Exhaust Soot problem

[TurboDave]

Well, I guess it's time I broke down and asked the board for some insight into this nagging problem I've had for more than a decade.
Basically it's an exhaust soot problem on my 86. The stuff just pours out of the exhaust pipes and little drain holes in the muffs, especially when the car is cold, but also most of the time it's setting idling. Leaves nasty black spots under the car on the ground and also on the ground and garage wall near the exhaust tips.

The car runs perfectly, strong, etc. No black smoke, no rich smell, nothing. Just a lot of condensation, and as a result, soot.

As a side note I don't have this problem with my 87 (only a tiny bit immediately after a cold startup, like any car).

The 86's setup:
bone stock motor
vigilante 7 disc
(billet parts) 200R4
PTE44 turbo
MSD 50's
V2 FMIC
Translator +
LS1 MAF
GM heated O2 (AFS-74 I think)

This has been an ongoing problem for more than a decade, and during this time various parts have been added/changed, so I can't pin it down to any particular part on the above list. I think the larger injectors may have something to do with it, but not sure.

The car has almost perfect BLM's, the O2 is extremely active and always indicates that it's working perfectly, and I think it is because it immediately shows any "tuning adjustments" I make in the T+

As I said, the car runs perfectly, except for the soot problem :frown:

Hopefully someone has some insight on this.

 

[Mac in SD]

Dave,
Try putting an all-aluminum Stage 2 in it, and see if that helps.

 

[MSDGN]

My GN does the same thing...start it up and after it warms a little black spots on the garage floor...I have to keep from blipping the throttle or else it looks like someone splattered black paint all over the floor..walls and anything else that gets in it's way...my feelings are it's because of the Thrasher chip that I ran for so long and also had a 7th injector on for awhile...it tended to run on the rich side...the pipes are just coated now...the condensation moisture then mixes with it and spits out this black wet stuff...

 

[Mad_Trbo]

I know none of us are contributing to the solution, but I have the same issue with my T-Type. A lot of moisture and black sooty substance left on the garage floor. I figured it was from a rich condition, when looking at the A/F ratio I am @ about 12.5 on warm up. When I am warmed up the motor leans out to abou 14.1. I figure I could pull fuel to lean it out a bit but when I do that the motor stutters.

No help, but at least it helps to know we are all in the same boat.

 

[HellOnWheels]

Well, I guess it's time I broke down and asked the board for some insight into this nagging problem I've had for more than a decade.
Basically it's an exhaust soot problem on my 86. The stuff just pours out of the exhaust pipes and little drain holes in the muffs, especially when the car is cold, but also most of the time it's setting idling. Leaves nasty black spots under the car on the ground and also on the ground and garage wall near the exhaust tips.

The car runs perfectly, strong, etc. No black smoke, no rich smell, nothing. Just a lot of condensation, and as a result, soot.

As a side note I don't have this problem with my 87 (only a tiny bit immediately after a cold startup, like any car).

The 86's setup:
bone stock motor
vigilante 7 disc
(billet parts) 200R4
PTE44 turbo
MSD 50's
V2 FMIC
Translator +
LS1 MAF
GM heated O2 (AFS-74 I think)

This has been an ongoing problem for more than a decade, and during this time various parts have been added/changed, so I can't pin it down to any particular part on the above list. I think the larger injectors may have something to do with it, but not sure.

The car has almost perfect BLM's, the O2 is extremely active and always indicates that it's working perfectly, and I think it is because it immediately shows any "tuning adjustments" I make in the T+

As I said, the car runs perfectly, except for the soot problem :frown:

Hopefully someone has some insight on this.

Do the cars have the same exhaust system? Is there any way that air could be pulled into the system, maybe during an exhaust pulse??

Just a wag here,

HOW

 

[turbo2nr]

I hire a chimney sweep once a year to go thru all my cars. No problems here.

 

[asd60303]

I hire a chimney sweep once a year to go thru all my cars. No problems here.

haha...my gn and my dad's does this too. It's all on the walls of our garage when we get done working with it.

 

[DonnieShort]

My does this too, old stock motor and new motor. I think it's just the black carbon that coats the inside of the exhaust and it's mixing with the condensation in the pipes. Sounds logical anyway

 

[salvageV6]

Mine does it too, for 18 years now.

I think the warmup calibration in most of the chips are a bit rich.

Blame TurboBob.

Real bad in winter here when the temps. are just above freezing to 45 degrees or so and high humidity.

Lots of condensation soot and water.

Has never fouled a plug or anything on me however, must be the daily alky. tests.

I agree with Donnie.

 

[onefastcar]

I haven't installed my alky system in and thought it might alleviate this problem but by what i see in your signatures that won't be the case, oh well.

 

[TurboDave]

From the responses that I've recieved here and email (thanks flyinggn!) it sounds like a more common problem than I thought.

I'm quite convinced that it's a lot to do with the combination of injectors, and open loop fuel delivery (which is needed for the silky smooth idle we all enjoy these days). But it even tends to do it when the car's been driven around in closed loop for quite some time, although not nearly as bad.

To the question of exhaust systems, no the two have COMPLETLY different systems. The 86 gas an ATR dual 2.5" system with tiny little bullet race mufflers. The 87 has a dual 3" system with big round Ultra Flows. (Might have something here, as I don't remember seeing my Daughter's T puke any soot either) Hers has the ATR dual 3" system with stainless Pit Bulls. Hmmmmm

 

[TurboGN]

Mine didn't soot up the garage floor until the ATR 2 1/2 system was installed. Come to find out, the old system had a lengthy crack in the y-pipe and holes in the mufflers. I've changed injectors, chips, ecms, turbos, heads, yadda and all did the same. I came to believe that condensation would form, mostly when the engine was cold, if the exhaust system did not have leaks.

 

[B.B.]

I have no exhaust, just straight 2.5" pipes that turn down at the rear axle. (Sounds sweet with the TE-44) and mine too leaves 2 big sooty spots in the drive and will even leave 2 foot STRIPES of black soot after I back out of the drive and accel down the road.

I'm glad to hear its not that big of a deal!!

 

[soundguy]

seems it comes down to basic physics. After driving it, the entire exhaust path is gonna be quite hot. As it cools down condensation is gonna form inside thru the entire pathway. Only way to stop that would be to run out quick after shutting down and putting a plug in the exhaust tips. As more foms it'll eventually build up enough to run down and pool at low points. So as you start up and begin to run, the air running past will push it toward the exit till it dries up. After market exhausts will show this more as factory mufflers are so restrictive and the material inside them will absorb the moisture that is pushed out and any that tries to enter when it's shut down. The open muffler setups we love for the spool up allows for more moisture flow.