991.2 GT3 Strut tower failure??
05-25-2018, 08:05 PM
#76
Originally Posted by Diablo Dude
B.) If this is the strut tower bracket that you are referring to, I really dont see how this can be very effective.
This has already been fairly well discussed in the GT4 forum.
05-25-2018, 08:20 PM
#77
Rennlist Member
+1 given the nature of the failures (cracking around/below the "shoulder" of the tower), the only way I can see to "reinforce" or avoid this is to either reduce the resulting force applied (bump stop/travel) or strengthen the "walls" (or shoulder) of the mount ... a strut tower brace *might* transfer some of the impulse across the car ... but I doubt it...
05-25-2018, 08:41 PM
#78
Nordschleife Master
It's a design flaw there's no question about it in my mind! It has nothing to do with lowered cars IMO. Will lowering the car further increase the chance of this happening?! I say ABSOLUTELY! But it's not the core problem.
I haven't read everything about these failures,but I remember clearly a few instances where it happened to 100% stock cars driving on the street. It's a design flaw,let's not kid ourselves...
I haven't read everything about these failures,but I remember clearly a few instances where it happened to 100% stock cars driving on the street. It's a design flaw,let's not kid ourselves...
05-25-2018, 08:44 PM
#79
Rennlist Member
It's a design flaw there's no question about it in my mind! It has nothing to do with lowered cars IMO. Will lowering the car further increase the chance of this happening?! I say ABSOLUTELY! But it's not the core problem.
I haven't read everything about these failures,but I remember clearly a few instances where it happened to 100% stock cars driving on the street. It's a design flaw,let's not kid ourselves...
I haven't read everything about these failures,but I remember clearly a few instances where it happened to 100% stock cars driving on the street. It's a design flaw,let's not kid ourselves...
05-25-2018, 09:58 PM
#80
Nordschleife Master
Originally Posted by Larry Cable
if it walks like a duck, and quacks like a duck ... its probably ... a duck!
PAG has also " designed " the finger followers to such low tolerances to make sure no oil gets between them and the camshaft lobes,thus assuring themselves they'll soon be able to adhere to the " amazing " 20K miles oil change interval. They've also designed bursting coolant pipes to make sure even the lazy owners flush their coolant every once in awhile.
The Kool-Aid is strong with this one!
05-26-2018, 01:52 AM
#81
Rennlist Member
There are a lot of 250,000+ mile 911s, 912s, and 914s out there with steel strut towers that are still in great shape after 40-50 years of use on road and track, and many of those cars have unibodies compromised by rust, accident repairs, etc.
While strut tower failure rates seem to be very, very low in 981s/991s, these Porsches are still new relatively new with relatively low miles—and the cost for repair is extraordinary. Then again, I'm not sure there's enough info on contributing factors to draw too many valid conclusions. I do, however, wonder if whatever weight saved or rigidity added was worth it? My guess is no.
Seems like a good solution would be a steel plate designed to bolster the strut tower and spread shock loads—which should be an easy piece to design and manufacture for a suspension company with savvy engineering resources. Something like these:
http://www.bimmerworld.com/Suspensio...lates-E36.html
http://www.bimmerworld.com/Suspensio...ement-Kit.html
While strut tower failure rates seem to be very, very low in 981s/991s, these Porsches are still new relatively new with relatively low miles—and the cost for repair is extraordinary. Then again, I'm not sure there's enough info on contributing factors to draw too many valid conclusions. I do, however, wonder if whatever weight saved or rigidity added was worth it? My guess is no.
Seems like a good solution would be a steel plate designed to bolster the strut tower and spread shock loads—which should be an easy piece to design and manufacture for a suspension company with savvy engineering resources. Something like these:
http://www.bimmerworld.com/Suspensio...lates-E36.html
http://www.bimmerworld.com/Suspensio...ement-Kit.html
05-26-2018, 04:03 AM
#82
Rennlist Member
Thread Starter
05-26-2018, 07:35 PM
#86
The strut towers are part numbers 991 501 477 00 GRV /left
991 501 478 00 GRV /right
@$312.22 ea
991 501 478 00 GRV /right
@$312.22 ea
05-26-2018, 08:07 PM
#87
Rennlist Member
I retweeted - need more people to pile on this issue!
05-26-2018, 08:37 PM
#88
As I understand it based on data from Porsche the 991 chassis is 25% more torsionally rigid than the 997.
I'm not sure many 918's are being pushed to their limits to make that model a valid comparison. There are way more 911's on the road than 918's and they all share the same suspension mount design. So far I've only heard of a handful of failures.
I understand what your saying but adding suspension travel and more elastomer in the suspension train is great to dissipate energy but does not make handling any better. In fact the more energy dissipating elastomers you use the more difficult it is to model and predict suspension behavior. The best way to control the suspension damping and overall performance is to have everything rigid except the shock. Then you can adjust spring rates and shock damping and get the exact suspension behavior you want.
Understandably there is a trade off between weight of the car and strength of the suspension mount points. You could make them infinitely strong and never fail, sure, but that would mean increased weight in places that may not make the car perform very well. All road cars carry some compromise in design. I'm not sure this constitutes a design flaw if cars that are subject to significant force show failure at high stress points.
Any part on a car is susceptible to failure given a force application that pushes its material past the plastic portion of the deformation curve. It seems that a few of these cars have had similar failures. If 25% of the mount points failed I would worry that there is a design flaw. I haven't seen any data that suggests mass failures and many cars are taken to the track and many 991's, not only gt cars, are driven every day and I'm sure hit large potholes and don't have these failures routinely.
I'm not sure many 918's are being pushed to their limits to make that model a valid comparison. There are way more 911's on the road than 918's and they all share the same suspension mount design. So far I've only heard of a handful of failures.
I understand what your saying but adding suspension travel and more elastomer in the suspension train is great to dissipate energy but does not make handling any better. In fact the more energy dissipating elastomers you use the more difficult it is to model and predict suspension behavior. The best way to control the suspension damping and overall performance is to have everything rigid except the shock. Then you can adjust spring rates and shock damping and get the exact suspension behavior you want.
Understandably there is a trade off between weight of the car and strength of the suspension mount points. You could make them infinitely strong and never fail, sure, but that would mean increased weight in places that may not make the car perform very well. All road cars carry some compromise in design. I'm not sure this constitutes a design flaw if cars that are subject to significant force show failure at high stress points.
Any part on a car is susceptible to failure given a force application that pushes its material past the plastic portion of the deformation curve. It seems that a few of these cars have had similar failures. If 25% of the mount points failed I would worry that there is a design flaw. I haven't seen any data that suggests mass failures and many cars are taken to the track and many 991's, not only gt cars, are driven every day and I'm sure hit large potholes and don't have these failures routinely.
^This
01-04-2019, 11:04 PM
#90
Race Car
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This is a misunderstanding. A) the 991 is not significantly stiffer than the 997 or many other vehicles that don’t exhibit the same issue (including the 918, etc). B) there is no need to rely on chassis flex if the suspension package is properly designed. Additional travel with the right elastomer is far more effective at preventing a failure than chassis flex.
Flat cornering and a chassis that doesn’t fail catastrophically are not mutually exclusive. Don’t kid yourself: this is not a necessary compromise, it’s (...another...) a design flaw. If Porsche engineers are worth half their salt the 992 won’t suffer from the issue.
not to mention the 991.2 3L "meh" engine turbo fixes nor the 991.1 GT3 known issues,
thanks god most are garage queen or shopping cars treated better than babies,
but this brings a question, are we the beta tester for 150/200k third suppliers parts bin cars that they don t have neither the time to design and test?? When they show mules in Sweden or any desert claiming for mega german millions miles testing (inflating the perceived value) are they just marketing kidding while sitting in a pub at Stocholm waiting for Christmas shopping? They have good engineers, if instructed and given the resources, so at this price levels 1st have to come the quality then tne mega profits vice-versa you will kill the cow..
Last edited by fxz; 01-05-2019 at 04:00 AM.