Pre Cat Removal - Should I / Shouldn't I
Discussion
Zipee
"if you really want to do it properly it may be worth trying to source a de-catted y-piece with a much smaller dustbin piece."
This is new to me, I know that the y pieces vary with bolt fixings vs clamps but different size dustbin pieces, are you referring to the "proprr" de-catted pipes as fitted to pre-cat Griffs?
If so I am not sure if they would fit as i undertand that the manifolds are different?
Any thoughts?
Thanks in anticpation.
Steve.
"if you really want to do it properly it may be worth trying to source a de-catted y-piece with a much smaller dustbin piece."
This is new to me, I know that the y pieces vary with bolt fixings vs clamps but different size dustbin pieces, are you referring to the "proprr" de-catted pipes as fitted to pre-cat Griffs?
If so I am not sure if they would fit as i undertand that the manifolds are different?
Any thoughts?
Thanks in anticpation.
Steve.
LATEST UPDATE
Right, got home on Friday and found out I was wrong
. The gaskets as shown, are to small for a 5 ltr head by about 2-3mm, so I guess I'll be giving ACT or V8D a ring for some composites.
Iv'e cleaned up the surfaces of the manifolds and heads with no damage / scoring so all's well.
As for the cats, they're now gone. I started off by getting an old long reach spartplug box spanner and cut a hole in it 100mm up it and cut a slot out the side. I then opened the end out so it fit around the lamda and hey presto
a .99p lamda sensor removal tool. Yes I suppose a nice socket would have been better, but as the grinder was at work I didn't want to be cutting away at a socket for the next 3 hrs with a hacksaw.
Next came the removal of the cats and I can say it is a pain. Mine were fairly well stuck in but I found by putting around 10 small pilot holes with a 450mm long possi drive and then going at it with a 10mm SDS drill bit on hammer soon gets them out
, well........soon as being and hour each.
As you can see, the cats themselves are made of a radiator matrix type material except very tightly packed, so I can see why it would make the exhaust alot more free flowing and reduce the back pressure..............aw well, to late now.
I then cut down a cheap wire brush and put it inside the manifold where the cat was and cleaned up the inside surface as I was left with the od bit of vain still stuck to the inside surface and dont fancy them coming loose in the future and geting blown into the main cat and plugging that up.
Guess now it's just a case of putting the manifold back on and seeing what it sounds like. (hopefully minus the ticking)
>> Edited by crazycraig on Monday 19th December 09:02
Right, got home on Friday and found out I was wrong
. The gaskets as shown, are to small for a 5 ltr head by about 2-3mm, so I guess I'll be giving ACT or V8D a ring for some composites. Iv'e cleaned up the surfaces of the manifolds and heads with no damage / scoring so all's well.
As for the cats, they're now gone. I started off by getting an old long reach spartplug box spanner and cut a hole in it 100mm up it and cut a slot out the side. I then opened the end out so it fit around the lamda and hey presto
a .99p lamda sensor removal tool. Yes I suppose a nice socket would have been better, but as the grinder was at work I didn't want to be cutting away at a socket for the next 3 hrs with a hacksaw. Next came the removal of the cats and I can say it is a pain. Mine were fairly well stuck in but I found by putting around 10 small pilot holes with a 450mm long possi drive and then going at it with a 10mm SDS drill bit on hammer soon gets them out
, well........soon as being and hour each. As you can see, the cats themselves are made of a radiator matrix type material except very tightly packed, so I can see why it would make the exhaust alot more free flowing and reduce the back pressure..............aw well, to late now.
I then cut down a cheap wire brush and put it inside the manifold where the cat was and cleaned up the inside surface as I was left with the od bit of vain still stuck to the inside surface and dont fancy them coming loose in the future and geting blown into the main cat and plugging that up.
Guess now it's just a case of putting the manifold back on and seeing what it sounds like. (hopefully minus the ticking)
>> Edited by crazycraig on Monday 19th December 09:02
To be honest.......no difference when running in the garage, but then I haven't had the car out on the road so it may sound different when under load.
I got the exhaust back on Wednesday from having it sleeved and temporarily fitted it last night, and it sounds quite different now.
Didn't realy give it some as I only put the manifolds back on the other day but it definatley sounds lounder and on tick over the note has changed from a deep drone to more of a deep glug, glug, glug noise.
Not sure if it'll change over time as it beds in, maybe someone could advise?
Craig
I got the exhaust back on Wednesday from having it sleeved and temporarily fitted it last night, and it sounds quite different now.
Didn't realy give it some as I only put the manifolds back on the other day but it definatley sounds lounder and on tick over the note has changed from a deep drone to more of a deep glug, glug, glug noise.
Not sure if it'll change over time as it beds in, maybe someone could advise?
Craig
crazycraig said:
To be honest.......no difference when running in the garage, but then I haven't had the car out on the road so it may sound different when under load.
I got the exhaust back on Wednesday from having it sleeved and temporarily fitted it last night, and it sounds quite different now.
Didn't realy give it some as I only put the manifolds back on the other day but it definatley sounds lounder and on tick over the note has changed from a deep drone to more of a deep glug, glug, glug noise.
Not sure if it'll change over time as it beds in, maybe someone could advise?
Craig
I'm presuming you mean the sleeves in the rear silencer? If so then yes, the noise does change a little as it beds in and cokes up. It gets deeper and bassier, when first done it does sound a little hollow but certainly improves with age.
Yes.
I cut the box open, removed all the packing (quite like horsehair), cut out the original pipes (which have holes in) and had some solid pipes welded in their place, then repacked and had it welded shut. All in all a couple of hours works.
As for getting deeper.
I've already had most of the neigbours looking out to see what's causing their windows to vibrate and setting off their car alarms.
Guess I'll be Mr Popular in the summer when I go out for those early morning runs.
Great. I can't wait.
I cut the box open, removed all the packing (quite like horsehair), cut out the original pipes (which have holes in) and had some solid pipes welded in their place, then repacked and had it welded shut. All in all a couple of hours works.
As for getting deeper.
I've already had most of the neigbours looking out to see what's causing their windows to vibrate and setting off their car alarms.
Guess I'll be Mr Popular in the summer when I go out for those early morning runs.
Great. I can't wait.
I had a good discussion with my garage on this subject the other day as I asked about him doing this to my Griff (There is no way I could attempt this myself). His view was quite negative on this as
- The cost would be quite high. He also taked about replacing the manifolds
- He had experienced both passes and failures at MOT stage due to this work being done so it was not a forgone conclusion that the Griff would pass , based on emissions
- The national network of MOT stations are in the process of being 'live' linked to the DVLA so borderline passes/failures which may have been passed before based on friendship/local knowledge etc , would now be less likely to pass
Based on this I didnt go ahead with the work. Im not averse to having it done its just that Im not technically competant enough to have the courage to just do this and hang the consequences. Oh I also have an ongoing problem with oil burn ing with my Griff as well which im onclined to sort first before anything else.
I still would like the extra noise though.....
- The cost would be quite high. He also taked about replacing the manifolds
- He had experienced both passes and failures at MOT stage due to this work being done so it was not a forgone conclusion that the Griff would pass , based on emissions
- The national network of MOT stations are in the process of being 'live' linked to the DVLA so borderline passes/failures which may have been passed before based on friendship/local knowledge etc , would now be less likely to pass
Based on this I didnt go ahead with the work. Im not averse to having it done its just that Im not technically competant enough to have the courage to just do this and hang the consequences. Oh I also have an ongoing problem with oil burn ing with my Griff as well which im onclined to sort first before anything else.
I still would like the extra noise though.....
jeffsy said:
- He had experienced both passes and failures at MOT stage due to this work being done so it was not a forgone conclusion that the Griff would pass , based on emissions
I've never heard of a correctly working car failing an MOT just because it has had the pre-cats removed. They are only there to past cold-start emissions which are not tested during an MOT.
The main cat is another issue, it is extreemly likely to fail an MOT without a main cat (unless you happen to know a bloke who works in an MOT testing centre).
Ian A.
Must admit....................I wasn't quite sure if I should go for both and the missus didn't want it done at all as she likes the original exhaust note.
It started off by having the old ticking noise and a black soot mark from the manifold gasket so I had to have them replaced, with dealers wanted between 2-4 hrs per side for what is a fairly straight forward job, if you can get access to below as well as above and have a selction of different profile spanners to make it easier.
I decided to do one side at a time as I wasn't to confident that if I took off both sides and the exhaust I get it all to line up with the Y piece correctly. Off side I found the easiest, albeit bottom number 8 (above starter motor) is a little sh*t, with the near side alot easier, as you remove the exhaust to get access to the bottom and there's also abit more room to undo the top bolts when the AFM is removed.
After removing the manifold, cleaning off the surfaces I was time to look at the options. The cat looked in good shape, and I was quite happy to leave it in as I wanted to try to keep the car original, but as was said earlier, 'just cos it looks good, it doesn't mean it's not blocked or coked up inside'. That, the fact that it so say does not adversly effect the system by removing them and you wouldn't know by looking that they have been removed, then I though what the hell.
I knocked/SDS drilled them out and put the manifolds back on the car, run up to temp a few times and rechecked / tightened the bolts each time.
As said, personnaly I didn't notice any difference from before to after so I then decided as the exhaust was only temporarily connected to the car by the clamp at the front I'd take it off and have it sleeved.
Now it's done though, I'm more than happy and even the wife, who said she would be honest, thinks it sounds great, with the pair of us spending most of Sunday afternoon getting carbon monoxide poisoning by crouching down behind the car while the otherone blips the throttle, with both of us having silly grins on our faces and doing thumb up gestures to each other while the neighbours stare out their windows in disgust...........F'ing Great.
I haven't had the car on the road yet so am not sure about the new volumn or tone, but from what I've heard already..............it 'will' be worth it.
Worst case.................on a long journey and it gets to much.........We'll just have to look a pair of t*ts and wear ear defenders, but it'll still be worth it.
>> Edited by crazycraig on Tuesday 10th January 12:30
It started off by having the old ticking noise and a black soot mark from the manifold gasket so I had to have them replaced, with dealers wanted between 2-4 hrs per side for what is a fairly straight forward job, if you can get access to below as well as above and have a selction of different profile spanners to make it easier.
I decided to do one side at a time as I wasn't to confident that if I took off both sides and the exhaust I get it all to line up with the Y piece correctly. Off side I found the easiest, albeit bottom number 8 (above starter motor) is a little sh*t, with the near side alot easier, as you remove the exhaust to get access to the bottom and there's also abit more room to undo the top bolts when the AFM is removed.
After removing the manifold, cleaning off the surfaces I was time to look at the options. The cat looked in good shape, and I was quite happy to leave it in as I wanted to try to keep the car original, but as was said earlier, 'just cos it looks good, it doesn't mean it's not blocked or coked up inside'. That, the fact that it so say does not adversly effect the system by removing them and you wouldn't know by looking that they have been removed, then I though what the hell.
I knocked/SDS drilled them out and put the manifolds back on the car, run up to temp a few times and rechecked / tightened the bolts each time.
As said, personnaly I didn't notice any difference from before to after so I then decided as the exhaust was only temporarily connected to the car by the clamp at the front I'd take it off and have it sleeved.
Now it's done though, I'm more than happy and even the wife, who said she would be honest, thinks it sounds great, with the pair of us spending most of Sunday afternoon getting carbon monoxide poisoning by crouching down behind the car while the otherone blips the throttle, with both of us having silly grins on our faces and doing thumb up gestures to each other while the neighbours stare out their windows in disgust...........F'ing Great.
I haven't had the car on the road yet so am not sure about the new volumn or tone, but from what I've heard already..............it 'will' be worth it.
Worst case.................on a long journey and it gets to much.........We'll just have to look a pair of t*ts and wear ear defenders, but it'll still be worth it.
>> Edited by crazycraig on Tuesday 10th January 12:30
crazycraig said:
Must admit....................I wasn't quite sure if I should go for both and the missus didn't want it done at all as she likes the original exhaust note.
Now it's done though, I'm more than happy and even the wife, who said she would be honest, thinks it sounds great, with the pair of us spending most of Sunday afternoon getting carbon monoxide poisoning by crouching down behind the car while the otherone blips the throttle, with both of us having silly grins on our faces and doing thumb up gestures to each other while the neighbours stare out their windows in disgust...........F'ing Great.
Thank goodness for that!! I was worried we were the only ones doing that!! Just love the sound of it, driving through Brent Cross multi-storey car park is the best!!!!
Hi Paul.
As I said, I don't think the removal of the pre cats made any difference, but then again, maybe I'm abit deaf from all the live firing I've done in the past and couldn't notice.
Sleeving, is like I said above. All it is, is you remove the original pipes with the holes in, that were inside the back box which allow the exhaust gases to flow into the back box and deaden the sound, and replace them with solid pipes that are welded inside in their place so in essense making a straight through from the front to the back of the box.
In reality, because most places only cut open the box on 1 side, you can only weld part way round those pipes, I guess thats 1 of the reasons why they repack the back box as you probably still get some gases flowing into the box and if you didn't you'll get this hollow boxy sound. (think that's correct????)
Anyway, the car won't be making it again this weekend, full chassis blitz at the mo, give us a bell and pop round if you want.(no. in back of Sprint)
Speak to you later.
Craig
As I said, I don't think the removal of the pre cats made any difference, but then again, maybe I'm abit deaf from all the live firing I've done in the past and couldn't notice.
Sleeving, is like I said above. All it is, is you remove the original pipes with the holes in, that were inside the back box which allow the exhaust gases to flow into the back box and deaden the sound, and replace them with solid pipes that are welded inside in their place so in essense making a straight through from the front to the back of the box.
In reality, because most places only cut open the box on 1 side, you can only weld part way round those pipes, I guess thats 1 of the reasons why they repack the back box as you probably still get some gases flowing into the box and if you didn't you'll get this hollow boxy sound. (think that's correct????)
Anyway, the car won't be making it again this weekend, full chassis blitz at the mo, give us a bell and pop round if you want.(no. in back of Sprint)
Speak to you later.
Craig
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