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The owner of this Triumph Bonnie America was a switched on type of chap and as he’d added free-breathing pipes was concerned about his fuelling. He was running one of Triumph’s own maps (to suit the pipes) but it didn’t work for him so he brought it in for a remap.

And it was immediately obvious why once we’d gone and and read the map; it was massively lean. So an awful lot of fuel was needed to sort the throttle response out. One of the main tables that we work in is the switching table between the Manifold Air Pressure map (MAP) and the main throttle position map.

This makes a huge difference because what Triumph (and many others) do is to get the engine to run on the lambda and MAP map, because then the ECU can control the fuelling. When it goes onto the throttle map the rider has a lot more input – this is purely to squeak by the Euro 4 emissions testing.

The result after the remap was like night and day – a very pleasing engine feel and 54bhp at the rear wheel.

Open pipes and a Bonnie America running lean – nothing an ECU remap couldn't fix.

Open pipes and a Bonnie America running lean – nothing an ECU remap couldn’t fix.

We’ve done a few of these now, and a Mr Plummer was kind enough to email his thoughts. We haven’t got a picture of his bike though, sorry!

Dear BSD,

 The America now feels:

Ø       Fully dialled into the exhausts (Triumph Off Road Hi Flo)

Ø       More power at lower revs

Ø       Nice and sharp

Ø       Direct feel to throttle, woollyness gone

Ø       Exhaust note mellow and crisp

Ø       Popping on overrun completely gone

Ø       Spot on for standard engine

 Thank you for a job well done – a must for any bike alterations

 D. Plummer