Mike in CA

Super, I've heard the homologation argument before and I've never been able to understand it. The RS is sure to come with ABS, PASM, PSM, etc. and those features aren't allowed in racing either. I don't see why RWS should be any different.

mgent

Would the RWS change any suspension mounting points which need to be homologated? That's the only reason I can think of...

If it's closer to 180 and as described (500hp, 4.0L, PDK-S, really light), then a 110k GT4 is likely a reality and would be a beast of a car...

Zulu Alpha

I don't know why Mike, but I feel that price deep down in the bowls of my gut .


Thats very interesting Super D, while I am only going of speculation, it seems odd to me that they would go through all that RWS shpeal and then take it out of their top 'track car' after making a big deal about the GT3 being "faster" with it.

Zulu Alpha

If you see the link by Elephant Racing :

http://www.elephantracing.com/tool-b...n-overview.htm

You can see all they do, is replace the track rod with an actuator, nothing more nothing less practically.

SuperDarius

Guys,i don't know why they tell me no RWS,and Mike,you are right,it will have ABS,etc. So,maybe is right the reason of the sospension mounting points...

Sure in February when they tell me these things,they where sure of these,becouse they call me after a meeting on future models.THen the problem of the Gt3 engines,maybe changed all plans...And maybe also some specs.

Really can't wait to know more,this time is a looong wait,maybe too much that i/we wait...

GrantG

I continue to think the reason for the lack of RWS on the RS is due to the enormous stress on that system with the ability to use real slicks (not allowed on GT3), more aero downforce, wider rear track, and additional power/torque.

They also would like to make the RS lighter than the GT3 by a reasonable margin and removing RWS is one of the easiest (system is heavy and requires heavy full-size battery to make it work). Removing RWS and adding Lithium battery will make a significant weight savings.

Petevb

Not sure this pencils. The Turbo and 918 both use the same system and can push 3700 lbs depending on spec and more power and torque. That suggests the lighter RS would likely need to pull ~20% more Gs to generate identical loads on the actuator, and the 918 is making decent numbers already. Thus it seems if slicks would overload the actuator it wouldn't be by much. Meanwhile the peak stresses the system need to cope with come from things like bumps, curbs and potholes- much higher stress peaks than simple cornering loads.

GrantG

I forgot that the 918 uses it too - good point. What do you think about the weight argument then (including option for Li battery without RWS)?

Petevb

I think Porsche is about four years behind the times with their current Li battery technology. You'll shortly be able to buy a safe aftermarket ~6 pound Lithium solution including circuitry for over and under-voltage protection, thermal shutdown, etc that could handle the load for $400 to $500. They can power the entire 918 up to 100 mph with lithium batteries, but they can't run RWS? That's a long way of saying that I'm expecting a new Li battery from Porsche that doesn't have this limitation, at which point the weight savings don't seem very worthwhile.

A friend of mine had an interesting experience in a 991 Turbo S the other day that we caught on video. Trail braking into an autocross element after turn-in the rear of the Turbo suddenly popped out of line unexpectedly as he decelerated, and required quick hands to catch. We're quite suspicious that it happened as the car crossed the speed at which the RWS kicks in, though we'll need to re-mount the camera to watch the rear tires and see if that's really the case. It's perhaps jumping the gun to say this, but it's possible the programming on the RWS needs to get a little more sophisticated in some corner cases- I'm not sure about the on/off nature.

One theory for why they would drop RWS, assuming they do, is that it's tires and slip angle. Larger wheels, fatter tires and radial slicks all tend to run lower slip angles, and build up grip much faster. This means the rear will react much faster even without RWS, so the benefit is reduced.

It also means the "correct" angle of RWS for a street tire would be far to much for a slick, assuming that's allowed. You'd not only feel the angle change but it would be disconcerting. Thus ideally you'd want a switch or system on the RWS to change between street tires and slicks. Or, since it's not as critical anyway, you could just focus on making low slip angle tires and chuck it. Looking at the tires on the RS I could imagine them going that direction.

GrantG

BTW, the new BMW M3/M4 comes standard with Lithium battery and it has a full complement of current drawing accessories...

Zulu Alpha

Im not quite so sure that RWS is the cause for the rear end to kick out as you can see in the vid illustrated below in a 991S the rear end kicked out quite a few times with no RWS. unless you are referring to something completely different...

Zulu Alpha

I was reading a segment on the "Good to Know" app that on the 991/S the reason the say not to use slicks is that there would be a great deal of Gs and oil starvation would occur. I have no clue why they keep using different excuses for not using slicks.

I am no suspension expert, but in my limited knowledge, I wouldn't think RWS be a factor to use slicks due to the rake of the castor being quite upright and forces are not so strong on the actuator. I would think that the greater castor angle on the front wheels would cause more stress on the steering rack (as appose to the actuator on the rear wheels). Not sure, maybe the Elephant guys can provide their valuable feedback on this.

tcsracing1

It is like trying to guess what is in the box under the christmas tree at this point.

GrantG

Right, but the GT3 has a true dry sump with separate oil tank (unlike Carrera S) and it can't run slicks either. I think the RS will be the one 991 that can.

Petevb

Any 911 is going to try and rotate when trail braking into a corner. The issue was the way it let go. My friend's a very good driver, just won the Porsche parade autocross again to prove it, and he's driven most modern Porsches in competition. He clearly felt the car do something "strange", slip-stick, and you could see a big correction. It caught another instructor out and he spun the car in the same location. It wasn't something a 997 GT3, 997T or other cars would be expected to do, so the question was why... The rear wheel steering on the TT should increase rear slip angle when decelerating at 50 mph and then again at 31 mph by 2.8 degrees, significantly more than the GT3. It's possible that in autocross conditions that might have upset the car- clearly something did, but it's difficult to say what so far. All systems off, btw.