MOT emissions insight required
Discussion
Hi All,
Hoping for some insight and maybe advice.
The car has a full exhaust system with 'race' manifold including a sports cat (200 cell) and has been mapped to suit.
On checking emissions, the hydro carbon and CO levels are both too high when at constant throttle. I have been told this is down to the map and over fuelling and that the cat is working fine as the oxygen dioxide levels are good which indicates the cat is doing what it needs to do. Been told that whoever mapped the car needs to tweak the map so that under constant throttle the fuelling is reduced to lower the CO and hydrocarbons, maybe just at lower rpm for emissions testing.
Spoke to the people that mapped the car and they've said it isn't the map as haven't changed the fuelling at constant throttle or idle and it is the cat that is the issue. Apparently can't alter the fuelling with this kind of ECU (basically needs chipping rather than mapping, is 2003 car). This raises query of if can't change the fuelling, then how has extra power been achieved? My knowledge isn't great but I thought a map or chip altered the fuel to air mixture at certain rpm to smooth out power curve and increase power?
My thinking is it must be one of these two thing as that's all that has changed. I wouldn't of thought mapping the car with a standard exhaust system and cat would cause the same issue? Would going back to 400+ cell cat help? Can the map actually be altered?
Thoughts or comments welcome,
Thanks
Hoping for some insight and maybe advice.
The car has a full exhaust system with 'race' manifold including a sports cat (200 cell) and has been mapped to suit.
On checking emissions, the hydro carbon and CO levels are both too high when at constant throttle. I have been told this is down to the map and over fuelling and that the cat is working fine as the oxygen dioxide levels are good which indicates the cat is doing what it needs to do. Been told that whoever mapped the car needs to tweak the map so that under constant throttle the fuelling is reduced to lower the CO and hydrocarbons, maybe just at lower rpm for emissions testing.
Spoke to the people that mapped the car and they've said it isn't the map as haven't changed the fuelling at constant throttle or idle and it is the cat that is the issue. Apparently can't alter the fuelling with this kind of ECU (basically needs chipping rather than mapping, is 2003 car). This raises query of if can't change the fuelling, then how has extra power been achieved? My knowledge isn't great but I thought a map or chip altered the fuel to air mixture at certain rpm to smooth out power curve and increase power?
My thinking is it must be one of these two thing as that's all that has changed. I wouldn't of thought mapping the car with a standard exhaust system and cat would cause the same issue? Would going back to 400+ cell cat help? Can the map actually be altered?
Thoughts or comments welcome,
Thanks
Tankrizzo said:
They've mapped the car without changing the fuelling?!
Something very fishy going on here.I would have thought that the OP's issues in this case are most likely due to the cats which are well known to have trouble passing emissions tests. Even more so if the car has been remapped somewhere along the road.
What car is this OP?
Can you put the original cats back on?
It's a Lupo GTi and don't have original cat and VW don't make them anymore. Thought about getting one fabricated.
As for the map, I was told the fuelling wasn't changed at idle or constant throttle so guess they did change it under load but then to say they can't change the fuelling help sounded odd unless they don't want to as see it as an MOT get around.
As for the map, I was told the fuelling wasn't changed at idle or constant throttle so guess they did change it under load but then to say they can't change the fuelling help sounded odd unless they don't want to as see it as an MOT get around.
HC and CO being too high is the cat. Even when a modern engine is misfiring (e.g. due to a coil pack failure), the HC and CO should be within spec. The cat will be getting VERY hot managing this, and eventually fail, but it should manage it.
Thrashing it may help - I have several cars that will not light the cat if they are just idled from cold, which is what usually happens at an MOT. Drive them straight onto the ramps from a decent drive and they are perfect.
Thrashing it may help - I have several cars that will not light the cat if they are just idled from cold, which is what usually happens at an MOT. Drive them straight onto the ramps from a decent drive and they are perfect.
SturdyHSV said:
Give the thing a bloody thrashing before you drop it to the garage and get them to do the emissions test first. In my experience with sports cats they need to be nice and hot to do their job properly for an MOT.
Agreed. Get it really hot and test the emissions straight away. I MOT a handful of cars with sports cats fitted and most struggle with emissions, an Aston V8 being the worst.Sorry, I see you've tried that.
rxe said:
HC and CO being too high is the cat. Even when a modern engine is misfiring (e.g. due to a coil pack failure), the HC and CO should be within spec. The cat will be getting VERY hot managing this, and eventually fail, but it should manage it.
Thrashing it may help - I have several cars that will not light the cat if they are just idled from cold, which is what usually happens at an MOT. Drive them straight onto the ramps from a decent drive and they are perfect.
I wondered whether changing plugs, oil and air filter would help with hydro carbon levels but don't think this would help the CO.Thrashing it may help - I have several cars that will not light the cat if they are just idled from cold, which is what usually happens at an MOT. Drive them straight onto the ramps from a decent drive and they are perfect.
rogerpoger said:
Hi All,
Hoping for some insight and maybe advice.
The car has a full exhaust system with 'race' manifold including a sports cat (200 cell) and has been mapped to suit.
On checking emissions, the hydro carbon and CO levels are both too high when at constant throttle. I have been told this is down to the map and over fuelling and that the cat is working fine as the oxygen dioxide levels are good which indicates the cat is doing what it needs to do. Been told that whoever mapped the car needs to tweak the map so that under constant throttle the fuelling is reduced to lower the CO and hydrocarbons, maybe just at lower rpm for emissions testing.
Spoke to the people that mapped the car and they've said it isn't the map as haven't changed the fuelling at constant throttle or idle and it is the cat that is the issue. Apparently can't alter the fuelling with this kind of ECU (basically needs chipping rather than mapping, is 2003 car). This raises query of if can't change the fuelling, then how has extra power been achieved? My knowledge isn't great but I thought a map or chip altered the fuel to air mixture at certain rpm to smooth out power curve and increase power?
My thinking is it must be one of these two thing as that's all that has changed. I wouldn't of thought mapping the car with a standard exhaust system and cat would cause the same issue? Would going back to 400+ cell cat help? Can the map actually be altered?
Thoughts or comments welcome,
Thanks
It would be helpful if you actually told us the results from the emissions test. Without them, the thread is meaningless.Hoping for some insight and maybe advice.
The car has a full exhaust system with 'race' manifold including a sports cat (200 cell) and has been mapped to suit.
On checking emissions, the hydro carbon and CO levels are both too high when at constant throttle. I have been told this is down to the map and over fuelling and that the cat is working fine as the oxygen dioxide levels are good which indicates the cat is doing what it needs to do. Been told that whoever mapped the car needs to tweak the map so that under constant throttle the fuelling is reduced to lower the CO and hydrocarbons, maybe just at lower rpm for emissions testing.
Spoke to the people that mapped the car and they've said it isn't the map as haven't changed the fuelling at constant throttle or idle and it is the cat that is the issue. Apparently can't alter the fuelling with this kind of ECU (basically needs chipping rather than mapping, is 2003 car). This raises query of if can't change the fuelling, then how has extra power been achieved? My knowledge isn't great but I thought a map or chip altered the fuel to air mixture at certain rpm to smooth out power curve and increase power?
My thinking is it must be one of these two thing as that's all that has changed. I wouldn't of thought mapping the car with a standard exhaust system and cat would cause the same issue? Would going back to 400+ cell cat help? Can the map actually be altered?
Thoughts or comments welcome,
Thanks
And oxygen dioxide ??? WTF ?
rxe said:
HC and CO being too high is the cat. Even when a modern engine is misfiring (e.g. due to a coil pack failure), the HC and CO should be within spec. The cat will be getting VERY hot managing this, and eventually fail, but it should manage it.
What does the cat do to lower HC? Edit: a little googling tells allBut echo the above please post the emissions test result if you can OP.
Edited by Krikkit on Thursday 17th December 21:50
It sounds like you have 2 issues here.
1. A replacement cat should get you away.
2. You need to get it mapped somewhere that actually maps it on load on a rolling road & does it properly going forward.
I hear what several have said about 200 cell cats but with a good quality metal (not ceramic) 200 cell cat a car can easily be mapped to pass current emissions tests.
Mine does, every year.
1. A replacement cat should get you away.
2. You need to get it mapped somewhere that actually maps it on load on a rolling road & does it properly going forward.
I hear what several have said about 200 cell cats but with a good quality metal (not ceramic) 200 cell cat a car can easily be mapped to pass current emissions tests.
Mine does, every year.
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