c4 vs. c4s awd

Does the 2000-2004 C4 use the same all wheel drive system as the 2002-2004 C4S? If not, is there a significant advantage to the C4S system? Thanks, Robert

Same system in all 996 C4's. I don't think they changed it until the 997.2 which just came out.

How's the current version different, if you know?

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Thanks for the quick response.

The new awd system is a computer sensor controlled system. Ours and the first gen 997 is mechanical controlled viscous coupling system . I believe the new system can send 100% power to any wheel, while the older system can only deliver 5% - 40% tp the front diff. It uses the braking system to cut power from one side to the other side.

I understood C4S differed in the electronics (software, and maybe hardware) - perhaps in how it uses the brakes, perhaps in PSM, maybe both. Though I've wondered if they didn't upgrade the C4 after introducing the C4S.

Prior to the 997.2 the Porsche AWD system was/is virtually useless, a true no-op.

The 996 AWD system (whether C4 or C4S) is entirely mechanical. PSM is a different system, which is a standard feature on the AWD cars. The AWD system on the 996 wasn't designed for use in snow/ice/slippery conditions, which is the reason it is "useless" in these situations as wwest mentions above. It is useful in spirited driving and on the track to help the car accelerate more quickly out of corners, which is exactly why it was designed.

I've never found our AWD system to be useless in any reasonable situation and the unreasonable situations (wrong tires, snow higher than the front lip, etc..) weren't a fault of the system.

From what I've read, The AWD system used in the 996 was first introduced in the 993 series, before that starting in 1989 with the 964 C4 it was an electronically controlled clutch pack system fore and aft, same as the 959. The 996 C4S has the turbo brakes and suspension, which all other flavors of C2 and C4 lack. IMHO based on owning both cars, the 996 AWD is mellowed and subdued, yet omni present when needed, versus the electro mechanical system of the 964. Incidentally, no manufacturer could make the silicone filled viscous clutch system available until sophisticated machine tooling was invented that could economically produce the required parts.

Mine's useless, but that's probably due to it sitting in pieces in my garage.

Snow ? what's that ? The C4S with turbo underpinnings is as sure footed as a mountain goat on a slate mountain. Rain, slippery roads, curves, lateral sideways moves in traffic all handled with incredible stability. the only thing comparable is a sport bike motorcycle. The fastest driver of its era street Porsche on or off track.

Although the PSM is too abrupt and intrusive. I turn PSM off for fun runs and consistently am amazed at what the C4S can do.

With PSM deactivated, the AWD system comes into play much more often. I agree with you - I'm quite amazed by the capabilities of this vehicle. I think the issue that some people have is that they believe that AWD = good snow traction. The AWD system in the 996 wasn't designed for snow, so this isn't necessarily the case.

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I didn't necessarily mean to suggest any of the electronics are part of the awd system per se, rather that they might be the kind of significant difference the OP was asking about. As per Jumper5836's post, I understand the car sends power to the left side when a right wheel spins by braking the right, thus acting as an e-diff. Some would say any diff, whether e or not, is part of the system. I guess it depends on where one draws the line between the electronics and the mechanical system. (Is this function disabled when PSM is switched off? I can imagine not - it might continue to send power to a wheel with more grip regardless how much the car is understeering/oversteering/spinning. Or not.)

Now back to the interesting part - the significant differences. When the C4S was introduced, journalists seemed to regard it's handling as infinitely superior to the C4's, and I always wondered why. I presumed the shocks and dampers were basically the same - just a bit stiffer to handle more weight. I understood the mechanics of the 4wd were the same too. So the only things I could think of was the electronics, which I knew were different, and the width. And perhaps tire sizes? (Need to check that.) Maybe the journalists simply never tried a C4 with the sport suspension and the 18" wheels? Otherwise, if the did - if the C4S really is much better - could the electronics be the reason? Or the width? Or perhaps I'm mistaken and the C4S suspension has nothing to do with the regular (-10mm) sport suspension? Or is there some other difference no one mentioned on this thread yet???

I think the reviewers bought into the faster lap times that Porsche fed them. The lap times could be 100% legit, or they could have been the product of something as simple as better tires. If the times were legit, going faster with the same engine but an additional 100 pounds requires good engineering. The C4S got bigger brakes too, they would be a noticable advantage on a track but all but invisible during normal driving.

I think it's the combination of upgrades to the suspension and brakes coupled with the wider tires. The C4S essentially shares suspension components with the turbo (with a few minor differences).

the C4's body is essentially a Gt3 frame and the C4S is a turbo body.... its AWD drive system is made for stability rather than for AWD... that is why you can drift with this system. If you ever drive a C2 vs a C4 it essentially drives similar. The big difference between the two is steering feedback... the C4 steering is heavier and has more feedback, being connected to to front wheels. Im sure you know about the viscous coupling Porsche uses.

It's not the lap times that won the C4S so much journalistic praise - at least not in the magazines I read (Evo and Car). It's the handling. And it's not the brakes that make the C4S faster on the Nurburgring. The Nurburgring is not demanding on brakes. Also, the turbo brakes probably give it zero braking advantage over the C2. The C2's brakes are fully capable of braking at the tires' limit of grip. The Turbo needs bigger brakes because slowing the heavier turbo down from higher speed generates more heat - and bigger brakes enable the same braking with less heat. Since the C4S is also a bit heavier, it may also need bigger brakes. And I'm not sure it's the suspension, because the C2 used by SportAuto had the 10mm lower sport suspension. And the C4S is said to have pretty good ride quality, so it's unlikely the suspension is much firmer. So if suspension, it would have to mean fine-tuned spring and anti-roll bar rates and higher quality dampers. What helps the lap time is the width, slightly wider rear tires (295 vs 285), the weight distribution, and the 4wd. What hurts the lap times are the weight, drag, and 4wd. The shorter the track (or actually the shorter the straights and the tighter the turns) the more the advantages of 4wd outweigh the disadvantages. As a result, pretty much every 2wd watercooled Porsche is faster on the ring than it's 4wd equivalent, and slower on short tracks. (The C4S has no 2wd equivalent.) So if the C4S is faster on the Ring, it will be significantly faster everywhere else. However, the C2 used by SportAuto didn't have the LSD and the tires may have been an older and therefore inferior model. I figure the LSD is probably good for about 3-4 seconds at the Ring; it's said to be good for ~1 at most tracks, but it will help less per km at the Ring for the same reason 4wd helps less - the turns aren't as tight. In sum, the reason the C4S can do better Ring times than a C2 without LSD are the width, weight distribution, slightly wider rear tires, maybe superior suspension design (IF there are any real differences), maybe newer model tires, and maybe superior PSM - if von Saurma left it on or if the e-diff function remains on even when PSM is off - and maybe there is some other difference no one on this thread has identified yet ... . The reasons it can go faster than a C4 are the same, except weight distribution, and maybe the C4 didn't have the sport suspension - don't know.

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I haven't had the pleasure of drifting any 4wd Porsches :-( A friend who drifted a 996 Turbo at a snow driving event didn't like it. Hard to control the drift, and generally huge angles. I remember hearing at least the bigger angles thing from other sources, and not on snow. Maybe the hard to control part is from the Turbo boost. (No clue whether the car was chipped, which might make the Turbo even peakier.) I can imagine the Turbo is also worse than other 4wd 996s because it's a lot heavier in the back. On the other hand, I just read an old article in Car saying the Turbo drifts wonderfully on track (presumably when trying to go fast, not when going for bigger angles). Still, if I were going drifting, the Turbo would be my last choice. Should I expect the C4 (or C4S) to drift significantly better?

But interesting though lap times and drifting are, what I'd really like to know - along the lines of the OP's question - is whether the C4S is really so much better than the C4 - and also the C2. Which means, since I'm pretty sure it's the handling that impressed Car and Eco, whether the handling is really so much better. And if so, why? (Or did Car and Evo get it wrong? Perhaps they never tried C2s and C4s with the sport suspension, and the LSD (for the C2)? Perhaps others have different views?)

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Not useless but not as efficient as today's AWD systems. Most of the time it feels like a RWD car which isn't a bad thing.

Its a completely different car and suspension. Handling is much better than a C4 which is really just a C2 with AWD added.

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I was wondering about this (about how the C4S suspension compares to the Turbo suspension). Are the parts exactly the same? If Porsche wanted the two cars to handle and ride the same, they should give the C4S slightly softer springs and dampers, due to lower weight, especially at the rear. And I've heard the Turbo has a rough low-speed ride, which I've never heard about the C4S. I'd quite like to know - if the Turbo has basically the same suspension, then I'll be even more tempted to get one. (Yes, I know the purpose of a Turbo isn't to go slow, but the route to the right roads is often over the wrong ones.) On the other hand, are you sure the C4S suspension is substantially different from the C4 sport (-10mm) suspension (in terms of spring rates, damping, and anti-roll bar stiffness)? More than explained by the width (which makes an equal diameter anti-roll bar less stiff) and the weight?

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Um...no. As someone said above, the c4 chassis is completely different than a c2 as the c4 is essentially the same chassis as the gt3 and more rigid. Most of the reinforcement comes from a revised front tub area in front of the windshield. One of the reasons why I technically can't extract the most from my gt3 setup on my c2...

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I'm not a Porsche engineer, so I'm only relaying things I've read about and things I've researched. The C4S suspension is very similar to that of the turbo, but there are subtle differences due to overall weight and weight distribution. It is very different from the standard C2 or C4 suspension. Many people (including Excellence Magazine) consider the C4S to be a "magical" combination of suspension, brakes and handling because it was really designed to handle the much more powerful turbo car. There are also aero differences to compensate for the difference in weight - this is the reason that the front splitter for the C4S is different from the turbo splitter.

Oops, forgot to include the quote, but can't figure out how not to post this, and can't figure out how to delete it either ... :- (

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Interesting - would love to know if the ride quality is the same. I'm trying to find an opportunity to test either the C4S or the Turbo on local roads b/c I'm afraid the ride quality will be too harsh. If I knew the suspensions were the same, at least I'd only need to try one of them ...

The suspensions are not identical. They are very similar, but not identical. The damping rates are slightly different on the C4S. That being said, the ride quality is very similar.

Far from "useless," unless you're driving in deep snow (in which case, guess what, you brought the wrong vehicle). Agree with the guys above ... on road and track, AWD in the C4S is all about acceleration out of corners. Which for me, more than offsets the "push" criticisms about AWD. I've tracked my C4S hard for five years and I love it. Sure, I'd go for a GT3 if that were a possibility financially for me. But other than that, I wouldn't want any other 911 configuration for the track. The C4S is just awesome.

I've been doing some reading, and it turns out both of the magazines I read (Evo and Car) dislike the Turbo's low speed ride. (And like just about everything else). I don't remember hearing that about the C4S. Maybe Porsche had to sacrifice low speed ride so the Turbo's suspension would work at even higher speeds? Or maybe with an extra year or two, they were able to make big improvements for the C4S? Or maybe the journalists simply never drove the C4S on a slow, bumpy road ... ?

I've owned a C4S and a turbo as well as a few C2s. I would agree that the turbo's ride is noticeably worse at low speeds. I do agree that the C4S is the most pleasant and possibly best handling of the bunch. The turbo is noisier, rides rougher, consumes a lot more, etc. but it's also quite a bit more exciting, especially with a few modifications. As for drifting, especially with decent tires the C4S takes way too much prodding, and the turbo is quite hard to be smooth with. A C2 w/an LSD probably would be my choice if that was a priority.

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Something tells me the C4S won't take too much prodding when it snows :-) (And when it's dry, I'd rather my rear wheels more or less follow my fronts.)

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Thanks for the very helpful post! Two things you said about the C4S caught my attention. First, "most pleasant" means/includes the ride? I assumed a C2 without the sport suspension would be better, no? Even with 17s? (Though strangely Evo wrote that Porsche said the 18s improved the ride over the 17s on the 996.2 C2 ... wonder if they got that mixed up somehow.) And I'm very curious in what way you found that it handles better than a C2 (or Turbo, for that matter)? (It's generally praised for it's handling, I know, but I've never been able to figure out the pluses and minuses. Is it just quicker turn-in?)

There was some discussion earlier in this thread about why the C4S is faster at the Nurburgring than the C2. I did some reading and found 2 or 3 more differences: First, the C4S has ~50% less lift front and rear. This "huge" difference probably makes no difference in lap times, because ~50% of ~zero is still zero. Second, the C4S had Pirelli Asymmetrico's designed just for it; the C2 didn't; it may have had P Zero Rosso's. I can easily imagine this accounting for most or all of the 4 second difference. I can only remember hearing bad things about P Zero Rosso's. When I drove a BMW with them a few years ago, I thought they were rubbish versus tires available at the time. And though I'm not 100% sure I've seen test reviews, I think I have, and were the Rosso's among the winners, I would have been surprised enough to remember. Finally, I seem to remember the C4S also has wider wheels at one or both ends (not sure). With any given tire width, a wider wheel means more tread on the road.

The C4S is lower, wider, and heavier. It is amazing in turns and beats the C2 hands down.

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My experience certainly doesn't contradict yours. While I've surely got a lot less experience, and it's been a while since I had a long drive in a C2, my C4S memories are indeed more positive. Have to wonder how they'd compare with the same tires though. Especially if the C2 has the same height as the C4S (via the ROW sport suspension) and the LSD. (The main criticisms I've seen leveled at the C2 are about (i) the turn in, and the front not feeling "keyed to the road", whatever that means, and (ii) the rear being less throttle adjustable/almost impossible to break loose versus the 3.4 liter car. I can easily imagine the first being addressed by better tires. If they tame understeer, they should make the rear feel more mobile. So should the LSD. And I suppose the C4S is even harder to break loose at the rear.)

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This is a serious question - how do you know that? You don't seem to drive your car at all and you certainly seem afraid to even track it

Here is Richard Hammond's explanation of the difference between the C4, C4s and turbo "Why pay for a fake" fast fwd to 6:20 and catch the end where he brings out 3 different bikini models to explain You Tube