All,

Why does the average MPG drop after an exhaust filter clean?

DD

 

Actually the MPG drops during the cleaning. That is because you are dumping raw fuel in the engine during the exhaust stroke which helps heat up the soot and burn it off to clean the exhaut filter. Once the MPG goes back up, the cleaning cycle is complete (~10 minutes).

 

Good to know - thanks, Thom.

 

And it causes the engine to start missing nearly every time, which then makes the truck start hopping. Very annoying.

 

Here is another question on exhaust cleaning. On my message center the exhaust cleaning comes on for about 5 seconds and then shut off. Never had it run ten minutes yet. So does anyone have an answer for that?

 

never had any effect for me.. only time I notice is when the MPG starts to drop.

only seen the message flash once.

Sam

 

The message on the dash appears for 3-5 secs. The actual regen process takes 10-20 mins. It dumps raw fuel into the cylinders on the exhaust stroke on one bank of cylinders to heat the exhaust so it can burn up the soot in the filter.

Not all fuel makes it out the cylinders, some washes down the cylinder walls into the oil. Most refer to this as 'making oil' and is something one should keep an eye on. The more active regens the truck has and/or excessive idling while the engine is not up to temp, the more you should check your oil level/quality.

 

I have seen the message numerous times and it stinks that it lasts all of 2 secs...but that is just to alert you that a regen has started....it will continue until it finishes like Thom12 says in roughly 10 minutes. And here is the stupid part - there is no indication when it finishes!

Of course if you shut the vehicle off during the regen and it is not complete it will try to finish the next time engine temps get back up to normal, about the time I am pulling into work or the driveway.

I have tried to watch the instant MPG to determine if it has finished or not and sometimes (during an active regen) you can let of the accelerator and see that the mpg does not go up, which indicates it is doing the regen. If it is doing a passive regen (and this is where I am totally unsure what the hell this is ) forget using the instant mpg as an indicator of anything....:-

 

and the alternate design is to have an additional injector in the exhaust pipe someplace after the turbo and before the DPF filter.
it adds another place to leak, and different injector part than the one in the cylinder, a different fuel pressure, some wiring, some hoses, and some different computer programming..

Ford decided their approach (in the cylinders on the exhaust stroke) was less expensive, lower maint, overall. Chevy went with the additional injector

Sam

 

they made the message flash, cause when it was up all the time it caused problems too.. (on my 08 it said, 'press reset to cancel', what? the message, the regen, ?? how do I see the odometer when that message is up?.. etc)..

out of sight, out of mind.

I just drive.. if the system thinks I should do something special (drive to clean exhaust filter), it will tell me.

Sam

 

I think the 9th injector would have been the better choice. More to deal with yes, bit more cost as well but much better on the engine. Much less fuel in the oil as well.

Either way, just something to keep an eye on and it shouldn't be a problem.

If you have alot of active regens you should stick to the severe duty maintenance schedule too.

 

I have to assume the engineers' work was reviewed.. three are nasty tradeoffs in every choice. save $5 and blow up every engine probably wouldn't make the bean counters happy.

a little computer programming, and some teeny failure rate risk probably won out. and they updated the user guide for severe,
and probably adjusted the oil change minder to increase the safety window to account for it..

I wanted to say I agreed with you on the 9th injector, but I really don't care.. so long as it continues to work. Fords way seems more trustworthy.. the injectors have to fire to get the truck running so, not a lot more checking has to be done.. the 9th injector could fail independently, and the dpf could fill.. etc..

regardless, follow the maint schedule and you should never have to think about it.

Sam

 

Paul ( an engineer from Ford) came online addressed this discussion in the fall of 2010. His information was that with the new CGI engine, there is very little fuel wash going into the oil. Most owners have experienced very little oil dilution compared to the older 6.4L engines, where it was a common problem.

The discussion was also made about there not being much room in the engine compartment to add more components to support a 9th injector. Any of you who have tried to get a hand in and turn a wrench know just how tight our engine compartments are.

Also the 6.7L only pumps raw fuel thru 4 cylinders vs the 8 cylinders on the 6.4L this also reduces the possibility of fuel wash.

As far as a Regen not completing. If you shut down during a regen, The system will not restart the regen until the soot % level again reach the trigger point.

I never notice any change in my engine or it's performance during regen. To me it has just become a Non-Event. Let the truck do it's thing. It's a lot like the cooling system, The thermastat opens and closes when ever the coolant temps trigger it. I never have to initiat coolant to flow. A regen on ur 6.7L engines has become alot like that. Just let it do it's thing.

 

My truck does the same thing, gets all jittery and jerky about 20/30 seconds before I get the regen pop up.

 

This isn't normal.
The engine clatters a bit more but the truck should still has full power.
Much better than the 6.4L DPF cleaning IMO.