while on the rollers at the recent John Nobles Rolling Road day, my scooby shot out 2 big puffs of Black smoke from the exhaust! this occured towards the end of the test around 5000 - 6000 rpm in think.

is this normal? caused by overfuelling or is there something wrong!? as i didnt see any other scoobys that day doing this.

video clip: right click and save target as...

small file...
http://www.ntptransmit.co.uk/peccy/peccyRollers.wmv

BIG file...
http://www.ntptransmit.co.uk/peccy/peccyRollersHI.wmv

MODS: full decat / induction / TEK2.5 remap / VTA dump valve

cheers, peccy

 

See what you mean, but i guess it is nearer 5krpm

Does your graph indicate anything?

 

P20SPD,

the graph didnt show anything, and the RR guy even mentioned that everything seemed spot.

PS. I get lots of pops / bangs / flames so wonder if it was just all the crap and carbon build up getting blown out???

 

Probably is all the crap being puffed out. Most cars i have seen puff soot out, mine included is when they suddenly get booted of when on lift off.

Not when they halfway through a progressive load like on the rollers.

 

How long's your exhaust been on? One incident sticks in my mind -- a couple of years back I was following a Skyline on the motorway for 10+ miles in medium traffic. He had a big-bore exhaust on.

The outside lane cleared suddenly, he must have dropped a cog and booted it because it puffed out a HUGE cloud of soot as he cleared off ahead -- it was literally like a dark grey-black smokescreen ... but it wasn't oil smoke. I caught up later at the next knot of traffic and there were no further emissions.

What I'm getting at is I'd followed the guy for about 10 mins with him on modest throttle openings, but when he cracked it open there must have been some resonance or pressure build-up which blew out all the cack in the exhaust boxes.

If the RR results gave the car a clean bill of health, sounds like much the same happened with yours.

 

Yeah but that is different to being on the rollers. When on the rollers they put their foot down, or should do, so no sudden kick, just a progession. Very much different to coasting off boost, and then booting it like you say.

It could be that it was knocking and being retarded, possibly letting unburt fuel into the exhaust, the subsequent pop blows out the soot.

I dont know, maybe John Banks, Pat, Pavlo or Bob Rawle may be better at answering that one.

 

black smoke usually means its running rich..!! could just have been a blip where the fueling went rich...???

Dan

 

I've seen loads of cars do this....

Especially ones with Booster...

Cant see it being such a problem.. except on the fuel bill!

 

There were actually four instances with two much heavier than the others, looks like around 4800 then 5800 then 6-7000 as a guess, could be a couple of things, car running through a very rich part of the fuel map is one, the other is detonation, that causes the carbon to come off the piston crown and also induces a sort of misfire that has the same effect. The det could be very light, since JB mapped it I would think it unlikely although poor fuel would make it spit and the Jecs does miss instances like those seen as its mainly a transition effect. The run up is relatively steady, assuming a top mount charge temps would be much higher than on the road again causing the car to spit.

Just some thoughts