Fuel economy - what am I doing wrong?

oilhammer · Aug 15, 2019

jmodge said:
Mack refuse trucks had constant issues. They never ran down the highway unless one of us mechanics took them out. On and off the throttle and they never properly regened because they would get shut down. Worst part there is the ecu would derate the engine and the operators generally didn't bring them in until it was too late. Once past a certain point a regen could not be forced without dealer specific software.
Point being, a diesel with DPf's need to stretch there legs on a regular basis. Tough on manufactures also as the government mandated a 5yr warranty. Backhoes were especially troublesome also.

Don't most of those types of applications just have a manual regen method? I lamp that comes on telling the operator one is required, and then a switch that starts the process? I know John Deere does. They use two modes: Auto and Parked. In either case, the light will flash and then come on steady during. Which is something I think would/could be useful in passenger cars and light duty trucks.

Technically, the DPF light coming on is supposed to tell you a regen NEEDS to occur, as it has failed X many attempts. However a lamp that comes on telling you when the process has started would be helpful, because then you would KNOW and, if at all possible, you could slightly change your current driving to allow it to complete.

But the way Volkswagen (and I assume MB and the rest?) have it, once the light comes on, you've already failed any passive attempts.

jmodge · Aug 15, 2019

Yes they do. However, municipal management priorities are not inline with common sense and can be extremely frustrating. Operators of refuse trucks get pushed hard.GPS systems and tracking systems on cart tippers. The videos provided some entertaining moments for us. Philosophy went from PM maintenance to damage repair.
But yes, the warning system is very good thing to have.

oilhammer · Aug 15, 2019

jmodge said:
Philosophy went from PM maintenance to damage repair.
....

Boy isn't that the truth?

jmodge · Aug 15, 2019

They ended up with a revolving door on the shop. An open job posting for mechanics. People used to claw at the door to get in there, now they go the other way. Quite sad actually because it was a great job except for about the last two years I was there.

oilhammer · Aug 15, 2019

I think most decent professionals would rather maintain than repair. I know I certainly would. Stuff breaks no matter what, but on vehicles that get regular proper PM it is FAR less frequent, and many things can be done proactively if it gets seen regularly.

jmodge · Aug 15, 2019

When I started PM’s were performed monthly with oil changes at 150 hours. Even if a vehicle didn’t need oil changed it got looked over and greased. It was rare to have a vehicle break down in the field. Then oil got pushed beyond 350, fuel filters often past 1200, break in oil on roots blowers that should have been changed at 100 was going nearly 2000. Mechanics were bored and disgusted and the ones who weren’t lifers in the defined pension system left. Quite depressing change to a job that was once fun and highly sought after. Once I was vested in the pension I no longer had a desire to work there and simply walked off. Nothing to take pride in.

eagle · Aug 30, 2019

oilhammer said:
Yep, not ideal use for one. Which, ironically, makes me wonder why you'd be complaining of poor fuel mileage, since you hardly drive anywhere anyway. I mean, heck, you could be driving a V10 Excursion and it wouldn't be a huge deal, LOL.

So, I have decided that I don't care about fuel economy and am now driving more sportingly and more in manual mode. Interestingly, the trip computer shows greater fuel economy now, but I don't believe it -- real computed FE is stillstuck at 25 mpg, and it doesn't seem to matter how I drive. At least now I get to have fun with it.

The question now is: how much fun can I have? But that's a thread for a different forum, and I'll start a new post about that in the appropriate forum.

Clawdog60 · Sep 3, 2019

regen

So if the cooling fan is running when the car is turned off it's doing a regen?

Clawdog60 · Sep 3, 2019

exactly! how much for how long.

kjclow · Sep 3, 2019

Clawdog60 said:
So if the cooling fan is running when the car is turned off it's doing a regen?

Not exactly. It could also be running the cooling fans just to get the radiator temp down.

eagle · Sep 3, 2019

kjclow said:
Not exactly. It could also be running the cooling fans just to get the radiator temp down.

If I'm correctly understanding what my car is doing, the fan speed during regen is very fast, and the fan speed during radiator cooldown is much slower.

kjclow · Sep 3, 2019

On my 10 and 11 TDIs, I don't think I could tell a difference in fan speed. It was more odor of the burning soot that told me that a regen had been taking place.

eagle · Sep 3, 2019

Gotcha - maybe it's just a difference between my 2003 1.8T and my 2013 TDI: the 2003 1.8T often ran a radiator cool-down mode with a fan speed that is much lower than what I hear the TDI do. I don't often hear the TDI fans run after I shut it off, but when I do, the TDI is much, much louder, with obviously faster fan speed.

El Dobro · Sep 8, 2019

jmodge said:
Mack refuse trucks had constant issues. They never ran down the highway unless one of us mechanics took them out. On and off the throttle and they never properly regened because they would get shut down. Worst part there is the ecu would derate the engine and the operators generally didn't bring them in until it was too late. Once past a certain point a regen could not be forced without dealer specific software.
Point being, a diesel with DPf's need to stretch there legs on a regular basis. Tough on manufactures also as the government mandated a 5yr warranty. Backhoes were especially troublesome also.

Mack's solution.
https://electrek.co/2019/05/08/mack-electric-garbage-truck/

jmodge · Sep 8, 2019

Interesting, a still garbage truck though, maybe the rats chewing on wires will get zapped with a good dose of amperage

Clawdog60 · Sep 9, 2019

Regen can complete at idle?

roadlust · Sep 10, 2019

Clawdog60 said:
Regen can complete at idle?

Yes, it is best to let them complete.

IndigoBlueWagon · Sep 10, 2019

I don't think it will complete. Not enough heat at idle. It'll interrupt. Still, many believe it's a good idea to let the car idle a while if you stop during a regen, to prevent hot oil sitting in the turbo.

El Dobro · Sep 10, 2019

It may depend on the circumstances. I'd pull into the parking lot at work and the car would be in full regen. I'd just let it run until everything calmed down before I'd shut it off.

Lightflyer1 · Sep 12, 2019

I would think it quits regen but takes some time to cool down just sitting there. The real test is to see if it starts back up again soon after interrupting it like that. Like with VCDS or VagDpf.

bigb · Sep 12, 2019

I have shut down during a regen and restarted right away, the regen continued where it left off. Once I shut down just as it started and went inside for the night. Next day the regen started over as soon as operating temp was reached. I have been able to get my regens down to 12 minutes in town. I keep the rpms between 1,500 and 2,000, if I hit a red light I pop it into neutral and hold the brake and nudge the accelerator with my right foot (I have size 16D feet) to keep it at 1,500. The soot load continues to tick down just as if I were moving. 12 minutes she finishes and a couple more minutes for the EGTs to cool down to normal. All verified with VAG-DPF.

Lightflyer1 · Sep 13, 2019

The question is though will it complete just sitting in a parking lot at idle? I think not.

jmodge · Sep 13, 2019

Does the software allow a forced regen like trucks do, raising the idle and monitoring egt’s and pressure differential?

bigb · Sep 13, 2019

jmodge said:
Does the software allow a forced regen like trucks do, raising the idle and monitoring egt’s and pressure differential?

Yes, a standing regen can be initiated by VAG capable diagnostic software. OBDeleven will do it.

bigb · Sep 13, 2019

Lightflyer1 said:
The question is though will it complete just sitting in a parking lot at idle? I think not.

Shall I be the guinea pig?

Lightflyer1 · Sep 13, 2019

The software in the car does not allow you to initiate a forced regen on demand. If you have the factory tool or VCDS or similar then yes you can do it. Not something you would want to carry around and hook up and do in the parking lot though. It would be easier and faster to just keep driving for 10 minutes or less.

Diesl · Sep 14, 2019

Regeneration DOES finish at idle!

Lightflyer1 said:
The question is though will it complete just sitting in a parking lot at idle? I think not.

Regenerations most definitely continue at idle on my 2012 TDI Sportwagen. It's easy to observe if you monitor the exhaust gas temperatures.

jmodge · Sep 14, 2019

Diesl said:
Regenerations most definitely continue at idle on my 2012 TDI Sportwagen. It's easy to observe if you monitor the exhaust gas temperatures.

Probably injects diesel fuel upstream of the dot. Unless you inject def. trucks would do the same, ecu watches egt’s and controls injection

Diesl · Sep 14, 2019

jmodge said:
Probably injects diesel fuel upstream of the dot. Unless you inject def. trucks would do the same, ecu watches egt’s and controls injection

The TDI does late fuel injections in the cylinder; this is all known and has been discussed here.
An advantage of idle regenerations is that the turbo temperature is lower, at least from what I am seeing.

theaterlightman · Sep 20, 2019

My tdi is experiencing low fuel economy, 32 mpg in the past ive gotten 40mpg with a 2 bar map and vnt17 turbo.
Ive gotten a check engine light with intermittent excess fuel in the exhost and when i looked at my egr it was gunked up so i cleaned it. I was wondering if my problem a dirty intake or bad fuel injectors. Listed below will be my readings.

Fuel economy - what am I doing wrong?

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