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terra
Newbie


Joined: 21 Feb 2017
Posts: 3



PostPosted: Sun May 07, 2017 12:48 pm    Post subject: Reply with quote

Ok thanks for that ELA.
The question actually came about due to some calcs I already did on your mods.

I'd read that the 911 'front end bobbing' was noticeably less on a 996 C4 compared to a C2. This was attributed to the extra load of the awd set-up aft of the rear axle. It raised questions if your mods could achieve a similar shift and improvement in stability...

Doing a (very) rough back of envelope calc on the major items you modified/eliminated indicated about 2.5% shift forward (using 'before weight' of 1380kg and the same 39:61 you mentioned).

But in calculating the moments I could only guess-timate the distances of the items to rear axle centre, so the shift could be more/less.

It will be interesting to see real world results. Good luck with the rest of it.
 
  
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ELA
Suzuka


Joined: 30 Aug 2011
Posts: 1059
Location: Nurburgring Doorstep


PostPosted: Mon May 08, 2017 8:59 am    Post subject: Reply with quote

Mirrors finally ready and have been shipped out today Very Happy







Terra I have nothing scientific to verify the CofG or Weight distribution just yet but I did some high speed testing last week (multiple 150mph runs upto 181mph) and the front end, upto say 165 seemed quite stable. from 165-180 it was light but how this compares to stock I can't remember and also at this speed on public roads (legally over here), the concentration levels are perhaps skewing your ability to focus as intently as you would like into just this one area.
_________________
1275kg 997GT3RS with:
Kessels 458bhp 3.8l & vgs-MS ECU
Akrapovic titanium exhaust
Cup 9:35 diff, Airbox, PAS, front lip
BBS 19's
H&R Suspension
Carbon wings/doors/bonnet/door cards
 
  
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Martin996RSR
Trainee


Joined: 08 Dec 2016
Posts: 81



PostPosted: Mon May 08, 2017 9:12 am    Post subject: Reply with quote

I've had my GT3 body kitted 996.1 up to 154mph and the stability at that speed was good. I'm totally convinced the stability was due to the wing. I really could feel it working above about 120mph.

Any more rake than stock should help stability because of the relatively flat floor the car has. (I'm not talking any serious downforce here, just a reduction in turbulence under the car that would cause lift).

A proper splitter would make a big difference at high speed but I guess it would be outside the aesthetic that is trying to be acheived on this car. I don't have the little front lip on mine that goes under the bumper chin as I know they get smashed off all the time, however, perhaps one of these might be subtle enough and settle the nose down at autobahn speeds?
 
  
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EGTE
Nürburgring


Joined: 06 Jul 2015
Posts: 422



PostPosted: Mon May 08, 2017 2:40 pm    Post subject: Reply with quote

Nose-down rake also improves the angle of attack of the whole car and the wings, as well as because of the floor pan.
 
  
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stevemfr
Newbie


Joined: 07 Oct 2015
Posts: 32



PostPosted: Fri May 12, 2017 1:37 pm    Post subject: Reply with quote

Hi ELA,
Love your thread and your project! And I was happy to see the GT3 still in the garage in the pics from several weeks ago. I can imagine that the wife is unhappy. I am up to 10 cars total ( Surprised ) which makes my wife occasionally...

ELA wrote:
...I looked into buying some corner weight scales the other day but just can't justify the cost just yet...

I do my own alignments using the smart strings method, and I have a hard time justifying corner scales as well. Just in case you did not see it and are interested, there is one seller in the US offering scales at $690 on Amazon and ebay, but there are also numerous people using less expensive scales and beams to distribute the load. Even Jack Olson couldn't jsutify the cost and is using bathroom scales Laughing

I do not have enough time to play with this in the coming months, but I hope to be able to try a 2:1 beam similar in construction to those below and these scales next winter (insert "ebay.de" if the link doesn't work).
https://rennlist.com/forums/993-forum/638137-diy-corner-balancing-scales.html
 
  
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ELA
Suzuka


Joined: 30 Aug 2011
Posts: 1059
Location: Nurburgring Doorstep


PostPosted: Sun May 21, 2017 7:46 pm    Post subject: Reply with quote

Sorry guys, been flat out and to be honest, I underestimated just how much time all the set-up and testing phases would take. I must have removed and adjusted the suspension 6 times now since the last Geo. Also had a few unexpected issues crop up that are causing a headache right now:

- Gearbox rebuild.
- Possible engine drop to sort out a noise that so far I have been unable to diagnose.
- Many others...

stevemfr wrote:
Hi ELA,
Love your thread and your project! And I was happy to see the GT3 still in the garage in the pics from several weeks ago. I can imagine that the wife is unhappy. I am up to 10 cars total ( Surprised ) which makes my wife occasionally...

ELA wrote:
...I looked into buying some corner weight scales the other day but just can't justify the cost just yet...

I do my own alignments using the smart strings method, and I have a hard time justifying corner scales as well. Just in case you did not see it and are interested, there is one seller in the US offering scales at $690 on Amazon and ebay, but there are also numerous people using less expensive scales and beams to distribute the load. Even Jack Olson couldn't jsutify the cost and is using bathroom scales Laughing

I do not have enough time to play with this in the coming months, but I hope to be able to try a 2:1 beam similar in construction to those below and these scales next winter (insert "ebay.de" if the link doesn't work).
https://rennlist.com/forums/993-forum/638137-diy-corner-balancing-scales.html


Many thanks for this post Steve Thumb
I do still have the 997 but 10 cars is another level Grin that'll take up some serious space.
I did look into those vet or industrial scales but they only went up to 300kg; no problem for the front axle but 400kg would be needed for the rear for a 911. With all the issues I have on the go right now though, I will have to come back to the scales another time.
_________________
1275kg 997GT3RS with:
Kessels 458bhp 3.8l & vgs-MS ECU
Akrapovic titanium exhaust
Cup 9:35 diff, Airbox, PAS, front lip
BBS 19's
H&R Suspension
Carbon wings/doors/bonnet/door cards
 
  
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stevemfr
Newbie


Joined: 07 Oct 2015
Posts: 32



PostPosted: Mon May 22, 2017 10:49 am    Post subject: Reply with quote

ELA wrote:
I did look into those vet or industrial scales but they only went up to 300kg; no problem for the front axle but 400kg would be needed for the rear for a 911. With all the issues I have on the go right now though, I will have to come back to the scales another time.


That's what the 2:1 beams are for: you make 600kg scales out of the 300kg scales. If I get to this sooner than you, I'll let you know.

It does sound like you have your hands full - sorry to hear. Gearbox repair is actually one of the few areas where I think DIY is not always the best solution (assuming the inclination is given). There are many items in a rebuild where experience plays a role. It starts with inspecting the components on teardown so that you don't reuse worn components and goes to being able to reassemble without having all the expensive factory tools. That said, with enough preparation and diligence... It's not rocket science. Unfortunately almost all DIY rebuild threads I've seen are GT3/turbo transmissions.

Edit: I bookmarked this a while back and forgot about it.

https://www.dropbox.com/s/0yie0ew0cb774fe/2002BoxsterSTransmissionRebuildDecember2011Revision3.pdf

Somewhat superficial, but still...
 
  
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ELA
Suzuka


Joined: 30 Aug 2011
Posts: 1059
Location: Nurburgring Doorstep


PostPosted: Mon May 29, 2017 8:38 pm    Post subject: Reply with quote

^Many thanks once again Steve Wink

About time for an update. I almost had to cancel the 'Simple Porsche' trip due to a gearbox issue, but I have just this minute fitted it so will be making my way over to the UK tomorrow. Whilst the gearbox was being completely overhauled I also decided to try a custom made trick diff with dual ramp angles (40/60) and a fairly light pre-load of 25lbft. Hopefully it will still retain some road manners. A few pics during the rebuild and re-fit:









_________________
1275kg 997GT3RS with:
Kessels 458bhp 3.8l & vgs-MS ECU
Akrapovic titanium exhaust
Cup 9:35 diff, Airbox, PAS, front lip
BBS 19's
H&R Suspension
Carbon wings/doors/bonnet/door cards
 
  
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New997buyer
Dijon


Joined: 17 Oct 2010
Posts: 7739



PostPosted: Mon May 29, 2017 9:19 pm    Post subject: Reply with quote

As always worship
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"Learning never exhausts the mind"
Leonardo da Vinci
 
  
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Jamesx19
Monza


Joined: 10 Jul 2015
Posts: 162
Location: Brighton


PostPosted: Tue May 30, 2017 8:15 pm    Post subject: Reply with quote

Nice one ELA.

As usual, no messing about with half measures!

Is the diff a GT Guard item or something sourced in Das Vaterland? Judging by the signs in the backround of the pics, the gearbox was built locally as well?

Look forward to your feedback of the on road characteristics. I'm thinking of a GT Guard rebuild kit for my standard GKN LSD, ($1800 plus postage and taxes) or go with the Wavetrac Torque sensing type. The advantage of the proper LSD is that it works during braking. But is that what you need or want for road use......??

Very interested to hear your thoughts,
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Martin996RSR
Trainee


Joined: 08 Dec 2016
Posts: 81



PostPosted: Wed May 31, 2017 8:12 am    Post subject: Reply with quote

I have a 1998 C2 manual with the 220 diff. You can feel it working even on the road under acceleration, but on the track it was obvious it had nothing left to give under deceleration. The back end was very loose under braking and clearly a fresh clutch pack in the diff would have made a difference. I'm not so sure I would get to appreciate it on the road though, I simply don't drive that close to the edge when not on a track.

When I put my spare gearbox in I will be swapping the LSD over and I'll be getting it freshened up as well, as I'm keen to see if I can make use of the stability it provides under braking.
 
  
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demon
Monza


Joined: 19 Apr 2011
Posts: 161



PostPosted: Wed May 31, 2017 10:03 am    Post subject: Reply with quote

I'm assuming the weight saving target escalated as much as it did to compensate for the size of your balls....?!!! Surprised
- impressive (if as crazy) as ever - easily my "go to" thread on the forum whenever I sign in after a few days.......
 
  
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ELA
Suzuka


Joined: 30 Aug 2011
Posts: 1059
Location: Nurburgring Doorstep


PostPosted: Fri Jun 09, 2017 2:09 pm    Post subject: Reply with quote

Sorry guys, it's been crazy the last few weeks. I was under a lot of pressure to get the box overhauled with the new diff going in at the same time, it is also quite a tricky process to set the diff up. I then needed to bed in and test on the way to the UK as I had no other chance. It wasn't quite plain sailing and I had no room for manoeuvre. In the UK the car underwent it's first independent test with a motoring journalist and even the Editor of the magazine was in attendance, to get a feel for the project. I believe it will be in the next issue of the magazine so I look forward to hearing their thoughts.


Jamesx19 wrote:
Nice one ELA.

As usual, no messing about with half measures!

Is the diff a GT Guard item or something sourced in Das Vaterland? Judging by the signs in the backround of the pics, the gearbox was built locally as well?

Look forward to your feedback of the on road characteristics. I'm thinking of a GT Guard rebuild kit for my standard GKN LSD, ($1800 plus postage and taxes) or go with the Wavetrac Torque sensing type. The advantage of the proper LSD is that it works during braking. But is that what you need or want for road use......??

Very interested to hear your thoughts,


The diff is basically a custom plated type diff which was developed in conjunction with a Motorsport company in Germany.
The Auto Torque Biasing diffs are a bit of a compromise and not something you would ever see fitted in a competitive environment. I decided to go for a full fat diff but went easy on the settings. To my mind this meant I should meet the objectives of Fast road rather than full attack but safe in the knowledge that I have the real McCoy fitted. So 40/60 dual ramp angles were chosen with only a 25lbft pre-load, which after full shake down should settle somewhere in the 20lbft region.
At first I thought there was a serious issue when I fitted it. It was seriously noisy and a very unfamiliar driving experience. It also took much longer than quoted to settle down; around 600miles rather than 60. But it is now far better than when first fitted. There was a little issue with a leak, I think from the L/H diff output flange but I have dropped the car off at the gearbox specialist to look into this yesterday. Still waiting to hear back from them.

First impression (once settled) is it has massively transformed the character of the car; probably more than any other change I have made. It is a serious bit of kit and probably on the edge in terms of what most would want in a out and out road car. I live in area where I have some wonderful driving roads on my door step and this car is for those special times when I want to have the ultimate driving experience, so for me this diff is magical and the slight slow speed/tight turn issue I can live with. The stability under braking and acceleration is phenomenal. Transitions are pretty smooth so long as you drive understanding what the diff is designed to do. I will however give a better review of the diff once I get a few more miles under my belt.

demon wrote:
I'm assuming the weight saving target escalated as much as it did to compensate for the size of your balls....?!!! Surprised
- impressive (if as crazy) as ever - easily my "go to" thread on the forum whenever I sign in after a few days.......


Very funny demon Grin
I've not been able to do many updates of late, but at this stage now it is all about the testing/set-up... so no big component changes anymore. I still have the Brakes and Re-map to do but other than that, the TUV Approval process is all that remains. There are however going to be some independent testers trying the car over the coming months (also the one last week in the UK), so hopefully you'll be able to get a better feel about what this car is like from those that know how to write and their opinion will be completely unbiased, which I feel is probably a better way to go about it that me babbling on.

Many thanks for all the other comments and words of encouragement guys Thumb
_________________
1275kg 997GT3RS with:
Kessels 458bhp 3.8l & vgs-MS ECU
Akrapovic titanium exhaust
Cup 9:35 diff, Airbox, PAS, front lip
BBS 19's
H&R Suspension
Carbon wings/doors/bonnet/door cards
 
  
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Martin996RSR
Trainee


Joined: 08 Dec 2016
Posts: 81



PostPosted: Wed Jun 14, 2017 10:37 am    Post subject: Reply with quote

Please do keep the updates coming. You may not think some of it is very interesting, but trust me, we really are hanging on your every post. Perhaps you could do a video of some of the remap process/rolling road, or tell us more about the brake set up and other fine tuning.

Sorry I couldn't get to Beaulieu, like a tit I had left the master switch on in the plane and had to go back on sunday morning and pull the cowlings off and jump start it from a car for a fellow owner. I had been hoping to fly down to Goodwood and see another car mate, then fly back and take the 911 to see you. In the event I achieved neither.

Do you have any plans for another visit to England any time soon?
 
  
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ELA
Suzuka


Joined: 30 Aug 2011
Posts: 1059
Location: Nurburgring Doorstep


PostPosted: Wed Jun 14, 2017 11:41 am    Post subject: Reply with quote

Martin really sorry to hear of the troubles with your A/C and the knock-on effects. I currently have no plans for another trip to the UK just yet, but I see T8 is planning a little Spa trip in September which I may pop along for Wink

I am honored that you have taken an interest in this project and will try my best to keep you up to speed with developments.
So latest news upon return from the UK; I took the car directly back to where the Gearbox had been overhauled with the new custom diff fitted due to a leak. Well they have stripped down the diff again and found a few technical issues which I don't want to discuss on a public forum and aim to sort ASAP. The diff is now being sent to an engineer for analysis and hopefully I'll get a report back early next week. The trouble is the company where the car is, after today will be closed until the last week of June. I have arranged for a serious motoring journalist (read as the best Wink ) to review the car later in June, with the aim of producing a video. I have not informed him yet of this latest development as I am hoping by some miracle to get this problem resolved, like yesterday. I also planned on sorting out a few fine details like noises... but am now stuck with the car a 5 hour train ride away. Disaster to put in mildly Sad

As alluded to above though, I have now had it confirmed by the author that the review/article will be published next months magazine which should be released around 1st July, if I'm not mistaken.

Below are a couple of pics I was sent of the diff this week.





_________________
1275kg 997GT3RS with:
Kessels 458bhp 3.8l & vgs-MS ECU
Akrapovic titanium exhaust
Cup 9:35 diff, Airbox, PAS, front lip
BBS 19's
H&R Suspension
Carbon wings/doors/bonnet/door cards
 
  
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911munKy
Spa-Francorchamps


Joined: 26 Nov 2014
Posts: 281



PostPosted: Wed Jun 14, 2017 11:58 am    Post subject: Reply with quote

Martin996RSR wrote:

Sorry I couldn't get to Beaulieu, like a tit I had left the master switch on in the plane and had to go back on sunday morning and pull the cowlings off and jump start it from a car for a fellow owner. I had been hoping to fly down to Goodwood and see another car mate, then fly back and take the 911 to see you. In the event I achieved neither.



Ha, you weren't the first and won't be the last.
I remember the chief pilot, back in the the day when I was on turbo-props, having to explain to David Bowie why he couldn't fly the band to the next leg of their tour for the same reason, he couldn't jump start it from his car either!
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Last edited by 911munKy on Fri Jun 16, 2017 5:42 pm; edited 1 time in total
 
  
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demon
Monza


Joined: 19 Apr 2011
Posts: 161



PostPosted: Fri Jun 16, 2017 2:48 pm    Post subject: Reply with quote

ELA wrote:
Mirrors finally ready and have been shipped out today Very Happy


Any more details re. these...? (meant to ask before getting side-tracked by gearboxes and diffs)

I started fantasising about RUF RGT mirrors recently as well as staring hard at pictures of 996.1 Cup cars.....
- your mirrors look very much the same vein (although I'm ultimately staying in the body-coloured rather than cleared carbon route)
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