Slippydiff
Imola
- Joined
- 22 Nov 2007
- Messages
- 867
Following on from these threads :
http://911uk.com/viewtopic.php?t=134448
http://911uk.com/viewtopic.php?t=122766
This will be the equivalent of 'Marky's 996.2 GT3 thread"... (with a lot less updates, a soupcon less OCD and definitely without the superb images that Mark seems to be able to take whilst in the middle of his car fettling processes)
As previously documented, the ZanziCup's previous long term owner operated on an open cheque book basis when it came to maintaining and upgrading the car. In short, the car wanted for nothing. Regrettably the individuals tasked with upgrading/fettling the car operated on an 'Open wallet surgery" basis ...
Having bought the 997 Cup engine, paid for its installation and its mapping, funds were getting increasingly tight, so to save paying what is frequently £100 an hour labour charges, I elected to rattle some spanners myself (it's always a good way to bond with a car I find)
The car is intrinsically an excellent example, all original panel (except the bumpers, more of which later) but the thick end of a year parked outside Fearnsport in all weathers, from the hottest summer in 43 years and a long, wet, cold, Winter meant pretty much every area was in need of some real TLC.
Exhaust
With the engine installed and mapped, it became clear there was an issue with the very expensive BTB exhaust. Matt at Fearnsport had noted the issue, but didn't make me aware of it until I noticed it whilst test driving the car with Wayne Schofield.
The issue was a heavy metallic knocking/rattle at tickover through to 3000rpm. When I mentioned it to Matt, he said he had noticed it and checked all the joints and it's routing, all were perfect, but beyond that, nothing had been done to rectify the problem.
The more I drove the car, the worse the noise seemed to be getting.
Whilst it was up on a ramp at Fearnsport, I took the opportunity to establish the source of the rattle. Gently punching the manifold, cross pipes and link pipes, showed nothing to be amiss, but doing the same to the silencers (and specifically their end cases) soon revealed the source of the knock/rattle.
At this point I wasn't aware of how the internals of the silencer were formed, but I had a pretty good idea that the small, innocent looking screw in the centre of the end cap had something to do with the issue ... :
Upon the car's return, the exhaust became the first in an ever increasing hit-list of jobs to do.
The lightweight titanium silencer casings are made from two parts, the main body of the silencer with it's end cover welded to it, and a separate end cap (retained by Titanium screws no less) which is removable to enable the silencer to be repacked.
I removed both the silencers and stripped one down. The removable end cap proved tricky to remove, such was the accuracy required when fabricating the two parts to ensure a gas tight seal between them, but after attaching the 2 titanium (what else ?) silencer clamps to the silencer body, I had something to hit with my best rubber mallet whilst I held the end cap/tailpipe assembly to enable me to separate the end cap from the body. Here's what I found (packing already removed) :
As can be seen, the 'U" section :
slides over the two straight perforated sections and these in turn slide into two 'stubs" formed from the inlet tube and the outlet (tailpipe) , thus enabling the perforated section to 'float" and to allow the whole silencer to be stripped for re-packing.
The 'U" bend has a nut welded to it :
which enables it to be attached to the end cap via one small 4mm titanium screw .
My guess is the cams in the Cup engine were setting up massive pressure waves within the silencers that were causing the end cases to resonate, after a while the perforated tubes loosened in their sleeves and proceeded to float excessively, and the more they loosened, the more easily they floated, to the point they started to hammer into the end cases.
I'd already taken the car to Joe Ellis at BTB to show him the issue, and he'd agreed to look into the problem. Removing the exhaust myself meant I didn't have to wait for a space in their 'ramp schedule"
Joe kindly emailed me to tell me what he proposed to do to rectify the issue.
The end case would need some kind of additional bracing to stop it from resonating with the engine's firing pulses, and the 'U" bend needed a more substantial method of attachment to the end cover :
And the end result :
The exhaust is now rattle/knock free.
As a footnote, Joe only charged me for the expensive packing material used to re-pack the silencers. I genuinely appreciate him fixing this problem FOC, bearing in mind the exhaust is now some 8 years old and I'm its third 'owner".
So a big thank you to both Joe and Will at BTB.
http://911uk.com/viewtopic.php?t=134448
http://911uk.com/viewtopic.php?t=122766
This will be the equivalent of 'Marky's 996.2 GT3 thread"... (with a lot less updates, a soupcon less OCD and definitely without the superb images that Mark seems to be able to take whilst in the middle of his car fettling processes)
As previously documented, the ZanziCup's previous long term owner operated on an open cheque book basis when it came to maintaining and upgrading the car. In short, the car wanted for nothing. Regrettably the individuals tasked with upgrading/fettling the car operated on an 'Open wallet surgery" basis ...
Having bought the 997 Cup engine, paid for its installation and its mapping, funds were getting increasingly tight, so to save paying what is frequently £100 an hour labour charges, I elected to rattle some spanners myself (it's always a good way to bond with a car I find)
The car is intrinsically an excellent example, all original panel (except the bumpers, more of which later) but the thick end of a year parked outside Fearnsport in all weathers, from the hottest summer in 43 years and a long, wet, cold, Winter meant pretty much every area was in need of some real TLC.
Exhaust
With the engine installed and mapped, it became clear there was an issue with the very expensive BTB exhaust. Matt at Fearnsport had noted the issue, but didn't make me aware of it until I noticed it whilst test driving the car with Wayne Schofield.
The issue was a heavy metallic knocking/rattle at tickover through to 3000rpm. When I mentioned it to Matt, he said he had noticed it and checked all the joints and it's routing, all were perfect, but beyond that, nothing had been done to rectify the problem.
The more I drove the car, the worse the noise seemed to be getting.
Whilst it was up on a ramp at Fearnsport, I took the opportunity to establish the source of the rattle. Gently punching the manifold, cross pipes and link pipes, showed nothing to be amiss, but doing the same to the silencers (and specifically their end cases) soon revealed the source of the knock/rattle.
At this point I wasn't aware of how the internals of the silencer were formed, but I had a pretty good idea that the small, innocent looking screw in the centre of the end cap had something to do with the issue ... :
Upon the car's return, the exhaust became the first in an ever increasing hit-list of jobs to do.
The lightweight titanium silencer casings are made from two parts, the main body of the silencer with it's end cover welded to it, and a separate end cap (retained by Titanium screws no less) which is removable to enable the silencer to be repacked.
I removed both the silencers and stripped one down. The removable end cap proved tricky to remove, such was the accuracy required when fabricating the two parts to ensure a gas tight seal between them, but after attaching the 2 titanium (what else ?) silencer clamps to the silencer body, I had something to hit with my best rubber mallet whilst I held the end cap/tailpipe assembly to enable me to separate the end cap from the body. Here's what I found (packing already removed) :
As can be seen, the 'U" section :
slides over the two straight perforated sections and these in turn slide into two 'stubs" formed from the inlet tube and the outlet (tailpipe) , thus enabling the perforated section to 'float" and to allow the whole silencer to be stripped for re-packing.
The 'U" bend has a nut welded to it :
which enables it to be attached to the end cap via one small 4mm titanium screw .
My guess is the cams in the Cup engine were setting up massive pressure waves within the silencers that were causing the end cases to resonate, after a while the perforated tubes loosened in their sleeves and proceeded to float excessively, and the more they loosened, the more easily they floated, to the point they started to hammer into the end cases.
I'd already taken the car to Joe Ellis at BTB to show him the issue, and he'd agreed to look into the problem. Removing the exhaust myself meant I didn't have to wait for a space in their 'ramp schedule"
Joe kindly emailed me to tell me what he proposed to do to rectify the issue.
The end case would need some kind of additional bracing to stop it from resonating with the engine's firing pulses, and the 'U" bend needed a more substantial method of attachment to the end cover :
And the end result :
The exhaust is now rattle/knock free.
As a footnote, Joe only charged me for the expensive packing material used to re-pack the silencers. I genuinely appreciate him fixing this problem FOC, bearing in mind the exhaust is now some 8 years old and I'm its third 'owner".
So a big thank you to both Joe and Will at BTB.
