How does an engine conversion affect MOT emissions?

[busta]

I have a 1994 Peugeot 106 Rallye and the original 1.3 engine has been replaced with a 1.6 from a 2001 saxo VTS. However I've never notified the DVLA of the change on the V5 (I do declare the bigger engine and all the other mods for insurance, before you ask.).

Every year at MOT time it fails dismally on emissions. This is regardless of whether I use the original exhaust, CAT and air filter or aftermarket ones. The emissions machine woks off the cars registration so obviously still expects the gasses from a 100hp 1.3, not a 130hp 1.6. Luckily I get on quite well with the MOT chap, who has been known to accidentally put it through as a pre-cat 1.6XSI, and it passes.

I am now sending off the V5 with the details of the bigger engine (better late than never!), but is the DVLA system clever enough to do the sums and solve my MOT emissions woes? I had heard that the emissions test is simplified for cars with engine conversions.

[m444ttb]

Sounds like nonsense to me. My '96 XSi used to pass with a 16v under the bonnet and a cat in place.

[mk2 24v]

it should be tested as the rallye, as that is older and can be proven what age it is
even the later lump should sail through the same emission test to be honest, unless its a tad on the hot side of tune

[Herman Toothrot]

Its tested to regulations in line with whatever age the chassis is, I got a 1989 Chassis to put my 1995 engine in so I didn't have to mess around with CAT's are difficut to pass emissions.

[busta]

mk2 24v said:

it should be tested as the rallye, as that is older and can be proven what age it is
even the later lump should sail through the same emission test to be honest, unless its a tad on the hot side of tune

Well it fails as a Rallye. Without the cat on it does run a tad rich- pops and bangs a bit on overrun, but it's still running a standard ecu and fuelling. Maybe the cat I have is just knackered.

[busta]

Just done a bit of research. According to this flow chart from mot.co.uk, it should come under the non cat test anyway, which I think is what the MOT chap has been doing after it failing the cat test. I'm using a different test station this year, so maybe I won't have any problems after all.

Can anyone confirm this? The way I read that chart, even though it obviously comes up on the computer, my reg. number won't bring up an 'exact match' because it isn't the standard engine, so it is therefore applicable for a non-cat test.