4WD system in C4

[tuteez]

I realize I could probably just search on my question, but I'm bored and want a little discussion. My question is, what type of 4WD or AWD (which one is it) system is in the C4? Is it similar to the Haldex or Torsen systems in Audi's, or is it different?

Also, what is the "default" ratio if there is one - ie. is it mostly FWD at a certain % and then kicks in as needed? is it always 50/50? RWD? - what?

[Raven Flyer]

The default ratio is 95 rear, 5 front.

The front is connected by a viscous coupling, no idea which of your options that matches.

[damianc4s]

.....and will distribute up to 40% power to the front when needed.

It uses a viscous multi-plate clutch, not quite as advanced as that found in the 20 year old 959 but derived from it.

[tuteez]

So is it a system developed by Porsche only used on Porsches?

[damianc4s]

tuteez said:

So is it a system developed by Porsche only used on Porsches?

Exactly.

Have a look here:

www.autozine.org/technical_school/traction/tech_traction_4wd.htm

Damian

>> Edited by damianc4s on Friday 10th March 23:26

[tuteez]

Thanks....I see now.

So, from a different angle, is it safe to say the C4 will be more prone to understeer under pressure due to the amount of power to the front?

[damianc4s]

Power only goes to the front if you continue to press on, no acceleration the car behaves like a rear wheel drive car. You are right to say that the C4/C4S/Turbo do understeer more than RWD cars, whether that's down to 4WD, chassis dynamics/geometry setup or driver education it's your choice

[johnny g-pipe]

The first AWD porsche was the 959 with a longitudinal planetary diff, inherited by the 964 Carrera 4 but changed for the simpler system in the 993 and later.

The 964 is preset for 31-69 distribution, but alters fore or aft if it senses loss of traction.
The 993 is more like 5-95 under most conditions. A 993 will do donuts in a snowy car park, a 964 won't.

AWD cars need a specific driving style to eliminate their inherent understeer..
Porsche calls it AWD. I think 4wd and 4x4 is more discriptive of the fixed, off road type systems..

[hog 1]

Can anyone then explain why they only offer an LSD option on the C4S along with the sport suspension package. I've asked OPC and its not an option with the standard PASM.
997 TT has LSD as an option, so what is the difference there?