[Mark M]

Over the last couple days my commute trip mpg has been down ~8% = 4 to 5 mpg. This is right after having the dealer replace the leaking red charge hose with new including seals.

Trip is ~75 miles mostly highway. Zero rain. Zero to no wind. Temps in 70s to 80s.

Observations:
- Cruise control at a steady 77mph
- Tires are at correct pressure
- Per OBD monitor, Engine coolant temp remains 78 to 80 degrees C (normal)
- Per OBD monitor, Engine load ranges from 27% to 50% (seems high for steady interstate cruising)
- Per OBD monitor, Fuel usage ranges from 4.5 to 10 liters per hour (seems high for steady interstate cruising)
- Per OBD monitor, EGR is being commanded thus car is not doing a DPF regen
- Car’s instantaneous mpg gauge is also showing down as well, dipping into the teens on uphill stretches
- Car has had full carbon clean up 10k miles ago and ever since EGR has been blocked off.
- Slight diesel smell upon shutdown in garage.

Thoughts? TDI, I heard you get paid in beer for armchair diagnosis?  Could there be a hose or sensor that was mishandled during the charge pipe replacement that would result in this decline in mpg?

[Puerto Rican 335d]

How can that be something else is wrong here

[TDIwyse]

Wow, that's a huge change... Did they by chance re-flash your DDE when you were there? Or did they reset adaptations (BMW documentation calls for reseting fueling adaptations after messing with things in the intake or fueling ... see attached)?

If they did either of those two things then your car could be settling into a whole new fueling configuration/calibration.

Is it possible there's a loose connection somewhere around the areas they were fussing with? Can you log requested boost and actual boost? That could show an air leak in the intake if there is one.

Sure others can chime in with more thoughts, but that's my arm-chair-for-beer thoughts this morning.

[Puerto Rican 335d]

TDi I believe they did both cause remember last time i lost my Flash a while ago, I inquire about this and they told me that they were directed to reflash cars anytime they felt like it, which didnt make sense to me but thats the way they operate

[Yozh]

If you are leaking boost your mpg will drop. Make sure that the connections between the red charge hose are secure. Check turbo outlet and intercooler inlet. Especially the last one. It could have popped off. But for that drop in mpg you should hear hissing of pressurized air. Hope they did not re flash you. Did they know about EGR block?

[Mark M]

The paperwork makes no mention of reflashing the DDE or resetting adaption. Paperwork only cites changing the parts.

Also, the car feels strong, no lack of punch.

[135i_vs_]

Maybe running the a/c more?
Or the current fuel in the tank?

What is your MPG now?

[TDIwyse]

Originally Posted by Mark M

The paperwork makes no mention of reflashing the DDE or resetting adaption. Paperwork only cites changing the parts.

Also, the car feels strong, no lack of punch.

Interesting. If that's the case and everything on the intake is correctly installed and not leaking boost, then not sure what it could be. Unless it's something completely unrelated that happened to rear its head. Is your MAF functioning correctly? Are your brakes dragging? Did you fill up with sub-par fuel?

Not sure what else to suggest at this time. Please keep us posted with how this evolves. And good luck figuring it out.

[Masstar]

Originally Posted by TDIwyse

Interesting. If that's the case and everything on the intake is correctly installed and not leaking boost, then not sure what it could be. Unless it's something completely unrelated that happened to rear its head. Is your MAF functioning correctly? Are your brakes dragging? Did you fill up with sub-par fuel?

Not sure what else to suggest at this time. Please keep us posted with how this evolves. And good luck figuring it out.

Maybe he just ran a DPF regen?

[TorqueAddict]

Originally Posted by Masstar

Maybe he just ran a DPF regen?

or may be regen did not finish properly, and DDE is trying to force it over and over again?

[TDIwyse]

Originally Posted by TorqueAddict

or may be regen did not finish properly, and DDE is trying to force it over and over again?

Possible, but from his original post: "- Per OBD monitor, EGR is being commanded thus car is not doing a DPF regen"

I've never seen a regen in process that has the EGR at any other position than 0%.

[Masstar]

Originally Posted by TDIwyse

Possible, but from his original post: "- Per OBD monitor, EGR is being commanded thus car is not doing a DPF regen"

I've never seen a regen in process that has the EGR at any other position than 0%.

Oh, woops.

[kiel_dafo_kenyg_as]

If temp is always between 70 and 80 C there's something wrong with the tstats. Temp should go up to 98-100 C.

[TDIwyse]

Originally Posted by whiteblue

If temp is always between 70 and 80 C there's something wrong with the tstats. Temp should go up to 98-100 C.

Maybe there's a difference with the North American and European thermostats then, because I've never seen mine go above 190F (usually 185-187F...~86C) except during DPF regens in the hot summers when it might creep up to 195F.

This is data from when the car was less than a year old and comparing coolant temp behavior during drives to work when a DPF was being commanded vs no regen.

[Mark M]

Took the family on a 170 mile round trip yesterday. Obc reported 30.3 mpg. But on the return I filled up the tank. 477 miles yielded 34.13 hand calculated mpg. Better than I was expecting.

My loose theory is that perhaps the DDE correction values for mpg calculation could be off.

Recall back in March I adjusted this correction factor as the car was consistently reporting higher mpg than what was being shown by hand. Now it seems it is reporting lower than hand calculations.

Could a leaking red charge hose result in optimistic obc mpg which I masked with a correction factor adjustment? Or perhaps the dealer recently did some DDE reset.

Going to track it over the next tank of fuel to assess further. But initially pleased to see hand calcs show mpg greater than obc calcs.

The car definitely feels better with the new charge hose. Instant response off throttle.

[ihbase]

Originally Posted by TDIwyse

This is data from when the car was less than a year old and comparing coolant temp behavior during drives to work when a DPF was being commanded vs no regen.

This is really interesting. Thanks for posting.

Do you have data comparing temp with the EGR open versus blocked? Blocking should definitely raise head temps but at the same time eliminate EGR cooler demand. I'm curious to see how this modification impacts the cooling system and exhaust temps.

-Mike

[TDIwyse]

Originally Posted by ihbase

This is really interesting. Thanks for posting.

Do you have data comparing temp with the EGR open versus blocked? Blocking should definitely raise head temps but at the same time eliminate EGR cooler demand. I'm curious to see how this modification impacts the cooling system and exhaust temps.

-Mike

This is similar to the EGR blocked where I could force the car to trigger a pending code that shut the EGR to 0 until the next key cycle. This is back to back comparisons on the same route at same speeds with and without EGR. Comparing boost, EGT's, coolant temps, rail pressure, injector timing/opening times, etc...

http://www.bimmerfest.com/forums/sho...0&postcount=60

[TDIwyse]

Originally Posted by Mark M

Could a leaking red charge hose result in optimistic obc mpg which I masked with a correction factor adjustment? Or perhaps the dealer recently did some DDE reset.

Interesting. Maybe the leaking pipe threw off your air/fuel mixture from what the system thinks it should be doing (the air mass flowing by the MAF will be lower than what gets to the intake due to the leak) which could mess up the injector calibration routines? Not sure how much of a leak you had... was it really bad?