BMW will recall diesel models to fix emissions glitch

Originally Posted by floydarogers

This "mileage has gone down" is, unfortunately, entirely anecdotal. For instance, it seemed like the first couple tanks after I had the recall work done it "seemed" like mileage was down. However, the latest tank and an extended drive returned just the same good mileage that I had last year driving the same routes.

Many things can affect mileage, and many things can affect mileage reporting. I'm not convinced at all that there is a loss of mileage.

YMMV

Same situation with my car (posted earlier in the thread about this). Hand calculated mpg spreadsheet shows mileage returned to "normal" in short order when comparing year ago data to the same time frame. Comparing data from now to ~2 months ago time frame shows a slight drop. But that's because it's summer and extremely hot/humid so the A/C is run more and that causes a ~2 mpg drop on my commute and the winds are more likely to be stronger causing additional wind drag at times. Getting apple-to-apple comparisons, even on the same course, is difficult.

I find it hard to believe that A/C would have this much of an impact on MPG, but I will have to wait for cooler weather to know for 100% sure. But the change in MPG was pretty dramatic, right after the recall.

Is it possible they rasied the frequency of DPF regens? That would lower the MPG.

Originally Posted by KeithS

I find it hard to believe that A/C would have this much of an impact on MPG, but I will have to wait for cooler weather to know for 100% sure. But the change in MPG was pretty dramatic, right after the recall.

Is it possible they rasied the frequency of DPF regens? That would lower the MPG.

I have a hard time with the AC comments too. But over the years on here I have seen multiple people confirm it. I don't live in a climate where I am willing to experiment with no AC on this car.

My first tank after the recall had a lot of regens. Not sure if I have done a second tank or not.

Originally Posted by KeithS

I find it hard to believe that A/C would have this much of an impact on MPG, but I will have to wait for cooler weather to know for 100% sure. But the change in MPG was pretty dramatic, right after the recall.

Is it possible they rasied the frequency of DPF regens? That would lower the MPG.

On shorter trips like my comutte, the AC impact is more dramatic than long hwy trips as it takes a lot of energy to lower the radiant and ambient temp conditions of the cabin after it's heat soaked all day in the parking lot. Once lowered it takes much less energy to maintain desired temps.

The mpg impact is observed with Bavarian Technic fuel injection parameter data as well as the onboard average mpg function.

I also track the DPF regen events and the frequency is still right at every 400 ml for my vehicle. It doesn't seem to vary from this distance no matter how I drive, and BT data for the DPF parameters (differential pressure, loading, etc) doesn't seem to consistently trigger the DPF regen event, so I'm guessing it's some default mileage limit that is triggering it on my vehicle.

For some examples of BT data collected on DPF and fueling parameters (as well as Evolve remap stacked with JBD stacked with H2O/methanol injection) you can check out this thread: http://www.bimmerfest.com/forums/sho...d.php?t=598240

TDWyse, With the data you are capturing, have you seen any changes made that would impact MPG? As we have (un scientifically) eliminated many of the factors, it sounds as it's related to fuel injection profile and/or amount of EGR. Are we running less efficently but producing lower amounts of soot that clog the EGR system? If that is the case all I want is BMW to acknowledge as such and tell me that is the reason for loss of MPG..

Originally Posted by KeithS

TDWyse, With the data you are capturing, have you seen any changes made that would impact MPG? As we have (un scientifically) eliminated many of the factors, it sounds as it's related to fuel injection profile and/or amount of EGR. Are we running less efficently but producing lower amounts of soot that clog the EGR system? If that is the case all I want is BMW to acknowledge as such and tell me that is the reason for loss of MPG..

About the only thing I've noticed is the amount of EGR utilized seems to be lower than before until the coolant hits 140F. Also there seems to be more "fluttering" of EGR/Throttle than before. Usually under light load conditions the EGR rate is extremely high and the throttle position is more restricted (during DPF regens the EGR goes to 0 and throttle is fully open). However now I'm seeing what appears to be more small, short term variants in the EGR/Throttle position. Almost like they're purposely moving things more to keep them from getting "stuck" with carbon build up.

I haven't been able to see urea injection data, so uncertain if they are having to inject more urea during those times of lower EGR use, but I'd guess they'd need to to keep NoX emissions down?

edit: "(during DPF regens the EGR goes to 0 and throttle is fully open)" was incorrect. I noticed today during regen that the EGR was 0 and throttle was consistently only ~20% open for ~60mph flat road conditions in 84F temps.

Originally Posted by TDIwyse

On shorter trips like my comutte, the AC impact is more dramatic than long hwy trips as it takes a lot of energy to lower the radiant and ambient temp conditions of the cabin after it's heat soaked all day in the parking lot. Once lowered it takes much less energy to maintain desired temps.

+1
I would add that AC compressors - for any given interior cabin temperature - draw more power (reduces mpg) at higher exterior temperatures. This occurs in 2 ways - the ac compressor cycles longer to cool & maintain the cabin temp AND The greater the temp differential the greater the load on the compressor while it is cycled on.
The mammoth torque that our mighty Ds produce, mask the affect of the compressor draw on performance so it might not be that noticeable - but I see a BIG difference in fuel efficiency with the AC on in hot temperatures.
I agree that the recall - which is predominately occurring during the summer months - could be a factor to the reduced efficiency that folks are attributing to the Recall.

Regarding AC impact to mpg's, here's a neat little online calculator that allows you to see theoretical fuel efficiency for various vehicles when entering their respective parameters (our cars weigh ~4000 lbs, Cd ~0.3, frontal area ~2.17m^2). You can also enter a "parasitic" element (the A/C drag in this case) to see its impact (1hp ~ 745.7 Watts).

http://ecomodder.com/forum/tool-aero...resistance.php

I'm not sure how much hp our compressors use, but a quick look online shows typical automotive compressors requiring from ~1 to 10'ish depending upon load. See below for an example.

http://answers.yahoo.com/question/in...1043257AAKydfc

Hi All,
I'm not sure if this helps, but i have been tracking my fuel economy pretty aggressively since purchasing my 2011 D about 13 months ago.

I consistently average 26 MPG's per tank regardless of time of year. I keep my climate control set to auto at 74 and I try to drive consistently.

The reason i bring this up is my friend has 2010 D and drives a similar route with similar settings. He consistently averaged 31 to 32 MPGs. His car's fuel economy was so much better than mine, that we actually switched cars for 2 weeks to see if it was just a quirk of our commutes, but no I got 32 MPGs driving his car as well.

The only way i can come close to my friend's MPGs is to drive with my AC completely off. In my car, driving the same way with the same commute, I can get close to 32 MPG with the AC off. I asked my service advisor about the significant drop off in fuel economy, but he just said a loss of 6-7 mpgs was normal while using the AC, even in the winter when it's barely running.

Now, back to the recall. My friend's car fell into the recall, so he had it performed by a dealership in our area. Interestingly enough, after the recall his MPGs was almost identical to my car. He discussed this with his service advisor, who told him his fuel economy was normal, despite seeing his historical fuel economy on fuelly.com My friend was so upset that he ended up trading in his D for a Merc C class coupe.

My theory, is the folks reporting a decrease of fuel economy received a mapping / programming that came with 2011 or new Ds. Not to be a conspiracy theorist, but isn't there an incentive for BMW to decrease our fuel economy now. Especially considering their plans to pump up sales of the 4 cylinders, 320D and 330D. Let's be honest, the 335D puts BMW in a tough spot with marketing their 335I's vs 328 or 330D's.

Very good information. Explains why there seems to be differences in MPG among different owners. Information is power. I have a very early 2011 model and sounds like had the older mapping, before BMW reduced the peak possible MPG. This was of course until the "upgrade" I received from the recall. So for many people they are thrilled when they get 35mpg on the highway. But when I use to get over 40mpg, 35 is not thrilling to me.

The conspiracy theory behind the reasoning really doesn't add up. The 335D is already discontinued, it's no longer competition for the other engines.

I also have an early 2011 and both before and after the recall the car can still break 40 on the hwy.

Was your DME program upgraded?

2010 d here. Had computer reprogrammed in late 2010 or early 2011 - not sure why. Either way, city mpg went down but highway mpg did not change. Still get 36-40, depending on driving.

Originally Posted by KeithS

Was your DME program upgraded?

Yes.

A variable that could be at play, which is difficult to quantify without expensive tests, is that your local fuel distributors have been getting lower BTU base stock for their diesel product. The BTU content of diesel can vary quite a bit. One example below showing large variations.

http://hypertextbook.com/facts/2006/...ektalova.shtml

If you use that ecomodder calculator and vary the BTU content of diesel (for example use the "standard" vs "winter") you can see how just that single variable can have a significant impact to mpg's.

Originally Posted by TDIwyse

Yes.

. . .

If you use that ecomodder calculator and vary the BTU content of diesel (for example use the "standard" vs "winter") you can see how just that single variable can have a significant impact to mpg's.

Yes there is a BTU drop when refineries lighten up their diesel base stock during winter months. That said, for a premium brand diesel (Chevron, Shell, etc), it is unlikely the BTUs will shift significantly intra-summer or intra-winter months. Why - my understanding - these pumps are supplied from large refineries, and these refineries do not change their crude slate very often.

In other words BTU variance in a Shell or Chevron diesel would be less than those found at say Rotten Robie.

Again, I don't know this for sure - but Rotten Robie is more likely to source their diesel from different refineries versus say a Shell or Chevron.

They might still come from the same refinery and just handle things via different additives done at the depot to get the fuel quality to where they want it for their branding.

I still want to run more tanks through my car but my log book goes back for more than one summer and I did not consistently get 26.x in any of those like I got since the recall. It does not bug me that I am getting what I am getting though, just offering the numbers for some data.

Originally Posted by RPsX5d

In other words BTU variance in a Shell or Chevron diesel would be less than those found at say Rotten Robie.

Again, I don't know this for sure - but Rotten Robie is more likely to source their diesel from different refineries versus say a Shell or Chevron.

Here's some reasons why this may not be true.

http://www.pipeline101.com/overview/products-pl.html

http://www.competitiondiesel.com/for...ad.php?t=16022

It's unlikely there is much of a choice at the local distribution center on being picky about the base stock diesel.


Now, there may be differences in the additive packages used between the brands, but the base diesel from the distribution center should be pretty much the same. Similar with gasoline.

http://www.smartmoney.com/spend/rip-...ell-you-19750/

And the base diesel coming from refineries change significantly based on market conditions and which combination of refined products will generate the best value for the refinery owner.

http://www.fuelmanagementservice.com...uel_Basics.pdf

http://www.chevronwithtechron.com/pr...ech_Review.pdf

Note there is no spec for BTU content, but it's the single biggest factor in fuel efficiency (page 4 of the chevron pdf). Note all the variable ways/combinations the diesel can be formulated to meet specs, some of which result in more/less BTU's.

I have 2 full summers in this car. Also my buddy and I frequent the same gas station on a regular basis, yet he was still getting 5-7 mpgs more prior to the recall. My car's fuel economy hasnt changed by more than .5 to 1 mpg throughout the year. The weird thing is my friend's car is now getting the same fuel economy as mine.

It makes me think the programming has a lot to do with the change in fuel economy.

Originally Posted by Arch_Angel35

I have 2 full summers in this car. Also my buddy and I frequent the same gas station on a regular basis, yet he was still getting 5-7 mpgs more prior to the recall. My car's fuel economy hasnt changed by more than .5 to 1 mpg throughout the year. The weird thing is my friend's car is now getting the same fuel economy as mine.

It makes me think the programming has a lot to do with the change in fuel economy.

Makes perfect sense but still annoying to those of us who have enjoyed years of higher mileage. I used to routinely get mine to hover on 50mpg on the instant gauge(sure not the most trusting source) but I can any more, more like around 40 now. When I first got this car I was annoyed that my old Mercedes was better on fuel. Now, if my current rates hold true, the Mercedes is a ton better.

Thanks TDIwyse for taking the time to post this detailed response. For most part I agree with the info you attached.

Always difficult to explain something like this in a post and at the same time keep it brief. Also many readers may not care to get into such details. So here are a few comments, in no particular order.

• Fuel stations like Shell, Chevron, etc fall into two types - company owned and company operated (COCO) and retailer owned and company operated (RORO, think franchisee)
• Both RORO and COCO are required to sell their branded fuel - i.e. Chevron RORO cannot sell Shell gas. Yes fuel companies do conduct random checks. Places like Costco, Safeway and Walmart can purchase their fuel from anywhere, cost almost always drive these purchase decisions.
• Independently owned RORO's and no-brand stations really keep a close eye on the fuel cost/margin they can generate
• COCOs on the other hand are more sensitive to their brand - cashier's uniform is clean, coffee tastes good, etc etc along with very good housekeeping when it comes fuel storage and delivery. COCOs are less sensitive to the margins they generate . . . as I understand it, ROROs are far more profitable than COCOs.
• Talking to folks I found a COCO near where I live - 95% of my purchases are from this fuel station for the past 12+ years. When we drive long distance I always look for a fuel station with lots of pumps, lots of traffic and are very well maintained. Inventory turns is key . . . I will never fuel from a station in the middle of Death Valley that sees about ten cars a day!
• My comment regarding brand name refineries - for example, the Richmond refinery in the Bay Area might be receiving its crude from say Alaska or Venezuela. My point, it is very unlikely they will all of a sudden start getting their crude from Saudi Arabia or Africa. Similarly an indy fuel station owner is more likely than a COCO to switch their supplier for cost reasons. For a COCO that switch has to be authorized by someone at the oil company and even if that change results in a higher margin, the station manager still earns the same paycheck. This is why I prefer to use a COCO. I agree, generally speaking, all fuel in a given region come from the same refinery/terminal.
• Fuel additives - for most part these additives are not going to make a huge difference in mpg. MPG is most impacted by the base fuel. Additives' effects are more pronounced around detergency, foaming, lubricity, cold weather performance, cetane, etc etc. Yes cetane has a mpg effect . . . but if the indy fuel meets the minimum required by CARB (or other regulatory bodies), the impact of increased cetane would be minimal.
• All fuels - COCO, RORO and indies - have to meet the minimum required standards. Autos generally design to this minimum fuel requirements.

Now to the central issue of why mpg is dropping after completing this recall - no, I do not believe BMW did this intentionally, so their next generation 4 cylinders will look really good. Yes, as part of this recall they must have uploaded a new fuel injection profile . . . most likely BMW engineers were faced with some less than acceptable EGR/other related equipment performance. Changing the fuel consumption profile slightly must have been the most cost effective solution for cars already on the road.

Post recall, my mpg dropped about 10%. I plan to chat with the tech during my next visit, doubt he will be able to anything, but if I learn something new I will post the new info here.

Originally Posted by RPsX5d

Post recall, my mpg dropped about 10%.

RPsX5d, well thought out response.

As a note, back on page 9&10 of this thread I posted observations post recall/reprogramming. Initially the onboard predicted mpg's were at least 10% lower than before recall. And I also had the largest difference between hand calculated vs predicted mpg's on my spreadsheet (with predicted being significantly below actual, whereas normally the predicted tends to be just a tad higher). However, for my vehicle the adaptations soon brought hand calc vs predicted mpg's back in line, with essentially the same mpg's as before recall.

Another potential variable is that vehicle owners driving patterns post recal are different enough to affect the adaptations (which according to the linked documents back on page 10 are quite complex and affect many injection/transmission parameters) than compared to when initially breaking in their vehicles? But I'm not familiar enough with all the short term/long term tradeoffs in those adaptation algorithms to know with any certainty.

Peace

Originally Posted by TDIwyse

Another potential variable is that vehicle owners driving patterns post recal are different enough to affect the adaptations (which according to the linked documents back on page 10 are quite complex and affect many injection/transmission parameters) than compared to when initially breaking in their vehicles? But I'm not familiar enough with all the short term/long term tradeoffs in those adaptation algorithms to know with any certainty.

This of course is a decent sized variable if people actually purposely drive differently for break in periods. In the almost three years I have owned my car it has seen now two reprogrammings and had to go through the adaptation twice now. The first time there was a slight drop in mpg for the first tank or two which is why I have not been super worried about this second time. I will say though that without even going back and looking that I am pretty certain my average mpg per tank did not drop 3.x mpg with the first adaptation. My car has for the most part been very consistent with mpg since day one, spikes in my logs almost always are around either adnormal extended highway driving or adnormal amounts of vehicle idle time.

Just got back from a road trip and the freeway MPG seems to have recovered after the recall. I got 38.9 MPG from Santa Cruz to Sacramento. The overall MPG from Santa Cruz (sea level) to Lake Tahoe (6,250 feet) was 36.1. Not bad. The city mileage still seems to have taken a 2 MPG hit.

wow, my mpg has dropped by like 4-5 mpg since the major update.
I am taking the car from San antonio to Houston today, will make aure tires are
at the right pressures and report what mpg, I will get.
Mine is a 2009 335d with 30K miles.
So, which mpg has dropped since the major update, we should start a poll
is it city or hwy or both?
I used to get like 36-37mpg on hwy, and like 28-29mpg in city.
Now I get like 24-25mpg in city and like 32 mpg on hwy (driving like 15-20 miles).
so, today will be a good test. I use either Chevron or Shell diesel.

My d has a July 2011 build date and has never gotten the fuel numbers some of you guys are getting.

Under good conditions (meaning weather, wind, traffic, driver state of mind) I get 33 mpg highway maybe 34. My city driving is brutal, so I get about 20 mpg. And I'm happy with these numbers btw, given the level of performance.