Rennteam 2.0 - EN - Forum - Re: Disappointed in 7th gear ratio for PDK - Page1

Jun 6, 2008 1:22:53 PM

Grant: Rennteam VIP; Loc: Denver, CO , United States; Posts: 12586, Gallery; Registered on: Aug 21, 2002

Disappointed in 7th gear ratio for PDK

Looks like 7th gear in the PDK is just a cruising gear. 6th gear in manual and PDK are identical ratio (with same final drive) and 7th is just for fuel economy and low noise.

PDK does have some slightly closer ratios (like shifts between 2nd & 3rd gears), but there is no complete realigning of the ratios for pure performance. Top speed will be achieved with 6th gear in the PDK, like a Corvette in 5th

Gear Manual PDK
1st 3.91 3.91
2nd 2.32 2.29
3rd 1.56 1.65
4th 1.28 1.30
5th 1.08 1.08
6th 0.88 0.88
7th ----- 0.62

Final 3.44 3.44

I bet they will save the real benefits of the 7 close ratios for the new GT3 (make new 7th gear close to the former 6th and move all the other ratios closer together)...

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Jun 6, 2008 1:47:51 PM

Carlos from Spain: Rennteam Moderator; Loc: Spain. , Spain; Posts: 21148, Gallery; Registered on: Feb 9, 2003; Reply to: Grant

Re: Disappointed in 7th gear ratio for PDK

Quote:
Grant said:(make new 7th gear close to the former 6th and move all the other ratios closer together)...

I was convinced this is what they would do with all 911 PDK's , its a sportcar for heaven's sake... dissapointing indeed.

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Jun 6, 2008 1:48:07 PM

reginos: Rennteam VIP; Loc: Nicosia , Cyprus; Posts: 12130, Gallery; Registered on: Mar 20, 2005; Reply to: Grant

Re: Disappointed in 7th gear ratio for PDK

I would have preferred 7 "driving" ratios myself. But fuel economy, noise and emissions are important too.

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Jun 6, 2008 2:31:15 PM

69bossnine: Rennteam Pro; Loc: FL, USA , United States; Posts: 2028, Gallery; Registered on: Jan 27, 2005; Reply to: reginos

Re: Disappointed in 7th gear ratio for PDK

Sorry, but it reinforces my argument that for real-world use, more than 6 gears is getting a bit silly/gimmicky/bragging-rights-ish...

7 driving ratios? If better performance were the "basic" goal, and "X" amount of R&D resources were available, wouldn't 30-40 lbft more torque be more enjoyable and useable than an extra gear stuffed in? Call me a caveman, but if Porsche came to me and said "we've got $150 million to spend, would you like a 7-speed PDK, or a far thriftier-to-bring-to-market 6-speed along with 30 more lbft of grunt?".... I wouldn't even stutter.

Yes, it's a "sports car", but it's a street car also... I'm guessing that they geared it so that it wouldn't be absolutely annoying to street drive, i.e. all of those ratios packed into your typical speed ranges, whereby you spend all day shifting and shifting with so little difference between gears. At least with a true manual, you can easily 1-3-5 shift, or 1-2-4-6, when you're just plinking around town or taking it easy... It's no sweat, you can drive your 6-speed like it's a 3-speed just by adjusting your pattern.

But with PDK, that set sequence is always in your way, isn't it?

It's just my guess, my attempt at slipping into the noggins of the engineers who put together this package.

I get the "optimal performance" mechanical-engineering argument for 7 driving-range gears completely. I get the race-car argument.

But hey, chalkboard math and real-world utility/interface don't always make a good marriage.

Besides, I'd sooner drive an airport van than have one of those techno-geek clutchless-manuals anyhoo...

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Jun 6, 2008 3:00:05 PM

Grant: Rennteam VIP; Loc: Denver, CO , United States; Posts: 12586, Gallery; Registered on: Aug 21, 2002; Reply to: 69bossnine

Re: Disappointed in 7th gear ratio for PDK

Quote:
69bossnine said:If Porsche came to me and said "we've got $150 million to spend, would you like a 7-speed PDK, or a far thriftier-to-bring-to-market 6-speed along with 30 more lbft of grunt?".... I wouldn't even stutter.

I guess I'm greedy, since I'd like more power/torque and better gearing.

Especially with the additional power and higher redline of the new DFI motors, 7 close ratios makes more sense than ever, imho...

I guess the silver lining is that for those of us Luddites who like to shift with 3 pedals, there is not the performance penalty I expected by staying with a 6 speed manual...

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Jun 6, 2008 3:02:20 PM

KresoF1: Rennteam VIP; Loc: Croatia , Croatia; Posts: 7856, Gallery; Registered on: Dec 3, 2005; Reply to: Grant

Re: Disappointed in 7th gear ratio for PDK

Also interesting is the fact that PDK cars are little bit slower in top speed:
300km/h for S(302km/h manual)
287km/h for non S(289km/h manual)

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Jun 6, 2008 3:03:51 PM

Grant: Rennteam VIP; Loc: Denver, CO , United States; Posts: 12586, Gallery; Registered on: Aug 21, 2002; Reply to: KresoF1

Re: Disappointed in 7th gear ratio for PDK

Quote:
KresoF1 said:
Also interesting is the fact that PDK cars are little bit slower in top speed:
300km/h for S(302km/h manual)
287km/h for non S(289km/h manual)

Due to increased friction in PDK?

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Jun 6, 2008 3:07:10 PM

KresoF1: Rennteam VIP; Loc: Croatia , Croatia; Posts: 7856, Gallery; Registered on: Dec 3, 2005; Reply to: Grant

Re: Disappointed in 7th gear ratio for PDK

Quote:
Grant said:
Quote:
KresoF1 said:
Also interesting is the fact that PDK cars are little bit slower in top speed:
300km/h for S(302km/h manual)
287km/h for non S(289km/h manual)

Due to increased friction in PDK?

Honestly, I do not know. We need that dealers info PDF with all technical explanation...

Just one question-what would happened if you manually shift up at say 299km/h in sixth?

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Jun 6, 2008 3:07:54 PM

intouch1: Rennteam Master; Loc: Red Sea , Egypt; Posts: 5752, Gallery; Registered on: May 22, 2004; Reply to: Grant

Re: Disappointed in 7th gear ratio for PDK

Quote:
Grant said:
Quote:
KresoF1 said:
Also interesting is the fact that PDK cars are little bit slower in top speed:
300km/h for S(302km/h manual)
287km/h for non S(289km/h manual)

Due to increased friction in PDK?

or weight ??

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Jun 6, 2008 3:09:43 PM

Ferdie: Rennteam VIP; Loc: Europe , Germany; Posts: 8234, Gallery; Registered on: Jul 2, 2004; Reply to: Grant

Re: Disappointed in 7th gear ratio for PDK

In fact I do not see the problem. The higher redline encourages to use the 7th ratio as an economical gear and I found the six ratios on the current car quite sufficient. If you use the car on the motorway at cruising speed it does make sence. Funny that it is you guys in the restricted US that complain about that setup.

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Jun 6, 2008 3:12:17 PM

Grant: Rennteam VIP; Loc: Denver, CO , United States; Posts: 12586, Gallery; Registered on: Aug 21, 2002; Reply to: intouch1

Re: Disappointed in 7th gear ratio for PDK

Quote:
intouch1 said:
Quote:
Grant said:
Quote:
KresoF1 said:
Also interesting is the fact that PDK cars are little bit slower in top speed:
300km/h for S(302km/h manual)
287km/h for non S(289km/h manual)

Due to increased friction in PDK?

or weight ??

More weight wouldn't cause a lower top speed, it would just take longer to get there...

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Jun 6, 2008 3:13:21 PM

Grant: Rennteam VIP; Loc: Denver, CO , United States; Posts: 12586, Gallery; Registered on: Aug 21, 2002; Reply to: KresoF1

Re: Disappointed in 7th gear ratio for PDK

Quote:
KresoF1 said:
Just one question-what would happened if you manually shift up at say 299km/h in sixth?

The car would slow down due to less power at lower rpms

Peak power is at 6,500 rpm and I imagine 7th gear would give far less than that at 299kph. Maybe the slightly lower top speed is actually in 7th gear (compared to 6th in manual), but I would expect the loss to be greater than that

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Jun 6, 2008 3:26:15 PM

4trac: Expert; Loc: SK , Canada; Posts: 1920, Gallery; Registered on: Nov 6, 2006; Reply to: KresoF1

Re: Disappointed in 7th gear ratio for PDK

Quote:
KresoF1 said:
Just one question-what would happened if you manually shift up at say 299km/h in sixth?

In this case the PCM screen flashes a large "NEIN!!!" and the car stays in 6th.

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Jun 6, 2008 3:30:19 PM

69bossnine: Rennteam Pro; Loc: FL, USA , United States; Posts: 2028, Gallery; Registered on: Jan 27, 2005; Reply to: Grant

Re: Disappointed in 7th gear ratio for PDK

Points taken, but in all things, Porsche has to weigh the desires of the minority against the preferrences of the majority of their prospective PDK customers...

They've gotta avoid being annoying to most, just to please that rabid lunatic fringe..

Unfortunately, for every one of you who opt for the new PDK for its real-application cutting-edge track performance, you'll have 10 goofballs who are simply too lazy to shift, and got it because its cool-factor and gizmo-video-game appeal.

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Jun 6, 2008 3:30:34 PM

Grant: Rennteam VIP; Loc: Denver, CO , United States; Posts: 12586, Gallery; Registered on: Aug 21, 2002; Reply to: 4trac

Re: Disappointed in 7th gear ratio for PDK

Actually, I just computed that 7th gear is 29.5% taller than 6th, so shifting at 7,500 rpm at 300kph into 7th gear would put the revs at 5,288rpm (too low to maintain 300kph, I would think).

I need to compare power at 7,500rpm (lower than peak at 6,500) to the power at 5,300rpm (also lower than peak).

Optimum gearing would put top speed at 6,500rpm in 7th gear (my guess, it would be well over 300kph with a 7th gear ratio around 0.73).

Maybe Porsche chose this compromise, so that top speed would be about the same in either 6th or 7th, but neither can reach the potential top speed of the car with its power and aerodynamics

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Jun 6, 2008 3:43:30 PM

ResB: Rennteam Pro; Loc: Yorkshire, where roads are twisty... , United Kingdom; Posts: 2858, Gallery; Registered on: Jan 19, 2006; Reply to: Grant

Re: Disappointed in 7th gear ratio for PDK

It's all to do with MPG. Drop the revs, more MPG. I bet the new MPG figures are with the car stuck in 7th at 56mph I'm sure. I wonder how much more efficient the DFI engine is for that matter as the MPG figures will be a bit distorted.

On the subject of PDK, I wonder why you can't hear any of the gear changes, surely that would have made sense to show how quick it actually did change gear. We'll know soon enough I'm sure...

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Jun 6, 2008 6:25:22 PM

sws1: Junior; Loc: USA; Posts: 83, Gallery; Registered on: Aug 2, 2006; Reply to: ResB

Re: Disappointed in 7th gear ratio for PDK

7th gear is for claiming MPG increase. That's all. Don't use if it you don't want.

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Jun 7, 2008 2:15:46 AM

donkeyman: Junior; Loc: Hong Kong; Posts: 113, Gallery; Registered on: Jun 16, 2005; Reply to: sws1

Re: Disappointed in 7th gear ratio for PDK

Quote:
sws1 said:
7th gear is for claiming MPG increase. That's all. Don't use if it you don't want.

I agree - this is for fuel consumption etc. Porsche, as with all other manufacturers, is under a lot of pressure to improve fuel economy and CO2 emissions. This was there way of trying to keep people happy. I'm sure they would have rather had 7 "driving" gears as well.

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Jun 7, 2008 2:36:11 AM

ADias: Rennteam Pro; Loc: Southwest USA , United States; Posts: 2495, Gallery; Registered on: Apr 9, 2004; Reply to: donkeyman

Re: Disappointed in 7th gear ratio for PDK

Quote:
donkeyman said:... This was [their] way of driving to keep people happy. I'm sure they would have rather had 7 "driving" gears as well.

But would it make any practical difference if to have 7 close-spaced cogs instead of 6? To take advantage of that one would be shifting all the time.

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Jun 7, 2008 3:24:54 AM

Grant: Rennteam VIP; Loc: Denver, CO , United States; Posts: 12586, Gallery; Registered on: Aug 21, 2002; Reply to: ADias

Re: Disappointed in 7th gear ratio for PDK

Quote:
ADias said:
But would it make any practical difference if to have 7 close-spaced cogs instead of 6? To take advantage of that one would be shifting all the time.

I think it would be great. It's not much effort to flex your thumb or forefinger and there's no lapse in the power delivery (just more of it with better gear spacing)...

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Jun 7, 2008 9:29:51 AM

fritz: Rennteam VIP; Loc: BaWü , Germany; Posts: 10248, Gallery; Registered on: Jul 23, 2003; Reply to: ResB

Re: Disappointed in 7th gear ratio for PDK

Quote:
ResB said:
It's all to do with MPG. Drop the revs, more MPG. I bet the new MPG figures are with the car stuck in 7th at 56mph I'm sure. I wonder how much more efficient the DFI engine is for that matter as the MPG figures will be a bit distorted.

The driving cycle conditions at which the "official" consumption figures are measured are prescribed by law, so manufacturers do not have the freedom to "optimize" the figures in the manner you describe.

The standard driving cycles are intended to make the "urban", "extra-urban" and "combined" fuel consumption figures you read in car ads directly comparable with each other amongst different car models.

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Jun 7, 2008 11:57:54 AM

sws1: Junior; Loc: USA; Posts: 83, Gallery; Registered on: Aug 2, 2006; Reply to: fritz

Re: Disappointed in 7th gear ratio for PDK

They absolutely can optimize the engines for certain speeds. Here are how the tests work:

Two separate fuel economy tests simulate city driving and highway driving: the city driving program consists of starting with a cold engine and making 23 stops over a period of 31 minutes for an average speed of 20 mph (32 km/h) and with a top speed of 56 mph (90 km/h); the highway program uses a warmed-up engine and makes no stops, averaging 48 mph (77 km/h) with a top speed of 60 mph (97 km/h) over a 10 mile (16 km) distance. The measurements are then adjusted downward by 10% (city) and 22% (highway) to more accurately reflect real-world results.

It's fairly easy to lean out the engine and design it for the upper 40 / low 50s mph range.

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Jun 7, 2008 12:52:39 PM

fritz: Rennteam VIP; Loc: BaWü , Germany; Posts: 10248, Gallery; Registered on: Jul 23, 2003; Reply to: sws1

Re: Disappointed in 7th gear ratio for PDK

Quote:
sws1 said:
They absolutely can optimize the engines for certain speeds. Here are how the tests work:

Two separate fuel economy tests simulate city driving and highway driving: the city driving program consists of starting with a cold engine and making 23 stops over a period of 31 minutes for an average speed of 20 mph (32 km/h) and with a top speed of 56 mph (90 km/h); the highway program uses a warmed-up engine and makes no stops, averaging 48 mph (77 km/h) with a top speed of 60 mph (97 km/h) over a 10 mile (16 km) distance. The measurements are then adjusted downward by 10% (city) and 22% (highway) to more accurately reflect real-world results.

It's fairly easy to lean out the engine and design it for the upper 40 / low 50s mph range.

If you re-read my post you'll see that the "optimization" which I said was not possible involved a proposal that the consumption be measured "at (constant) 56 mph in 7th. gear".

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Jun 8, 2008 7:47:10 PM

davew (cincy): Veteran; Loc: Cincinnati, OH , United States; Posts: 1164, Gallery; Registered on: May 10, 2004; Reply to: Grant

Re: Disappointed in 7th gear ratio for PDK

Grant,

If I understand the double clutch correctly, the added weight is not just added, some of it is also rotating.

A question I have related to the double clutch, is how quickly you can downshift two gears...?

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Jun 8, 2008 8:17:32 PM

amazon: Rennteam Pro; Loc: Belgium , Belgium; Posts: 2110, Gallery; Registered on: Jul 5, 2004; Reply to: fritz

Re: Disappointed in 7th gear ratio for PDK

Quote:
fritz said:
Quote:
ResB said:
It's all to do with MPG. Drop the revs, more MPG. I bet the new MPG figures are with the car stuck in 7th at 56mph I'm sure. I wonder how much more efficient the DFI engine is for that matter as the MPG figures will be a bit distorted.

The driving cycle conditions at which the "official" consumption figures are measured are prescribed by law, so manufacturers do not have the freedom to "optimize" the figures in the manner you describe.

The standard driving cycles are intended to make the "urban", "extra-urban" and "combined" fuel consumption figures you read in car ads directly comparable with each other amongst different car models.

Fritz is right but as always, you'll never achieve the manufacturer's figures in real life. A porsche that does less than 10 liter/ 100 km ... what a joke!

If you do achieve it, that means you're not driving properly. You can go buy a golf diesel instead, you won't see the difference.

Even a boxster can't drink so little.
.

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Jun 9, 2008 7:44:45 AM

intouch1: Rennteam Master; Loc: Red Sea , Egypt; Posts: 5752, Gallery; Registered on: May 22, 2004; Reply to: davew (cincy)

Re: Disappointed in 7th gear ratio for PDK

Quote:
davew (cincy) said:
Grant,

If I understand the double clutch correctly, the added weight is not just added, some of it is also rotating.

A question I have related to the double clutch, is how quickly you can downshift two gears...?

even gears are on 1 shaft uneven on another. you could shift directly from 7th to 3rd....
the rotating assembly is not heavier. the whole transmission is heavier due to the double set of gears involved. still, pdk is lighter than tiptronic.

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Jun 10, 2008 3:58:32 AM

xandi911: Senior; Loc: brasil; Posts: 688, Gallery; Registered on: Feb 14, 2006; Reply to: intouch1

Re: Disappointed in 7th gear ratio for PDK

another question... since we know the PDK has a lower TOP SPEED...

will be the PDK really faster?

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Jun 10, 2008 3:59:49 AM

Grant: Rennteam VIP; Loc: Denver, CO , United States; Posts: 12586, Gallery; Registered on: Aug 21, 2002; Reply to: xandi911

Re: Disappointed in 7th gear ratio for PDK

Quote:
xandi911 said:
another question... since we know the PDK has a lower TOP SPEED...

will be the PDK really faster?

It will be quicker to accelerate and faster on a racetrack, but less fun imho...

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Jun 10, 2008 4:01:08 PM

acrobat: Co-Pilot; Loc: Europe , Hungary; Posts: 250, Gallery; Registered on: Apr 15, 2008; Reply to: Grant

Re: Disappointed in 7th gear ratio for PDK

Carrera S:
1. 69 km/h @ 7500 rpm
2. 117 km/h @ 7500 rpm
3. 174 km/h @ 7500 rpm
4. 212 km/h @ 7500 rpm
5. 251 km/h @ 7500 rpm
6. 302 km/h @ 7350 rpm
___________________________
Carrera S PDK:
1. 69 km/h @ 7500 rpm
2. 118 km/h @ 7500 rpm
3. 164 km/h @ 7500 rpm
4. 209 km/h @ 7500 rpm
5. 251 km/h @ 7500 rpm
6. 300 km/h @ 7300 rpm
7. 300 km/h @ 5150 rpm

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Jun 10, 2008 4:07:51 PM

mex99: Pilot; Loc: UK; Posts: 335, Gallery; Registered on: Feb 28, 2008; Reply to: acrobat

Re: Disappointed in 7th gear ratio for PDK

Interesting - although a reduced top speed in 3rd the pdk is a closer ratio in the 2nd/3rd/4th acceleration zone

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