Particulate Filter - How hot?

[mrerk]

I am a dealer for a certain major spray on truck bedliner company. (Not sure if we can name names here) I just had a customer call me and ask if I could spray a bedliner in his 2008 truck. (brand omitted) He says the dealer told him it couldn't be done because the bed floor would get too hot and blister the liner. I've only sprayed a few of the new diesels with the particulate filters and haven't had any problems yet. I called my regional manager, who is also a dealer, and he hasn't had any problems either. I can't imagine that any of the OEM's would allow a truck bed floor to get hot enough to blister a liner. What do you guys think?

[trbankii]

My first thought would be that it would blister paint before a spray-in liner... Hard to say...

And you'd think that they'd be facing all sorts of liability issues if the bed got that hot. Who's to say what would be carried in the bed that would get scorched or catch fire? Try explaining to the customer that they cannot actually carry anything in the bed or it may get damaged by heat?!?

[DmaxMaverick]

Long before the heat blisters the bedliner, there'll be other, more serious issues to deal with. I agree about the liability issue. Can't imagine a kid (or anyone) walking in the bed and having his/her feet blistered off. If it will melt a bedliner, it'll surely melt a plastic fuel can. I'm certain they took that into consideration.

[More Power]

The GM diesel particulate filter is limited in temperature to a max of ~1400 degrees F exhaust gas temperature (during a regeneration cycle) to protect the filter's honeycombed substrate. External temperature of the filter's steel case could see a max of about 1000. This isn't all that much higher than the temperatures seen by the earlier non-filter equipped diesel exhaust systems - it'll just occur more often.

Jim

[jharden1]

Just had a Line-x sprayed in. No problems so far.

[Dakster]

I can't imagine the bed getting hotter than the passenger floorboard of a Caprice Classic or Crown Vic. The cat is really close to the floorboard and in a car with a vinyl floor would get too hot to comfortable put your bare feet on and would really task my cooler to keep drinks cold.

So I guess the question is how hot does a gas Catalytic Convertor get in comparison? I agree if it gets hot enough to blister a spray-in bed liner I think we have more problems to worry about. I feel sorry for the first person to transport a plastic gas container that spills some. I guess this is something else to watch out for so we can either confirm or bust this myth.

[AndyL]

I wouldn't suggest spraying any of these:

http://youtube.com/watch?v=321LwkM7i90

[More Power]

The Duramax isn't a Powerstroke....

A Duramax DPF regen cycle can only occur at speeds above 30-mph.

It won't happen in a parking lot, it won't happen while sitting at a stoplight, it won't happen while motoring through a school zone, it won't happen while driving slowly or idling in a farmer's field, etc. etc.... ;)

Jim

[Dakster]

The Duramax isn't a Powerstroke....

A Duramax DPF regen cycle can only occur at speeds above 30-mph.

It won't happen in a parking lot, it won't happen while sitting at a stoplight, it won't happen while motoring through a school zone, it won't happen while driving slowly or idling in a farmer's field, etc. etc.... ;)

Jim


That's good and bad... There are times when sitting in traffic I never hit 30 mph (at least for any discernable distance) What happens if I need a regen and the next 200 miles I drive I never hit 30mph?

[High Risk]

That's good and bad... There are times when sitting in traffic I never hit 30 mph (at least for any discernable distance) What happens if I need a regen and the next 200 miles I drive I never hit 30mph?

Then I hope you have a case of cold beer with ya cuz that will be a sloooooow 6 hours. :)

[More Power]

Originally Posted by Dakster
That's good and bad... There are times when sitting in traffic I never hit 30 mph (at least for any discernable distance) What happens if I need a regen and the next 200 miles I drive I never hit 30mph?


It'll wait patiently... :) If the ECM determines that the soot loading is at 125%, it'll illuminate a DPF service light. The dealer tech can use a Tech II scan tool to do it while the truck sits in the parking lot. I'd just take it out for a drive. Also, the system will do a DPF regen in steps if the process is interrupted once it begins - it'll pick up where it left off once conditions are in place to allow it to resume.

Jim

[JohnC]

Captain: "The DPF light just came on and we're surrounded by Klingon warships!"

Scotty: "She's gonna regen soon, Captain, and there's not a thing I can do about it!"

[D_R_C]

What kind of effect do you think will happen when towing, like
13K :confused: especially on a 6-7 % grade.
I would think/hope with the rpms up and working the engine harder,the regen process would work smoother,and not cause a large power loss :eek:.

[More Power]

What kind of effect do you think will happen when towing, like
13K :confused: especially on a 6-7 % grade.
I would think/hope with the rpms up and working the engine harder,the regen process would work smoother,and not cause a large power loss :eek:.

I doubt the system would need to perform a regen if you're towing a 13K trailer. The higher turbine outlet temps will more than do the job just fine. ;) Some docs I've read (non-GM) suggest the DPF will continuously regenerate all on its own with inlet temps of just 400 degrees F. You can read more about the theoretical here (http://www.thedieselpage.com/features/dtforumMT.htm).

Jim

[jmoser]

Idle is the WORST time to regenerate any DPF.

Couple points:

The GM system may be designed to keep temps manageable but under UNCONTROLLED regenerations extreme temps can easily exceed 1000 deg C or close to 2000 deg F. This depends on how much soot is in the filter and would only occur at idle as there would be almost no convective exhaust gas flow to cool the DPF. They call it uncontrolled for a reason - you cannot put it out. Sensors, injectors, etc. all can fail in the field leading to unpredictable behavior. [I think the GM system may be designed for 1400 deg C max, not F? 1400 F is only 760 C, very hard to keep DPF regens below that level all the time.]

For self-sustaining 'continuous' regeneration you typically need exhaust temps above 350 deg C [or 650-700 F.] 400 deg F is barely over 200 deg C and NOT enough to keep soot from loading up on the DPF. Full load towing is about the best you can get for this to happen - you burn as much soot as you trap, there is no buildup on the DPF. If you start with a fully loaded DPF you may trigger a regen while hauling but you have massive exhaust gas flow which keeps the DPF under safe temps. High speed and load drive cycles are the best case for DPF operation - low speed and extended idle are the worst.

FYI temps in a conventional [gasoline] catalytic converter reach maximums of near 900-1000 deg C or 1800 F. This usually only occurs at full throttle / high speed driving. FYI the original Ford Ranger pickups had problems with people - you guessed it - burning their feet while riding or standing in the bed. Ford had to add extra heat shields between the converter and the bed.

[More Power]

[I think the GM system may be designed for 1400 deg C max, not F? 1400 F is only 760 C, very hard to keep DPF regens below that level all the time.]


Actually... The DPF substrate could be damaged by excessive temperatures. According to GM, regeneration will be terminated if DPF temperatures exceed 800

[jmoser]

[QUOTE=More Power]Actually... The DPF substrate could be damaged by excessive temperatures. According to GM, regeneration will be terminated if DPF temperatures exceed 800

[More Power]

Perhaps...

Back in the 80's I bought a hi-tech wood stove for our home, which incorporated a catalytic converter. It came with a thermostatic coil pyrometer, which was calibrated in degrees F from 0-2000. Cat temp is controlled by manually regulating intake air to help maintain cat temp somewhere between 800-1500 degrees F.

GM's LMM is using an air intake valve to control intake air, and the ECM can regulate regen fueling. GM is using a pryometer both before & after the DPF.

The Edge Attitude w/Monitor has been regulating EGT for several years now. It is quite effective.

I think till we know differently, perhaps we should rely on the engineering data and theory of operation supplied by GM and the various DPF manufacturers - i.e. Johnson Matthey.

Jim

[DmaxMaverick]

Only in GM's dreams do they have that much control over the DPF! The 800 deg C limit is likely aimed to protect the catalyst coating, not the DPF substrate itself.

GM uses a Silicon Carbide DPF which can withstand 2000 deg C, much more expensive and much heavier than the cheaper cordierite which melts above 1400 C. If GM could really regen at 200C they could save huge $$$ per truck by using cordierite DPFs and reducing Platinum catalyst loads. Realistic regen inlet gas temps are closer to 350 - 550 deg C for catalyzed DPFs regardless of NO2 interactions. 'Mid-bed' DPF temperatures are much higher due to the exothermic soot oxidation burn.

Only time will tell what realistic real world temps are like under all duty cycles but I learned many many years ago not to believe GM propaganda.

Are you suggesting GM should make sense? Why would they start now? The white paper I read is inline with MP's description. Do you think GM is being dishonest or omitting information? Why would they?

[Dakster]

I think real world experience will tell us whether this DPF theory works or not. All of us operate in different real world conditions.

I am in a HOT, HUMID, Sea Level (or below) climate and regular duty will be city speeds and little weight. About once a month I can see a heavy load in the bed going from Home Depot or to and from the dump while I work on my house. At times when I go on vacations (and my bi-monthly mini-vacations) I'll hit long stretches of highway speeds and heavier loads. I'm sure everyone else here sees different duty.

Certain weaknesses in design will show if present. I've noticed by reading the blogs here of weak injectors in certain year trucks. Ford has already showed a design flaw in there DPF system that they have to correct with software. However, I believe Ford's trucks hit the market in great numbers first and the jury is still out on the Dodges and Chevy/GMC's.