Emissions ?

[Julian64]

How the hell does a 4.5 cerbera ever pass the emissions check on an MOT? Recently had mine MOT'ed. failed dismally. The check comes in two parts.
1) Natural Idle running 450-1500prm
2) Fast Idle. Car must stay between 2500 and 3000 rpm for 30secs.

At idle CO: was 0.41, fantastic. anything under 0.5 % vol gets through.
However at fast idle which was 2500-3000 (his MOT book listed 3000 for a cerbie 4.2 but the cerbie 4.5 was unlisted) CO: 0.01% and HC: 1049. To pass this had to be under 200!!! ppmvol and lambda 1.204 (0.970-1.030) Also a straight fail. Because he's quite a frendly chap he let me retest every rpm between 2 and 3 thousand to find if it COULD pass.

At this point I'm in tears, there is no way this cars ever gonna get through an emissions test and I'm wondering what the rest of you do.

Any ideas, then I'll let you know what happened next.
We need more suspense on this board.

Julian

[Julian64]

Assuming for one moment that the cerbie (as originally designed) can pass a 'normal' MOT. So lets ignore the 'take it to a hooky MOT station', although lets call that plan B. My cerbie has standard pipes which have a common back box and therefore you can't do a check on either side.
Lots of neat fuel goes through on overrun so I can understand that cats die young on a cerb. But what changes in the lamda, CO and co2 would you expect to see if it was cat rather than engine? I'm interested in the run it at a higher rpm idea. Why do you think that would work?

[Julian64]

Just my opinion, but I think taking it to a dealer and telling him to 'tune' it up and MOT it is just throwing money away. I bet he does nothing to tune it up but takes it to a MOT station he has a relationship with and gets a hooky MOT at the same time as relieving you of tune up money. Incidently mine already passed but at a higher RPM than it should have. Interestingly at a flat spot the car has at 3,300rpm. Possibly an intentional flat spot for passing emissions at?
The point of this thread was not to whinge about emissions but to fully understand what happened. Cerbies have an adaptive map below 3000 rpm. Maybe its better to go into an MOT with your adaptive map cleared or reprogramed weak. Do any of you gurus have a fuller understanding?

[Julian64]

Confused, the more I think about this the more I realise I don't know. Why have an adaptive map at all. Why not let the processor simply calculate on the fly. Why does the ECU look at the adaptive map at all. The adaptive map by definition is always old data. If changing it simply causes the ECU to immediately overwrite? It can't be time limitation as the ECU is way fast enough to handle it. When you look at the circuit board the non volatile ram is a seperate chip. NV's are always slow compared to the processor so the processor is actually taking a 'time out' relatively speaking to read it. So there must be some mileage in being able to play with it. I'm going to take a break here and go and research this. If there's any interest I'll present back what I manage to find out.