DK7

Thanks. Do you know anything about limited and/or really expensive ?
Spyder RS too?

Wild Weasel

Seems perfectly reasonable to me considering that 7th isn't meant to be a close-ratio upshift from 6th. It's a gas-saving overdrive so the bigger difference would be expected.

These are the gear ratios I found for it, with a final drive ratio of 3.62.

1 3.909
2 2.292
3 1.654
4 1.303
5 1.081
6 0.881
7 0.620

GrantG

I think in the GT4 and other 4.0L variants, they lowered the 7th gear ratio around 15% to 0.71 (will make 7th a bit less lackluster, but still very much an overdrive cruising gear). Pretty sure they did this to offset the low torque of the 4.0L at low revs (wouldn’t pull such a tall gear as the turbo 2.5L is able to do with more low-end torque)…

Thus would adjust the rpm of the lower 7th ratio to around 6,013 rpm at 188 mph (still way less horsepower than the same road speed in 6th gear and unable to get close to 188 mph in 7th gear).

Wild Weasel

Why make it "less lackluster"?? It's ENTIRE PURPOSE OF EXISTENCE is to BE LACKLUSTER.

Johnauto

Yes that is my question too. Will the GT4 RS be limited edition production and only in production in 2022?

TXshaggy

7th is wrong above and why your calcs showed such a drop off.

Should be around half what you calculated with 0.71 7th.

GrantG

Check my post above #2043. It's only 15% different...

Jon H

"If Porsche were to make a PDK-S gearbox for the GT4....." -

What would a PDK-S gearbox do that's different from the one that's on the 718 GT4?

GrantG

The PDK on the GT4 has only 6 performance gears (and even 6th is a bit taller than it needs to be). 7th gear contributes nothing to performance (it's only a cruising gear unnecessary on a GT car).

PDK-S would put 7 performance gears in the space of the current GT4's first 6 ratios (or potentially packed even slightly tighter). This means the engine stays near max power (7,600 rpm) longer and makes the car faster in virtually all circumstances. When upshifting, the rpm's fall much less, due to the closer stacking of the ratios. PDK-S on the GT3 also includes electronic control of the locking of the LSD.

This why GT4 PDK is only faster than the Manual when launching (0-62mph) and then there is no advantage (and the Manual is even faster than PDK from 100 mph and faster). With the PDK-S, the GT3 is faster everywhere.

Here are Porsche's numbers for 718 GT4 acceleration (PDK and Manual):




You can see PDK is faster at launch (0.5 sec) to 100kph (62mph), then takes the same time as Manual from 100kph to 160kph (100mph), and then Manual is faster to 200kph (124mph) and continues on to a higher top speed...

TRZ06

The gearbox is totally separate from the diff. Porsche could have used the e-diff on the GT4 if they wanted to, but they chose to keep it mechanical for both PDK and manual versions, albeit with different locking %'s between the two.

TXshaggy

I think we’re saying the same thing…it’s far less that a 2200 RPM drop.

The PDK in the GT cars has same functionality as 991.2 GT3.

Different gearbox due to chassis differences.

Porsche doesn’t even use PDK-S terminology — these are simply GT PDKs.

GrantG

delete

CAlexio

What happens if this car has a 9000 RPM engine... The way the current G3 engine and gearbox matched up ideal?

Jon H

GrantG - Thanks for your detailed response to my question, it all makes sense.

wizee

Going from 6th to 7th gear, you go from a ratio of 0.88 to 0.71. That’s a drop from 8000 RPM in 6th to 6450 RPM in 7th. That’s a drop of 1550 RPM, much less than 2200.

It would be interesting if Porsche changes the final drive to make 7th a performance gear rather than an overdrive in the GT4 RS. The spacing between 6th and 7th on the GT4 is right in line with spacing between the other gears, so it should be possible to do this.