X15 down on fuel economy recently?

[marek4792]

Down 1mpg for the past month, down a gear on hills, coolant temps sitting higher when cruising around 185-190 degrees, hmmm what could this be? Opens up insite this is what I find..
   
   
Even with yearly Egr tune-ups and recently removed and cleaned the Egr Valve and new DPF differential pressure sensor. The turbo burn mark has moved closer to center of the housing too.. DPF was baked at 315k miles approximately, now have 520k miles. Definitely got my moneys worth but will update when it gets pulled to determine which route to take...

[Rawze]

If everything is well cared for, the DPF, DOC is usually good for about 500-600k miles, then they are typically done for. SCR lifespan is right behind that, maybe another 100k more, and its done for as well.

It gets somewhat expensive to replace all those units as they reach end of life and that engine/truck gets past the half-million mile mark.

The big question of the day is what to do about it. Having the cans baked, de-ashed, etc. is the place to start.. but this may only a bande-aide/temporary fix once they become that old and the precious metals start to fade away.

Evaluating the engine to ensure it is not making excess soot and that it is not consuming any coolant or oil, etc. is the first step. No sense in investing in new $$$$ pricey DPF/DOC/SCR cans if you cannot keep them clean, or if they are going to be gutted out in the next 100k miles or less... unless someone has no choice in the matter, and cannot de-mandate for one reason or another.

========================================
(some general speculation related to trucks getting older, unrelated to the thread) ...
This also leads to the next part... If an engine is set to 1850 trq or more .. and especially if the truck is geared tall, and/or a lot of PTO operations occur .. then someone can also expect to have to inframe the engine at about the 650k ~ish mark too. Add in the fact that the turbo likely reaching its end of life @ 600k miles, the CAC and other components likely needing replacing soon if not already, etc...

Combine those costs together, and a person is looking at a LOT of moneys. This is on a well cared for truck, so the average used truck buyer these days is just living in some kind of pipe dreams world if they think they can buy into a truck that is not ready for some major expenses right away... especially if it is geared tall and has big HP/torque set into it.

The only sure-fire way to combat all these expenses long term are to have the engine set to about 1720 trq, gear it so that its 3,79's or better, learning to drive it slower while still making deliveries. Keeping the RPM above 1500+ in any sort of hill climb + maintaining everything really well with lots of preventative maintenance. Only then, does the the long term profit margin start to become decent.

Anything short of this, and all that moneys that someone made running their arsse off the last 4-5 years inevitably always ends up getting sunk right back into that equipment, and at the end of the day, they are actually getting no further ahead.

(the beer is talkin now)...
I yell the obvious formula that actually works for making some d$ammned decent long term profits in trucking on here time and again, but most people would rather have that big torque, --'Get-R-Done" factor.. and they pay for it dearly, complaining about how their s$it is always broke down or the engine blew that head gasket .. when all they wanted to do is make it another years or 2 so they can afford that inframe.. never getting ahead at the end of it all.

They have become a slave to the system .. only its by choice, though they would get mad at you and argue it away real fast if you even tried to point it out to them.

So.. the next time someone goes blasting down the freeways blowing past someone like me who drives like a grandPa below 63 mph or so, and has their truck turned down so that it only creeps up the steep hills, etc. ... just know that I am the one making real moneys and long term profits that I can keep. Moneys that can actually be put towards an actual retirement instead of having to pour it all back into the truck every few years.

Just remember that I will always smile at those people who blast past me at 70+ mph like that, and especially at the ones who have all the chrome and the big square noses ... not because I am such a nice guy.. but because I think to myself.. "You go super-trucker.. you go be that nice little slave that the system has brainwashed you into being".

Just my random beer rant for the day about fuel economy and worn out trucks, etc. in general.

[Rawze]

(08-26-2023 )marek4792 Wrote:  Down 1mpg for the past month, down a gear on hills, coolant temps sitting higher when cruising around 185-190 degrees, hmmm what could this be? Opens up insite this is what I find..


Even with yearly Egr tune-ups and recently removed and cleaned the Egr Valve and new DPF differential pressure sensor. The turbo burn mark has moved closer to center of the housing too.. DPF was baked at 315k miles approximately, now have 520k miles. Definitely got my moneys worth but will update when it gets pulled to determine which route to take...

Yeah, those regen numbers are showing something is definitely wrong. should be averaging below the 3.0 mark.

Make sure that the Doser injector and exhaust piping itself is also in good shape, it often gets overlooked and makes the DPF regen numbers climb like that.

[JimT]

Well, I'm not the expert Rawze is here, but based on the info you presented I'd be less concerned about the DPF/DOC at the moment and more focused on the engine and the exhaust stream. Burning oil, coolant, excess soot or just anything out of the ordinary. Regens seem to be very consistent every 100 hours or so, max temps are all about equal, but max differential pressure has been going up each time. The increased ash load could just be from normal regens, or it could be the result of contaminated exhaust. Baking the DPF should lower the ash level but if there's something in the exhaust causing the problem then you'll just work your way right back to where you are now. I believe Rawze has said that there's only so many times they can be baked before they loose their effectiveness.

Anyway, just my 2 cents

[marek4792]

Jim. That's what has me scratching my head. Soot counter has never been really high. No Oil consumption. No coolant consumption. Fuel system is holding pressure. Injectors can also be ruled out by straight piping it and see if it's dumping fuel out no 7th injector in this engine.. So based on that makes me think the DPF is infact getting full. I think from what I've heard was twice or maybe three times? To make matters worse I'm in the middle of a run 2000 miles from home and it's flashing the check light every hour or so at me reminding me of it.. So it's definitely gonna be a fun time getting back home to "fix it"

[Nilao]

For what it's worth my 2021 truck had 550k on it when I had the dpf pulled and baked. Not for being full as my soot gauge was at 35% but because I had the system open to fix a DEF issue in the mixer pipe. Figured while I had the teardrop cover off I may as well do it.

[marek4792]

Just an update, so 3500 miles later made it home with the "check" light (Volvo) blinking ever 1-2 hours. Got the cans yanked, DOC cleaned by stealership was an even black across the inlet from what I could see. DPF got cleaned and baked at my local stealership, said it was partially clogged prior to and passes the flow test, also is missing a small piece of honeycomb on the inlet side.
Did a forced regen after maintenance reset and now shows 0.3inhg(Not .03) difference. Also installed a new reman Outlet NOX sensor since the inlet one had failed earlier this year. Along with new cam and crank sensors early on which helped smooth the idle out somewhat prior to the oem damper and pisspoor balancer combo...
This is why having the engine software is so important, stealerships would throw the parts cannon based on assumptions and not look at basic data. This truck threw no fault codes on the dash whatsoever for anything DPF related in the last 200 hours until that maintenance code reared itself despite my symptoms within the last 400 engine hours..
With fuel prices as they are, this can make or break a guy if treated in the wrong way..
   
   
   
   
   

[Rawze]

Let us know about how much improvement/changes in fuel mileage, etc. that resulted, for future reference if ya can.

thanks.

[marek4792]

Not much of an update, power is back mpg is so so. Soot level seems to be stabilizing after climbing to the moon a couple times and a few rolling regens later..

But an issue I didn't mention earlier but I thought I'd pass on, so I had noticed an oil pressure drop-off at lower end of spec at 1500rpm warm. Idle at 700rpm was 26psi warm. Decided to have new rods and mains rolled in and oil pump put in based on a recommendation from a friend with x15 who had done his the previous week at 570k miles mines at 533k miles. Went from low 30's psi at 1500 rpm warm to 40ish psi at 1500rpm warm, big difference! Oil sample pre repair came back clean. Had a picture of the worst main bearing smooth when scraping with fingernail, but rods looked clean all across, but if you're above 500k miles and noticed a pressure drop off that seems to be no apparent reason. Oil pump sounds like a very likely culprit in my situation.