I went to the dealer today. My new Catalyst did not produce an easy pass. CO was the problem. The idle was OK, limit is 0.300, score was 0.285. But the fast idle, limit is 0.200, and the score was 0.516, so way over. The lambda was good.
The issue was that increasing the idle speed, was richening the mixture, off the scale. This was not due to the catalyst but could have been a throttle body issue, an engine temp sensor issue, or the ECU mapping. The diagnostic showed that the engine temperature sensor indicated 103c, so that appeared to be OK.
So I had a dilemma. The dealer doesn't have access to the Aero Racing ECU upgrade, without sending the box through the post to Morgan, and it was suggested a while ago, that this may not be possible soon, or even 'now'. So I could either return home with a second fail, or have the standard ECU map re-applied, but lose the AR mapping.
Way back in 2018, I first picked up my AR Clubsport manifold and exhaust system from the factory, and fitted it at home. There was a distinctive improvement just with that change. So I then returning to the factory to have the ECU flash, and immediately found stronger revving at the top end. With this experience I decided to go back (risky) to the standard re-map today, and that gave an immediate MOT pass. The idle limit is 0.300, score was 0.264. The fast idle, limit is 0.200, and the score was 0.019, so well under.
As standard, 2016-2018, the throttle was hair trigger, and the tailpipe was black soot. The AR flash softened the throttle and cleaned the tailpipe, with hardly any deposits, but the colour turned black after my bad running experience in October 2024. The new catalyst cleaned the tailpipe again with hardly any deposits.
After todays changes, the throttle is not hair trigger, but maybe slightly harsher. The tailpipe is now black and sooty again.
This has been my experience today, and if I need to keep the standard ECU set-up to get an MOT pass, so be it. On the drive home, 55 miles, quite honestly, there was no discernable difference. The clean revving was still apparent.
