Discussion
Advice needed please.
What are the chances of getting through an MOT if I take the cat out of my 99 car?
Car is 4.0 litre with supercharger and Emerald ECU which could run a map just for MOT if this helps.
Trying to reduce under bonnet temperatures as the bonnet is suffering from the heat and I understand this will help.
What are the chances of getting through an MOT if I take the cat out of my 99 car?
Car is 4.0 litre with supercharger and Emerald ECU which could run a map just for MOT if this helps.
Trying to reduce under bonnet temperatures as the bonnet is suffering from the heat and I understand this will help.
Whatever the emissions are, just having a cat removed is a fail. In the case of a modified TVR I doubt the tester will be aware of what cats it is supposed to have, but at that age he will know it should be catted.
I very much doubt that you will be able to make the emissions passable without some sort of cat fitted, even if you do tweak the map to suit.
I very much doubt that you will be able to make the emissions passable without some sort of cat fitted, even if you do tweak the map to suit.
Just find an understanding MoT station and tester, every TVR Specialist will have one and any right minded tester who's also a car enthusiast will tend to be lenient in respect of emissions on a specialist car like a TVR. Its just a matter of asking about within your local TVR club or enthusiast car community and you really shouldn't have any trouble finding the right local guy.
Or do what I did and convert to LPG which immediately means you only have to pass a pre-cat emissions test which at it strictest (1.8.1992 to 31.7.1994) is somewhere around 0.3% on the CO & 200ppm on the HC with a Lambda reading between 0.97 - 1.03.... Basically it's not worth turning the machine on for so other than a quick super old school visual smoke test no one gives a damn.
Removing the pre-cats alone will still see you passing the test so they should be the first to go, but its removing the big 'Y' Piece cat that brings the greatest benefits, some say as much as 10hp but certainly it will improve throttle response and idle quality if nothing else.
An internal combustion engine is just a big air pump, it's efficiency is governed by the amount of air it can ingest and the amount of exhaust gas it can pump out, so anything you can do to help your big air pump breath will make a difference. That's why when were tuning for power we port heads and inlets and open up the exhaust, essentially you're improving the volumetric efficiency of the pump.
Get shot of those cats as they're just a big restriction, its one of the cheapest and easiest things you can do to enhance the performance, idle quality and drivability of your TVR, if that isn't worth investing a small amount of time asking about to find a kindly tester.... I dont know what is?
Or do what I did and convert to LPG which immediately means you only have to pass a pre-cat emissions test which at it strictest (1.8.1992 to 31.7.1994) is somewhere around 0.3% on the CO & 200ppm on the HC with a Lambda reading between 0.97 - 1.03.... Basically it's not worth turning the machine on for so other than a quick super old school visual smoke test no one gives a damn.
Removing the pre-cats alone will still see you passing the test so they should be the first to go, but its removing the big 'Y' Piece cat that brings the greatest benefits, some say as much as 10hp but certainly it will improve throttle response and idle quality if nothing else.
An internal combustion engine is just a big air pump, it's efficiency is governed by the amount of air it can ingest and the amount of exhaust gas it can pump out, so anything you can do to help your big air pump breath will make a difference. That's why when were tuning for power we port heads and inlets and open up the exhaust, essentially you're improving the volumetric efficiency of the pump.
Get shot of those cats as they're just a big restriction, its one of the cheapest and easiest things you can do to enhance the performance, idle quality and drivability of your TVR, if that isn't worth investing a small amount of time asking about to find a kindly tester.... I dont know what is?
If you hold up the exhaust gasses heat will also build up, so yes removing the cats will help in this respect, but the biggest reason the exhaust manifolds run so hot on Chimas & Griffs is the 10-12 degrees of ignition timing the 14CUX period Rover V8 was forced to run at.
Retarding the idle ignition timing was a trick developed in the early 70's in the States as a sticking plaster solution to help older dirty and less efficient engine designs meet ever stricter emission regulations over the pond, emission targets these engines were never intended to meet. The way car makers did this was to apply a ported vacuum reference to the vacuum advance unit on the side of the distributor, basically at idle ported vacuum gives no vacuum whatsoever so no advance is added to the base timing.
This strategy did help older engines meet ever stricter emissions regulations but its a work-around that has disadvantages too including the production of a lot of heat in the exhaust manifolds as it essentially means combustion is still taking place when the exhaust valve starts to open. This is what delivers heat to the manifolds and also loses you torque at and just off idle, if you switch to a full manifold vacuum signal rather than ported vacuum you will get the 10 degrees of base/mechanical timing plus roughly 8 degrees from the vac advance unit which is now working at idle as well as on cruise just as it was intended to when Buick designed our engine in the late 1950's.
Running 18 degrees at idle should deliver a smoother idle, more torque as you pull away, better fuel economy in town where a lot of time is actually spent at idle, and much cooler exhaust manifolds too. Combine this with the removal of all three catalytic converters and while you will never pass another emissions test in your life you will notice a big improvement in the way the car idles and drives especially below 2,000 rpm.
Cat deletion and switching to full manifold vacuum (18 degrees at idle) are two simple things you can do to your TVR that will give a much bigger improvement than any expensive Mark Adams chip can ever hope to, and they are much much cheaper to implement too. After that ditch your dreadful leaky and misfire promoting plug extenders, renew your HT leads with quality items (not Magnecor), then switch to a set of NGK BPR6EIX plugs and you'll have yourself a TVR that's never driven better
Retarding the idle ignition timing was a trick developed in the early 70's in the States as a sticking plaster solution to help older dirty and less efficient engine designs meet ever stricter emission regulations over the pond, emission targets these engines were never intended to meet. The way car makers did this was to apply a ported vacuum reference to the vacuum advance unit on the side of the distributor, basically at idle ported vacuum gives no vacuum whatsoever so no advance is added to the base timing.
This strategy did help older engines meet ever stricter emissions regulations but its a work-around that has disadvantages too including the production of a lot of heat in the exhaust manifolds as it essentially means combustion is still taking place when the exhaust valve starts to open. This is what delivers heat to the manifolds and also loses you torque at and just off idle, if you switch to a full manifold vacuum signal rather than ported vacuum you will get the 10 degrees of base/mechanical timing plus roughly 8 degrees from the vac advance unit which is now working at idle as well as on cruise just as it was intended to when Buick designed our engine in the late 1950's.
Running 18 degrees at idle should deliver a smoother idle, more torque as you pull away, better fuel economy in town where a lot of time is actually spent at idle, and much cooler exhaust manifolds too. Combine this with the removal of all three catalytic converters and while you will never pass another emissions test in your life you will notice a big improvement in the way the car idles and drives especially below 2,000 rpm.
Cat deletion and switching to full manifold vacuum (18 degrees at idle) are two simple things you can do to your TVR that will give a much bigger improvement than any expensive Mark Adams chip can ever hope to, and they are much much cheaper to implement too. After that ditch your dreadful leaky and misfire promoting plug extenders, renew your HT leads with quality items (not Magnecor), then switch to a set of NGK BPR6EIX plugs and you'll have yourself a TVR that's never driven better
Thanks Dave
As to timing, I'm not sure what I've got as my Mac doesn't speak Emerald so will have to get hold of a windows machine.
Mapping was done by Kits and Classics so would hope it is OK.
Plug leads are indeterminate and I do still have the extenders and yet the car seems to run OK but I will give it a go anyway.
As to timing, I'm not sure what I've got as my Mac doesn't speak Emerald so will have to get hold of a windows machine.
Mapping was done by Kits and Classics so would hope it is OK.
Plug leads are indeterminate and I do still have the extenders and yet the car seems to run OK but I will give it a go anyway.
RedFI said:
Thanks Dave
As to timing, I'm not sure what I've got as my Mac doesn't speak Emerald so will have to get hold of a windows machine.
Mapping was done by Kits and Classics so would hope it is OK.
Plug leads are indeterminate and I do still have the extenders and yet the car seems to run OK but I will give it a go anyway.
Ah, that's a bit different then As to timing, I'm not sure what I've got as my Mac doesn't speak Emerald so will have to get hold of a windows machine.
Mapping was done by Kits and Classics so would hope it is OK.
Plug leads are indeterminate and I do still have the extenders and yet the car seems to run OK but I will give it a go anyway.
Hi Ken, cats do retain a lot of heat, but even though you are supercharged most of your driving will still be under light loads, so the heat in the engine bay shouldn't be dis-similar to a normally aspirated car most of the time. Assuming your bonnet heat shields are intact though there's not much you can do except remove the heat sources.
I can't remember if you are decatted on the manifolds or not .. if not the best* route forwards to reduce the heat is probably to decat the manifolds and get a cliveF y piece .. that way you can run decatted most of the time, and just replace the decatted Y piece for MOT time should your tester require it (they may just let it through as it is, but at least if you have a catted Y piece in the boot at MOT time they can see you have the opportunity to put it back in ..).
Removing the cats on a catted car will very probably improve your airflow to the point that you might need the mapping tweaking anyway, or at the very least checking.
The other bit of good news is that yes you can keep one map back for MOT test purposes, and the other 2 maps can be richened up slightly to further improve the drivability (as you'll be running a cat friendly mixture still through much of the normal driving range of the maps at the moment which is a bit weak for best drivability)
give me call or email if you need to discuss it further
best wishes.
I can't remember if you are decatted on the manifolds or not .. if not the best* route forwards to reduce the heat is probably to decat the manifolds and get a cliveF y piece .. that way you can run decatted most of the time, and just replace the decatted Y piece for MOT time should your tester require it (they may just let it through as it is, but at least if you have a catted Y piece in the boot at MOT time they can see you have the opportunity to put it back in ..).
Removing the cats on a catted car will very probably improve your airflow to the point that you might need the mapping tweaking anyway, or at the very least checking.
The other bit of good news is that yes you can keep one map back for MOT test purposes, and the other 2 maps can be richened up slightly to further improve the drivability (as you'll be running a cat friendly mixture still through much of the normal driving range of the maps at the moment which is a bit weak for best drivability)
give me call or email if you need to discuss it further
best wishes.For those of us with a turbo fitted where the Y piece used to live, what are the choices re fitting a cat further downstream of the turbo to enable an unfriendly MOT pass?
Loads of catalytic convertors are available, presumably one of the same tube bore as the TVR exhaust could be found.
Is there a place where it could be fitted without causing bodywork heat damage, for example, instead of the first six inches of the exhaust itself?
Or even a pair of these somewhere at the rear? They are £70 a piece on the Bay of the Magic Flea
Loads of catalytic convertors are available, presumably one of the same tube bore as the TVR exhaust could be found.
Is there a place where it could be fitted without causing bodywork heat damage, for example, instead of the first six inches of the exhaust itself?
Or even a pair of these somewhere at the rear? They are £70 a piece on the Bay of the Magic Flea
Edited by QBee on Tuesday 20th November 14:11
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