Crown

I finally got a chance to drive a 2010 PDK Turbo with PDK today. It was a 30 minutes drive without co driver in a well broken in car. (Well if it wasn't before, it is now. ) A few things that stood out about the suspension that might not have received enough emphasis from reviews so far:

Gen. 2 PASM: ***Totally*** changed and improved from previous system. Gen. 1 PASM in C2S/Turbo/GT2 in my opinion is at best a work in progress. In all 3 cars, my impression is the Firm setting is jittery/choppy/nervous.
In contrast, gen. 2 PASM Firm setting is very much useable on surface street. Normal and Firm are "closer" together in overall stiffness (similar to Bilstein Damptronic), and not opposite ends of the spectrum. The firm setting has no nervousness at all.

Vertical Motion: 997.2 stock has much less vertical motion than 997.1 stock. 997.2 still leans, but the car suspension now feels like it has less excessive motion. It also appears to dive and squat less. It's been a while since I drove a stock 997.1 Turbo, so you might want to take this with a grain of salt.

Alignment Settings: First thing I would do to 997.2 is to bring it to tuner for more front negative camber. The car still understeers quite a bit and turn-in response is only so so.

Steering Assist: I am not sure about this but it seems the assist has been reduced, and perhaps so has the steering ratio?? Could someone confirm this? The steering feels firmer and better than 997.1, but still on the lazy side with the stock alignment setting and there is still a lag in response.
Love the paddles on the steering wheel btw. Also, the steering wheel itself *seems* firmer, and maybe a little thicker than 997.1's.

PTM: From my brief time with the car, and taking it through a few freeway exits, the rear end rotates more. The car feels less "4 wheel-drivey." I do not know if this car has Porsche torque vectoring (PTV), and maybe I wasn't taking the corners that fast, so I think these benefits come from revised PTM and not necessarily PTV.

Exhaust Note: Definitely warmer sounding (lower frequency) and more of a crackling/staccato nature, versus the hair dryer continuous whining of 997.1. However still very quiet, similar to normal C2S for example, and nowhere near the level of my Cargraphic.

Sense of insulation: Somehow the car feels more "insulated." Like there is a layer between me and the road. I do not know if this is entirely in my head, or if it's because I am more used to my noisy, and stiff, and lowered car.

The acceleration, or THE HOLY ACCELERATION : Nothing I've read prepares me for the astounding sense of acceleration of the PDK Turbo. As predicted, if I pin the throttle, it's one incredible and unbelievable continuous rush, with no drop in boost. I know the objective number is only 0.7 second or so difference in 0-60 versus my car, but the subjective sense is a whole new ball game. Simply put, this car wipes out and overwhelms every thing I've driven previously (F430, Gallardo, GT2, Ford GT, Corvette, my Turbo). Anyone into straight line power and the thrill of acceleration -- PDK has made the manual box obsolete (I remain a manual die-hard however; very much so.).

So the summary:
1. Several improvements, including stiffer and "cleaner" suspension and totally changed PASM, but still very much a grand touring car. Suspension feels less loose and more like a C2S (a compliment). Stiffness and comfort are between stock 997.1 Turbo and a Bilstein Turbo.
2. Faster than a speeding bullet. Really.

Congratulations to the lucky owners!

--

Regards,
Can
997 Turbo + Bilstein Damptronic ( Review ) + GIAC ECU Tune ( Fast as a torpedo & reversible to stock - Review ) + Cargraphic Exhaust ( Oh heavenly noise! )

Thanks Can, seems that the Mk2 Turbo has finally polished the few details that prevented the Mk1 from being the complete package (at least for me). If only it would have a "proper· exhaust note...

BTW, the previous one was too fast for the road... so I guess the new one is as silly as it could be!

997 GT3 RS

You are welcome. The change is evolutionary in nature and I actually think the new car needs the same modifications as the old: exhaust and suspension. (No ECU mod needed for 997.2 Turbo for the majority of people IMO. The acceleration made me nauseous/dizzy at first. No kidding.)

In other words, outside of the amazing PDK, I still think a manual 997.1 Turbo is an absolute steal at its current price and the one to get, but only if exhaust and Bilstein coilover are planned. A modded 997.1 yields very little to stock 997.2, and in fact exceeds in driver's involvement. (Less "insulation"; I feel the road and the rear wheels better in my Bilstein Turbo.)

For those not familiar: A Bilstein coilover takes care of the PASM problem of all first generation car. Bitlstein PASM is very similar to 997.2 PASM: both Firm settings are excellent, with Bilstein the stiffer one.
 

--

Regards,
Can
997 Turbo + Bilstein Damptronic ( Review ) + GIAC ECU Tune ( Fast as a torpedo & reversible to stock - Review ) + Cargraphic Exhaust ( Oh heavenly noise! )

Thanks for sharing your experience and observations cannga

 
RT Moderator - 997.1 Carrera S GT Silver/Cocoa, -20mm/LSD, PSE, short shifter, SportDesign rims, Zuffenhausen collection

Great write-up - many thanks for posting..

"Things turn out best for people who make the best of the way things turn out."

I drove a 997.2 TT Cab this weekend and I found the acceleration to be akin to the sensation one gets from that first drop on a rollercoaster. It is definitely a rush. I found the steering to be as you described, more effort (less assist?) than my 09 C2S, w/ slightly more tactile communication. I assumed it was related to the AWD, but perhaps not? I liked the fact that the power trasmission felt like a C2, with the push clearly coming from the rear, something I have not noticed w/ other C4s I've driven.  I appreciate the Jekyll and Hyde personality of the Turbo, docile one minute, an utter beast the next.  Of course a Turbo Cab configured to the same specs as my C2S Cab comes in at $176K w/ centerlocks rather than the P40s I have on the C2S.

Carpe Diem--life is but a crack of light bounded by eternities of darkness (Nabokov)

Thanks for the write-up!  If it was not for the price I would get one immediately... Given how much the 997.1 Turbo has dropped in value I would expect the 997.2 Turbo to do the same. In a year or two, then maybe 

987 Boxster S, Arctic Silver with 'Martini Racing' Livery, H&R Monotube Coil-Overs, H&R Anti Roll Bars, Strut Brace, FVD ECU, BMC Air Filter, Sachs Racing Clutch, Single-Mass Flywheel, Recaro Racing Shells, PSE.

997 Carrera 4S, Guards Red, Bilstein PSS10 Damptronic, H&R Anti Roll Bars, IPD Plenum, Dension Gateway 500, PSE.

cannga:

The acceleration, or THE HOLY ACCELERATION : Nothing I've read prepares me for the astounding sense of acceleration of the PDK Turbo. 

Drove the 997.2 Turbo at Silverstone (Porsche driving experience) last week. Launch control has to be tried to be believed. Did 6 runs in all - Totally addictive. Unlike other reports on PDK, I found the shifts to be instant. I'm still not completely sold on automatics but have to say it was handy to have both hands free when on the low friction surfaces (icehill & kickplate).

All in all I'd say this facelift is a marked improvement over a stock 997.1

On my return I contacted my OPC regarding my build slot. Turns out the Turbo S is due May but only 4 vehicles per dealer. As already posted expect 530BHP, PCCB & Carbon Fibre detailing. No news on price yet!

Regarding PDK and lap times - just take a look at the attached chart. The chart shows a GT2 (on Pirelli Corsa, i.e. not on Cup tires, blue line) and Scuderia (red line) in Leipzig (Porsche track).

In essence, the chart tells a simple story: the GT2 has a major disadvantage whenever an upshhift at higher speeds is required (around 172kph) whereas the Scuderia has a very smooth acceleration and gains about a second per lap just because the upshifts at higher speeds are so efficient.

In essence, this indicates that a track car needs PDK or F1 

We will also post a chart comparing the GT2 on "normal" tires (i.e. Michelin Cup). WIth the Michelin the GT2 should be in a position to gain enough time in the curves to more than compensate for the disadvantages of the manual gear-box. But still, what lap time would be doable in a GT2 with PDK?

Great write up Can,

I take your words are spoken from experience and you certainly not only know how to feel and drive cars, but you also express this information very well.

I applaud porsche for making the 997.2 considerably better and faster!!! 

indeed shifting is ancient technology - so is a fuel burning engine..  I happen to like both :) 
_____________________________________________________________________
1984 BMW 323i 5spd 2.3L 141 hp (105 kW) More door. Black on black (parting out) 
1986 BMW 325e 5spd 2.7L 121 hp (172 lb·ft) Le Mans Blau on Tan leather.
1986 BMW 325is 5spd 2.5L 168 hp (164 lb-ft) White on Tan leather (parted out) 
2005 Ford Focus S, 5spd 2.0L 136 hp (120lb-ft) CD silver on grey (sold)
1986 Porsche 944, 5spd 2.5L 150 hp (168lb-ft) champagne gold on grown leather. (sold)

cannga:

I finally got a chance to drive a 2010 PDK Turbo with PDK today. It was a 30 minutes drive without co driver in a well broken in car. 

Exhaust Note: Definitely warmer sounding (lower frequency) and more of a crackling/staccato nature, versus the hair dryer continuous whining of 997.1. However still very quiet, similar to normal C2S for example, and nowhere near the level of my Cargraphic.

Not driving  this magnificent beast with your friend was selfish.

Glad to see that these monsters are getting quieter. When Porsche offers the Panamera's Burmester and double glass as options, I may just get one.

aGrant:

Not driving  this magnificent beast with your friend was selfish.

Glad to see that these monsters are getting quieter. When Porsche offers the Panamera's Burmester and double glass as options, I may just get one.

OT: aGrant, very funny. You like to be flamed by the Turbo forum, don't you?

BTW, I was going to write a review on the Panamera's Burmester system but held back because I found out there might be some tone control function gimmick  that I missed during the audition. Maybe that is why it sounds so painfully bright (For any audiophiles reading this, Burmester: pinpoint imaging -- best in the business, deep and layered soundstage -- best I've ever heard in a car. But... so bright my ears were bleeding.)
 

--

Regards,
Can
997 Turbo + Bilstein Damptronic ( Review ) + GIAC ECU Tune ( Fast as a torpedo & reversible to stock - Review ) + Cargraphic Exhaust ( Oh heavenly noise! )

(For any audiophiles reading this, Burmester: pinpoint imaging -- best in the business, deep and layered soundstage -- best I've ever heard in a car. But... so bright my ears were bleeding.)
 

cannga, thanks for your review!  I can't wait to test it once it arrives on our shores!

re: music systems in cars, unfortunately, most people in cars it seems think that brighter means better sound, since the first impression of this type of sound is always good.   Maybe that's why many systems err on the brighter side?  But then we find that we keep reducing the volume as the ear fatigue sets in!

MKSGR:

 

In essence, the chart tells a simple story: the GT2 has a major disadvantage whenever an upshhift at higher speeds is required (around 172kph) whereas the Scuderia has a very smooth acceleration and gains about a second per lap just because the upshifts at higher speeds are so efficient.

In essence, this indicates that a track car needs PDK or F1 

 

Markus, very interesting data. I thought that the influence of PDK is mostly in the lower gears, since 1 to 2 and 2 to 3 shifts in manual gear box **seems** so slow (1 to 2 in particular always such a momentum-stopper downer), but from your data the advantage is there in the higher gear shifts as well.

For the foreseeable future, I think us enthusiasts will continue debating the PDK versus Manual dilemma. I remain a 6 speed die-hard and will stick to my stick-shift, but I must admit the word "obsolete"  came to mind when I drove my 997.1 immediately afterwards.

IMO, not for me, but for those whose interest is the track or sheer speed, the question must be answered. Is the "driver's involvement" worth ignoring the truth: PDK is the faster car and if your goal is to be fast, PDK is a must.

I continue to wonder what PAG will do with future GT3's, perhaps keep Mezger engine with manual gear in the GT3 RS for homologation purpose, and brings DFI engine with PDK to the GT3? But then, how would PAG then explain the "situation" of GT3 ending up beating GT3 RS at the track?  The future is fun and exciting!

--
 

Regards,
Can
997 Turbo + Bilstein Damptronic ( Review ) + GIAC ECU Tune ( Fast as a torpedo & reversible to stock - Review ) + Cargraphic Exhaust ( Oh heavenly noise! )

cannga:

MKSGR:

 

In essence, the chart tells a simple story: the GT2 has a major disadvantage whenever an upshhift at higher speeds is required (around 172kph) whereas the Scuderia has a very smooth acceleration and gains about a second per lap just because the upshifts at higher speeds are so efficient.

In essence, this indicates that a track car needs PDK or F1 

 

Markus, very interesting data. I thought that the influence of PDK is mostly in the lower gears, since 1 to 2 and 2 to 3 shifts in manual gear box **seems** so slow (1 to 2 in particular always such a momentum-stopper downer), but from your data the advantage is there in the higher gear shifts as well.

For the foreseeable future, I think us enthusiasts will continue debating the PDK versus Manual dilemma. I remain a 6 speed die-hard and will stick to my stick-shift, but I must admit the word "obsolete"  came to mind when I drove my 997.1 immediately afterwards.

IMO, not for me, but for those whose interest is the track or sheer speed, the question must be answered. Is the "driver's involvement" worth ignoring the truth: PDK is the faster car and if your goad is to be fast, PDK is a must.

I continue to wonder what PAG will do with future GT3's, perhaps keep Mezger engine with manual gear in the GT3 RS for homologation purpose, and brings DFI engine with PDK to the GT3? But then, how would PAG then explain the "situation" of GT3 ending up beating GT3 RS at the track?  The future is fun and exciting!

 

You wrote the perfect summary  The key point indeed is that there does exist a trade-off between driver involvement and pure performance (track and full acceleration on straights).

If lap times are of key concern there is nothing better than PDK/F1. In these diagrams you can also see a (comparatively smaller) side-effect of the manual gear box: while simultaneously braking hard and changing gears (heal-and-toe) the amateur (like me...) always runs the risk of not applying 100% of possible brake power. The Scuderia seems to be a tad harder on the brakes (might also be a result of the GT2 being on the "wrong" tires, i.e. regular Corsas and not the normal MS Cups).

Both effects seem to add up. Meaning: you need to gain much time in bends and on long straights to just compensate for the time lost by switching gears manually.

BTW, the time lost at up-shifts at higher speeds is even larger than at lower speeds as the aerodynamics do a lot of harm while the gears are being changed 

cannga:

aGrant:

Not driving  this magnificent beast with your friend was selfish.

Glad to see that these monsters are getting quieter. When Porsche offers the Panamera's Burmester and double glass as options, I may just get one.

BTW, I was going to write a review on the Panamera's Burmester system but held back because I found out there might be some tone control function gimmick  that I missed during the audition. Maybe that is why it sounds so painfully bright (For any audiophiles reading this, Burmester: pinpoint imaging -- best in the business, deep and layered soundstage -- best I've ever heard in a car. But... so bright my ears were bleeding.)

Regarding sound, two points:

First, given that you've converted your chariot into a mobile rocket, including ear-splitting-level anti-social sound, I think you've lost your license to challenge the brightness of any sound system. (And, parenthetically, you no doubt are among the select few adults with no dental cavities, because your extraordinarily stiff-suspensioned Turbo would long ago have jarred loose the fillings!)

Second, assuming, arguendo, that you have somehow managed to maintain your youthful audiological acuity, others who have reached or exceeded the near-geriatric threshold (thus, enabling them to more easily afford Porsche extravagances) tend to have upper-frequency hearing depressions that "painfully bright" sounding systems are perhaps designed to complement, yielding the equivalent of "normal" audiophile-level sound. N'est-ce-pas?

^Alright we'll turn this into a sub-thread for audiophiles.

Guilty as charged on the first point, but it is actually not as much an anti-social sound as it is anti-lady noise. 100% of female co-workers, well those whom I have the nerve to ask, and my wife, do not appreciate the subtle elegance of a loud exhaust at all.  100%!

On the second point: The brightness I heard from the Burmester was not from a rising treble, but a depressed mid-bass. In that sense it does not compensate for age-related hearing loss, which as you mentioned is high frequency related. Folks with age-related hearing losss will hear depressed bass, AND depressed treble, in the Burmester.

System is so bright that I keep thinking I must have missed something, some tone control hidden in the menu. Anyone here familiar with Burmester?

--
 

Regards,
Can
997 Turbo + Bilstein Damptronic ( Review ) + GIAC ECU Tune ( Fast as a torpedo & reversible to stock - Review ) + Cargraphic Exhaust ( Oh heavenly noise! )

MKSGR:

 

You wrote the perfect summary  The key point indeed is that there does exist a trade-off between driver involvement and pure performance (track and full acceleration on straights).

If lap times are of key concern there is nothing better than PDK/F1. In these diagrams you can also see a (comparatively smaller) side-effect of the manual gear box: while simultaneously braking hard and changing gears (heal-and-toe) the amateur (like me...) always runs the risk of not applying 100% of possible brake power. The Scuderia seems to be a tad harder on the brakes (might also be a result of the GT2 being on the "wrong" tires, i.e. regular Corsas and not the normal MS Cups).

Both effects seem to add up. Meaning: you need to gain much time in bends and on long straights to just compensate for the time lost by switching gears manually.

BTW, the time lost at up-shifts at higher speeds is even larger than at lower speeds as the aerodynamics do a lot of harm while the gears are being changed 

 

Fascinating discussion, particularly that last line. Thanks for sharing the experience.

I also find quite interesting the "circumstance" of your test : Scuderia and GT2 in Porsche's home ground? Official test or is this someone playing around with the cars? Is this your play ground?

BTW, does PAG own the Leipzig track or is it open to the public?

--
 

Regards,
Can
997 Turbo + Bilstein Damptronic ( Review ) + GIAC ECU Tune ( Fast as a torpedo & reversible to stock - Review ) + Cargraphic Exhaust ( Oh heavenly noise! )

I'm also preparing for a test-drive in the pdk turbo, since we started to get interested in the 997.1 turbo......Our dealer simply said that the pdk turbo is just weapon in the road

I can imagine how fast it is, specially since I test-drove some days ago the 997.1 turbo with tiptronic S, its just absolutely insane the power push it gives you, so the pdk must be even better

However, on the other hand.....and from my personal opinion, I would never spend 170.000€(basic with no options), so with pdk and some more options 190.000€..... in a new one, like you said wait some months or one or two years, and get it for 100.000€ less..........of course this is only my opinion and my personal experience with other cars we have owned (most of them Porsche of course )

cannga:

I also find quite interesting the "circumstance" of your test : Scuderia and GT2 in Porsche's home ground? Official test or is this someone playing around with the cars? Is this your play ground?

BTW, does PAG own the Leipzig track or is it open to the public?

 

 The test track in Leipzig is also used for Porsche's own driving school and track day events. A very nice track, more on the complex side.

The funny thing is: even though it is Porsches home territory, this track suits the Scuderia better than let's say Hockenheim (where the GT2 has an advantage). The reason for this seems to be the relative length of the straights (thinking of my post above) and the rather complex procedure of braking and turning into rather difficult corners a number of times per lap. Hockenheim is more "fluid", the car can drive with a more constant speed in Hockenheim.

Sorry for the delay Can,but i read this topic only today.

Well,i don't what to test drive the new Turbo in way to leave happy with mine

And know that the PDK would be the best solution,well.. is not a good news for me.

I whant a fast car,the fastest,but i love manual gearshift..so..if i must buy NOW a 997TT Mk2 would be a big trouble for me to choose if manual or PDK.

When i use my wife's Golf GTI DSG i use it every time in auto,i use the paddles only to downshift to have more engine brake when i'm on sport mode.

So my fear if i take a PDK is to go to use it every time in auto,and i hate this thing.

But if i will take a manual,i will hate to be burn by a PDK twin

so,better to wait the 991 TT to take the final decision

..c'mon. Take the PDK and you'll  have forgotten the manual in less than 3 seconds...

Just my own experience driving a 997.1 manual and testdrived a 997.2 PDK

Cannga...very nice evaluation.

I'd like to ask your opinion on something I noticed on my test drive.  When you click on the paddle shift, did you get a sense of delay before the car actually shifted, especially on downshifts beyond 1 gear ie 5-3?  The shift themselves was lightning quick, but the time from when you actually click the paddle to the actual shift seemed, well, irritating.

Does anyone else notice this?

bob

Bob,
I only had 30 minutes and was paying more attention to the suspension and acceleration. I only tested the upshift, and felt no delay. I did not test the downshift. I only had a short time so will rely on others for pointing out if this delay is for real. I didn not feel it.

Darius,
Agreed. My opinion is that there is zero reason for 997.1 Turbo owners to upgrade, unless one's life depends on winning races. 991 is simply too close to be ignored, and:

1. My brief "review" by necessity magnifies the differences between the 2 cars. Take away the PDK and new and old Turbo's are not different ENOUGH from each other to lose US $60k. I am willing to bet most people wouldn't even notice the increased rear drive bias for example.
2. "Driver involvement" is a VERY REAL issue and a big dilemma with PDK. I do not think this controversy is going away and the answer is perhaps I need to keep 2 Porsche's. It's like asking a model airplane hobbyist why he wastes time putting together planes that don't fly. Perhaps, the act of shifting is the means that is as important as the end. Manual box forces one to be aware of the gear and engine speed at all times, and maybe that is why manual shift IS by definition more involving.
3. I have one criticism of the new Turbo: Suspension is much improved, but it is still a soft car and feel "insulated." A 997.1 Turbo with Bilstein is stiffer, more sporty, allows me to feel the rear wheel and the chassis better, and IMHO is the better handling car.

BTW, the PDK Turbo is really "the perfect storm." The combination of 4WD traction and uninterrupted power flow results in a car that took my breath away. Don't doubt that 3 second 0-60 time, and look up and see how many other cars do this.  Porsche is ruling the world once again.  
But I digressed there. The question is then why I would call the gear box of this speeding bullet  a dilemma.  It is because to me PDK is fun only at 10/10 driving. At less than all out driving (majority of times), we have a debate and I am sticking with my stick-shift!
--
 

Regards,
Can
997 Turbo + Bilstein Damptronic ( Review ) + GIAC ECU Tune ( Fast as a torpedo & reversible to stock - Review ) + Cargraphic Exhaust ( Oh heavenly noise! )

cannga:

  It is because to me PDK is fun only at 10/10 driving. At less than all out driving (majority of times), we have a debate and I am sticking with my stick-shift!
--
 

Regards,
Can

I have been living now for 17 month with my PDK ( Carrera S ) and I must say that at the moment I am sooooo bored driving it, as I only use it as a commute to work.

PDK is fun when you can drive fast, and go to the limits , or when you want to make a very quick lap on a track, or  be better then ''supposed better cars ''  There is no daught that on a track I am faster with the PDK, and that when I go on my local mountain drives it am always very impressed, the car is so fast compared to my previous 997.1  6 speed. Straight acceleration is also very rewarding . BUT :

In winter I do not go to my local mountain drives, I do not go to the track, I do not do any fast accelerations.... so I sit in my Porsche and drive it like an automatic .......... sooooooooo boring when it is repeated day after day after day

I am considering getting a GT3 instead.....but then I will have the dilema with PDK or not , as on the track to go fast PDK is fantastic !!! Specialy when one has to 'compete' agains other's  , ( like F430 scud ) and every second is important .

 997.2 C2S, PDK, -20mm

bbywu:

I'd like to ask your opinion on something I noticed on my test drive.  When you click on the paddle shift, did you get a sense of delay before the car actually shifted, especially on downshifts beyond 1 gear ie 5-3?  The shift themselves was lightning quick, but the time from when you actually click the paddle to the actual shift seemed, well, irritating.

bob

If you try to shift down 2 gears and experience a delay before the shifts are completed, then I suspect that you were still carrying too a high speed which would result in the engine over-revving in the lower gear, so the control unit suppressed that downshift until the road speed had fallen further.

By over-revving, I do not mean that the engine would necessarily be red-lined. A lower engine speed may have programmed in deliberately for such downshifts to better match "real world" requirements. I'm just speculating here. 

fritz

 Shifting down 2 gears means that the asked gear isn't engaged already, hence more time is needed.

(clutch "1": R, 1, 3, 5, 7 / clutch "2": 2, 4, 6)

fritz:

If you try to shift down 2 gears and experience a delay before the shifts are completed, then I suspect that you were still carrying too a high speed which would result in the engine over-revving in the lower gear, so the control unit suppressed that downshift until the road speed had fallen further.

 

A plausible explanation.

I experienced no such delay when shifting down, although having the opportunity to drive a PDK with paddles followed by one with buttons, the paddles definitely introduce a delay. Though the paddles are more intuitive, I found the buttons work really well.

DuckieRS:

 Shifting down 2 gears means that the asked gear isn't engaged already, hence more time is needed.

(clutch "1": R, 1, 3, 5, 7 / clutch "2": 2, 4, 6)

 True, but this applies to upshifts as well as downshifts. 

fritz

PowderJunky:

fritz:

If you try to shift down 2 gears and experience a delay before the shifts are completed, then I suspect that you were still carrying too a high speed which would result in the engine over-revving in the lower gear, so the control unit suppressed that downshift until the road speed had fallen further.

 

A plausible explanation.

I experienced no such delay when shifting down, although having the opportunity to drive a PDK with paddles followed by one with buttons, the paddles definitely introduce a delay. Though the paddles are more intuitive, I found the buttons work really well.

That delay must have been caused by some other factor, because the buttons and paddles are surely  just plain vanilla electrical switches passing a brief electrical impulse to the electronic control unit when a shift is initiated by the driver.
Since the control unit is the same regardless of which type of "switch" is fitted to a particular car, then  -  all other things being equal  -  the speed of shift initiation would have to be the same. 

fritz