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@jimmuller
great explanation (y)

I would just add that time lost is on up-shifts, not down-shifts, as downshifts generally occur under braking.
So... if you down shift entering a corner that puts you marginally at the lower end of the power band,
the time lost on that extra up shift exiting the corner can be very costly.
 

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@jimmuller
great explanation (y)

I would just add that time lost is on up-shifts, not down-shifts, as downshifts generally occur under braking.
So... if you down shift entering a corner that puts you marginally at the lower end of the power band,
the time lost on that extra up shift exiting the corner can be very costly.
Thank you.

It figures that someone whose name is InTgr8r would appreciate the math!:geek:
 
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Here's an interesting head to head comparison.

Flatsixes
Not sold on that. Invariably the drivers had different driving skills. Can't say which was better, but I don't think that is a meaningful comparison. I don't think the PDK driver was using the manual mode either, may be wrong.
 

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Not sold on that. Invariably the drivers had different driving skills. Can't say which was better, but I don't think that is a meaningful comparison. I don't think the PDK driver was using the manual mode either, may be wrong.
Well the driver of the PDK was a two time World champ rally driver. Not sure about the guy driving the manual. They obviously both had above average driving skills.
 

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I'm not implying either driver was less than experienced. However, unless all factors are "controlled" except for the car's performance, there is a certain amount of error in the outcome.
 

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I'm not implying either driver was less than experienced. However, unless all factors are "controlled" except for the car's performance, there is a certain amount of error in the outcome.
Well yes that's correct especially for us track novices and street rodders. That kind of makes the whole PDK vs MT debate kind of silly when referencing times and speed around a circuit. Drive what you like and have fun with it. No one here is driving Le Mans this weekend.
 

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The other driver is Jason Plato, who is a two time BTCC Champion and as far as I can see from this video Marcus Gronholm was using the manual shifters on the PDK.

The main reason you can't say which is better is that neither is "better", they are simply different and appeal to people who prioritise different things. As @GTS18BGTS says "Drive what you like and have fun with it" (y)
 

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Hey, that is pretty cool. My WRX does a high 10 quarter finishing in 5th gear. I should have launched in 5th and it would do a 6!!
 

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When you are in automatic and you use the paddle shifters, your are overriding the PDK's gear determination. It will politely wait 10 seconds for you to come to your senses and, if you don't add any paddle or stick input, it will take over and put you in the gear it thinks you ought to be in... automatically.

If you are in automatic and you want to begin driving manually, that is, you want to shift the gears at your preferred RPM using the paddles or the stick or both, pull the stick to the left towards your leg. You are now in manual shift mode. Whatever gear you are in when you do that is your gear. The PDK will not attempt to shift for you from that point on unless you return the stick to Automatic. The ten second takeover will NOT happen when the stick is in manual.

I track my 718S (w/PDK) once or twice a month at Laguna Seca using the PDK in automatic mode. Why? Because PDK is few seconds faster every lap, than manually shifting. Seconds add up. The only time I use the paddles is when I up-shift to reduce exhaust and engine noise as I sneak by the infamous Laguna Seca sound microphone (If you break the sound limit, 90db, you are black flagged and have to leave the track). After I have gone by the microphone, I paddle down-shift and go hard to the next corner (6). So each lap, I do one upshift and one down shift with the paddles.

Coaches will tell you that every shift costs the average driver about one second. I cannot tell you how many shifts the PDK does for me each lap, but I can tell you that there are no one second loses. The gear selection is just amazing both decelerating and accelerating.

Pros will tell you that you use the brakes to slow the car, NOT the transmission. If you want to hot rod a bit around town, go ahead and use the engine to slow down, but really, that isn't the way it is done around the track. You shift to control RPMs you brake to control speed. Your engine and transmission, which are built to go not to stop, will thank you.

The only time you might want to downshift to slow the car, other than getting your ya yas out (which is entirely legitimate) is in a panic situation. Even then, you're probably better off with both hands on the wheel so you can concentrate on braking and steering away from trouble. Let the PDK pick the gear while your are spinning like a top! When you go to the track and you hear those downshifts before the corners, those drivers aren't trying to slow the car so much as to get the car in the right gear to come out of the corner as hot as possible.
This 1 second per shift thing doesn't pass the sniff test. I am not a particularly fast driver, in my 6 speed CS:

2:15 at Watkins Glen with 6 upshifts
2:11 at VIR with 5 upshifts

So the idea that a driver with no additional skill or pace through corners would put down a 2:09 at WGI or 2:06 at VIR by just hopping into a PDK equipped Cayman S sounds a little hard to believe.
 

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It's obvious some people with little to no real world racing/track experience get an ego boost from their PDK selection and I'm ok with that. What ever floats your boat, is all good. If you feel it's faster, well then it must be true. That's usually the way things work in certain circles. But be respectful in your response to others and the choices they've made that make them happy. Some of those people have way more practical experience of driving fast on a track than others here, including me. But none of us here, to my knowledge, are professional drivers and I don't believe the transmissions we selected matters as to the times we would post. The vast majority of us probably do not do these cars justice as to how they could potentially be driven. That assessment doesn't take much math at all.
 

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I had a loaner today from the Porsche dealer that was performing an oil change on my car. The dealer group also owns Audi and BMW and are located together. The loaner was a BMW 640i. It had paddle shifters, so I thought I'd play around with them. I know it's not Porsche PDK, but nah, that system is not for me. BORING!
... But be respectful in your response to others and the choices they've made that make them happy. ...
I guess this is what you consider respectful!...
 

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I guess this is what you consider respectful!...
My friend, my post expressed my opinion about a drivetrain and my lack of appreciation for it. My post did not in any way criticize or denigrate anyone for their choices or opinions. I have not criticized anyone for their love affair with PDK. It's their money and their choice.

Please ignore my posts and I will similarly ignore yours.
 

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Then you could be sniffing the exhaust of another car. Go look at the math.
Disclaimer: I don't care what kind of gearbox anyone prefers, or what is faster. Just want to clarify that on a normal 1:30 - 2:30 laptime road course the delta between PDK and Manual is not in the order of 5+ seconds, more like a second per mile or per minute.

I looked at your math. "less over a shorter distance or at higher speeds" is the key here and can't just be handwaved away as it reflects reality. There are almost no tracks that have more than a single 1/2 mile straight after any upshift point starting at a low speed (60mph you mentioned), and many have none. Oak Tree at VIR is probably one of the few most extreme examples. The real world scenario is a shift towards the middle (or later) of a straight at much higher speeds (3 - 4 shift at ~100mph) where the delta won't be as large since the car isn't pulling as hard and the distance travelled is not that great.

Here's an example Road and Track did for NCM using math similar to yours but indexed against the actual track and came up with ~0.9 second delta.
What's the Real Impact of Dual-Clutch Transmissions on Lap Times?.

Another real world example to confirm the math is off: Based on the 1s per shift example, I would be 1 second faster than Mike Skeen in a GT4 at VIR if I just swapped over to a PDK in my S. As much as my ego likes the idea of that, it's more likely that there's actually not more than a couple of seconds difference.
 

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Some of the posts here are hilarious. Are you really quoting Ross Bentley's advice? That guy coaches drivers who are at 10/10ths with little effort...they need to squeeze a fraction of a second wherever they can find it and therefore the question of PDK vs manual. ****, even a gallon of fuel +/- in the tank affects their times...that's how consistent they are.

This DOES NOT apply to a bunch of geezers in the yellow and green run groups who polish their PPF between sessions and then go home to tell their wife & friends that they went 'racing'. I can't count how many times I've been held up by somebody in a GT3, GT4, Cayman S etc. who is braking mid-corner, too overwhelmed to give point-bys, but somehow has the lowdown on the best transmission for lap times. And this is coming from somebody who drives a 300hp (on the best day) BMW with street tires.
 

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Then you could be sniffing the exhaust of another car. Go look at the math.
The math is wrong. Your math says if you drive at low speed without accelerating for a distance you can get a 1.5 second difference... like that is a surprise. On a race track a car is never cruising without accelerating. And the speed is much higher. Apply your speed difference to a quarter mile at 130MPH.

I have not had the time, but I have a datalog of my 6MT WRX doing a quarter mile. As an engineer I am well qualified to do the maths. I could simply calculate the speed lost in gear changes and apply that speed lost across the distance at an average speed to get a close approximation. I did 4 gear changes, so it should be around 4 seconds. I know it will be well under a second so I have not bothered.

Also, my WRX has a flat shift feature. I had to set how long a gear change takes. I tuned it for a while and found that I could always get my gear change done in under 250ms. Even if I was just cruising, under 500ms is super easy.
 

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Some of the rebuttals here miss the point. First, it isn't about PDK vs. manual gearbox. It's about how much time you can lose by shifting when you are just barely at a reasonable shift point. Which is to say, if you just stayed in the previous slightly sub-optimal gear and waited you might be better off. At no time did I ever criticize anyone's choice of transmission.

I know VIR, never ran it in competition but worked as a flagman back in the early 70's. Oak Tree is followed by a longer than average straight and you start that straight slower than the 60mph I used to illustrate the point. So that's an extreme example. But any time you are shifting you are losing speed instead of gaining it, or instead of maintaining it if you are already at the power limit of the engine or traction limit of the tires. The time lost is not during the shift. It is accumulated over the subsequent acceleration period due to the speed lost during the shift. Any time the shift is slower than instantaneous you are losing speed. The new gear might be better, but unless it is a lot better it may not be enough.
 

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I actually think the initial point from driving instructors was to teach students to stay in a higher gear in a corner rather than the lower gear that puts you close to peak power. My experience on the track is that if I drive through a corner at around the lower end of when boost is available (3500-4000RPM in my WRX), I am quicker than if I choose one gear lower and am close to peak power on the exit. A small part of this is the time lost in the gear change, but the major part is that the boost builds up slower (or in a NA car, less torque to the wheels is available) and you don't need as accurate throttle control on corner exit to apply smooth power delivery. Therefore you are less likely to overcome grip which then requires you to back off again. It is always quicker to apply power once and not have to back off and reapply because you overcame the available grip. Also you want to avoid requiring a gear change while you are still exiting the corner as that would upset car balance.

I don't think they intended the 1 second loss to apply to straight line acceleration as it is way off the mark for that. Quarter mile of 718s PDK vs 6MT is enough proof to show it is closer to 1-2 tenths of a second per gear change. In fact I believe most of the difference between 6MT and PDK in quarter mile times is in the launch as PDK has a proper launch mode. 0-100kph is about 3-4 tenth quicker in PDK with 1 gear change. My guess is that is about half split between launch and gear change.
 

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Some of the rebuttals here miss the point. First, it isn't about PDK vs. manual gearbox. It's about how much time you can lose by shifting when you are just barely at a reasonable shift point. Which is to say, if you just stayed in the previous slightly sub-optimal gear and waited you might be better off. At no time did I ever criticize anyone's choice of transmission.

I know VIR, never ran it in competition but worked as a flagman back in the early 70's. Oak Tree is followed by a longer than average straight and you start that straight slower than the 60mph I used to illustrate the point. So that's an extreme example. But any time you are shifting you are losing speed instead of gaining it, or instead of maintaining it if you are already at the power limit of the engine or traction limit of the tires. The time lost is not during the shift. It is accumulated over the subsequent acceleration period due to the speed lost during the shift. Any time the shift is slower than instantaneous you are losing speed. The new gear might be better, but unless it is a lot better it may not be enough.
"It's about how much time you can lose by shifting when you are just barely at a reasonable shift point. Which is to say, if you just stayed in the previous slightly sub-optimal gear and waited you might be better off."

This is a totally different point than and one I agree with. However:

faizaan2000 said:
This 1 second per shift thing doesn't pass the sniff test.
You reply: "Then you could be sniffing the exhaust of another car. Go look at the math."

Seem pretty clear this is about your comments on 1 second per shift on a track.

"The time lost is not during the shift. It is accumulated over the subsequent acceleration period due to the speed lost during the shift."

I did not disagree with this. I very clearly showed an article and an explanation that agreed that time loss was both due to shifting and accumulated loss of speed. However, the point was that this amount was much smaller on real tracks vs. the theoretical half mile drag from your math.

I saw on another post you don't track the car. Maybe that's why the real world context or the laptime delta your math implies is not useful in correcting your model. Anyone that tracks will know that attributing 5+ seconds a lap to gearbox is completely unreasonable, and there is a huge difference in saying there's a 1-2 second difference for the entire lap vs. 1 second per shift.

Anyway, not interested in continuing this further as I don't think this is going to get anywhere.
 
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