The owner of this Triumph had fitted an end-can plus removed the catalyser, and brought it in to get sorted out with an ECU remap. We started by switching off the lambda sensor and secondary air; it was running very lean in the bottom end (its ‘normal’ cruise rpm range, up to 6,000rpm). And it felt horrible, too…

On the Dyno it showed to be lean in this area to the point of being dangerous for the engine’s long-term health. Also up top, because it was breathing free it also needed more fuel. Between 6-7,000rpm it was actually fine!

The important detail to note here is that bunging an end-can on can have consequences that will need sorting – there’s a myth that the lambda and ECU will correct the fuelling. Wrong! The lambda is there to keep the cat’ warm, no more, no less. It’s not a fuel correcting device…

Woefully lean pretty much everywhere – if you fit a can, you're fuelling will need sorting for engine health...

Woefully lean pretty much everywhere – if you fit a can, you’re fuelling will need sorting for engine health…