08+ Exhaust Temp Light

[EngineerMike]

If you have been having trouble sleeping, here is some help:

Our 08 has a warning light on the dash for Exhaust Temp High (upper left light in the upper warning light group). The graphic isn't obvious as to meaning, so we had to look it up in the owner's manual. I guess it is a thermometer with exhaust blowing on it.

The 07 and later engines (probably only on 08 & later coaches) have a more robust Cataclysmic Converter, also referred to as a Particulate Filter. Late in the cylinder rotation cycle, when called for by the engine computer due to exhaust back pressure and/or CC temp, the injector will pop a small amount of diesel into the cylinder just before the exhaust vavle opens. When this unspent fuel hits the CC, it ignites and runs the exhaust gas temp up to 1100 degrees to burn out all the accumulated soot (one of the more egregious components of diesel exhaust health-wise due to its minute particle size which is capable of passing the lung wall/blood vessel barrier). This is called a "regeneration" or regen. Cummins performs a forced regen prior to delivering a new engine to prove it will operate correctly.

Motorhomes have the idiot light so the (properly informed) driver knows not to pull of & park in tall grass while the tailpipe & muffler are hot enough to start a fire.

WRV might more fully explain the operational meaning of the idiot light in their manual. What they say is, "HIGH EXHAUST SYSTEM TEMPERATURE- Indicates that the exhaust system is or is about to be elevated above normal operating for the operating mode of the engine." The regen is a normal part of the emission system operation, takes 20 to 40 minutes of driving (if you don't worriedly pull off the freeway, park, and idle while calling WRV and Cummins to see if maybe the light is really a normal occurence and not "above normal...for the operating mode...").

What the manual should say, IMO, is "Indicates high or impending high exhaust temperature. This is probably a normal operating mode of the engine used to clean the emissions system. Do not drive or park your coach near combustible materials like tall grass while this light is lit. Otherwise, continue to drive your coach as normal. If the light does not go off within approximately 40 minutes of normal highway driving, have your emissions system checked by a qualified service facility as soon as practical."

The left-most light in the lower warning light group is also related to regens. This yellow light description in the owner's manual reads: "PARTCULATE FILTER LAMP (DPF)- Indicates the need for the particulate to regenerate when past engine/vehicle operation has not provided sufficient conditions for the filter to automatically regenerate." IMO, this is another of the light descriptions in the owner's manual that is great for someone with familiarity with regen protocol, but leaves the average owner without a clue as to what to do or not do about the situation. IIWwrv, I'd reword it to state the engine/vehicle operation requirements for running the regen, and follow it up with a statement about under what conditions to seek service. From what I know about the regen operation (not an expert), any more or less steady state highway driving over an hour or so should provide the computer with its necessary operating conditions, and a persistent light after such opportunity would indicate service is needed.

[EngineerMike]

If you have been having trouble sleeping, here is some help:

Our 08 has a warning light on the dash for Exhaust Temp High (upper left light in the upper warning light group). The graphic isn't obvious as to meaning, so we had to look it up in the owner's manual. I guess it is a thermometer with exhaust blowing on it.

The 07 and later engines (probably only on 08 & later coaches) have a more robust Cataclysmic Converter, also referred to as a Particulate Filter. Late in the cylinder rotation cycle, when called for by the engine computer due to exhaust back pressure and/or CC temp, the injector will pop a small amount of diesel into the cylinder just before the exhaust vavle opens. When this unspent fuel hits the CC, it ignites and runs the exhaust gas temp up to 1100 degrees to burn out all the accumulated soot (one of the more egregious components of diesel exhaust health-wise due to its minute particle size which is capable of passing the lung wall/blood vessel barrier). This is called a "regeneration" or regen. Cummins performs a forced regen prior to delivering a new engine to prove it will operate correctly.

Motorhomes have the idiot light so the (properly informed) driver knows not to pull of & park in tall grass while the tailpipe & muffler are hot enough to start a fire.

WRV might more fully explain the operational meaning of the idiot light in their manual. What they say is, "HIGH EXHAUST SYSTEM TEMPERATURE- Indicates that the exhaust system is or is about to be elevated above normal operating for the operating mode of the engine." The regen is a normal part of the emission system operation, takes 20 to 40 minutes of driving (if you don't worriedly pull off the freeway, park, and idle while calling WRV and Cummins to see if maybe the light is really a normal occurence and not "above normal...for the operating mode...").

What the manual should say, IMO, is "Indicates high or impending high exhaust temperature. This is probably a normal operating mode of the engine used to clean the emissions system. Do not drive or park your coach near combustible materials like tall grass while this light is lit. Otherwise, continue to drive your coach as normal. If the light does not go off within approximately 40 minutes of normal highway driving, have your emissions system checked by a qualified service facility as soon as practical."

The left-most light in the lower warning light group is also related to regens. This yellow light description in the owner's manual reads: "PARTCULATE FILTER LAMP (DPF)- Indicates the need for the particulate to regenerate when past engine/vehicle operation has not provided sufficient conditions for the filter to automatically regenerate." IMO, this is another of the light descriptions in the owner's manual that is great for someone with familiarity with regen protocol, but leaves the average owner without a clue as to what to do or not do about the situation. IIWwrv, I'd reword it to state the engine/vehicle operation requirements for running the regen, and follow it up with a statement about under what conditions to seek service. From what I know about the regen operation (not an expert), any more or less steady state highway driving over an hour or so should provide the computer with its necessary operating conditions, and a persistent light after such opportunity would indicate service is needed.

[jerry and toni smith]

Perfectly logical and well explained. Fortunately it does not apply to my 06 (please tell me that it doesn't apply to my 06. Thanks

Jerry Smith
2006 34 ( nothing wrong for the moment)

[TerryM]

E-Mike,

Thanks for this post. You probably saved me a lot of worry and time for when we head south in a couple of days. Hopefully, the new Cummins engines will perform as well as the older Cummins.....and I will miss that sweeeeet Alpine rumble.

Terry McGuire
'09 36 FDTS SE
Almost ready to go

[EngineerMike]

Jerry- Yours has a smaller Cataclysmic Converter w/one each pressure sensor & gas temp probe. It is essentially a one stage CC w/one stage of sensors. The Next Gen. CC has 3 stages & one pyrometer at each stage (haven't determined how many pressure sensors yet). So the older engines (including ISC's) don't "regen" their CC, and you don't have this automated high temp exhaust process.

Terry- I haven't figured out what is wrong yet, but I'm showing 9.4 miles per gallon w/4300 miles on the rig. That's up from 8.9 at 3000 miles. At this rate, by the time I've got 20k on the rig I should be getting about 20 mpg . Or else the Actia mileage report is snafu'd . If the actual mileage comes out above 9, I'm throwing a party
Otherwise, the new engine sounds different at the curb due to the advanced muffling of the CC stuffing, and the exhaust smells way different. And other than as reported above, the "425 HP" N.G. engines behave exactly as the 05 engine I had in our 06.

[jerry and toni smith]

Mike, Thanks for the info. Jerry

[TerryM]

E-Mike,

I asked Kemo at the factory about the exhaust and diesel smell that you're getting in the coach at the regen. He checked into it and got back to me that some of the first coaches with that engine were missing a gasket....but he wasn't sure where. He said that later 08's with the gasket weren't having that problem. May be something to check into.

Terry McGuire
09 36FDTS almost stocked and ready to head south.

[OldForester]

E-Mike

I'm at the ACA Quartzsite rally and ran into a guy with an early 2008 who formerly had an early 07 with the 400 Cummins. He is complaining that his 08 with the 425 Cummins doesn't have nearly the power of his 07, and they're both 36 FDTS. He says it's like 60% of the power. He said Cummins looked at his engine and that it's fine. He doesn't have Silverleaf installed so he doesn't know what torque and hp he's really developing while he's driving.

I'm curious as to whether you notice any difference in power from your 06 vs. the 08. I suggested he have Cummins hook up to his engine and drive it, or take it to a dyno to see what was really happening at the wheels; maybe he's having a transmission issue,.

Anyway, if you could let me know if you've seen a big reduction in power I'll pass it on to him. (I seem to remember you saying it was about the same as the 06) He doesn't have internet access.

Thanks--

[rchaf]

Mike

Trombetta interconnect controllers do you use!!