Technical Exhaust Smoke when Changing Down Gears

[Boggie]

Hi All.

I just collected my daughter's car (a 2011 Twinair with 42K miles) from having a new exhaust fitted. On the drive home, I noticed that occasionally, when changing down a gear to slow for a corner, quita a big puff of bluish / grey smoke came out of the rear of the car. This cleared as I accellerated away but happened 2 or 3 times during the journey. The car seems to be running well and pulling as expected. Any ideas what this might be, please?

Thanks.

 

[Pugglt Auld Jock]

might just be the new system "burning in" - especially if it was one at the more bargain end of the market. If this is the case it should go away pretty quickly, certainly within the first 50 miles or so. Have you been able to get some idea of what it smells of? If it's just it settling down then it'll probably smell of burnt paint, especially if it's a cheap system. Bluey grey smoke might be oil - but lets not go there until we find out if it's settled down after a few miles. Difficult to imagine what they might have done to make it burn oil simply by fitting an exhaust? Might be worth just keeping a daily eye on oil level? Dare I ask where it was done?

If the smoke persists then we'll need to get our thinking caps on.

 

[steveras57]

1st question is was it smoking before the new exhaust was fitted? or did it start smoking after the new exhaust was put on?-If its the later then its almost certainly some sort of internal contaminant to the new exhaust! be- it -all, paint, oil ,or some sort of internal coating ! or possibly even water/condensation either way this should burn off fairly quickly! go for a longish run(about 20miles) at higher revs if possible then check again!.

 

[Boggie]

Thanks, both.
I don't think it was smoking before, but there's a fair chance I might not have noticed it. I wasn't suggesting this is due to the new exhaust, though. I mentioned it purely to set the scene. If it was the paint or other contaminents, such as a little oil or grease to help sliding the centre pipe flexi end onto the downpipe from the cat, then I would imagine it would smoke a little (whereas this was quite a lot - a big "puff" at downshift point) and it would smoke all the time until burnoff is complete, particularly at tickover (where there was no smoke) rather than only at the point where the throtle is released as a lower gear was selected. I may be wrong though (it has been known... ). I was wondering whether there is a sticking crankcase breather (PCV) that is dumping oil into the inlet. I will see how it runs tomorrow, as well as check inside the airbox for oil, then report back.
Cheers!

 

[steveras57]

good plan!.

 

[Pugglt Auld Jock]

Thanks, both.
I don't think it was smoking before, but there's a fair chance I might not have noticed it. I wasn't suggesting this is due to the new exhaust, though. I mentioned it purely to set the scene. If it was the paint or other contaminents, such as a little oil or grease to help sliding the centre pipe flexi end onto the downpipe from the cat, then I would imagine it would smoke a little (whereas this was quite a lot - a big "puff" at downshift point) and it would smoke all the time until burnoff is complete, particularly at tickover (where there was no smoke) rather than only at the point where the throtle is released as a lower gear was selected. I may be wrong though (it has been known... ). I was wondering whether there is a sticking crankcase breather (PCV) that is dumping oil into the inlet. I will see how it runs tomorrow, as well as check inside the airbox for oil, then report back.
Cheers!

Aye, what you're describing doesn't sound so much like just a little "burn off" smoke. I await further reports with interest.