Precat removal: to be or not to be?
Discussion
Hi All,
Hope everyone had a cracking new year and xmas.
Only 4 months until I break the Chim out of jail, cannot wait.
I have a question about the "precats". I've read loads about getting them removed and the general consensus is that it's worthwhile for power outpout, efficiency and noise...sign me up!
There's a load of literature on the forum and frankly the more I read the more i get confused and I am seeking someone who knows their cookies to clear a few things up for me.
My cars a 96' 400. I have two questions:
1. Am I correct in thinking that since she's post '93 that she will have the 3 catalytic converter set-up and not the exhaust manifold "precats" that everyone seems hell bent on removing? (please correct me here if my terminology is wrong or if I'm getting things mixed up, highly likely). If this is the case then ignore the next questions as I won't go to the trouble of removing the cat converters and risk an MoT fail.
2. Is there a way to know categorically what your cars cat set-up is, or is it likely to be variable like everything else TVR?
Cheers n beers fellow Chim nuts
Hope everyone had a cracking new year and xmas.
Only 4 months until I break the Chim out of jail, cannot wait.
I have a question about the "precats". I've read loads about getting them removed and the general consensus is that it's worthwhile for power outpout, efficiency and noise...sign me up!
There's a load of literature on the forum and frankly the more I read the more i get confused and I am seeking someone who knows their cookies to clear a few things up for me.
My cars a 96' 400. I have two questions:
1. Am I correct in thinking that since she's post '93 that she will have the 3 catalytic converter set-up and not the exhaust manifold "precats" that everyone seems hell bent on removing? (please correct me here if my terminology is wrong or if I'm getting things mixed up, highly likely). If this is the case then ignore the next questions as I won't go to the trouble of removing the cat converters and risk an MoT fail.
2. Is there a way to know categorically what your cars cat set-up is, or is it likely to be variable like everything else TVR?
Cheers n beers fellow Chim nuts
You can tell by the exhaust Y piece at the front of the engine and the manifolds.
Basically, if the manifolds look like these with 8 bolts fixing the manifolds to the Y piece then you have no cats [from the factory]
http://www.actproducts.co.uk/product/ms01-griffith...
If your manifolds look like these with a V clamp fixing the manifolds to the Y piece then you would have had cats [from the factory]
http://www.actproducts.co.uk/product/ms03-griffith...
It is a pretty common and long standing mod to remove the cats in the manifolds so double check before getting too set up that they are still there. Removing the Y piece and simply looking up the manifold will tell you.
Basically, if the manifolds look like these with 8 bolts fixing the manifolds to the Y piece then you have no cats [from the factory]
http://www.actproducts.co.uk/product/ms01-griffith...
If your manifolds look like these with a V clamp fixing the manifolds to the Y piece then you would have had cats [from the factory]
http://www.actproducts.co.uk/product/ms03-griffith...
It is a pretty common and long standing mod to remove the cats in the manifolds so double check before getting too set up that they are still there. Removing the Y piece and simply looking up the manifold will tell you.
Chimaera27 said:
I have a question about the "precats"...
...Am I correct in thinking that since she's post '93 that she will have the 3 catalytic converter set-up and not the exhaust manifold "precats" that everyone seems hell bent on removing? (please correct me here if my terminology is wrong or if I'm getting things mixed up, highly likely)...
All cars with catalytic convertors have 3 cats in the system - the main cat in the Y-piece, and 2 smaller cats, 1 in each exhaust manifold (in the collector)....Am I correct in thinking that since she's post '93 that she will have the 3 catalytic converter set-up and not the exhaust manifold "precats" that everyone seems hell bent on removing? (please correct me here if my terminology is wrong or if I'm getting things mixed up, highly likely)...
These smaller cats are known as "precats" (coming before the main cat in the Y-piece), and were put in there for cold start emissions I believe - but are not required in order to pass the MOT test in this country.
If you have a car with catalytic convertors, then your car would have originally come with precats - but whether they are still in the manifolds remains to be seen...
Hope this clears it up for you
Dom
Thank you all very much for the info, that has cleared it up for me! Now I understand what is meant by the terms and what to look for, wicked.
If precats are present on my motor, what would you guys recommend as the most effective and quickest way to remove them??
I have read a lot of conflicting views on this too so would be good to get a couple of firm technqiues in the bag!
Ta
If precats are present on my motor, what would you guys recommend as the most effective and quickest way to remove them??
I have read a lot of conflicting views on this too so would be good to get a couple of firm technqiues in the bag!
Ta
One method is
Gloves and mask.
Chisels , long screw driver flat head
10mm masonry brill bit 300mm long and battery gun.
Two trains of thought here
1 Do in situ once Y piece removed.
2 Remove manifolds and do on a bench.
Using your assorted tools you simply drill into the honeycomb and slowly break it up, might come out in little bits or they might come out almost intact as one of mine did.
Messy job but basic stuff, be careful not to drill or tsp into the honeycomb to far or you'll hit the inner steel of the underside of the manifold and dink it outwards or even break through.
I did tNo 2 because I didn't want to risk bits of honeycomb being sucked into engine but I'm sure others have done it with manifolds on the car and had no apparent issues.
The other way still involves removing manifolds but then you cut them open and in half to reveal and release the pre cats.
Then just weld them up again. ( more skill required.) and a better way.
Gloves and mask.
Chisels , long screw driver flat head
10mm masonry brill bit 300mm long and battery gun.
Two trains of thought here
1 Do in situ once Y piece removed.
2 Remove manifolds and do on a bench.
Using your assorted tools you simply drill into the honeycomb and slowly break it up, might come out in little bits or they might come out almost intact as one of mine did.
Messy job but basic stuff, be careful not to drill or tsp into the honeycomb to far or you'll hit the inner steel of the underside of the manifold and dink it outwards or even break through.
I did tNo 2 because I didn't want to risk bits of honeycomb being sucked into engine but I'm sure others have done it with manifolds on the car and had no apparent issues.
The other way still involves removing manifolds but then you cut them open and in half to reveal and release the pre cats.
Then just weld them up again. ( more skill required.) and a better way.
My precats were in perfect condition and it took me about 10 hours of hell to remove them in situ. I swore I would never do it that way again but remove the manifolds instead. I believe others have found it much easier than I did in situ and you do need to consider the other risks of removing the manifolds like snapping a bolt.
I have had moments of regret since removing mine and I am still not sure what I prefer. A couple of downsides are noise and exhaust fumes. Mine is now fully decatted with cherry bomb aftermarket type exhausts and it is bordering on too lous. Noise under hard acceleration is LOUD and there is more drone on partial throttle. I don't mind this too much but has really annoyed me is the exhaust fumes entering the cabin, I know they always used to but now I am bordering on CO poisoning. I have improved the situation by improving the boot seal but it still isn't great and can be pretty bad even sat at the lights.
On the flip side though it now sounds bloody epic with more pops, bangs and crackles and on full chat, blimey! It also feels a bit more lively, I am not sure if this is because its a bit louder and angrier sounding but either way my arse dyno says it is!
Overall I am glad I did it but if I hadn't I probably wouldn't bother!
I have had moments of regret since removing mine and I am still not sure what I prefer. A couple of downsides are noise and exhaust fumes. Mine is now fully decatted with cherry bomb aftermarket type exhausts and it is bordering on too lous. Noise under hard acceleration is LOUD and there is more drone on partial throttle. I don't mind this too much but has really annoyed me is the exhaust fumes entering the cabin, I know they always used to but now I am bordering on CO poisoning. I have improved the situation by improving the boot seal but it still isn't great and can be pretty bad even sat at the lights.
On the flip side though it now sounds bloody epic with more pops, bangs and crackles and on full chat, blimey! It also feels a bit more lively, I am not sure if this is because its a bit louder and angrier sounding but either way my arse dyno says it is!
Overall I am glad I did it but if I hadn't I probably wouldn't bother!
Edited by dkr09 on Friday 6th January 15:07
and to think I was such a sleeved sceptic!I've got no cats at all (Act ss manifold clive Y piece) ,my silen cer box is half sleeved .The car sounds fabulous, not to loud at slow speed and cruising but with a deep growl on acceleration increasing with revs.To top it off it passed the mot comfortably tho must admit got it very hot before I took it in it's a 99 400 with most of the Act induction toy's.
Nice one lads, definitely think I'll have a crack at this, sounds like the benefits are well worth the time and effort.
Don't think I'll take the main cats out and/or sleeve the exhaust. The former because of the MoT risk and the latter because I want to take my lady out on track and don't want to be too noisy!
Am I right in thinking that the honeycomb is worth a small fortune at the scrappy as it's precious metals??
Don't think I'll take the main cats out and/or sleeve the exhaust. The former because of the MoT risk and the latter because I want to take my lady out on track and don't want to be too noisy!
Am I right in thinking that the honeycomb is worth a small fortune at the scrappy as it's precious metals??
Previously had a go at removing the precats through the open end of the manifold and found it hard work.
Had a go this afternoon with the help of a cutting disc, openings were made on the undersides.
All back together and running lumpy as ever but now slightly louder.
How the hell these things were supposed to breath properly with all that stuff in there I don't know
Had a go this afternoon with the help of a cutting disc, openings were made on the undersides.
All back together and running lumpy as ever but now slightly louder.
How the hell these things were supposed to breath properly with all that stuff in there I don't know
I'm having some induction mods done to my 4lt at the moment, stage 3 heads,45mm inlet manifold, 45mm shortened trumpets,72mm plenum, mc1 cam, when I asked about removing the pre cats I was told by jools who will be doing the remap that there was no power gains on a 4lt engine just a bit more noise.😉
Gassing Station | Chimaera | Top of Page | What's New | My Stuff