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#1586415 - 09/02/09 01:44 AM Exhaust carbon buildup vs clean
gaspo Offline


Registered: 10/15/05
Posts: 133
Loc: Cal
Wondering why some engines produce a lot of carbon deposits inside exhaust pipe and other remain squeaky clean for 100K+ ml. For instance - all Toyota Tacoma's i've seen year 2005 + getting charcoal black exhaust tip within first several thousand miles while Tacoma year 2004 and below mostly looking very clean . Seem like new engines design run much richer and if so what adverse effect can be in term of vehicle performance ? My Taco year 2005 / 47K ml, none measurable oil consumption if any at all. OCI ~7K ml f00l synthetic gr.III mostly PP or Synpower. Always top tier gas. My exhaust pipe color appear to be jet black (dry carbon buildup) since the first 5K miles. Same goes for all other 05+ Tacos i've seen in a parking lot.

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#1586441 - 09/02/09 05:11 AM Re: Exhaust carbon buildup vs clean [Re: gaspo]
crinkles Offline


Registered: 05/28/07
Posts: 5493
Loc: Australia
i have never seen an exhaust that was "stainless" clean.

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#1586458 - 09/02/09 06:27 AM Re: Exhaust carbon buildup vs clean [Re: crinkles]
Gary Allan Offline


Registered: 09/28/02
Posts: 39806
Loc: Pottstown, PA
I haven't seen a spotless exhaust since the later 70's. Oddly, when injection became the norm is when I started to notice never seeing a clean exhaust tip. That's not to say that older carb'd engines were any where near clean. It's just the only time I recall seeing "nothing" on the exhaust.
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#1586469 - 09/02/09 07:05 AM Re: Exhaust carbon buildup vs clean [Re: Gary Allan]
Boomer Offline


Registered: 09/19/08
Posts: 1711
Loc: Pennsylvania
My wife's 2003 Saturn L-300 V-6 has a very clean exhaust pipe(s). Only metal showing, no carbon. Same with the 2007 Frontier. Saturn has 64,000 miles on it, the Frontier about 19,500. I think this may be due to the fact that both vehicles get used on 250 miles trips about once a month.


Edited by Boomer (09/02/09 07:06 AM)
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2003 Saturn L 300 120,700 miles
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#1586475 - 09/02/09 07:16 AM Re: Exhaust carbon buildup vs clean [Re: Boomer]
MONKEYMAN Offline


Registered: 06/24/04
Posts: 1564
Loc: St. Louis
I have noticed a clean exhaust tip repeatedly on the Ford Focus in my area. I may see rust, but no carbon. My 99SL2 Saturn exhaust has about 1/4 inch black ring on the outside of the tip (something that seems common on those cars).
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#1586498 - 09/02/09 07:47 AM Re: Exhaust carbon buildup vs clean [Re: MONKEYMAN]
KrisZ Offline


Registered: 12/23/06
Posts: 4572
Loc: Toronto, Canada
My car used to have black soot on the bottom of the exhaust pipe, not all around. After I started using Lucas UCL and now MMO in gas the tip cleaned itself and it's bare metal now.
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2006 Mazda 3 - 127,000 miles
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#1586593 - 09/02/09 09:26 AM Re: Exhaust carbon buildup vs clean [Re: KrisZ]
ADFD1 Offline


Registered: 04/05/09
Posts: 1714
Loc: CA.
Originally Posted By: KrisZ
My car used to have black soot on the bottom of the exhaust pipe, not all around. After I started using Lucas UCL and now MMO in gas the tip cleaned itself and it's bare metal now.


Same here, if I get lazy and don't add MMO to the gas the tip starts turning black, MMO back into the gas it gets clean again. Longer highway runs certainly help.

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#1586595 - 09/02/09 09:27 AM Re: Exhaust carbon buildup vs clean [Re: KrisZ]
Quest Offline


Registered: 12/19/04
Posts: 6774
Loc: beaver land EH?
With emissions control in place for gasoline cars (remember Cat converter?!?), which serves as an "afterburner" post engine, it will burn off all carbons or anything "burnable" in the exhaust downstream when it's sufficiently warmed up.

Trouble is, it will pass unburned carbon/HC along if it's not hot enough and that's what happens when people drives aggressively immediately after the cold engine is started. That's the time that regardless of whether it's EFI or carb'ed, engine is to take on a rich mixture so as to keep the engine running properly and when driver accelerates aggressively during that warmup phase, it will dump lots of unburned gasoline into the system which results in soot.

I've been a slow/gentle driver during warmup phase on all my cars so far, and none of them EFI/carb'ed cars(properly adjusted) have any carbon build up on the end tip.

Q
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#1586679 - 09/02/09 10:34 AM Re: Exhaust carbon buildup vs clean [Re: Quest]
KrisZ Offline


Registered: 12/23/06
Posts: 4572
Loc: Toronto, Canada
I never drive hard when the car is not fully warmed up, but having winter for close to 6 months (gotta love Canada Canada ) doesnt' help with warmups.
In summer if I cleaned the tail pipe it would stay clean longer than in winter but eventually the carbon would come back.

Ever since I started using Lucas and now MMO the tail pipe is always clean and my driving habits stayed the same. I noticed that on most of the new cars the tail pipe has soot and it's because cars run very rich at startup to warm up the cats. faster. This is part of the new emission testing, and that's why older cars don't have soot from burning rich, but most of the time from burning oil.


Edited by KrisZ (09/02/09 10:35 AM)
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2006 Mazda 3 - 127,000 miles
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