So, now that the GT4 specs are finally known....
Poll: So, now that the GT4 specs are finally known....
Total Members Polled: 158
Discussion
HokumPokum said:
I have been told that it is the X51 lump with a restrictive exhaust, but i am not too upset if it isn't. what matters is that the rear axle is double wishbone. Or isn't it?
I have seen no mention of it being X51 anywhere other than in the speculation that was swirling around before hand. As for double wishbone rear suspension. That would certainly be more important than the engine power output and it would be great if the GT4 had that fitted to deal with the weakness in the rear strut set up.
Again though, I am not seeing this coming on the actual car. The Porsche literature states only specialised wheel hubs and additional reinforcements at the rear. It seems like Autocar got a bit confused with that one.
check out the evo website on the GT4......
At the rear it’s almost all-new, again with aluminium wishbones and also height adjustable dampers and a helper spring. The GT4 also has a mechanical limited-slip differential – not an e-diff as on the GT3, but it does have the Torque Vectoring system that brakes an inside wheel to reduce understeer. The Cayman GT4 also does without the rear-wheel steer function of its big brother.
At the rear it’s almost all-new, again with aluminium wishbones and also height adjustable dampers and a helper spring. The GT4 also has a mechanical limited-slip differential – not an e-diff as on the GT3, but it does have the Torque Vectoring system that brakes an inside wheel to reduce understeer. The Cayman GT4 also does without the rear-wheel steer function of its big brother.
PorscheGT4 said:
Slippydiff said:
"Like a mid engined 996 GT3 in terms of feel" ??????? but rest assured, no Cayman R/S, modded or not, will feel anything like a 996 GT3 (in your head or otherwise)
That's a good thing :-p But remind me, what front suspension is it your GT4 will be using ............
I wonder if you'll be able to cope with all that understeer that you claim afflicts every iteration of the GT3
HokumPokum said:
check out the evo website on the GT4......
At the rear it’s almost all-new, again with aluminium wishbones and also height adjustable dampers and a helper spring. The GT4 also has a mechanical limited-slip differential – not an e-diff as on the GT3, but it does have the Torque Vectoring system that brakes an inside wheel to reduce understeer. The Cayman GT4 also does without the rear-wheel steer function of its big brother.
I dont know what point you are making with that quote? It says nothing about double wishbones there either, instead restating what AP said in his interview. The GT4 is still running a lower control arm and strut package at the rear just as the Caymans always have done by the sounds of it, by the info in the literature thats been released and from looking at the rather low res cut away drawing that in the wild.At the rear it’s almost all-new, again with aluminium wishbones and also height adjustable dampers and a helper spring. The GT4 also has a mechanical limited-slip differential – not an e-diff as on the GT3, but it does have the Torque Vectoring system that brakes an inside wheel to reduce understeer. The Cayman GT4 also does without the rear-wheel steer function of its big brother.
BTW, the mechanical LSD is the 20 something % lock up (accel and decel) zero preload diff thats in the Cayman already. At least having this in the gearbox opens an option to install a better unit from Guard etc if owners are considering getting serious with the car once delivered.
fioran0 said:
I dont know what point you are making with that quote? It says nothing about double wishbones there either, instead restating what AP said in his interview. The GT4 is still running a lower control arm and strut package at the rear just as the Caymans always have done by the sounds of it, by the info in the literature thats been released and from looking at the rather low res cut away drawing that in the wild.
I'm not sure why some are keen to see double wishbones/multilink at the rear. While accepting that double wishbones do give the designer considerably more freedom - is there actually any real advantage on the Cayman? The criticism in many quarters is a relative lack of front grip. Porsche's answer is to lose rear grip by increasing rear roll stiffness (strictly speaking it causes a transfer of grip from rear to front) with SS and Torque Vectoring with PTV (standard on GT4). So, unless you can increase front grip significantly any increase in rear grip would be counterproductive.The rear strut design negatively impacts the ability to get power down, particularly on corner exit.
It also suffers from loss of negative camber in response to suspension travel, particularly as ride height is reduced though this is not isolated purely to the rear.
I am curious to see if the lower control arm shape has been changed to something similar to that now used on the 991 Carrera. This resembles an actual wishbone shape, employing a horizontal attachment point at the wheel carrier rather than the previous coffin arm shape with the vertical attachment point at the wheel carrier.
The 991 GT3 uses a straight control arm at the rear that also uses a horizontal connection point at the wheel carrier (instead of the previous vertical one) but this arm is length adjustable where the 991 Carrera is not.
The current Caymans (981) still use the coffin style arm with vertical attachment to the wheel carrier.
It also suffers from loss of negative camber in response to suspension travel, particularly as ride height is reduced though this is not isolated purely to the rear.
I am curious to see if the lower control arm shape has been changed to something similar to that now used on the 991 Carrera. This resembles an actual wishbone shape, employing a horizontal attachment point at the wheel carrier rather than the previous coffin arm shape with the vertical attachment point at the wheel carrier.
The 991 GT3 uses a straight control arm at the rear that also uses a horizontal connection point at the wheel carrier (instead of the previous vertical one) but this arm is length adjustable where the 991 Carrera is not.
The current Caymans (981) still use the coffin style arm with vertical attachment to the wheel carrier.
Edited by fioran0 on Saturday 7th February 14:14
te???!fioran0 said:
The rear strut design negatively impacts the ability to get power down, particularly on corner exit.
It also suffers from loss of negative camber in response to suspension travel, particularly as ride height is reduced though this is not isolated purely to the rear.
While I appreciate that there certainly could be theoretical traction impact, in reality traction in the dry is very good - Porsche quoted 0-60 times are fully comparable with 911s with similar power to weight - and 911s ought to have a traction advantage by virtue of their engine location. It also suffers from loss of negative camber in response to suspension travel, particularly as ride height is reduced though this is not isolated purely to the rear.
Edited by fioran0 on Saturday 7th February 14:14
Likewise limited negative camber (though I'd be amazed if actual loss of negative camber occurs on a Cayman with the degree of strut inclination it has) - but the bottom line is rear grip mostly exceeds that at the front. So I'm not convinced that a change of design principles at the rear ALONE would yield any great benefit.
Let's face it two of the outstanding handling sports of their era - the Lotus Elan and now the Boxster/Cayman use struts at the rear and out handle and out grip pretty much all of their peers whatever potential theoretical advantages different suspension designs might have.
The problem with the CR is that the negative camber range is very limited.
My impression from AP (Evo vid) -- is that this would no longer be an issue.
Regarding the opening question, I love the Cayman for it's greater agility and smaller size on B roads.
I appreciate that a professional driver can really use the weight transfer of the GT3.
But I appreciate also that Porsche have worked incredibly hard to minimise the effect of this --- for mere mortals
My impression from AP (Evo vid) -- is that this would no longer be an issue.
Regarding the opening question, I love the Cayman for it's greater agility and smaller size on B roads.
I appreciate that a professional driver can really use the weight transfer of the GT3.
But I appreciate also that Porsche have worked incredibly hard to minimise the effect of this --- for mere mortals
ChrisW. said:
The problem with the CR is that the negative camber range is very limited.
My impression from AP (Evo vid) -- is that this would no longer be an issue
From the standard options of the specification sheet I picked up today ....My impression from AP (Evo vid) -- is that this would no longer be an issue
"Adjustable chassis for race track use (toe, camber, anti roll bars)"
Could be very interesting ...
Slippydiff said:
It is for 996 GT3 owners, not so much Cayman owners :-p
But remind me, what front suspension is it your GT4 will be using ............
I wonder if you'll be able to cope with all that understeer that you claim afflicts every iteration of the GT3
well as the only way to get a 911 to turn in was fit rear wheel steer system , then yes the Cayman has got a better platform(ie more weight over the front) and now 245 tyres and -2 neg front camber, it's going to turn in like hell.But remind me, what front suspension is it your GT4 will be using ............
I wonder if you'll be able to cope with all that understeer that you claim afflicts every iteration of the GT3
ChrisW. said:
The problem with the CR is that the negative camber range is very limited.
My impression from AP (Evo vid) -- is that this would no longer be an issue
From the standard options of the specification sheet I picked up today ....My impression from AP (Evo vid) -- is that this would no longer be an issue
"Adjustable chassis for race track use (toe, camber, anti roll bars)"
Could be very interesting ...
bcr5784 said:
While I appreciate that there certainly could be theoretical traction impact, in reality traction in the dry is very good - Porsche quoted 0-60 times are fully comparable with 911s with similar power to weight - and 911s ought to have a traction advantage by virtue of their engine location.
Likewise limited negative camber (though I'd be amazed if actual loss of negative camber occurs on a Cayman with the degree of strut inclination it has) - but the bottom line is rear grip mostly exceeds that at the front. So I'm not convinced that a change of design principles at the rear ALONE would yield any great benefit.
Let's face it two of the outstanding handling sports of their era - the Lotus Elan and now the Boxster/Cayman use struts at the rear and out handle and out grip pretty much all of their peers whatever potential theoretical advantages different suspension designs might have.
back to front in terms of reply...Likewise limited negative camber (though I'd be amazed if actual loss of negative camber occurs on a Cayman with the degree of strut inclination it has) - but the bottom line is rear grip mostly exceeds that at the front. So I'm not convinced that a change of design principles at the rear ALONE would yield any great benefit.
Let's face it two of the outstanding handling sports of their era - the Lotus Elan and now the Boxster/Cayman use struts at the rear and out handle and out grip pretty much all of their peers whatever potential theoretical advantages different suspension designs might have.
All that needs to happen for the car to start losing negative camber is for the lower arm to go past the horizontal. Its the same at the front of the car, just as it is on the front of the 911. Start lowering ride height and the arm can easily get to this point under static conditions alone.
Its a problem on the front of the 911 race cars that was addressed and somewhat mitigated by the use of updated wheel carriers to force the control arm angle downwards at ride heights where it would become an issue (though the RSR now runs double wishbones up front).
You may like to refer back to my post regarding power down where I mentioned corner exit. Not drag racing.
The strut package is inferior to a multilink or double wishbone set up. I can point you to some books if you want to read up on the reasons why in detail.
Not only does it present an issue with respect to camber (see above) but is equally an issue with respect to wheel control. There is very little wheel control with the strut setup - especially in terms of roll center height changes, anti squat, and often toe changes. These limitations come out on the Cayman as you start to push it on. Power down on corner exit is the obvious place it shows but not the only one. There is an obvious lack of consistency in terms of grip and handling from the back end of the Cayman anyways but it really presents when you try to put power down. A better (read less cheap) design would mitigate much of these issues.
Note, the cayman will always be able to apply power less or later in this corner exit situation than a 911 simply due to engine location trade off. I have plenty of experience and seat time in mid engined platforms far superior to the Cayman, each requires quite different things from a driver, however the above comments are over and above this.
Its unfortunate that Porsche don't appear to have addressed this much in the GT4. Though I am still hoping that the wheel carrier will carry some change to address the camber issue at least.
Your out handle and out grip comment is such an odd one that I am going to ignore it completely.
Edited by fioran0 on Saturday 7th February 19:22
fioran0 said:
back to front in terms of reply...
All that needs to happen for the car to start losing negative camber is for the lower arm to go past the horizontal. Its the same at the front of the car, just as it is on the front of the 911. Start lowering ride height and the arm can easily get to this point under static conditions alone.
Its a problem on the front of the 911 race cars that was addressed somewhat mitigated by the use of updated wheel carriers to force the control arm angle downwards at ride heights where it would become an issue (though the RSR now runs double wishbones up front now).
You may like to refer back to my post regarding power down where I mentioned corner exit. Not drag racing.
The strut package is inferior to a multilink or double wishbone set up. I can point you to some books if you want to read up on the reasons why in detail. Not only does it present an issue with respect to camber (see above) but is equally an issue with respect to wheel control. There is very little wheel control with the strut setup - especially in terms of roll center height changes anti squat and often toe changes. These limitations come out on the Cayman as you start to push it on. Power down on corner exit is the obvious place it shows. This is where the maximum force is on the rear wheel. There an obvious lack of consistency in terms of grip and handling from the back end anyways but it really presents when you try to put power down. A better (read less cheap) design would mitigate much of these issues.
Note, the cayman will always be able to apply power less or later in this corner exit situation than a 911 simply due to engine location trade off however the above is over and above this.
Its unfortunate that Porsche don't appear to have addressed this much in the GT4. Though I am still hoping that the wheel carrier will carry some change to address the camber issue at least.
Your our handle and out grip comment is such an odd one that I am going to ignore it completely.
I've read and (mostly) understood Milliken and Milliken (and lots of other stuff) so I do know much of the theory. Just seems that in practise, and for road cars at least, development triumphs over basic theory. Otherwise the 911 would be utter rubbish - and I don't think even its detractors would say that. (I could also say the same about a live axled Caterham, but for very different reasons)All that needs to happen for the car to start losing negative camber is for the lower arm to go past the horizontal. Its the same at the front of the car, just as it is on the front of the 911. Start lowering ride height and the arm can easily get to this point under static conditions alone.
Its a problem on the front of the 911 race cars that was addressed somewhat mitigated by the use of updated wheel carriers to force the control arm angle downwards at ride heights where it would become an issue (though the RSR now runs double wishbones up front now).
You may like to refer back to my post regarding power down where I mentioned corner exit. Not drag racing.
The strut package is inferior to a multilink or double wishbone set up. I can point you to some books if you want to read up on the reasons why in detail. Not only does it present an issue with respect to camber (see above) but is equally an issue with respect to wheel control. There is very little wheel control with the strut setup - especially in terms of roll center height changes anti squat and often toe changes. These limitations come out on the Cayman as you start to push it on. Power down on corner exit is the obvious place it shows. This is where the maximum force is on the rear wheel. There an obvious lack of consistency in terms of grip and handling from the back end anyways but it really presents when you try to put power down. A better (read less cheap) design would mitigate much of these issues.
Note, the cayman will always be able to apply power less or later in this corner exit situation than a 911 simply due to engine location trade off however the above is over and above this.
Its unfortunate that Porsche don't appear to have addressed this much in the GT4. Though I am still hoping that the wheel carrier will carry some change to address the camber issue at least.
Your our handle and out grip comment is such an odd one that I am going to ignore it completely.
But re your point about loss of negative camber. Loss of negative camber only occurs when the lower arm is at an angle greater than 90 degrees from the strut - not the horizontal. Since the strut is inclined quite a bit it's unlikely to occur. See http://www.racingaspirations.com/apps/macpherson-g... and drag the wheel up and you will see what I mean.
And while at very high power outputs traction may be an issue I don't really think it's a big one for a road/track day car with the Caymans output and an LSD.
Re out handle and out grip I'm not sure what betters a Cayman now or an Elan then which isn't (wasn't) very compromised for the road or in a completely different price bracket.
Putting bigger engines in the cheaper platforms is car maker 101 golf gt3, BMW 330i etc and more and more m3 type overhauls
Porsche has been different in this regard as they have considered themselves to be more performance orientated the typical 520d driver will not give a hoot that the 335d is much quicker. The 911 c2 buyer however, to this point, has been assumed by porsche to care quite a bit if it is much slower than a cayman.
This path porsche is taking is natural, they have been able to get away with unfortunately as their cars are so far ahead of everyone else people will still by cars which are deliberately being held back. But as they become more and more a mainstream car maker now with 2 suvs and an estate they can push the boat out on the Cayman and a gt edition is a perfect way to experiment.
Dare I say but can see them making future 911s more and more as luxury grand tourers and the Cayman will be the fun sports car with no restrictions to keep it in the game with the new v potent hot hatches
Porsche has been different in this regard as they have considered themselves to be more performance orientated the typical 520d driver will not give a hoot that the 335d is much quicker. The 911 c2 buyer however, to this point, has been assumed by porsche to care quite a bit if it is much slower than a cayman.
This path porsche is taking is natural, they have been able to get away with unfortunately as their cars are so far ahead of everyone else people will still by cars which are deliberately being held back. But as they become more and more a mainstream car maker now with 2 suvs and an estate they can push the boat out on the Cayman and a gt edition is a perfect way to experiment.
Dare I say but can see them making future 911s more and more as luxury grand tourers and the Cayman will be the fun sports car with no restrictions to keep it in the game with the new v potent hot hatches
Getting back to the OP's question - which was an interesting one.
Whilst the GT4 does not possess the exotic hardware and motorsport DNA of the 997GT3, it definitely appears to be a genuine attempt by Porsche to produce a car that is more driver focussed than recent offerings.
Would I buy one over a 997 GT3? As I said before, no I wouldnt, but I am hopeful that the GT4 proves to be the car that 'Tango'd' Porsche into remembering what they are slowly but surely forgetting - that for a sports car to be good, the driver should be at the very centre of the driving experience. For that reason, I genuinely hope that the GT4 is a very good car, that owners absolutely love it and that wins the hearts and minds of plaudits. Maybe then, some of the spotty 'lifestyle'' twerps sitting on design committees at Porsche HQ might be replaced by Chaps who understand how wonderful it feels to be at the very centre of the driving experience.
Fearing the worst, I cancelled my order for a GT4 and instead purchased a 964 which I intend to modify to suit my needs. In some ways, I'm hoping that time will prove that decision to be a big mistake.
Whilst the GT4 does not possess the exotic hardware and motorsport DNA of the 997GT3, it definitely appears to be a genuine attempt by Porsche to produce a car that is more driver focussed than recent offerings.
Would I buy one over a 997 GT3? As I said before, no I wouldnt, but I am hopeful that the GT4 proves to be the car that 'Tango'd' Porsche into remembering what they are slowly but surely forgetting - that for a sports car to be good, the driver should be at the very centre of the driving experience. For that reason, I genuinely hope that the GT4 is a very good car, that owners absolutely love it and that wins the hearts and minds of plaudits. Maybe then, some of the spotty 'lifestyle'' twerps sitting on design committees at Porsche HQ might be replaced by Chaps who understand how wonderful it feels to be at the very centre of the driving experience.
Fearing the worst, I cancelled my order for a GT4 and instead purchased a 964 which I intend to modify to suit my needs. In some ways, I'm hoping that time will prove that decision to be a big mistake.
Steve Rance said:
Fearing the worst, I cancelled my order for a GT4 and instead purchased a 964 which I intend to modify to suit my needs. In some ways, I'm hoping that time will prove that decision to be a big mistake.
You're spot Mr Rance. Its a very modern car the 964 and amazing how capable they are with a few tweaks. Even around a track they are far more fun than any modern machinary. A few pics of the GT4s great grandfather and grandfather to try and tempt you GT4ers to the dark side. I bet they look tiny if stood next to a GT4.
IMIA said:
Thread hijack
I bet they look tiny if stood next to a GT4.
I have to say that my consistent criticism of each new model of Porsche (and most other cars too) is their ever increasing girth. I parked my Cayman next to a 911 of even older vintage the other day and the Cayman looked VAST. Regrettably roads don't get any wider and so there are quite a lot of roads that are fun in a Caterham, but, for width reasons, aren't in a Cayman (which is literally a foot wider) . Not usually such an issue on track though.I bet they look tiny if stood next to a GT4.
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