8.1 Workhorse burns rich, need advice.

[mtnmike]

Our 2006 W-24 Adventurer 38J with 8.1 GM seems to burn rich. I have driven from sea level to 12,000' and everywhere in between and the exhaust pipes always seem black, rather than gray.

I don't see any visible black smoke, no oil consumption, and we only have about 30K on this rig.

1. Do you folks with the 8.1 engine have gray exhaust pipes?
2. Can mine be tuned?
3. Would an add-on power tuner help this issue?
4. What is your overall average mileage. (We never get above 7 overall).

Thanks in advance, Mike

[TomandGloria]

Mike, my exhaust pipes are black too. I have the Ultra Power upgrade (well worth the $$) along with Iridium plugs and Magnum Wires. Average around 7 mpg pulling my 2015 GMC Canyon 4 door p/u. I normally drive around 60 mph. Hope this helps.
Tom

[garyspang]

Hi Mike
Grey exhaust pipe coloring is out of style since lead (grey color) additives were outlawed in gasoline.
Black or carbon is the only color left since water vapor and carbon dioxide (monoxide) are colorless. The catalytic converters burn or carbonize the last trace of unburned Hydrocarbons (gasoline).

I shared your concern when I first got my motor home. When I obtained the proper monitoring tools I was able to witness the delicate and precise metering done with the injector timing in terms of short and long term trims while driving. Oddly enough a very slight over and undershoot for the perfect fuel to air mixture always exists due to the binary nature of the O2 sensors, so a very small amount of carbon will always escape total combustion.
This is what you see on the exhaust pipe.
To minimize the carbon in the exhaust even further, the O2 sensors are preheated to reach their required operating temperature faster, this causes early closure of the control loop.

[mtnmike]

TomandGloria,

I'm happy to know that I'm normal, several have questioned that condition. I forgot to mention that we tow a Liberty which has gray exhaust as well as does our Ford F-150.

Thanks for mentioning the Ultra Power addition. We are full time now and spend summers in Western Colorado and winters in Arizona, so high altitude and mountain passes are our nemesis. Did you notice any improvement or reduction in mileage with the Ultra Power?

Best, Mike

[TomandGloria]

Mike, there is a negligible improvement. Since most of my driving is east coast with trips to the mid/southwest yearly I don't do a lot of mountain driving. What became very apparent was it was not kicking down to 4th gear to climb overpasses.

We average around 7 mpg and I'm pretty happy with that. I've gotten as high as 9. I've got a friend with a 40' Phaeton and he averages close to 10. But the initial cost, plus maintenance associated with his Phaeton are higher than mine. So I'm not sure the deisel would be worth it me for a couple of mpg more.

We don't full time but do spend about 180 nights or so in our coach. The difference in power and torque were noticeable immediately and I am glad I had the upgrade done.

Hope this is helpful,
Tom

[mtnmike]

Tom, Thank you for your kind reply. It does sound as if Ultra Power would be a nice addition. I agree on the gas/diesel issue. We are parked in Arizona for several months and also in Colorado with trips in between, so it's not as if we are on the road constantly. Happy travels, Mike

[Oemtech]

From what I been told... The black exhaust is cashed mostly from extra fuel used to cool the cats...

[mfire1339]

I believe extra fuel kills cats.

[M&EM]

I thought the long exhaust path had something to do with carbon products condensing onto the cooler tailpipes..

Mine has always exhibited sooty tailpipes. MPG average past 100k miles has consistently been 7.0. with and without UP upgrade. All with 4100 lb tow and mostly W & NW travels..

[harleyjt]

Originally Posted by garyspang

Hi Mike
Grey exhaust pipe coloring is out of style since lead (grey color) additives were outlawed in gasoline.
Black or carbon is the only color left since water vapor and carbon dioxide (monoxide) are colorless. The catalytic converters burn or carbonize the last trace of unburned Hydrocarbons (gasoline).

I shared your concern when I first got my motor home. When I obtained the proper monitoring tools I was able to witness the delicate and precise metering done with the injector timing in terms of short and long term trims while driving. Oddly enough a very slight over and undershoot for the perfect fuel to air mixture always exists due to the binary nature of the O2 sensors, so a very small amount of carbon will always escape total combustion.
This is what you see on the exhaust pipe.
To minimize the carbon in the exhaust even further, the O2 sensors are preheated to reach their required operating temperature faster, this causes early closure of the control loop.

x2

Gary is exactly right. I don't understand your other vehicles having gray pipes. The gray that everyone used to see years ago was simply the lead from the fuel. Lead went out in the mid-70s and tailpipes got black at the same time.
jt

[mtnmike]

Thanks to everyone for your replies. It's good to know that our black pipes are normal on the 8.1. Perhaps the cats and the short exhaust on the Jeep and F-150 burn the pipes clean...as they are gray and clean.