Knackered old Porsche with loads of miles - 996 content
Discussion
This is a truly epic thread about a truly epic car, and has been a massive contributing factor to my bothering to sign up to PH.
The level of engineering on this car and your knowledge is staggering (and to be expected given your job I presume) and I salute you for taking the time to post.
The level of engineering on this car and your knowledge is staggering (and to be expected given your job I presume) and I salute you for taking the time to post.
Dammit said:
I like the idea of the wheel being closer to me, how tall are you PPBB?
As Paul says a smidge over 6ft. I have quite long legs though which means I find in order to get the leg position I need to heel and toe comfortably I end up with the seat fairly upright. The new wheel has really helped as I can tip the seat back a little more obviously it's a small thing as I've managed to do a quarter of a million miles with the old wheel and not exactly suffered but it's always nice to tweak the fit a little 
CornedBeef said:
PPBB, finally picked up my red 996 over the weekend! Absolutely over the moon with it and spent the whole weekend driving nowhere in particular.
Mines a 1998, so I know I've got the dual row IMS - do I benefit from the ferrous coated cylinder liners?
Yes you do, although it's the pistons which are ferrous coated rather than the liners. The pistons in all 996 have an anti scuff coating on the skirts. On the early cars this was a ferrous coating which was originally designed to work in Alusil and Lokasil bores, due to the nasty chemical shiz involved with getting this on the skirts and the general cost down on the later 996 this was changed to a plastic coating - which doesn't survive any where near as well and arguably whilst not the "cause" of bore scoring in a technical sense is part of the reason why later engines die of bore scoring. My 3.4 had got hot a lot of times, been launched hard after sitting and generally abused (i.e. I did all the things you aren't supposed to do) and yet had absolutely no scoring at 500K KMs. Mines a 1998, so I know I've got the dual row IMS - do I benefit from the ferrous coated cylinder liners?
Enjoy the new purchase. They really are a great thing!
Spitfires said:
This is a truly epic thread about a truly epic car, and has been a massive contributing factor to my bothering to sign up to PH.
The level of engineering on this car and your knowledge is staggering (and to be expected given your job I presume) and I salute you for taking the time to post.
Thank you - I never really gave the car a second thought as it has developed over quite a lot of time to the point it is at today. When something wore out we just made a better "thing" and a lot of the big things are just a by product of what I have been doing with it. It was only when several people told me I really should share it that it twigged it probably was quite a cool thing The level of engineering on this car and your knowledge is staggering (and to be expected given your job I presume) and I salute you for taking the time to post.
I'm amazed by the response it has got and really enjoy sharing bits about it. It really is a pleasure
Sa Calobra said:
What's the total mileage tally now?
12,700...... on the new motor - which isn't bad since the end of April but I'm not using it enough this year to be honest, it's managed a couple of two thousand mile weekends though, can't have it getting lazy! 320K something in total now but I'm not going to make it past 350K before the year is out I don't think.poppopbangbang said:
Yes you do, although it's the pistons which are ferrous coated rather than the liners. The pistons in all 996 have an anti scuff coating on the skirts. On the early cars this was a ferrous coating which was originally designed to work in Alusil and Lokasil bores, due to the nasty chemical shiz involved with getting this on the skirts and the general cost down on the later 996 this was changed to a plastic coating - which doesn't survive any where near as well and arguably whilst not the "cause" of bore scoring in a technical sense is part of the reason why later engines die of bore scoring. My 3.4 had got hot a lot of times, been launched hard after sitting and generally abused (i.e. I did all the things you aren't supposed to do) and yet had absolutely no scoring at 500K KMs.
Enjoy the new purchase. They really are a great thing!
Many thanks for the information mate, hopefully mine treats me as well as yours has! I've still got a massive grin on my face everyday.Enjoy the new purchase. They really are a great thing!
Little picture from the weekend -
What rate ARBs are you using please? I picked up some H&R 26/23mm ones for half price and I'm a bit concerned they are going to be too stiff. I won't fit them until I have upgraded the rest of the suspension.
I also bought my 996 based in part on this thread and Richard's Project Leichtbau over on 911uk.
I also bought my 996 based in part on this thread and Richard's Project Leichtbau over on 911uk.
nsa said:
What rate ARBs are you using please? I picked up some H&R 26/23mm ones for half price and I'm a bit concerned they are going to be too stiff. I won't fit them until I have upgraded the rest of the suspension.
I also bought my 996 based in part on this thread and Richard's Project Leichtbau over on 911uk.
Mine are 25/24mm which I think are about right for my car but my dampers have much firmer compression damping and a higher spring rate than a standard car so you would run a thicker bar on a softer damper/spring combination to get the same effect. I'd be tempted to give them a try to be honest, I suspect they'll work pretty well, especially if yours is on standard rather than sports/M030 suspension. I also bought my 996 based in part on this thread and Richard's Project Leichtbau over on 911uk.
As I mentioned above the car is due wheel bearings so it's apart at the moment, the wheel bearing has failed in a fairly normal way but not at a particularly high mileage:
As you can see it has lost it's grease due to a failed seal and as a result got very hot, you can see the bluing from the heat in some areas. The other side is fine so on the new uprights I have fitted the same spec of bearing as these and I will see if I have another failure, hopefully it is just a one off!
The new uprights are now built up ready to go on, I have carbon wrapped the outer face of the steering arm and outer face of the damper arm on these as both areas I have experienced some cracking on. The 996 uprights are hollow cast aluminum which is great for weight but they do seem prone to cracking from the top of the caliper boss across the damper arm. This may be just because on my car they experience much more load as the suspension is much stiffer and the angle the damper runs at a little more extreme than standard as my top mounts move the pickup point. To help prevent this I took a hint from Renault and their 2009 gearbox which was a thin wall Ti casting with carbon wrap on the high load areas (between the rocker posts etc.) Carbon wrapping boosts the stiffness of a thin wall casting significantly and as such reduces flex which can cause cracking, the effect of carbon wrapping in terms of stiffness increase is far more than just the stiffness of the thin layer of carbon itself, because of how it is bonded for the casting to flex it must pull apart the many hundreds if not thousands of bonds in the carbon to do so. It's a quick and easy fix for this sort of thing as well as a viable repair for small cracking/fatigue failures in castings as the crack can be stop drilled etiher end then over wrapped with carbon.
It's nothing fancy on my uprights, just a wet lay of four layers of 2/2 twill, the uprights surface is keyed using an abrasive wheel in opposing directions to provide a well keyed surface as this is key to providing useful structural reinforcement. Here's one curing:
Then roughly dressed:
It doesn't need to be pretty as it'll never really be seen.
Both uprights built up ready to go back on:
I've upgraded the original caliper mounts to use a Ti stud as the caliper fixing rather than a cap head as the cap heads corrode in situ making them a pain to remove and meaning the brackets are only really two or three use before the threads fail on removal of the mounting bolt. As an M12 K-Nut is the same OD as an M12 cap head the calipers require no modification to work with this setup. In hindsight the design of these is a bit of a cock up as it would have been better to make the bracket deeper at the ends where the caliper mounting bolt holes are located so the threaded hole was blind rather than open which in turn would have stopped road debris etc. getting to the rear of the bolt and causing it to corrode..... although I suppose solving it with Titanium is more flash than simply making them from a bigger billet and a bit heavier
This saves about 5 grams over a cap head
Also fitted new wheel speed sensors:
As life is too short to try to salvage them out of the old uprights to reuse
I'm going to do front drive shaft service whilst it's apart and fit a new set of track rod ends as whilst neither are due for a while I don't want to take it apart in another 15K miles to do them so they can get an early service and the front should be good for another 50K miles
As you can see it has lost it's grease due to a failed seal and as a result got very hot, you can see the bluing from the heat in some areas. The other side is fine so on the new uprights I have fitted the same spec of bearing as these and I will see if I have another failure, hopefully it is just a one off!
The new uprights are now built up ready to go on, I have carbon wrapped the outer face of the steering arm and outer face of the damper arm on these as both areas I have experienced some cracking on. The 996 uprights are hollow cast aluminum which is great for weight but they do seem prone to cracking from the top of the caliper boss across the damper arm. This may be just because on my car they experience much more load as the suspension is much stiffer and the angle the damper runs at a little more extreme than standard as my top mounts move the pickup point. To help prevent this I took a hint from Renault and their 2009 gearbox which was a thin wall Ti casting with carbon wrap on the high load areas (between the rocker posts etc.) Carbon wrapping boosts the stiffness of a thin wall casting significantly and as such reduces flex which can cause cracking, the effect of carbon wrapping in terms of stiffness increase is far more than just the stiffness of the thin layer of carbon itself, because of how it is bonded for the casting to flex it must pull apart the many hundreds if not thousands of bonds in the carbon to do so. It's a quick and easy fix for this sort of thing as well as a viable repair for small cracking/fatigue failures in castings as the crack can be stop drilled etiher end then over wrapped with carbon.
It's nothing fancy on my uprights, just a wet lay of four layers of 2/2 twill, the uprights surface is keyed using an abrasive wheel in opposing directions to provide a well keyed surface as this is key to providing useful structural reinforcement. Here's one curing:
Then roughly dressed:
It doesn't need to be pretty as it'll never really be seen.
Both uprights built up ready to go back on:
I've upgraded the original caliper mounts to use a Ti stud as the caliper fixing rather than a cap head as the cap heads corrode in situ making them a pain to remove and meaning the brackets are only really two or three use before the threads fail on removal of the mounting bolt. As an M12 K-Nut is the same OD as an M12 cap head the calipers require no modification to work with this setup. In hindsight the design of these is a bit of a cock up as it would have been better to make the bracket deeper at the ends where the caliper mounting bolt holes are located so the threaded hole was blind rather than open which in turn would have stopped road debris etc. getting to the rear of the bolt and causing it to corrode..... although I suppose solving it with Titanium is more flash than simply making them from a bigger billet and a bit heavier
This saves about 5 grams over a cap head
Also fitted new wheel speed sensors:
As life is too short to try to salvage them out of the old uprights to reuse
I'm going to do front drive shaft service whilst it's apart and fit a new set of track rod ends as whilst neither are due for a while I don't want to take it apart in another 15K miles to do them so they can get an early service and the front should be good for another 50K miles
I've had a productive morning solving an ongoing problem with the car. The rear undertray will not stay put at sustained high speed, it always finds some way to make a bid for freedom, either by cracking allowing it to drop into the airflow under the car enough to shred it or by pushing the plastic nuts off. So I've made a bit of a motorsport bodge to fix it, I've carbon fibre'd it;
It's not a pretty piece but then as it's under the car it doesn't need to be. To put some stiffness and strength into it which will hopefully stop it getting a flap on or cracking I've laminated two layers of 2x2 twill onto a new rear undertray. This has increased the stiffness hugely whilst still alowing it the bit of flex required to fit it, it should also completely stop it cracking and it's not really added any significant amount of weight either:
Setting having been cooked off with a hot air gun - circuit style :
Set:
Flapped over to take the high spots off - it's a wet lay onto a component so it is never going to aesthetically pleasing but if it stops it falling off I'll be happy!:
To solve the plastic nuts issue I've cut a proper thread into the studs which the plastic nuts originally fitted onto and drilled out and riv nutted the bracket which hangs off the gearbox mount. This will allow me to nut and bolt the undertray on with M5 K-Nuts and penny washers. In theory it shouldn't be able to get off then regardless but we'll see.
The theory for why it keeps getting off is the car runs a much lower ride height than a standard Carrera along with no front splitter and as such the air speed under the car is higher. The 996 Turbo runs a different rear undertray with some air take ups in it and the 997 extends the undertray back to the rear cross member covering the gearbox entirely - that might be a future mod!
It's not a pretty piece but then as it's under the car it doesn't need to be. To put some stiffness and strength into it which will hopefully stop it getting a flap on or cracking I've laminated two layers of 2x2 twill onto a new rear undertray. This has increased the stiffness hugely whilst still alowing it the bit of flex required to fit it, it should also completely stop it cracking and it's not really added any significant amount of weight either:
Setting having been cooked off with a hot air gun - circuit style
:
Set:
Flapped over to take the high spots off - it's a wet lay onto a component so it is never going to aesthetically pleasing but if it stops it falling off I'll be happy!:
To solve the plastic nuts issue I've cut a proper thread into the studs which the plastic nuts originally fitted onto and drilled out and riv nutted the bracket which hangs off the gearbox mount. This will allow me to nut and bolt the undertray on with M5 K-Nuts and penny washers. In theory it shouldn't be able to get off then regardless but we'll see.
The theory for why it keeps getting off is the car runs a much lower ride height than a standard Carrera along with no front splitter and as such the air speed under the car is higher. The 996 Turbo runs a different rear undertray with some air take ups in it and the 997 extends the undertray back to the rear cross member covering the gearbox entirely - that might be a future mod!
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