The main question here is does the MOT tester check to see that the DPF can is still in place or does he carry out a stricter smoke test to question if the can might be empty? I don't think the Tester would be allowed to remove and inspect the DPF casing or even to fail it if welded as it may have genuinely been repaired.

We have been installing LPG systems for many years and have removed the contents of many catalysts at customers requests. When sending these vehicles for MOT whilst running on LPG they still have to appear that a cat is fitted but a cat test isn't carried out, in these cases the old pre-cat emissions still apply, 3.5% co and 1200ppm HC i think.

We've carried out many DPF removals (emptying the contents) over the last 2 years and in most cases also installed a modified map for better performance and more economy, some of which smoke more than standard.

If these vehicles still were to pass the MOT visually but fail on excessive smoke then this could be easily temporarily corrected by further remapping or by turning down the fueling with a CRD tuning box.

Eddie Zyla
CRD Performance - Bolton.