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981 Gearing - MPH at redine in 2nd, 3rd?

 
Old 06-27-2013, 02:40 PM
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quickxotica
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Default 981 Gearing - MPH at redine in 2nd, 3rd?

Hi,

Title says it all: I am trying to find our what the road speed is at redline in 2nd & 3rd gears in the new 981 (base & S).

I cannot find this info anywhere yet, nor a downloadable owner's manual....but I read a European review of the base 981 complaining that the gearing was longer than it should be (which made the 2.7 feel less lively than it should).

Anyone with a gear-ratio chart? Or who owns one of these things and can simply report back? I'm guessing redline in 2nd ought to be around 65-70mph and 3rd ought to be around 100mph.

Thanks!
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Old 06-27-2013, 04:29 PM
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I don't think they changed the gearing for the 981, I believe it is the same and 987.
That makes 2nd a 1.95 and 3rd a 1.41. It is really tall and widely spaced. It's basically the kind of gearing that they use on the turbo cars with more torque and a lower redline.

With stock 265/40/18 rear tires and 7500 rpm rev limit, that's 77.5mph in 2nd and 107mph in 3rd.
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Old 06-27-2013, 06:00 PM
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Thank you GTgears. Helpful as always!

Now if you'll allow me, I'd like to stretch my arms wide and call out to the heavens "Why, oh why would the gods permit this tragedy?!? Nearly 80mph in 2nd gear?!? 107mph in 3rd?!? Damn you Porsche, damn you"

But seriously. On paper that little 2.7L sounds like a real honey of a motor for enthusiastic back road driving by people who love manual transmissions and prefer to "drive a slow car fast." But that gearing is absurd given that it has only a smidge over 200 lb/ft of torque to work with. That's like connecting the engine of my old 944S2 to the transmission of a 997 Turbo.

if I were king, redline in 2nd would be 63mph. 3rd would top out at 90-95 max. 4th would hit the limiter at 120. Then this little motor would come alive and you'd actually be able to recognize that it's making damn-near 100bp/liter.

Oh well.
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Old 06-27-2013, 06:08 PM
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Originally Posted by quickxotica View Post
Thank you GTgears. Helpful as always!

Now if you'll allow me, I'd like to stretch my arms wide and call out to the heavens "Why, oh why would the gods permit this tragedy?!? Nearly 80mph in 2nd gear?!? 107mph in 3rd?!? Damn you Porsche, damn you"

But seriously. On paper that little 2.7L sounds like a real honey of a motor for enthusiastic back road driving by people who love manual transmissions and prefer to "drive a slow car fast." But that gearing is absurd given that it has only a smidge over 200 lb/ft of torque to work with. That's like my only 944S2.

if I were king, redline in 2nd would be 63mph. 3rd would top out at 90-95 max. 4th would hit the limiter at 130. Then this little motor would come alive and you'd actually be able to recognize that it's making damn-near 100bp/liter.

Oh well.
When you stretch out your arms and call out to heavens you are facing the wrong direction.

Look straight down. The gearing is the way it is because the EU with its ever tightening fuel economy and CO2 emissions rules is driving all car makers to offer taller geared cars. It is way of gaming the fuel economy and CO2 emissions tests to get better numbers.

There's Hell to pay if automakers fail to take this into account.

Hence, look down when you cry out.
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Old 06-27-2013, 06:59 PM
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I've always thought the gearing was too long for America in Porsches. Granted, if you lived in Germany (or if you do try out top speed) the standard gearing is needed. But, you do sacrifice a lot of 0-60 or lower speed performance when you run out 2nd @ 77 mph and 3rd @ 107. That was one way Porsche kept the original Cayman slower than the 911 in acceleration times. In fact, the 944 turbo was even worse....3rd ran out at 110 and 4th was 140. Sound familiar?

My '05 Sti ran out 2nd @ ~58, and 3rd at ~89. It was a lot more fun to squirt around with gearing like that. That car actually felt faster than the posted magazine numbers as you had an extra shift right before 60 and an extra shift right before the end of a quarter mile--you lost a couple of tenths each time you shifted.
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Old 06-27-2013, 07:23 PM
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While we aren't going to be able to help with 2nd because it is stuck to the mainshaft, we are working on a solution to 3,4,5&6. More to come.
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Old 06-28-2013, 12:45 PM
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Originally Posted by GTgears View Post
While we aren't going to be able to help with 2nd because it is stuck to the mainshaft, we are working on a solution to 3,4,5&6. More to come.
Cool. Just out of curiosity, would another possible fix be swapping in a shorter R&P gear? I'm a little foggy on how transmissions & final drive ratios work, but wouldn't that lower all 6 fwd gears? (and reverse?) Sorry for my ignorance, but would love to know why you're choosing to pursue the approach you stated above.
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Old 06-28-2013, 02:38 PM
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Originally Posted by quickxotica View Post
Cool. Just out of curiosity, would another possible fix be swapping in a shorter R&P gear? I'm a little foggy on how transmissions & final drive ratios work, but wouldn't that lower all 6 fwd gears? (and reverse?) Sorry for my ignorance, but would love to know why you're choosing to pursue the approach you stated above.
A short ring and pinion (which we have also been working on but are considering killing off as a project) does increase the mechanical advantage in all gears. But what it doesn't do is decrease the rpm drops (the gap) between individual gears. So if you have an upshift that leaves you down at 5000rpm, the short r/p set will still have you entering that next gear that far down.

On race gearboxes we pretty much never have a shift that drops you more than 2000rpm, and it's more common to be around 1400-1500 on the lower gears and as tight as 1000rpm on the 5-6 shift. 2500rpm drop (like you see on the 2-3 shift with stock gears) is massive in our world.

So while the short r/p does make you faster (we raced on it at Detroit and Mid-Ohio with BGB in Rolex) it's not the end all solution to the problems. When we do gears, we'll do a variety of options for each position, 3,4,5&6 because top speeds for various tracks vary widely. We need to be able to go close to 180mph at Daytona, but we'll never see something more than +/-140mph at Laguna Seca. I don't think they got over 125mph at Belle Island for the Detroit race. Each of those tracks would require different gear stacks to optimize acceleration.

Not something a street car guy would be concerned with in the way that we are in racing. However, we're a motorsports company that often sells parts to street car and DE car owners. Our designs and offerings are dictated what will win races, and what trickles down to the street tuner market is a bonus, both to my company from a sales standpoint, and to you the consumer from a performance standpoint.

The whole reason we aren't going to do 2nd gear, and a new mainshaft is that even in motorsports, the Cayman market won't bear it. The number of people who will spend $5k for 4 gears is limited. The number of people who will spend another $5k on top of that for the mainshaft and 1&2 is almost non-existent, at least in today's market.
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Old 06-28-2013, 04:34 PM
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Roger that. Thanks again for 'splainin.

Have a great weekend!
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Old 06-28-2013, 09:37 PM
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As a DE guy [not a true racer] I'd be interested in a lower R&P. I did this on my '84 911 and was VERY happy. 8->31 became 7->31 and the car was much more lively
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Old 07-02-2013, 03:17 AM
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So, this is timely: the new Road&Track just arrived and it includes a data panel on the 2013 boxster S. They report the following gearing for the PDK:

Ratio. Max speed (rpm)
3.91:1 44mph (7800)
2.29:1 75mph (")
1.65:1 104mph (")
1.30:1 132mph (")
1.08:1 159mph (")
0.88:1 172mph (6850)
0.62:1 172mph (4825)

LSD diff
Final drive ratio: 3.89:1
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Old 07-02-2013, 11:48 AM
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Yes, PDk is better geared than the 6MT. Always has been. The marketing guys like to say the quicker acceleration of the PDk is because of shift times. I disagree. I think most of it comes from the superior gearing.
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Old 07-02-2013, 10:22 PM
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Originally Posted by GTgears View Post
I don't think they changed the gearing for the 981, I believe it is the same and 987.
That makes 2nd a 1.95 and 3rd a 1.41. It is really tall and widely spaced. It's basically the kind of gearing that they use on the turbo cars with more torque and a lower redline.

With stock 265/40/18 rear tires and 7500 rpm rev limit, that's 77.5mph in 2nd and 107mph in 3rd.
There's a bit of devil in the details though, the 981 is using a bigger stock tire, 235/35x20 (at least on the S versions) which I believe translates to 235/45 x18 &/or 235/40 x19 in the smaller rims sizes. So one might need to adjust those figures by +/- @ 4-5% if backing into a direct 987 gearing comparison. Then I believe Porsche has also bumped the rpm limits for the 981 up to 7,800 at least in some gears per C&D's chart posted by US Car & Driver in their August 2013 fact sheet. C&D gear ratios posted and max speeds in the C&D page agree within 1 -2 mph with the numbers given by Quikexoitca, above for a 7 speed PDK equipped car, C&D adds one additional column, MPH per 1000 rpm: 5.6 in 1st; 9.7 in 2nd; 13.5 in 3rd; 17.1 in 4th and 20.5 in 5th all running to 7,800 rpm. 6th is limited to 6,850 rpm @ 25.3 per 1000; and 7th 4,650 rppm at 35.5 per 1000.

HTH

Last edited by mlpor; 07-02-2013 at 10:35 PM. Reason: fix reference & numbers
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Old 07-03-2013, 01:46 PM
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Originally Posted by mlpor View Post
There's a bit of devil in the details though, the 981 is using a bigger stock tire, 235/35x20 (at least on the S versions) which I believe translates to 235/45 x18 &/or 235/40 x19 in the smaller rims sizes.
You measure at the rear, not the front tires, as you have listed. You are correct, the new rear tire is bigger at 265/40/19, which makes it 1" larger at makes 2nd go up to 80mph and 3rd go up to 111mph. Also, the Non-S still comes on an 18" wheel standard.

Actual electronically limited rev limit may be higher, but peak HP is down at 7400rpm. Unless you are racing the car and looking for the absolute fastest acceleration at all times, I wouldn't expect you would rap it out to 7800rpm, so 7500 remains a fair comparison number for our bench racing purposes.
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