De-cat Pipes. Cause and Effect
Discussion
Some of you may recall that I have been doing a few winter jobs on my de-catted S3C. The near side exhaust was blowing from the manifold and my sump was sat firmly on the ARB. The first problem needed a small weld repair to one exhaust flange and new gaskets. The second was fixed by fitting some Rally Design engine mounts. (The ones recommended on an earlier post. Can't remember the number)
I have just put the repaired manifold back on and started to fit the de-cat pipes and low and behold they don't fit. The bent pipes that pass under the chassis cross member now a have a hard foul. The straight pipes that connect to the manifolds are 11 inches long. I wondered if the pipes ( bent and straight) may have been made to measure when the car was de-catted? My logic being that by raising the engine with new mounts necessitates a modification to the exhaust.
Does anyone know if the de-cat pipes are a standard off the shelf item or bespoke to each car?
It seems that the simplest fix for me would be to get 2 news straight pipes about 1 inch longer. This would give some clearance from the chassis cross member.
I have just put the repaired manifold back on and started to fit the de-cat pipes and low and behold they don't fit. The bent pipes that pass under the chassis cross member now a have a hard foul. The straight pipes that connect to the manifolds are 11 inches long. I wondered if the pipes ( bent and straight) may have been made to measure when the car was de-catted? My logic being that by raising the engine with new mounts necessitates a modification to the exhaust.
Does anyone know if the de-cat pipes are a standard off the shelf item or bespoke to each car?
It seems that the simplest fix for me would be to get 2 news straight pipes about 1 inch longer. This would give some clearance from the chassis cross member.
Thanks Philpot, that might be needed as my last resort. I have taken a few measurements and the difference in length is about the same as the clearance gained using the new engine mounts. If I can find someone locally to weld in about 20mm insert into the down pipes, that should fix it. I just need to get hold of some stainless ( I think) tube. Time to hit yellow pages...
Mine was already de-catted when I got it a few years ago. However I have a couple of photos to show how it was fettled/bodged...
From the top down, I think is the std cat manifold (ie with connector for the sensor)...
...you may be able to see that the de-cat pipe is stepped, ie a smaller pipe inside a larger pipe about half way down...however...
...it looks like the hockey sticks (the 90 degree bit on the bottom)was bodged as the de-cat pipes were maybe too long (Otherwise the grounding out would have been even worse!)...
...it maybe messy, but it still goes fast...!
For info, this pic of cat and non cat std exhaust bits is somewhere on the web...
...good luck
From the top down, I think is the std cat manifold (ie with connector for the sensor)...
...you may be able to see that the de-cat pipe is stepped, ie a smaller pipe inside a larger pipe about half way down...however...
...it looks like the hockey sticks (the 90 degree bit on the bottom)was bodged as the de-cat pipes were maybe too long (Otherwise the grounding out would have been even worse!)...
...it maybe messy, but it still goes fast...!
For info, this pic of cat and non cat std exhaust bits is somewhere on the web...
...good luck
Edited by AutoAndy on Monday 6th January 18:17
Edited by AutoAndy on Monday 6th January 19:51
Edited by AutoAndy on Monday 6th January 19:53
When I got my old S3C that too was already de-catted, there was always a problem with the hockey stick shaped pipes catching, this was the mod that I did and worked a treat
Got the stainless flexy's from ebay and a local metal shop to do the welding and also replace the ends with stainless.
Cheers.....Tony..
Got the stainless flexy's from ebay and a local metal shop to do the welding and also replace the ends with stainless.
Cheers.....Tony..
Thanks for all your suggestions guys. After careful (ish) consideration I am opting for Philpots idea. Except, to keep up with normal Philpot Philosophy, I have ordered stainless steel joints. (Bling)
This method also gives some flexibility to optimize ground and chassis clearance. (He said hopefully)
This method also gives some flexibility to optimize ground and chassis clearance. (He said hopefully)
tozerman said:
Got the stainless flexy's from ebay and a local metal shop to do the welding and also replace the ends with stainless.
Cheers.....Tony..
Tried fitting a pair of them some time ago, was having trouble with the front of the silencer splitting, thought it might reduce any stress/strain.Cheers.....Tony..
Created a huge amount of resonance/vibration on the "hockey sticks" on the over-run
Took 'em back out and me and my mate made a whole new exhaust instead
phillpot said:
Tried fitting a pair of them some time ago, was having trouble with the front of the silencer splitting, thought it might reduce any stress/strain.
Created a huge amount of resonance/vibration on the "hockey sticks" on the over-run
That was one of the main reasons for putting them in mine, the shape of them and the stress I had to put them on in order to mate to the main exhaust section made vibrations go through the car, so when I did mine it actually removed any vibration Created a huge amount of resonance/vibration on the "hockey sticks" on the over-run
Cheers.....Tony..
Quick update. Plan A failed spectacularly. The SS jointers were 57mm ID and I thought this would be fine for my 54mm OD pipe. This was not the case when I put them together. The difference in size was too much. So in desperation I went to my local motor factors and they had in stock some Audi exhaust joints that could have been made for the job. Typical German engineering, which is arguably over kill, but who cares, they did the job.
If anyone wants more detail, I can take photos tomorrow and provide the BOSAL part number.
If anyone wants more detail, I can take photos tomorrow and provide the BOSAL part number.
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