Fabia VRS Smoking with and without tuning box

Hi,

Wondered if anyone has any advice on black smoke from a fabia VRS. I have a 5000 mile 54 plate VRS fabia.

I recently fitted an original tuning box and although it felt more lively (agree with comments on jerkiness etc) I noticed that it produced far more black smoke at low revs, especially when cold.

Later, when it was fully warmed up I gave it some hard acceleration on the motorway and noticed that it really smoked badly (this time white/grey smoke) above 3800 RPM.

Researching this indicated that the black smoke is over fueling, whilst the grey smoke is under fueling.

I decided to remove the unit as I didn't want to damage the car.

The difference wasn't as noticable as when I installed the unit, and since removing it my MPG has improved which can't be bad.

However, a friend that travels to work has been behind me twice this week and has commented on how bad the black smoke is, assuming I still had the tuning box fitted (they originally commented on the smoke when I had the box fitted).

So I'm now not sure if the unit did make much difference, although I'm still not happy with the grey smoke, that was very bad at the time and the car doesn't do this without the tuning unit.

Anyone had similar experiences?

Many thanks.

Andy