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Interesting. Thoughts on the power delta from road car to clubsport given that they're supposedly the same on paper?
Usually you'd expect the PDK to get worse wheel numbers all else being equal... but a dynojet is quite sensitive to lighter wheels and different tires etc... and assuming the clubsport is on the 68 rear tire it's definitely got shorter gearing on top of the PDK's already shorter ratios which helps WHP. Would the low miles on the road car matter also?
My buddy's 718CS MR traps the same at the end of the straights as a headers+IPD+software 981 CS MR which is a bit heavier. So the 718 race car doesn't seem "underrated" as such.
The dyno is for the 718 GT4 CS, which is basically a 3.8L w/ X-51 kit.
The dyno is for the 718 GT4 CS, which is basically a 3.8L w/ X-51 kit.
I know, but both it and the 718 GT4 road car are rated at the same 420 PS. The CS has PDK which has higher losses than the 6-speed manual of the road car. Yet it had more WHP. Wondering if this is due to smaller/lighter wheels or the road car being very new and the gearbox etc not being entirely broken in yet.
I know, but both it and the 718 GT4 road car are rated at the same 420 PS. The CS has PDK which has higher losses than the 6-speed manual of the road car. Yet it had more WHP. Wondering if this is due to smaller/lighter wheels or the road car being very new and the gearbox etc not being entirely broken in yet.
I'm thinking its a mix of things, and PDK + sm. wheels would make sense, and believe they rate what they did on the 718 GT4 a little higher (425hp vs. 414hp - road car) https://www.porsche.com/internationa...turesandspecs/
What I also noticed is the 718 GT4 CS is running 98 octane, that could hop up power too...
The higher octane shouldn't matter on a standard car unless the regular 93 fuel was really bad.
Nice to see updated numbers! could be the "100-cell metal catalytic converter complying with DMSB specifications" vs full cats and the awesome OPF blocking flows for road car.
Looking forward to seeing dyno comparisons between a stock 718 GT4 and a 981 GT4 with popular performance mods like street/race headers and a custom tune.
Interesting, what this kind of shows is Porsche gave the 718 GT4 Clubsport performance for the road. Add a Cobb OTS tune, and you're equal. If the upcharge for the 718 GT4 is GT3RS suspension components (improved rear end stability vs. 981), 4.0L / X-51 level engine power, and a warranty to go with it - that all-in-all sounds like pretty good value if you want more GT4 under engine warranty and a more solid base to get 500hp later.
I could easily see the 718 GT4 with Cobb Protune, Sports Cats, Exhaust can / OPF deletes getting 440hp crank easily.
I know, but both it and the 718 GT4 road car are rated at the same 420 PS. The CS has PDK which has higher losses than the 6-speed manual of the road car. Yet it had more WHP. Wondering if this is due to smaller/lighter wheels or the road car being very new and the gearbox etc not being entirely broken in yet.
Why does the PDK have higher drivetrain losses? It shouldn't matter since its still a clutch transferring the power.... An automatic, without a locking torque converter, sure, but not PDK as compared to a manual. Perhaps the difference on a dynojet is due to the gearing of the PDK vs. the manual (which is known to be longer).
To me, the 718 comparison is somewhat inconclusive until we get a street PDK vs. clubsport PDK. The 981 to 718 comparison is more valid since they have the same transmission. Unless the final ratio is exactly the same PDK to Manual, the results are kind of apple to oranges. And while I see the 718 power more consistent, I see some obvious detuning on the 981 around 6.5k and higher, which would make sense when you compare it to a 911 S engine of the same year.
Why does the PDK have higher drivetrain losses? It shouldn't matter since its still a clutch transferring the power....
It has not one but two clutches, a hydraulic pump and a lot more rotating weight. It's almost 2 gearboxes in one. The speed comes from being able to pre-select the likely next gear on the other shaft and then just release one clutch and close the other simultaneously. A 6-speed manual is a lot simpler and a lot lighter, with fewer parasitic losses. Not enough of a difference to make up for PDK's speed though obviously. But PDK cars dyno lower in terms of wheel power all other things being equal.
It has not one but two clutches, a hydraulic pump and a lot more rotating weight. It's almost 2 gearboxes in one. The speed comes from being able to pre-select the likely next gear on the other shaft and then just release one clutch and close the other simultaneously. A 6-speed manual is a lot simpler and a lot lighter, with fewer parasitic losses. Not enough of a difference to make up for PDK's speed though obviously. But PDK cars dyno lower in terms of wheel power all other things being equal.
two clutches acting separately, so while I would agree it has added sprung weight (including the weight of the hydraulic pump), I have been unable to find anything that supports the claim it has additional unsprung weight, but I’m open to those facts if you found them.
I agree, in theory, there is parasitic loss due to the hydraulic pump, but considering there’s no shifting on a dyno, I would expect the parasitic loss to be negligible given it’s probably not a positive displacement pump. Though, also in theory, since the PDK is quicker, there is less loss in engine output shaft inertia (rpm drop) which I would think offsets the parasitic loss from the shift engagement itself. Tho this wouldn’t be shown in a dyno.
not saying you’re wrong, but I’d be interested in seeing the data to support the unsprung conclusion since I’ve been looking for a while and haven’t found them.
also, do you know if the unsprung mass of electronic differential is heavier or lighter than the mechanical differential? This should also factor into the power loss. I can see the e-diff potentially being lighter, but at the cost of parasitic loss. Just curious.
The pump is providing pressure all the time to keep the cluctch closed and I've seen reported that its parasitic loss does go up quite a lot with RPM. But either way on an inertia type dyno like this where the sweep is pretty quick you'd see a loss just because there's more rotating mass inside the gearbox to accelerate in a hurry.
As a ballpark number dynojets seem to read about 7-10 HP lower on PDK cars. That's an absolute number of course that does not change with higher/lower power cars.
The higher octane shouldn't matter on a standard car unless the regular 93 fuel was really bad.
Perhaps on a dyno where lack of cooling can lead to higher aits and reduced power (pull timing) the extra octane makes a larger than expected difference in dyno results?
How about a comparison of a 718 GT4 4.0L vs. a 718 GT4 3.8L Clubsport AND a stock 718 GT4 4.0L vs. a stock 981 GT4 3.8L!?!
718 GT4 Clubsport Race Car (98 Octane) vs. 718 GT4 4.0L Street Car (93 Octane) 718 GT4 4.0L Street Car (93 Octane) vs. 981 GT4 3.8L Road Car (93 Octane)
Great dyno charts! My takeaway is the 981 3.8L just an intake, tune, and cams away from matching or exceeding the 4L in the 718
Great dyno charts! My takeaway is the 981 3.8L just an intake, tune, and cams away from matching or exceeding the 4L in the 718
Great observation! My takeaway is how much more room there is for the 4.0L to go per TDT's points above. 981 GT4 may come close, but doesn't seem to make sense to buy a prime/pristine example 981 GT4 @ $89k and then have to add another $10-$14k (Dundon D4 etc.) + catless fumes.
Might as well just pay for the 718 GT4, get that 4 year coverage to boot + a sweeter base for more power down the road with BGB level builds.
07-05-2020 | 05:03 AM
