Porsche "Virtual Gears"

"davesaddiction @ opposite-lock.com" (davesaddiction) 10/09/2015 at 15:48 • Filed to: None

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“In truth, the 991 Turbo also has virtual gears. But that car’s so specialized that no one really cared. Until now. Here’s how it works. Let’s say that for purposes of fuel economy, it would be better if a gear between second and third were engaged. For instance, your velocity is such that you don’t need all the power generated in second gear, but third gear would lower the engine revs too much. But that gear doesn’t exist! Not so fast. Thanks to the magic of Porsche Doppelkupplungsgetriebe (PDK), the new 911 has a near infinite number of virtual gears. There’s no easy way to explain how it works, so just read the following: “This function is achieved by partially engaging two adjacent gears simultaneously while slipping both clutches slightly to achieve an effective gear ratio in between them.” See? Simple! And helps to make the 991/2 14 percent more efficient than the 991.”

Letting the clutches slip in the name of efficiency sounds like a terrible idea...

Leon711 > davesaddiction @ opposite-lock.com 10/09/2015 at 15:53

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It sounds terrible but I’m sure it is fine. There’s a lot of talented people at porsche.

daender > davesaddiction @ opposite-lock.com 10/09/2015 at 15:54

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I think they over-German’d it. I foresee a lot of transmission issues coming up like IMS in the near future once these start getting used more and more.

Cé hé sin > davesaddiction @ opposite-lock.com 10/09/2015 at 15:54

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“Letting the clutches slip in the name of efficiency sounds like a terrible idea...”

It does at first glance but I’m guessing that Porsche and ZF have thought of this. Don’t they use wet clutches which aren’t subject to so much wear as dry ones?

JQJ213- Now With An Extra Cylinder! > davesaddiction @ opposite-lock.com 10/09/2015 at 15:55

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So it almost sounds like a CVT that has a “manual mode” where you can “select” a gear...

dogisbadob > JQJ213- Now With An Extra Cylinder! 10/09/2015 at 15:57

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came here to say this

ADabOfOppo; Gone Plaid (Instructables Can Be Confusable) > Leon711 10/09/2015 at 15:57

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We thought that same thing about VW as well until recently...

Bluecold > davesaddiction @ opposite-lock.com 10/09/2015 at 16:00

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So like the Ferrari FF’s front gearbox?

michael bleggi > ADabOfOppo; Gone Plaid (Instructables Can Be Confusable) 10/09/2015 at 16:03

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i think this whole scandal just proves that there are some very talented people at vw.... but now the EPA has some very talented people as well

Bob Loblaw Made Me Make a Phoney Phone Call to Edward Rooney > davesaddiction @ opposite-lock.com 10/09/2015 at 16:05

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Not the same kind of clutch. Wet clutches which don’t wear like a dry clutch. I’m sure it will obviously cause more wear, but I’d be surprised if it was catastrophic wear.

davesaddiction @ opposite-lock.com > Leon711 10/09/2015 at 16:07

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I'll believe if this proves reliable 10 years from now...

davesaddiction @ opposite-lock.com > Cé hé sin 10/09/2015 at 16:09

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I’m afraid they’ve thought about it and decided that efficiency was more important that long-term reliability.

Twingo Tamer - About to descend into project car hell. > davesaddiction @ opposite-lock.com 10/09/2015 at 16:09

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It’s interesting but yes maintenance costs will increase due to it. But what happens in a decade after the 1st owner has long since sold it doesn’t really matter.

ADabOfOppo; Gone Plaid (Instructables Can Be Confusable) > michael bleggi 10/09/2015 at 16:09

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Apart from the fact the the EPA didn’t even catch this and it was a couple of schools looking into diesel emissions that made their findings public that brought about the EPA’s attention.

There probably are several smart people working for the EPA, but the collective intelligence has yet to be proven. When the government body charged with testing emissions leaves it to the automakers and the honor system, I would not call that decision intelligent.

Teleph0nes > davesaddiction @ opposite-lock.com 10/09/2015 at 16:10

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Remember when everyone switched to timing chains because they would never wear out or break and that way we wouldn’t have to worry about timing belt maintenance?

JawzX2, Boost Addict. 1.6t, 2.7tt, 4.2t > davesaddiction @ opposite-lock.com 10/09/2015 at 16:11

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I believe this is exactly something that the Ford PowerShift transmissions do as well. It may be unadvertised, but it sure feels like EXACTLY what is described here. Don’t believe me? go get a Focus with the DCT, drive it up a long hill, press the accelerator enough to have it kickdown, say from 4 to 3, then let off the gas just a bit and notice how it doesn’t return to 4 with a crisp shift and lingers in variable slip until either engine RPM drops more, vehicle speed increases, or the slope of the hill changes, (it may also choose to kick back down to 3 depending on conditions...).

It’s a VERY STRANGE sensation, but for someone who actually pays attention to the way their transmission behaves, it’s clearly not exactly what a torque converter automatic or a CVT does, but not quite exactly what slipping the clutch in a true manual feels like... It may very well be one of the “features” that has caused The PowerShift so much grief. Of note: driven gently, at below 50MPH a PowerShift-equipped Focus can return hyper-mile-worthy fuel economy numbers. My ex-girlfriend’s 2012 could average nearly 45MPG over 100+ miles in secondary highway conditions. It does this A LOT when driving in those conditions.

davesaddiction @ opposite-lock.com > JQJ213- Now With An Extra Cylinder! 10/09/2015 at 16:12

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Not really, but it is a dual-clutch box that can act like it’s a CVT. I doubt if there’s infinite variability between gears; they’re just adding half-steps.

davesaddiction @ opposite-lock.com > Bluecold 10/09/2015 at 16:14

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Not quite. http://blog.caranddriver.com/funky-four-exp…

Opposite Locksmith > Bluecold 10/09/2015 at 16:15

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Absolutely nothing like that

davesaddiction @ opposite-lock.com > Bob Loblaw Made Me Make a Phoney Phone Call to Edward Rooney 10/09/2015 at 16:16

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I hope you’re right, just wonder what it means for these many years and miles down the road.

davesaddiction @ opposite-lock.com > Twingo Tamer - About to descend into project car hell. 10/09/2015 at 16:17

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... to Porsche.

davesaddiction @ opposite-lock.com > JawzX2, Boost Addict. 1.6t, 2.7tt, 4.2t 10/09/2015 at 16:18

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Interesting...

Twingo Tamer - About to descend into project car hell. > davesaddiction @ opposite-lock.com 10/09/2015 at 16:20

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Indeed. Most premium manufacturer only care about the 1st owner. They’re the ones they make the money off after all.

K-Roll-PorscheTamer > davesaddiction @ opposite-lock.com 10/09/2015 at 16:20

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Uhgg.......This will be interesting in 5-10 years.

bob and john > davesaddiction @ opposite-lock.com 10/09/2015 at 16:22

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the FF does something similar.

I dont agree with it.
3rd lowers the engine RPM to much? go faster to use 3rd properly!

Bluecold > davesaddiction @ opposite-lock.com 10/09/2015 at 16:23

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http://www.whyhighend.com/ferrari-4rm.ht…

The clutches that drive the front wheels were designed to be constantly slipping thereby allowing the two forward front gear ratios to run smoothly with the four gears they correspond with at the rear.

Seems similar. Not exactly the same, but the concept of driving wheels with constantly slipping clutches seems similar.

Bob Loblaw Made Me Make a Phoney Phone Call to Edward Rooney > davesaddiction @ opposite-lock.com 10/09/2015 at 16:23

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I’m certainly not putting my own money behind my assertion there...

But I’m lead to believe that current reliability information on first gen DSGs has been very positive, so it seems like they at least have some room to play with. It does sound insane on the face of it, either way.

Urambo Tauro > davesaddiction @ opposite-lock.com 10/09/2015 at 16:26

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I’m not going to pretend that I know more about engineering than these guys. This is a hard thing for me to wrap my mind around.

I thought that slippage caused heat, snowballing the wear effect. Forcing the clutches to continue slipping under load sounds like a great way to accelerate wear. Even if they managed to improve cooling in the system, it sounds like the slippage would polish the friction material before long.

I sincerely hope they didn’t throw longevity out the window in the interest of increasing efficiency and performance “because racecar”.

luvMeSome142 & some Lincoln! > davesaddiction @ opposite-lock.com 10/09/2015 at 16:30

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I’m dubious of this claim, but here’s an explanation that makes a bit of sense.

Forget the fancy PDK two gears at once thing. Think about your regular 6 speed. If you were travelling at a constant speed on level ground at say 50mph. The load on the engine is pretty light. It has to make just enough power to overcome drag. You could, in theory, reduce your engine rpms by slightly slipping the clutch while still maintaing speed. IF the energy savings of running the engine at the lower rpm is greater than the energy lost to heat at the clutch, there will be some improvement in fuel economy.

To adress the reliability aspect, these are wet clutches and this situation is under very low load. The heat generated will be very low as well. There will be wear of course. But, it’s probably orders of magnatude less than a normal 1st gear clutch engagement. The big question is, how much less.

davesaddiction @ opposite-lock.com > Urambo Tauro 10/09/2015 at 16:34

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More like “because EPA”.

davesaddiction @ opposite-lock.com > luvMeSome142 & some Lincoln! 10/09/2015 at 16:35

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I bet we’ll know in about 10 years.

davesaddiction @ opposite-lock.com > Twingo Tamer - About to descend into project car hell. 10/09/2015 at 16:44

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I’m not sure if that’s true. I’d argue that a good experience with a second- or third-hand car would make a person more likely to buy one new from the same brand down the road, no pun intended. And even if someone only buys used, demand can keep depreciation from being too great for original owners, which is attractive to some buyers...

davesaddiction @ opposite-lock.com > K-Roll-PorscheTamer 10/09/2015 at 16:46

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Doesn’t really matter to me, as I can’t see myself buying a PDK or a turbo’d Porsche that’s not a Turbo...

davesaddiction @ opposite-lock.com > bob and john 10/09/2015 at 16:48

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The FF has a separate gearbox in the front with 2 gears that cover 4 gears.

davesaddiction @ opposite-lock.com > Bluecold 10/09/2015 at 16:50

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And I'd be much more concerned of the wear on this Ferrari transmission than the Porsche one - ha!

Roman Savchuk > Cé hé sin 10/09/2015 at 16:52

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It may not wear, but it still wasting energy through the friction (not much, probably) . The idea doesn’t make sense outright, but I don’t know all the design details, it could work in some conditions... sometimes. Anyway, fine example of Ze Great German Engineering)))

bob and john > davesaddiction @ opposite-lock.com 10/09/2015 at 16:54

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yep. they slip the clutch in both of them to match the speeds.

davesaddiction @ opposite-lock.com > Bob Loblaw Made Me Make a Phoney Phone Call to Edward Rooney 10/09/2015 at 16:54

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Lots of puzzling decisions have been made in recent years in the name of efficiency. Porsche/BMW/Ferrari all move to turbos and EPS (not Ferrari yet) after being staunchly NA and “steering feel uber alles”, auto start/stop systems, and now this.

K-Roll-PorscheTamer > davesaddiction @ opposite-lock.com 10/09/2015 at 16:55

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I could see myself buying a PDK Porsche, a Cayman probably, one day...I’ll only ever be able to afford Caymans, not that there’s anything wrong with that. Hell, I won’t ever buy a turbo’d Porsche that isn’t suppose to be a turbo..

davesaddiction @ opposite-lock.com > K-Roll-PorscheTamer 10/09/2015 at 17:00

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I might buy my wife a PDK Macan S one day - ha! PDK is great, but I love driving a manual to much to give it up.

Urambo Tauro > davesaddiction @ opposite-lock.com 10/09/2015 at 17:06

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I was afraid of that. I didn’t even want to say it. But you’re probably right...

Bob Loblaw Made Me Make a Phoney Phone Call to Edward Rooney > davesaddiction @ opposite-lock.com 10/09/2015 at 17:10

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It’ll be interesting to look back on these technologies in 10 years or so. We’ve made a lot of progress over the past 20 years in vehicle life, but I have to wonder if that’s not going to slow/regress with the insane level of complexity now being built into your average economy car just to meet standards, much less your sports and exotic cars.

davesaddiction @ opposite-lock.com > Bob Loblaw Made Me Make a Phoney Phone Call to Edward Rooney 10/09/2015 at 17:21

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Yup. Lots of changes because makers feel like they have to, not because they want to.

K-Roll-PorscheTamer > davesaddiction @ opposite-lock.com 10/09/2015 at 17:34

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I like driving SMG, so PDK will most likely be my “holy grail” of paddle gearboxes. I’ve never had the chance to drive any Porsche gearbox that isn’t the 915 gearbox and the Porsche/Audi gearbox.

Twingo Tamer - About to descend into project car hell. > davesaddiction @ opposite-lock.com 10/09/2015 at 18:03

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I guess we’ll see soon enough whether it works out or not.

davesaddiction @ opposite-lock.com > K-Roll-PorscheTamer 10/09/2015 at 18:20

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I test drove an A3 with the DSG a few years back. Definitely slick tech, and I’m sure it’s only gotten better since then.

K-Roll-PorscheTamer > davesaddiction @ opposite-lock.com 10/09/2015 at 18:26

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Hell, I haven’t even driven a GTI with DSG, I’d only accept a GTI with DSG anyways. Fart noises are cool!!

I literally only want a paddle gearbox to fart around people all day. :p

davesaddiction @ opposite-lock.com > K-Roll-PorscheTamer 10/09/2015 at 18:46

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But... golf ball shift knob!

Leon711 > ADabOfOppo; Gone Plaid (Instructables Can Be Confusable) 10/09/2015 at 18:49

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Still talented, someone had to think of the cheat.

Leon711 > davesaddiction @ opposite-lock.com 10/09/2015 at 18:51

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The VAG DSG has been around for over a decade now, aside from some teething problem with the early ones they are reliable. My guess is that Porsche have heavier duty wet clutches in this.

K-Roll-PorscheTamer > davesaddiction @ opposite-lock.com 10/09/2015 at 19:05

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It looks cool, but I don't even like golf. :p

asindhidude > daender 10/09/2015 at 19:43

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Oh yeah. This is gonna break for sure.

davesaddiction @ opposite-lock.com > K-Roll-PorscheTamer 10/09/2015 at 19:46

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Hahaha - here’s the DCT release video, if you’ve never seen it.

davesaddiction @ opposite-lock.com > Leon711 10/09/2015 at 19:55

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But using a dual clutch system like this (two gears partially engaged at once) is clearly outside of the parameters of the original design.

C62030 > daender 10/10/2015 at 15:12

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Can we please use the term “over-German’d” more often?