After Burners On

[BarnFind]

My Chimaera has a LS engine which failed the MOT on emissions the other day,My Mechanic found I had a malfunctioning CAT so sent the Chim off to have both Cats replaced.
I collected the car the other evening drove for about 20 miles and on joining a Dual carriageway overtook a Porsche who decided a race was needed,I hit the gas and showered him in sparks which cooled his ardour somewhat,for the next 10 miles I spat sparks and I mean sparks 20 feet behind me on acceleration.
i have spoken to both my mechanic and the exhaust people who can't shed much light on the situation,I don't suppose anybody has any ideas on what was going on,no flames by the way just sparks...

[TrotCanterGallopCharge]

I'm no mechanic, can only think of;-

Dust from baffles or soot being blown out after cats replaced under heavy load/acceleration?
Dust/particles from new cats ditto.
Your exhausts or other piece of metal having a low point very close to tarmac, which under heavy acceleration touches tarmac to cause sparks?

An odd one. Whoever replaced cats may need to look at setup again, or get Cats manufacturer Tech Dept to comment.

Hope it's a bedding in item rather than something else.

[Byker28i]

Sounds like the Cats disintegrating?

[Granturadriver]

I am no expert either.

What I've read elsewhere suggests that substances other than the gas or gas mixture cause sparks in high heat.

There is talk of soot in the exhaust or the insulation wool from the exhaust burning or burned catalyst ceramic.

[GreenV8S]

If the sparks are staying bright long enough for the driver to see them, you've got metal in the exhaust. That's almost certainly from the cat.

Given that the other cat had failed, it's possible you have a missfire or mixture imbalance which is causing unburned fuel and oxygen in the exhaust. Perhaps this is what caused the previous cat to fail. Now that you have a working cat, it would have tried to burn the fuel on the way through. The resulting heat melts the cat. I expect the cars behind you now have holes burnt in the paintwork all over the front.

[spitfire4v8]

Sparks out of an exhaust are rarely good news. As peter says above this is most likely your lovely new cat destroying itself ..
first step is to go back to your garage as they would appear to have cured the symptom (no cat) but not the cause ...

[BarnFind]

Thanks for all that,still awaiting a reply from Exhaust Man and my Mechanic.I have Carbon Cans on the back of the exhaust but they seem to be intact.Fortunately the Porsche was the only car to get the sparks shower,must keep an eye out in the Porsche section for Fire Breathing TVR's !!