Turbo engine - black smoke when coming off boost?

[DannyVTS]

Afternoon guys

I was following a Sierra Cosworth the other day, which decided to boot it when we got to a NSL road.

I noticed that when he changed gear the car let out a lot of black smoke, along with a loud backfire. I was about 100 meters behind him and it was still bloody loud.

It got me thinking what causes this? The car was about 20 years old and was definitely a Cosworth (judging by the pace it took off at anyway)

-Danny

[trickywoo]

Over fueling.

It was probably running more boost than standard and the map was set rich. Too lean can lead to detonation and melted pistons.

[v8will]

trickywoo said:

Over fueling.

It was probably running more boost than standard and the map was set rich. Too lean can lead to detonation and melted pistons.

This, probably some old skool tuning going on.

[mnkiboy]

Ah the things you can get away with when you don't have to have a catalytic converter.

I'd love to see the emissions check at MOT time. "Unable to take a reading as the probe is covered in unburnt fuel. And on fire".

[Chrisw666]

trickywoo said:

Over fueling.

It was probably running more boost than standard and the map was set rich. Too lean can lead to detonation and melted pistons.

Sounds like it, it could also be some naughty (i.e. not strictly road legal) tuning using an anti lag system.

[ferkle]

Mapped like Forrest Gump, i.e. rich and retarded - come off boost, fuel dumped and escapes via exhaust ignited in the turbo/exhaust black smoke, pop etc... turbo won't last terribly long but good fun and make you look up, right?

[Mastodon2]

Sure it wasn't a diseasel engine dropped in, flying off on a mountain of torque, shooting gouts of black smoke as it went?

I often laugh when I see a big rep mobile derv (no doubt with the smallest engine size available) puffing off down the road, blasting smog as they go.

[wolves_wanderer]

mnkiboy said:

Ah the things you can get away with when you don't have to have a catalytic converter.

I'd love to see the emissions check at MOT time. "Unable to take a reading as the probe is covered in unburnt fuel. And on fire".

Mine has a cat and let out enough of a bang and flame to almost take the MOT chappies eyebrows off

[Lucas Ayde]

Mastodon2 said:

Sure it wasn't a diseasel engine dropped in, flying off on a mountain of torque, shooting gouts of black smoke as it went?

I often laugh when I see a big rep mobile derv (no doubt with the smallest engine size available) puffing off down the road, blasting smog as they go.

It's always amusing to see the big puff of black smoke when the diesel in front tries to boot it, a dead giveaway that the driver is really trying to give it some beans.

[DanSaff]

Does depend on which Cosworth as the ecu functions do vary but....

Sounds like he hit the revlimiter - which cut the spark so left fuel unburnt which gave the black smoke and the bang was it igniting in the exhaust blowing the cobwebs out.

Black smoke on acceleration is too much accel enrichment which decays off to let the ecu use the mapped main fuel table.

Blue smoke on acceleration engine fubar oil being sucked up through rings or down valve guides