Help Trying To Diagnose Exhaust Vapour/dust/oil

[ish]

hey!

I have a bit of a hypothetical question for a few cluey engine gurus

i am planning a trip to look at a a car (r32gtr) over 3000 kms away.

Now after pumping this guy for as much info on the phone as i can this is what i have managed to get out of the convo

the car has some sought of vapor coming out of it on down changes which the owner says he has been told the cat is buggered after he took it into get a new cannon put on it and that its whats causing it to blow smoke etc on a down change

he tells me that he reset the PFC back to base map because the engine was detonating after the exhaust mod which i would assume the car is running rough/Rich...

does a worn out cat (original or 14 year old Approx) make exhaust vapor/Dust on a down change or is there something maybe wrong elsewhere in the engine ?

the strange thing is that he only reset the pfc after the exhaust change so i am thinking its not fuel coming out of the exhaust as the exhaust place was the one that told him his cat was buggered and this maybe the cause of the mysterious gas/dust/fuel/oil comong from the exhaust pipe...

Could someone help me out on what maybe going on with this...

he is fairly sure its not blue smoke but in saying that he dosent understand engines to well either

thanks Dj

Edited March 5, 2008 by ish

[Jmaac]

Those vapours could be from an ATMO or hybrid BOV on a down change. At high rpm a blocked cat can cause a leak b/n flanges

Sounds ok, increase in breathing hence running richer thus noticably more smoke. Without a tune it would run rough, if not stall with the ATMO unless compensated for with the PFC. Not sure about the detonation, maybe it has something to do with the missing air that the atmo releases and the sys. cant meter

[ish]

Thanks Jmaac...

i am curious to see how and whats happening. Seems a bit odd to me the order he has described.

[foney]

LOTS AND LOTS OF SMOKE. FILLS UP THE CABIN, CANT BREATH, PINK SMOKE BLUE SMOKE YELLO SMOKE AND SMOKE SMOKE.. :-P

Pretty sure All skylines pump a bit of smoke out if they have not been drivin in a long period of time.. gotta remember its a 18 year old car..

CHEEEEEEEEEEEEEEEEEEEEERS

[RB30-POWER]

could be the pcv valve sucking excessive blowby in when the car decelerates and engine inlet manifold vacuum is high. pcv valve is closed under boost.

otherwise if the car is cold and has atmo bov, could be dumping fuel in on decel because of the unmetered air exiting the bov, when its hot it should fuel cut altogether (turn off injectors) on decel so you shouldn't get fuel smoke from atmo bov.

[ish]

disco smoke lol ... hurry up and get home so i can have a look Mr Fone....