Gentian21

One of the largely unmentioned differences between the manual and PDK cars is that the manuals only come with a mechanical limited slip diff, whereas the PDK has an electronic one. I'm assuming that an electronic unit is better, since mechanical units have been around a very long time. However, does anyone know whether there is a noticeable difference in performance between the two? 100 percent of my driving is on the street rather than the track, and I'm wondering whether the differences should be an important consideration in deciding between a manual car and a PDK.

Bluehighways

If the mechanical LSD is a Torsen LSD I'd take that over an electronic version. FWIW, I don't know off hand what type of mechanical LSD Porsche is using. But I'd be curious to know.

Richard_Wallace

Not sure if you could really tell the difference, if the mechanical is a quality one (which is most likely is). I have to assume they will function in the same way except the electronic one will have less lag in engaging. However the Mechanical LSD is less complex, which is not a bad thing for repairs if ever needed.

tgavem

Only Guards make a LSD for the 7MT and it is $3k + shipping and labor at your local shop.

regarding difference with LSD and eLSD. Preload could be a variable. If your have torque vectoring as well with the eLSD, it is a very good package.
I find the preload in the mechanical LSD a little lazy. For a long continuous corner and steady throttle you won’t feel it, you need to keep squeezing throttle to load the LSD. Can make for scary fast corner exit. Also, in very slow corner, easy to oversteer before LSD grabs but then TSC may have already cut throttle and brake one wheel before LSD loads up.

WestBank

edit: I drive a 2019 M4 CS

I can tell you if I had to choose between a mechanical and electronic version of a differential, I'd go electronic all day long. DSC (Dynamic Stability Control) and e-Diffs work in tandem for sure, I believe the differential lock up is controlled by the DSC and is in tandem with the traction control to optimize traction in any driving scenario. The portion of the DSC system that operates the differentials electric motor pulls data from sensors across the M4, such as steering angle, yaw, pitch, wheel speeds, etc. and decides on how much lock to set. The more aggressive the differential locks up, the less traction control interference and the better the acceleration.

There was an electronic differential deep dive on F8x ///M cars, and I quote, "Tuning of the Active M differential is performed hand in hand with that of the chassis and the control systems, such as the DSC. All in all, it is a repetitive process. The responsible engineers conduct their testing activities jointly. The interplay of the individual systems is optimised as they are developed."

I'd have to believe that Porsche has the same system. Data being derived from sensors on the car, and adjusting the e-diff on the fly as the situation develops.

Richard_Wallace

I don't disagree, but only if you are driving at 90%+, otherwise there is no way you are feeling the difference in normal driving conditions/capabilities. I do agree modern cars on the track, you can potentially feel the difference if you are capable to get to that limit.

I was curious though, as I thought other porsches in the past had eLSD with manual tranny, but the 992 had mLSD. (which is what I have). I think even the 928 had a eLSD, but not positive, as I do not remember, but I think I remember it being one of the first back in the day...

ipse dixit

On street makes no difference.

At the track, different story.

aggie57

Agreed. Now can someone confirm what type of diff the manual cars have? Torsen or plate/ramp? I’ve searched and can’t find a definitive answer.

Bluehighways

The Manual Transmission cars have a mechanical Wet Clutch (Plate) style Limited Slip Differential. Of that I am fairly certain. I was able to locate the attached exploded view courtesy Car & Driver. The Differential shown is pretty clearly a mechanical version.




The DCT's use what is being called an electronically controlled infinitely variable Limited Slip Differential. I can not find any wiring diagrams or exploded Parts Catalog views of this Differential. All I can find are line art pictures of the complete 8-Speed DCT assemblies.
https://www.eurospares.co.uk/parts/p...gearbox-248479

I did a LOT of searching to try and figure out how the Porsche electronically variable version actually works. eg. electro-hydraulically operated wet plate clutches by themselves like Honda uses on their Ridgeline Pickup -or- electro-hydraulically operated wet plate clutches that act on sets of planetary gears -or- there are other possibilities as well I'd imagine.

With either Differential Porsche is using the Rear Wheel Brakes to initiate the "Torque Vectoring" at a corner "Turn In". An effective but particularly in-elegant way of accomplishing this. Basically a computer controlled steering brake system.

The attached pictures are of the Honda Ridgeline electro-hydraulically operated wet plate clutch system.

ipse dixit

I think the last Porsche that had a Torsen differential was the 968.

Just about all modern mid/rear engined Porsches have a multi-plate clutch with ball ramp reinforcement.

John Mclane

By now most have already read this, link anyway:

https://www.porsche.com/middle-east/...11-carrera-4s/

aggie57

Thanks guys, real old school!