyd July, 2014
Just as an example of being wrong: Yes, putting mass at the outer rim is the best way of maximizing the flywheel effect with the least mass. But since the “chosen” flywheel effect should be zero for any engine with 8 or more cylinders – possibly with 6 cylinders as well – then designing a flywheel with a massive outer rim is poor engineering. And pointing out that a 4-banger requires flywheel inertia is not a valid argument for flywheel inertia on a V12.
Waaaaay back in the day when the Dodge Neon first came out, I rented one of those POS’s for a trip cross country. Came with a 5 speed auto. Driving across eastern Colorado, which is flat as a pancake, doing 70 mph on the expressway with the cruise control on. When approaching an interchange, the expressway would start climbing about a half mile in advance to go over a 20-foot high overpass. With the CC on, as the car started this .001% grade, it would suddenly and noisily downshift from 5th to 4th. Two seconds after that it would noisily downshift from 4th to 3rd. And another two seconds later it would downshift from 3rd to 2nd. Now it’s doing roughly 5000 rpm, and it’s still losing speed.
Lee Iacocca promised that they’d be exporting that car to Japan by the thousands. I dunno why any Japanese driver in his right mind would want one.
And how many production, manual-transmission street cars have you seen produced with effectively NO flywheel? I’ve never seen, or even heard of, a single one.
The need for a “massy” flywheel has far more to do with making the car easier to drive, mostly getting off-the-line, but also easing shifting, than it does the number of cylinders. Engines with fewer cylinders will generally have proportionally more massy flywheels to help smooth the power delivery, but I would expect an XK-engined var with NO flywheel would be nearly undriveable for the average driver. I’ve driven several E-types with lightweight aluminum flywheels, and they are decidedly more difficult to drive than those with the stock flywheel. I would expect even an 8-cylinder to be similar, but I can’t say for sure, as I’ve never seen an 8-cylinder with no flywheel.
Regards,
Ray L.
Regards,
Ray L.
Our 330Ci has a “computer” controlled standard clutch - called SMG in the M cars, SSG in Europe (apparently) in the non M’s. It is a different system in the non M’s and is Italian rather than German. This means it has fewer parts and is, in my opinion better. The thing is “better” just means it sucks less. These things manage to combine the worst of an automatic with all the disadvantages of a stick. A small cottage industry exists changing these back to standard sticks. Ours works OK, but my wife doesn’t trust it as they have a horrid reputation. IF you have an “M”, you have German arrogance, with the Italian you have no support if there is an issue.
Fortunately, I think those have now been long-since replaced with DCTs in all current production cars, no? SMGs were a poor, intermediate step between full manuals, and DCTs.
Regards,
Ray L.