TheOtherEric

At risk of bringing up an old debate, I'd love to hear people's opinions on the merits of C2 versus C4 for the racetrack. Here are the pros for RWD and AWD as I see them:

C2:
- 110 lbs lighter
- Easier to throttle steer
- Less mechanical stuff that can fail

C4:
- Added margin of safety
- Keeps the rear planted by relieving it of some of the work
- Good in the rain

Any experiences or opinions?

graham_mitchell

if the C4's VC fails, it doesn't adversely affect performance, it just reverts to RWD. So that is not really a significant factor WRT track performance

Mike in Chi

The C2 feels real nimble at speed. C4 has a different feel to it.

I agree about the advantages of AWD in the rain, but I used my C2 at Road America a few years ago in lots of rain. No problem, just drive the rain line, and use smooth application of pedals.

Greg Fishman

A friend of mine and I have virtually identical race cars except his is AWD. Our cars are within 50lbs of each other, he has Motons, I have JRZ shocks. The big, make that huge, advantage he has is that he can get on the throttle in certain corners much quicker. Dividing that hp between 4 corners vs. two pays big dividends. Add a slick track or wet conditions and it is no contest. I think he could out drive Schumi in a comparable 2 wheel car.....well, maybe not, but it is dang quick.

Given a equal set up I can't think of a reason why the 2wd cars would be quicker. When my friend has ridden in my car his comment that it had better transient response and felt more tossable. But I don't know if those things translate into quicker lap times.

I think there is a reason why most racing series do not allow awd cars as they really have an almost unfair advantage. Look at the Audi's in the Speed World Challenge GT series. When they aren't on the front row the RS6's pass about 3 cars or more from the standing start. I think they are also easier on their tires than their competitors.

chris walrod

Isnt the C4(S) basically a rear drive car until rear grip is violated? Of course its not that simple, just a thought..

As data point, ViperBob just converted his monster to RWD, curious to what his thoughts are?

Greg Fishman

Chris,
The 993's torque split changes with available traction from 5% to 50%, IIRC (please correct me if I am off on the numbers).

The 964 version has a fixed torque split. I recently drove a track prepared 964 C4 and the front wheels pulled the car through the turns, it was very noticeable. I drove the car at 9/10ths and in a turn or two I let the back end slide a bit, just give it some throttle and the front wheels pull the car through the turn. Given some more time (and ownership ) in the car I could really have some fun!

Rob 97 993c2

the c2 might just feel more fun for normal street driving.. i know my c2 felt more fun and tossable around the street than my TT - not a fair comparison, as the TT actually is heavier.

Speedraser

Greg,

There are at least two reasons why the RWD car would be quicker given similar horsepower -- less weight and less mechanical friction. The C4 AWD system adds 110 lbs, IIRC, and extra mechanical friction losses. As I understand it, a C4 is quicker on a very tight track because it can put the power down earlier in tight corners. On a faster, more open track with higher speed corners, the C2 is quicker because it can put the power down almost as early as the C4, but weighs less and suffers less mechanical drag through the drivetrain.

Greg Fishman

Todd,
When I said equal set up I meant weight as well, I should have clarified that. I can't disagree with the mechanical friction issue but in my real world experience the difference is not perceptible, at least not for an amateur like me.

For amateurs/weekend warriors, I believe the C4 (given equal drivers) will be faster due to the extra confidence it gives in high or low speed corners. For the higest level pro and club racers your premise about the C2 being quicker in the higher speed corners might be true. I had a pro driver drive my car and my friend's C4 and he liked the feel of the C2 better but thought the C4 would be quicker around Mid Ohio given equal drivers and conditions. Mid Ohio has mostly tight, low grip turns. This supports half of your theory at least.

914und993

I do not, and never have raced - just drove a lot of DE's at several different tracks in my 964 C4. My perception of the C4 was different. In tight, slow corners, the C4 understeered very badly due to the automatic locking of it's differentials under those conditions. A C2 could be pirouetted around the corner more easily with proper use of throttle steering. On high speed corners, the C4 felt much more stable than a C2 - you could put more power down without much fear of a surprise tail slide.

Again, I am no expert, and I'm told that some judicous suspension upgrades and tuning (my C4 was stock) would have taken away a lot of that low speed understeer, but there was my experience.

Of course, the 993 C4 is a different animal.

Chip

jbuchsba

Audi quattro's were outlawed for a long time....nothing else could compete unless a big weight penalty was used against the Audi cars.

They need a specific "method/technique" to drive...but if used, and the cars are close otherwise, 4wd should kill 2wd....if you believe that racing is a lab, the ETCC and BTCC with quattros pretty much proved that IMHO.


Just my 2c...different feel, and such, but for pure speed, the 4wd will get around faster. That being said, I think 4wd cars on the street use tires faster (at least my quattros do).


JB

Cloud964

A British magazine, top gear, march 1996 has an article comparing 2wd and 4wd cars. They lapped the C2 and C4 in both dry and wet courses, and here's the result:
Dry course: C2's lap time is 53.43 sec.,C4 did it in 53.01 sec.
Wet course: C2 in 25.27 sec.,C4 did it in 25.05 sec.
The magazine quoted: "The porsche carrera 2 proved to be a very close match for its 4wd brother in every department, including the specially wetted surface of the steering pad, though the 4 wheel drive model maintained a clear edge in handling and wet grip."
It concluded: "The porsche C4 is a clear favorite. There is little to choose between the 2 911s but in handling and grip as well as our timed laps the C4 has the edge. The message is clear. Four wheel drive costs more- but for a keen driver, it's a price worth paying for the added reassurance it can bring."

chris walrod

I loved that era of TransAm where the Audis gave the American entries a butt spankin with 1/3 the engine. Funny how they were forced to add weight each year until they finally pulled out and said 'its been fun'

Jean

This is a debate we often have without a clear answer I would agree with Greg that if you can drop the weight of the car to the same as the 2WD version, you might be very close as far as performance is concerned. It is very difficult on a street car to do so and keep it streetable after a certain limit, which is why I am going 2WD myself as well.

IMHO, There are other things to take into consideration, such as what goes with the 2WD version. A different LSD, different sway bar settings, camber, suspension and tire size and you can make it faster than a similarily balanced AWD. Just move from AWD to RWD and leave everything else the same and you might not match the performance.
The Audi is completely different when it comes to the AWD system, it is MUCH more noticeable and MUCH better than the 993, a true 4WD in a sense. I have driven an old rallye quattro and can tell you it is really planted on dry and slippery surfaces, the confidence levels are very dangerous as a result.
Apparently Bob is making 3-4" per lap better after his changes, it might be the 2WD or not, but something was done right.
Last but not least, the driver! Some people are more comfortable driving a 2WD and using throttle steering while others feel more comfortable driving a better "balanced" and predictable car, the same driver can have worse lap times on an AWD while another driver the contrary.
Net net, no idea

Paul E. Dodd

In my experience (mostly SCCA autocross) even the 993 version of the C4 understeers badly in stock form. This can be dialed out at least to some extent with proper suspension setup (if your class allows you to do so). On a tight, low grip autocross course in Albuquerque earlier this year I set fastest PAX time, and believe me, I'm not usually above midpack. In watching others drive the course, I could tell that I was able to get on the power MUCH sooner than RWD cars.

In general, I've had to adjust driving style to try to defeat understeer- heavy trailbraking to get the back to rotate, then get on the gas and let the front pull you through. Easy to say, but I still find it hard to convince myself to punch it when the back is sliding. My understanding is that this is even more important in the 964 C4. There was an excellent series of articles in Excellence a few years back entitled "Wringing out the Carrera 4" that goes over the 964 technique in detail, which can be found at: http://www.porsche964.co.uk/rev_rep/reviews.htm

That said, it should be noted that Paul Kozlak and his wife Lynne Rothney-Kozlak, both noted SCCA autocrossers, chose a 1997 C2 as their attack weapon this year and finished 4th and 8th in A-stock at SCCA Solo2 Nationals. You can find some discussion of why he chose the C2 vs. the C4 over in the Autocross forum, but basically it boils down to lighter weight, less understeer, and the narrow body IIRC. Plus I don't think Nationals usually has extremely tight courses.

Paul