Carbon Deposits on the exhaust tips of D.I. veh.

[VK56VD]

I have a Infiniti M56x (Q70 5.6L V8) and noticed that the exhaust is darker than any of my previous cars in between washing (mileage equivalent). Is this the nature of the beast and all direct injection engines? Vehicle designed to run rich?

 

[Danh]

Yes, it is common with DI engines though some brands are worse (look at Ford EcoBoost exhaust tips) than others. DI, while generally emission-friendly, does produce more particulate matter than port-injected engines and this is likely what you're seeing.

There has been speculation that standards may have to be modified to limit particulate emissions of DI gas engines, which in turn could require particulate filters like current diesels.

 

[Quattro Pete]

Yep, normal. Exhaust tips on wife's Q5 are pitch black, and it's impossible to clean them.

 

[Exit32]

Originally Posted By: Danh
Yes, it is common with DI engines though some brands are worse (look at Ford EcoBoost exhaust tips) than others. DI, while generally emission-friendly, does produce more particulate matter than port-injected engines and this is likely what you're seeing.

There has been speculation that standards may have to be modified to limit particulate emissions of DI gas engines, which in turn could require particulate filters like current diesels.


During the week after I took delivery of my 3.5 direct-injection EcoBoost Explorer, I noticed carbon deposits on the stainless-steel tailpipe tips. It was easy to clean, but I was dreading having to do this cleaning every few days. After the first tank of gas was gone (first tank was compliments of the dealership), I started using Mobil 93 octane exclusively. Mobil is a Top Tier fuel, and I'm pleased to report that my tailpipe tips are no longer covered in carbon.

From what I've seen, fuel quality is important if you want clean tailpipes on a direct-injected engine.

 

[buck91]

Yup, tips on our Ecoboost Explorer are terrible also. I hit them with simple green first and a HUGE amount of black [censored] rinse off- of course, the tips didnt look any different. Followed that up with Nev-R-Dull and that did help, but I have a long way to go.

Its the wife's car, so I'd love to just ignore the carbon tips, but its driving my ocd crazy. I do wonder if a PCV catch can would help at all...

 

[AZjeff]

Originally Posted By: buck91


Its the wife's car, so I'd love to just ignore the carbon tips, but its driving my ocd crazy. I do wonder if a PCV catch can would help at all...


Not if it's fuel causing it..

 

[buck91]

Originally Posted By: AZjeff
Originally Posted By: buck91


Its the wife's car, so I'd love to just ignore the carbon tips, but its driving my ocd crazy. I do wonder if a PCV catch can would help at all...


Not if it's fuel causing it..


True, true. My thoughts are that it may be related to the oil/pvc these engines are known for.

 

[JHZR2]

I noted this on my 135i, though it was when I was trying to run some tcw-3 in the fuel. Running plain fuel seems to minimize/prevent this.

 

[Ohle_Manezzini]

The lack of tulip turbulence have its toll. It acts as a mixture mixer, pre-volatizer ...

 

[opus1]

Same thing on my Cobalt SS, despite only using premium gas.

 

[itguy08]

Originally Posted By: buck91
Originally Posted By: AZjeff
Originally Posted By: buck91


Its the wife's car, so I'd love to just ignore the carbon tips, but its driving my ocd crazy. I do wonder if a PCV catch can would help at all...


Not if it's fuel causing it..


True, true. My thoughts are that it may be related to the oil/pvc these engines are known for.


A can will do NOTHING for the carbon. It will do nothing really either but that is another discussion. There are no "oil/PCV" issues - that is nonsense started by a certain catch can vendor to sell more cans. Cans also do NOTHING for valve deposits too.

 

[09_GXP]

On my 2009 Solstice, 2.0L turbocharged DI, I had to but cardboard strips behind the exhaust to prevent staining on my garage floor from all the soot. The first start each year would actually result in a small pile of soot underneath each exhaust tip. I was told that the it wasn't until 2010 when PM emissions really came down for gasoline engines despite having been lower for diesels for quite some time. Things are much better with my current Ecoboost so it seems like something has improved.

 

[DBMaster]

+1 for my Mazda3 Skyactiv. Since my car is white, even the inside of the bumper cutout shows darkening and that is darkening of the paint. I gave up on messing with polishing compound and just learned to live with the dark exhaust tip and gray bumper cutout.

 

[ls1mike]

I haven't really noticed that on the Malibu. The tips are still pretty clean.
I would seem it has gotten better since 09_GXP's Solstice, so I think is he on to something.

 

[ARCOgraphite]

I saw this on one of the managers new Colorado ext cab V6. Told him his fuel/octane choice was not good.

I find new cars ecu seeming to detune the engine at a drop of the hat. Retarded timing and rich mixtures.

Goota have enough octane to run 13/1 comp even though the Di is supposed to stratify charge to avoid preig. If the ecu hears preig you see retard.

I hate lambda control. Flakey more than not.

 

[DBMaster]

Eh, this is minor stuff for the tradeoff of stellar fuel economy and fun performance out of a small engine. I can live with it.

 

[ls1mike]

Originally Posted By: DBMaster
Eh, this is minor stuff for the tradeoff of stellar fuel economy and fun performance out of a small engine. I can live with it.

Yep, so far I have been really happy with the 2.0 LTG in the Malibu. It has been the first 4 cyl I have love in a loooonnngggg time.

 

[Quattro Pete]

Originally Posted By: DBMaster
Eh, this is minor stuff for the tradeoff of stellar fuel economy and fun performance out of a small engine. I can live with it.

The Q5 in the sig certainly does not deliver stellar fuel economy, but it does have good performance, for an SUV.

 

[andyd]

If the exhaust is sooty, what does that do for the Cats? No chemist, But doesn't soot mean wasted fuel?

 

[wtd]

Originally Posted By: itguy08
Originally Posted By: buck91
Originally Posted By: AZjeff
Originally Posted By: buck91


Its the wife's car, so I'd love to just ignore the carbon tips, but its driving my ocd crazy. I do wonder if a PCV catch can would help at all...


Not if it's fuel causing it..


True, true. My thoughts are that it may be related to the oil/pvc these engines are known for.


A can will do NOTHING for the carbon. It will do nothing really either but that is another discussion. There are no "oil/PCV" issues - that is nonsense started by a certain catch can vendor to sell more cans. Cans also do NOTHING for valve deposits too.


I'm not sure I totally agree and this is why. When my fiancee's 2007 Mustang GT had around 14,000 miles on it, I noticed that when she started it up, it would puff out blue smoke out of the tail pipes. I couldn't figure out why such a low mileage car would be doing this.

I went on the Mustang forums and asked about this and they suggested installing a catch can and that the smoke I was seeing was from the buildup of oil going through the intake from the PCV valve. I bought one and installed it and the car no longer blows blue smoke at start up. The hose going into the intake is also not soaked with oil like it was prior to the catch can.

It all might be a coincidence but it seems like the catch can did something useful.