Chimaera decat!!!!
Discussion
Hi need some advice re decatting a 4.0 98 chimaera.
Bit new to this stuff, so be gentle!!!!
Got a 98 4.0 completely standard, which I have owned for about 8 years.... Feels a little flat!!! No actual problem with it just feel it needs a little lift and little more presence would be nice.....
I am intending to take out the pre cats and I have bought a spare y piece....
1. Does removing the pre cats make any real difference , can it make it sound nasty and tinny???
2. Does removing main cat cause more probs than its worth???is it just as simple as an angle grinder, bash with a mallet and reweld up
3. Have read I need to change main resistor in the ecu if I remove the main cat???? What value does it require??
Finally
Thanks guys for any help!!!!!!!
Bit new to this stuff, so be gentle!!!!
Got a 98 4.0 completely standard, which I have owned for about 8 years.... Feels a little flat!!! No actual problem with it just feel it needs a little lift and little more presence would be nice.....
I am intending to take out the pre cats and I have bought a spare y piece....
1. Does removing the pre cats make any real difference , can it make it sound nasty and tinny???
2. Does removing main cat cause more probs than its worth???is it just as simple as an angle grinder, bash with a mallet and reweld up
3. Have read I need to change main resistor in the ecu if I remove the main cat???? What value does it require??
Finally
Thanks guys for any help!!!!!!!
From my minted knowledge:
1. Pre-cats out will give more power, some people quote 10+ when done in conjunction with main cat. Mostly though it will help with underbonnet temps.
2. If you have a spare Y-piece and don't mind changing it for MOT time every year then why not? Again it will help with power and underbonnet temps. Some say it makes the noise to 'agricultural' as there is to much space in the area where the cat was. Plenty of people do it and love it though.
3. This is the hard one, depending who you speak to. I do not have cats but still run the white cat tune resistor, she runs great. But when I was running with no cats and a Clive Y-piece she ran much better on the green non cat tune
1. Pre-cats out will give more power, some people quote 10+ when done in conjunction with main cat. Mostly though it will help with underbonnet temps.
2. If you have a spare Y-piece and don't mind changing it for MOT time every year then why not? Again it will help with power and underbonnet temps. Some say it makes the noise to 'agricultural' as there is to much space in the area where the cat was. Plenty of people do it and love it though.
3. This is the hard one, depending who you speak to. I do not have cats but still run the white cat tune resistor, she runs great. But when I was running with no cats and a Clive Y-piece she ran much better on the green non cat tune
Edited by NickM450 on Sunday 21st July 01:39
Mine was a four litre, and I know exactly what you meant in your first statement.
I felt that in February.
About £7000 later I now have a faster, noisier car worth about £2000 more than my 400.
Sell the 400 and buy a good 450 or 500.
Decatting. Many people who do this keep their old Y piece for MOTs. You don't need the precats for MOTs.
To take out the precats, You will need to remove the manifolds, which is a horrible job, and either:
1. Place them in turn in a vice and spend an hour on each manifold, bashing and drilling out the cats. Hard work, around a corner, and you need to get it all out, or
2. Have a listen before removal with a listening tube, and when you realise they are blowing where the four pipes become one, take them to a good welder, get him to cut them in half between the union and the cat, weld up where it is blowing, remove the cat while he has the open (easy) and weld them back up again.
Put them back on the car with new gaskets (horrible job again).
To change the main cat, I suggest you buy either a Clive Ford Y piece or an ACT one. Clive's are about £340, and he makes them a couple of times a year. They are a work of art in stainless steel and have a lovely brutal sound. I have never knowingly heard an ACT one, but they have their fans. If you decat your own Y piece you will need a spare for the MOT (or borrow mine), and I am told that due to the size of the cat chamber, it sounds very dustbin like.
So decatting will cost you about £500 if you do it yourself, probably £200 more if you get your TVR guy to skin his own knuckles. Manifold bolts might well be stuck (7 of my 400 bolts were stuck and had to be cut off and drilled out) and are a pig to Remove and replace yourself without a proper ramp, and not much fun with one.
If it was February again, and knowing what I did and spent, I would sell my 400 and buy a 500 that has had the chassis refurbed rather than doing an engine upgrade and full decat.
Being more positive, I now have a 14 year old car that has a nicely run in new engine, putting out over 300 bhp and 330 torques. I have had to change the outriggers too, and have another £2500 to spend on front suspension, brakes, respray, carpets etc
But that's part of the fun.....I am told.
Email me your phone number if you want a phone chat and I will expand on this. You can also try my car if you like, it's now a fully decatted five litre. I am around North Essex every week and can meet up so you can compare standard 400 with decatted 500.
I felt that in February.
About £7000 later I now have a faster, noisier car worth about £2000 more than my 400.
Sell the 400 and buy a good 450 or 500.
Decatting. Many people who do this keep their old Y piece for MOTs. You don't need the precats for MOTs.
To take out the precats, You will need to remove the manifolds, which is a horrible job, and either:
1. Place them in turn in a vice and spend an hour on each manifold, bashing and drilling out the cats. Hard work, around a corner, and you need to get it all out, or
2. Have a listen before removal with a listening tube, and when you realise they are blowing where the four pipes become one, take them to a good welder, get him to cut them in half between the union and the cat, weld up where it is blowing, remove the cat while he has the open (easy) and weld them back up again.
Put them back on the car with new gaskets (horrible job again).
To change the main cat, I suggest you buy either a Clive Ford Y piece or an ACT one. Clive's are about £340, and he makes them a couple of times a year. They are a work of art in stainless steel and have a lovely brutal sound. I have never knowingly heard an ACT one, but they have their fans. If you decat your own Y piece you will need a spare for the MOT (or borrow mine), and I am told that due to the size of the cat chamber, it sounds very dustbin like.
So decatting will cost you about £500 if you do it yourself, probably £200 more if you get your TVR guy to skin his own knuckles. Manifold bolts might well be stuck (7 of my 400 bolts were stuck and had to be cut off and drilled out) and are a pig to Remove and replace yourself without a proper ramp, and not much fun with one.
If it was February again, and knowing what I did and spent, I would sell my 400 and buy a 500 that has had the chassis refurbed rather than doing an engine upgrade and full decat.
Being more positive, I now have a 14 year old car that has a nicely run in new engine, putting out over 300 bhp and 330 torques. I have had to change the outriggers too, and have another £2500 to spend on front suspension, brakes, respray, carpets etc
But that's part of the fun.....I am told.
Email me your phone number if you want a phone chat and I will expand on this. You can also try my car if you like, it's now a fully decatted five litre. I am around North Essex every week and can meet up so you can compare standard 400 with decatted 500.
Edited by QBee on Sunday 21st July 06:30
Chilliman said:
QBee said:
Manifold bolts might well be stuck (7 of my 400 bolts were stuck and had to be cut off and drilled out)
Jesus H Anthony, your manifolds had 400 bolts???? that's amazing, no wonder they were difficult to remove Edited by QBee on Sunday 21st July 06:30
And yes, Alex, it is perfectly possible to take the cats out of the existing exhaust and put everything back for the cost of a set of gaskets, but the OP asked for advice and as far as I am aware, the resulting sound is not that good and it's a horrible job, especially without your legendary mechanical skills and small hands.
If he wants more power, should he be starting by making my mistake and upgrading a 400? I spent far too much goung from a 400 to a 500. You have just gone from a 450 to a 530 in search of more power. Was it cost and time effective? Or would you have been better doing what Phazed has done, selling his 450 and buying a 550 someone else has already done for only a modest amount more than his 450 was worth?
GasMunkey said:
QBee said:
the resulting sound is not that good
and it's a horrible job
Sound is the same as the Clive or act piece and it's a horrible job
Horrible job? That's a understatement!!
Is your'e car decatted yet?
I also went down the Clive route and love it. Having run with precats in for a couple of weeks after fitting the Y piece before taking them out, I completely agree on what has been said on other threads that taking them out is a must for the maximum snap, crackle and pop!
Although most people focus on the exhaust note, I have found you do get increased engine bay noise as a result too, a little at idle and more noticibly under load from low rpm. Once above 3k it sounds awesome though and I am more than happy with the overall package.
Although most people focus on the exhaust note, I have found you do get increased engine bay noise as a result too, a little at idle and more noticibly under load from low rpm. Once above 3k it sounds awesome though and I am more than happy with the overall package.
I have decatted, but also have a sleeved silencer (see pics below).
1. Removing the manifolds is the best way to remove the pre-cats. If you've not done you manifolds before, then allow a full afternoon to get them off. Once they're off, it is an ideal time to replace the manifold gaskets and cut slots in the bottom bolt holes to facilitate replacement and future removal. The first pre-cat will take you a couple of hours. Once you have the hang of this, the second will be quicker. Ensure you wear a mask as bashing the pre-cats out produces a lot of fine dust that isn't particularly good for you. Noise difference is not that much TBH.
2. The main cat will make the largest impact. Use a thin steel cutting disk on an angle grinder. Ensure you mark three points along the cut, so you can be sure that you are re-aligning and welding correctly. More than a couple of degrees out and it won't re-allign when you put it back in the car. My cat came out quite easily, however, I gather others have had a much harder time removing it. I had my spare Y-piece TIG welded at a local garage. Cost me £60. I intend to wrap it and reduce the hollowness of the sound.
3. As for the resistor, I haven't changed this as yet. I was told that as long as I had the Lambda sensors in, it didn't matter. The car seems to run okay.
If you still have a standard silencer, it won't be too loud. Sleeve it and it will be über loud! If you are still running the standard mid-silince box, it is also worth checking this as the original internals tend to decay and cause an impact on flow and performance.
When you come to replacing your Y-piece, get a cheap ratchet strap from Screwfix to help squeeze the manifolds together and facilitate refitting. A bit og exhaust paste around the clamping joints will also help eliminate leaks.
1. Removing the manifolds is the best way to remove the pre-cats. If you've not done you manifolds before, then allow a full afternoon to get them off. Once they're off, it is an ideal time to replace the manifold gaskets and cut slots in the bottom bolt holes to facilitate replacement and future removal. The first pre-cat will take you a couple of hours. Once you have the hang of this, the second will be quicker. Ensure you wear a mask as bashing the pre-cats out produces a lot of fine dust that isn't particularly good for you. Noise difference is not that much TBH.
2. The main cat will make the largest impact. Use a thin steel cutting disk on an angle grinder. Ensure you mark three points along the cut, so you can be sure that you are re-aligning and welding correctly. More than a couple of degrees out and it won't re-allign when you put it back in the car. My cat came out quite easily, however, I gather others have had a much harder time removing it. I had my spare Y-piece TIG welded at a local garage. Cost me £60. I intend to wrap it and reduce the hollowness of the sound.
3. As for the resistor, I haven't changed this as yet. I was told that as long as I had the Lambda sensors in, it didn't matter. The car seems to run okay.
If you still have a standard silencer, it won't be too loud. Sleeve it and it will be über loud! If you are still running the standard mid-silince box, it is also worth checking this as the original internals tend to decay and cause an impact on flow and performance.
When you come to replacing your Y-piece, get a cheap ratchet strap from Screwfix to help squeeze the manifolds together and facilitate refitting. A bit og exhaust paste around the clamping joints will also help eliminate leaks.
Edited by chris1972 on Sunday 21st July 11:25
Afore ye start, just search your heart and be sure that you aren't really looking for a fair bit more power. Decatting will add a little bit, and sound effects too, but if you are going to want more power, do yourself a favour, and pop over to somewhere like Kerridges and test drive a 5 litre before you start decatting.
Then either decat or advertise!
Then either decat or advertise!
I used stainless steel studs with nuts and spring washers. Others have used ARP bolts with allen key heads. The studs and the slots cut in the manifolds make it easier to replace them as you can get the nuts on the lower studs before slotting the manifolds in. Either way, there are mixed reviews about studs and ARP bolts.
As for studs, they cost me £10 off Ebay (standard RV8 studs). Manifold gaskets will be available from somewhere like Clever Trevor. When replacing the manifolds, make sure you get the bolts/ nuts on studs on 3 & 4 first as the manifold fouls the bolt/ nut. All will become clear when you remove them!
Whilst you have your manifolds out, it is also a good opportunity to replace the heat shielding on the inner wings and consider doing the fuel hose to the fuel rail.
As for studs, they cost me £10 off Ebay (standard RV8 studs). Manifold gaskets will be available from somewhere like Clever Trevor. When replacing the manifolds, make sure you get the bolts/ nuts on studs on 3 & 4 first as the manifold fouls the bolt/ nut. All will become clear when you remove them!
Whilst you have your manifolds out, it is also a good opportunity to replace the heat shielding on the inner wings and consider doing the fuel hose to the fuel rail.
OleVix said:
Just take off the main cat, then drill and pry out the precats while manifolds still on, s
t job but much faster than taking them off!
+1 on thist job but much faster than taking them off!Careful of the lambdas and be a little gentle spanking them out but easily done. A quick fire up before reassembly blows all the crap out.
Saying that my '93 ones fell out while my '02 ones took a beating!
Well worth the effort. Much free er revving, better noise and a definite increase in gee gees.
Win win win!!
chris1972 said:
Although I see that leaving the manifolds in is quicker, it must be a very awkward and uncomfortable job to do, unless you take the bonnet off? Would the hammering not put a lot of strain on the seams/bolts etc?
More than one way to skin a cat I guess...
Taking the bonnet off is a must when decatting the manifolds, for easy access and to prolong your back!More than one way to skin a cat I guess...
So long as your not too brutal with clearing out the old cat, then there should be no issue with damaging the manifolds/studs.
As has been said above, once they are out, fire it up to clear out the little bits and be sure to put an old pillow case or equivalent over the ends of the manifolds or you will have a garage full of dust!
Gassing Station | Chimaera | Top of Page | What's New | My Stuff