Go Back   AnandTech Forums > Social > The Garage

Forums
· Hardware and Technology
· CPUs and Overclocking
· Motherboards
· Video Cards and Graphics
· Memory and Storage
· Power Supplies
· Cases & Cooling
· SFF, Notebooks, Pre-Built/Barebones PCs
· Networking
· Peripherals
· General Hardware
· Highly Technical
· Computer Help
· Home Theater PCs
· Consumer Electronics
· Digital and Video Cameras
· Mobile Devices & Gadgets
· Audio/Video & Home Theater
· Software
· Software for Windows
· All Things Apple
· *nix Software
· Operating Systems
· Programming
· PC Gaming
· Console Gaming
· Distributed Computing
· Security
· Social
· Off Topic
· Politics and News
· Discussion Club
· Love and Relationships
· The Garage
· Health and Fitness
· Merchandise and Shopping
· For Sale/Trade
· Hot Deals with Free Stuff/Contests
· Black Friday 2014
· Forum Issues
· Technical Forum Issues
· Personal Forum Issues
· Suggestion Box
· Moderator Resources
· Moderator Discussions
   

Reply
 
Thread Tools
Old 11-03-2012, 10:19 AM   #1
Demo24
Diamond Member
 
Demo24's Avatar
 
Join Date: Aug 2004
Location: North GA
Posts: 7,868
Default What causes black soot on a gas engine car?

Yesterday on my drive home I ended up behind a douche in civic si who proceeded to tailgate a line of cars going up the on-ramp then 'blast' over immediately to the left lane before the merging area and got behind yet another line of cars. While I was watching this guy attempt to be a badass in a civic si I noticed that on his full throttle exploits a whole lot of black soot coming out the tail pipe. It occurred to me that I had no idea what causes that on a gas engine car, maybe direct injection and carbon buildup? It was a previous gen si coupe, so not brand new but only a few years at most, dunno if they had DI then or not.
__________________
.........
Demo24 is online now   Reply With Quote
Old 11-03-2012, 10:26 AM   #2
OVerLoRDI
Diamond Member
 
OVerLoRDI's Avatar
 
Join Date: Jan 2006
Location: San Francisco, CA
Posts: 5,290
Default

Burning oil?
__________________
TROOPER: Caselabs M8, i5 3570k, 16gb DDR3, 2x7970, X-1050
TARDIS: 750D, i5 2550k, 8gb DDR3, 7970, AX850, 8TB storage
CUBE: INWIN BQS656, Celeron something?, 4gb RAM, 32gb SSD
http://heatware.com/eval.php?id=73710
OVerLoRDI is online now   Reply With Quote
Old 11-03-2012, 10:36 AM   #3
Atty
Golden Member
 
Atty's Avatar
 
Join Date: Aug 2006
Posts: 1,513
Default

My '12 2.0T GTI has a massive amount of black soot around my exhaust pipes. Completely stock with less than 2k miles on it. Hope its not burning oil and just lots of powaaaaaa.
Atty is offline   Reply With Quote
Old 11-03-2012, 10:41 AM   #4
Demo24
Diamond Member
 
Demo24's Avatar
 
Join Date: Aug 2004
Location: North GA
Posts: 7,868
Default

Quote:
Originally Posted by OVerLoRDI View Post
Burning oil?

This was solid black and looked 'sooty' not smokey, and it only occurred at full throttle.
__________________
.........
Demo24 is online now   Reply With Quote
Old 11-03-2012, 10:42 AM   #5
Ferzerp
Diamond Member
 
Join Date: Oct 1999
Posts: 5,302
Default

Unburned/not fully burned gasoline appears black just as diesel does, it's just that diesel is far more prone to it.
Ferzerp is online now   Reply With Quote
Old 11-03-2012, 10:49 AM   #6
dawp
Diamond Member
 
dawp's Avatar
 
Join Date: Jul 2005
Location: here until I move again
Posts: 6,748
Default

possibly a badly done chip? or an extremely dirty air filter.

if it was a carbed car, the mix would be off.
__________________
We Have Met The Enemy and He Is Us

ASUS p8z77 v, i7 3770k, crucial Ballistix Sport 16GB, XFX HD7970 Black Edition
dawp is offline   Reply With Quote
Old 11-03-2012, 11:01 AM   #7
SyndromeOCZ
Senior Member
 
Join Date: Aug 2010
Posts: 606
Default

Burning alot of oil can do it as well. My brothers 05 gmc canyon goes through a quart every couple hundred of miles and it soots more than some diesels.
SyndromeOCZ is offline   Reply With Quote
Old 11-03-2012, 11:02 AM   #8
wirednuts
Diamond Member
 
Join Date: Jan 2007
Posts: 7,121
Default

its not burning oil, thats a blue-ish white smoke.

its because at full throttle, gas is being dumped into the engine at his max levels, which inevitably some of it doesnt burn. that goes to your cat which it smolders and spits out as black smoke.

if you can, just stay under WOT. if you continue to see black soot, then check your o2 sensors.
wirednuts is offline   Reply With Quote
Old 11-03-2012, 11:06 AM   #9
Pacfanweb
Lifer
 
Join Date: Jan 2000
Posts: 12,455
Default

Yep, it's gas. Happens to every car when you floor it.
__________________
I asked a ref if he could give me a technical foul for thinking bad things about him. He said, of course not. I said, well, I think you stink. And he gave me a technical. You can't trust em. -
Jimmy V

"One of the reasons I left Sabbath is Van Halen was blowing us off the stage every night. It was embarrassing." Ozzy
Pacfanweb is offline   Reply With Quote
Old 11-03-2012, 05:24 PM   #10
KentState
Diamond Member
 
KentState's Avatar
 
Join Date: Oct 2001
Location: Atlanta, GA
Posts: 5,742
Default

This happens under rich conditions in any car which typically at WOT. A/F is a ratio so a lot more un-burnt gas is seen if you are pushing 50+ psi per cylinder of fuel into the engine as compared to cruising down the road. The catalytic converter can only do so much in these conditions as well.
KentState is offline   Reply With Quote
Old 11-03-2012, 09:05 PM   #11
LTC8K6
Lifer
 
LTC8K6's Avatar
 
Join Date: Mar 2004
Location: Under an American chemtrail
Posts: 18,295
Default

I have never had a fuel injected car show any signs of running rich. Never had one get dirty near the tailpipe tip, either.

My 2008 Jeep GC 5.7L, which I floor quite often, has never had any soot on it.
__________________
no offense, but does he have some sort of mental dissability? -nick1985

Brainwashed, mentally unstable, and stupid Intel user, screwed by Intel and located directly under a chemtrail.

Don't be a moron! Buy AMD!
LTC8K6 is offline   Reply With Quote
Old 11-03-2012, 09:09 PM   #12
iamwiz82
Lifer
 
iamwiz82's Avatar
 
Join Date: Jan 2001
Posts: 30,505
Default

Direct Injection causes soot on new cars, not sure what year, or even if the Civic has DI.
iamwiz82 is offline   Reply With Quote
Old 11-03-2012, 09:15 PM   #13
Ferzerp
Diamond Member
 
Join Date: Oct 1999
Posts: 5,302
Default

Quote:
Originally Posted by LTC8K6 View Post
I have never had a fuel injected car show any signs of running rich. Never had one get dirty near the tailpipe tip, either.

My 2008 Jeep GC 5.7L, which I floor quite often, has never had any soot on it.
They shouldn't if working properly, but it's by no means impossible.
Ferzerp is online now   Reply With Quote
Old 11-03-2012, 09:16 PM   #14
phucheneh
Diamond Member
 
phucheneh's Avatar
 
Join Date: Jun 2012
Posts: 6,675
Default

Quote:
Originally Posted by KentState View Post
This happens under rich conditions in any car which typically at WOT. A/F is a ratio so a lot more un-burnt gas is seen if you are pushing 50+ psi per cylinder of fuel into the engine as compared to cruising down the road. The catalytic converter can only do so much in these conditions as well.
Um...what?

No, 'any car' does not emit black smoke. The engine has to be running VERY rich to putting out black smoke. Hell, on newer cars, you could disconnect the O2's and the ECT and I still doubt you would get any black smoke.

While the catalyst does trigger an oxidation reaction with the small amounts of hydrocarbons (and carbon monoxide) that are present in the exhaust, it is not intended for cleaning black soot out of the exhaust gas.

This is why diesel trucks have separate particulate filters. Gas engines can and do emit particulates, but they are so fine as to not be readily visible. Some people want particulate filters on gas cars, too- because the catalytic converter doesn't catch them.

And finally, fuel mixture in EFI cars is not controlled by fuel pressure. Fuel pressure is intended to remain relatively constant...fueling at various levels of RPM and load is controlled by duty cycle (how long and how often the injector solenoids are energized).

Christ, and people nitpick me...
phucheneh is offline   Reply With Quote
Old 11-03-2012, 09:23 PM   #15
Ferzerp
Diamond Member
 
Join Date: Oct 1999
Posts: 5,302
Default

He said any car running [sufficiently] rich could do it. Technically he's correct.

If you want to go off on someone, go off on the silly person who said *every* car does it.
Ferzerp is online now   Reply With Quote
Old 11-03-2012, 09:32 PM   #16
phucheneh
Diamond Member
 
phucheneh's Avatar
 
Join Date: Jun 2012
Posts: 6,675
Default

...I thought that was him?

Quote:
This happens under rich conditions in any car which typically at WOT.
Kinda Engrishy, but I took that to essentially mean 'this happens at WOT because the car is using more fuel.'

Even if the car is heavily overfuelling, WOT should actually smoke the least, shouldn't it? I'm not sure because an EFI car spitting black smoke just isn't something you have to deal with very often...the only instances I can remember seeing any significant amount of smoke involve forced induction blowing charge pipes off. Or just really awful 'custom' tunes.

Oh, you meant this guy-

Quote:
Originally Posted by wirednuts View Post
its not burning oil, thats a blue-ish white smoke.

its because at full throttle, gas is being dumped into the engine at his max levels, which inevitably some of it doesnt burn. that goes to your cat which it smolders and spits out as black smoke.

if you can, just stay under WOT. if you continue to see black soot, then check your o2 sensors.
Some of the OXYGEN doesn't burn. Ideally, all of the fuel (relatively speaking) should burn. Hence...oxygen sensors. Not hydrocarbon sensors.

Bad O2 sensors that set a CEL will make the car run in open loop (should not cause smoke). Ones that don't are just not as sensitive as they should be, which will make the car run lean, not rich- ECM sees too little oxygen, assumes the engine is running rich, and dials the fuel back.

Last edited by phucheneh; 11-03-2012 at 09:38 PM.
phucheneh is offline   Reply With Quote
Old 11-03-2012, 09:38 PM   #17
Vdubchaos
Diamond Member
 
Join Date: Nov 2009
Posts: 8,620
Default

Quote:
Originally Posted by Atty View Post
My '12 2.0T GTI has a massive amount of black soot around my exhaust pipes. Completely stock with less than 2k miles on it. Hope its not burning oil and just lots of powaaaaaa.
hehe

you just wait buddy

Last edited by Vdubchaos; 11-03-2012 at 09:41 PM.
Vdubchaos is offline   Reply With Quote
Old 11-03-2012, 09:44 PM   #18
Ferzerp
Diamond Member
 
Join Date: Oct 1999
Posts: 5,302
Default

Quote:
Originally Posted by phucheneh View Post
...I thought that was him?



Kinda Engrishy, but I took that to essentially mean 'this happens at WOT because the car is using more fuel.'

Even if the car is heavily overfuelling, WOT should actually smoke the least, shouldn't it? I'm not sure because an EFI car spitting black smoke just isn't something you have to deal with very often...the only instances I can remember seeing any significant amount of smoke involve forced induction blowing charge pipes off. Or just really awful 'custom' tunes.

Oh, you meant this guy-



Some of the OXYGEN doesn't burn. Ideally, all of the fuel (relatively speaking) should burn. Hence...oxygen sensors. Not hydrocarbon sensors.

Bad O2 sensors that set a CEL will make the car run in open loop (should not cause smoke). Ones that don't are just not as sensitive as they should be, which will make the car run lean, not rich- ECM sees too little oxygen, assumes the engine is running rich, and dials the fuel back.

Naw, I meant the "happens to every car when you floor it" guy.
Ferzerp is online now   Reply With Quote
Old 11-03-2012, 09:47 PM   #19
phucheneh
Diamond Member
 
phucheneh's Avatar
 
Join Date: Jun 2012
Posts: 6,675
Default

Quote:
Originally Posted by Ferzerp View Post
Now, I meant the "happens to every car when you floor it" guy.
Oh...I think I missed him because his sig is three times as long as his post.

Still though...I don't think I've posted anything incorrect. But if you think so, we can totally fight about it.

And then have makeup buttsex.
phucheneh is offline   Reply With Quote
Old 11-03-2012, 10:05 PM   #20
Ferzerp
Diamond Member
 
Join Date: Oct 1999
Posts: 5,302
Default

I'm just saying that one guy was not really wrong.

Last edited by Ferzerp; 11-04-2012 at 05:02 PM.
Ferzerp is online now   Reply With Quote
Old 11-04-2012, 07:10 AM   #21
Demo24
Diamond Member
 
Demo24's Avatar
 
Join Date: Aug 2004
Location: North GA
Posts: 7,868
Default

Excess gas makes sense now I think about it, also very much so in this situation as it looked fairly modified. Had a dealer tag on it too, sucks for that guy I guess, looks like he bought a car with a crappy tune.
__________________
.........
Demo24 is online now   Reply With Quote
Old 11-04-2012, 08:32 AM   #22
nerp
Diamond Member
 
nerp's Avatar
 
Join Date: Dec 2005
Location: Cranston, RI
Posts: 7,993
Default

No car should do this at WOT unless it's old or the victim of a hackjob mod.
__________________
iMac 27" i3 3.2 Mid 2010 | AMD A4-3400 Win 7 MCE | Atom D525 1.8 WHS 6TB
nerp is offline   Reply With Quote
Old 11-04-2012, 10:52 AM   #23
BUTCH1
Lifer
 
BUTCH1's Avatar
 
Join Date: Jul 2000
Posts: 13,147
Default

Quote:
Originally Posted by nerp View Post
No car should do this at WOT unless it's old or the victim of a hackjob mod.
No FI car anyway, back when "feedback" carbs were around this was common, I'd go with hackjob tune..
__________________
Would Jesus microwave a burrito so hot that he himself
could not eat it?? Homer Simpson.
BUTCH1 is offline   Reply With Quote
Old 11-04-2012, 11:07 AM   #24
jlee
Lifer
 
jlee's Avatar
 
Join Date: Sep 2001
Location: AZ
Posts: 44,521
Default

Quote:
Originally Posted by phucheneh View Post
Um...what?

No, 'any car' does not emit black smoke. The engine has to be running VERY rich to putting out black smoke. Hell, on newer cars, you could disconnect the O2's and the ECT and I still doubt you would get any black smoke.

While the catalyst does trigger an oxidation reaction with the small amounts of hydrocarbons (and carbon monoxide) that are present in the exhaust, it is not intended for cleaning black soot out of the exhaust gas.

This is why diesel trucks have separate particulate filters. Gas engines can and do emit particulates, but they are so fine as to not be readily visible. Some people want particulate filters on gas cars, too- because the catalytic converter doesn't catch them.

[b]And finally, fuel mixture in EFI cars is not controlled by fuel pressure. Fuel pressure is intended to remain relatively constant...[/n]fueling at various levels of RPM and load is controlled by duty cycle (how long and how often the injector solenoids are energized).

Christ, and people nitpick me...
Not necessarily. Toyota's 3S-GTE's fuel pressure varies based on boost level. Duty cycle does vary as well, of course, but fuel pressure is not constant once you're at positive manifold pressure.
__________________
Heat Tacoma MR2 LX450
jlee is online now   Reply With Quote
Old 11-04-2012, 01:58 PM   #25
exdeath
Lifer
 
exdeath's Avatar
 
Join Date: Jan 2004
Posts: 13,473
Default

Black stuff in any combustion process is carbon as a result of an imbalanced chemical reaction leaving behind carbon with no oxygen to combine with to form CO2; eg: rich mixture.

Anything from cars to the pilot light on your natural gas water heater, to random crap you burn with a cigarette lighter.

A burst of black exhaust in a tuned car is normal immediately following a transition to WOT. This is called "accelerator pump" logic or tip in enrichment. Air flow changes in an engine are instant, while fuel metering lags behind because the computer and fuel system can only respond to what JUST happened, not predict whats GOING to happen. There is a brief opportunity for knocking and engine damage to occur if the fuel system doesn't respond fast enough to the sudden unpredictable increase in airflow, compounded by the fact that this usually occurs under the heaviest load condition at lower RPM since you are accelerating and starting a pull.

To compensate, when a sudden swing in TPS and manifold pressure occur, an extra unmeasured shot of fuel is blindly added on top of the normal load/RPM value in anticipation of the incoming air to keep the mixture on the safe side during this chaotic transition. Too rich is better than too lean. This value cannot be measured or predicted by the computer, it is a static value tweaked by a human tuner. This enrichment shot only lasts a second or two until the transition to WOT completes and the sudden change stabilizes and becomes steady state.

On any kind of high performance engine with high compression, high boost, etc, this can be very rich, especially with a factory tune where they have to account for the worst possible climates, temperatures, terrible fuel octane, owner abuse, etc.

Normally a catalyst will clean up much of this and burn the remaining fuel, but on a higher performance car with a more aggressive tip in and aftermarket catless exhaust, black smoke on hard acceleration is normal. It doesn't matter if it's gasoline, diesel, natural gas, anything involving HC + O2 combustion.

Last edited by exdeath; 11-04-2012 at 02:17 PM.
exdeath is offline   Reply With Quote
Reply

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 03:54 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.