Jump to content
martinlink

320d high real fuel consumption, OBC optimistic

Recommended Posts

Hey!

Been a long time lurker but finally decided to get to the bottom of this issue, hopefully... :P

So, the car is a 5-speed manual from 2002. Well cared for, serviced (by yours truly) with only the best parts.
The issue is, it's giving me about 34mpg while the OBC reports about 45mpg. I've set the calibration factor in DIS to the maximum allowable 1.10, which brought the OBC down to 41mpg. That's a bit better, but still miles off from what it should be reporting. Average speed according to OBC is 20mph.

I do ~90% of my driving in the city, about 10 miles a day and 40 mile trips about once a month. I've been lead to believe this is a really high consumption for a manual car that is being driven like a granny (3rd gear 1700rpm @ 30mph constantly during commutes) - is this false information or is anyone getting similar/better/worse with their 320d's in the city?
Fuelly link HERE



What I've done:
Used newer injectors from a 330cd with same code (IMA codes written into the DDE) + injector cleaner - no change
New MAF and MAP + cleaned intake air temperature sensor + EGR block - no change
New pressure converter and vacuum hoses for the turbo - nothing
Every gasket imaginable (incl. boost hose o-rings, inlet manifold gaskets etc) new - no change
Changed fuel & air filter, new oil+filter (5W40 Mobil LL01) - nope...
New glow plugs (NGK D-power) and re-soldered glow plug relay (all faults gone for 6 months, saved £50 B)) - no change
Remapped for better economy, not so much for power + decat (both cats) - helped maybe 2mpg, used to be a tad worse before


One thing to note is, the turbo is a bit out of calibration (previous owner fitted a recon; the actuator and stop screw settings were totally off, built no boost whatsoever until I shortened the actuator!!) - now spools at 1700 but reaches 2.5bar at 3000rpm so it is pretty slow to spool still. If anyone is turbo savvy, maybe you can help me by looking at some INPA recordings of the desired/current boost and air flow and telling me whether the stop screw or actuator rod needs some more tuning etc. ^_^
But I highly doubt it's the turbo that is causing the massive difference in OBC and real fuel consumption...

Any ideas on the fuel consumption oddities or turbo issues are really appreciated. Have been at it for almost a year now, getting desperate here!
(Ales on me if we finally solve it!)

Edited by martinlink

Share this post


Link to post
Share on other sites

My 330d's OBC consumption read-out is wildly optomistic as well.  It regularly reads over 70mpg when the reality is a whisker over 50.  I once saw 93mpg on it (there's a pic on here somewhere)!  I've never managed to hook-up with anyone with the right software to adjust the calibration.  I read somewhere that some remappers adjust the OBC calibration to make their map look good, but I don't know how true that is.  It may be a coincidence, but since I stopped using supermarket fuel the OBC's discrepancy has reduced just a tad - maybe a couple of %.

At the end of the day the OBC is really just a gimmick and you're never going to get it 100% accurate (although +/- 10% would be good.......).

Share this post


Link to post
Share on other sites

Neither my current 320d or my last 320d were accurate on the OBC, as said above its a bit of a gimmick. You are far better off working it out properly with what fuel you put in and how many miles you have driven. Its just a guide really just take it with a pinch of salt.

Doing your city driving you are not going to get fantastic mpg, mine would undoubtedly be the same as yours. I only average 45 mpg with mine and thats doing 50% cruising on the motorway every day. 

 

Tho only question is how good was your map, was it done by a reputable place with good feedback? 

Share this post


Link to post
Share on other sites

The map was done by a local guy who is known here for decent maps. I've also tried it with the stock map after all the services and repairs and it's no better sadly :(

I've had a tankful with which I drove about 50/50 city and motorways. Average speed around 40mph and barely averaged 40mpg. Note that here the motorways have a speed limit of 55mph and I'm a very steady driver, so I'd definitely expect better mileage. Current tank is even worse with the cold weather slowly creeping near, at the moment sitting at the half tank mark and done 210 miles (so about 32mpg).

Other people here with the same cars seem to get about 40mpg when only doing short trips like me, and usually the ones with automatic transmissions get the mileage I'm getting. All the while, their OBC is off maybe by 1-2mpg, not 5+ like mine :mad:
I'd like to think it'll get better after I get the turbo calibrated, but to test that theory, I'd need someone with a bit of turbo know-how to take a look at my INPA live recordings.

Here's what it used to be before any adjustments:
CLICK!

Here's what it was after shortening the actuator only:
CLICK!

And finally, this is where I'm at now, after having shortened the turbo stop screw by about one full turn:
CLICK!

All of these recordings are made in 3rd gear at WOT from 1500rpm up to about 3000rpm or close to it. As you can see, the lag is still pretty bad and full boost takes 3-4 seconds to build...

Edited by martinlink

Share this post


Link to post
Share on other sites

Unless I've missed it you haven't mentioned changing any 'stats? They are the biggest killer of mpg by far. If you've got an EGR cooler, you can test the 'stat for that by removing it and blowing through it - if you can it's goosed. Next up is the main 'stat, fiddlier and more expensive but will need doing if your temp doesn't get above 88 Deg C and stay there. I've got a spare 2 day old EGR 'stat that can be for sale if yours is knackered.

Share this post


Link to post
Share on other sites

Ugh, I knew I've forgotten something with all this information crammed in one thread :P

The car only has one stat and I swapped it in june. Temperature reaches 93 degrees C after about 5 miles, so usually right when I get to the destination to park it.

Share this post


Link to post
Share on other sites

Cool, sounds in good order mechanically then.  Were the readings shown above before or after the map, I only ask as the requested boost is off the scale and you can see that the turbo is struggling and never meets the requested boost?  Do you have swirl flaps?

Share this post


Link to post
Share on other sites

It has no flaps, previous owner took care of that (and only that, I must add, as the whole car was a wreck when I got it <_<).

First video is pre remap so the desired value peaks at 2.39bar or so. Other two are with remap and the desired set to 2.55bar, that's where the difference is coming from. But the lack of spool is visible nonetheless. It is struggling because it is still out of calibration, which is why, I'm suspecting, the economy is as bad as it is. Just not sure how much I can safely shorten the stop screw without raising the exhaust pressures too high...

Also dug up a video of what it was like when I got it, before having done anything to it. Air filter was black like the night, crankcase breather was clogged etc etc.:
CLICK!

Share this post


Link to post
Share on other sites

You've got the cat's removed haven't you?  I'd not worry about exhaust pressure.

Share this post


Link to post
Share on other sites

Cats are removed, but I'm talking about the exhaust manifold pressure. If the geometry on the turbo is set too far to the "closed" position (where exhaust speeds are highest), there's a risk of having the geometry flaps tip-to-tail too close and gas just can't pass through bringing the pressure too high before it even passes the turbo.

All this info is from the VAG forums where the guys use the same turbo (VNT15 aka Garrett gt1749v). The sad part is there's no way to test the settings of the turbo like they do, where the car keeps the RPM at a constant 1400 and moves the actuator in and out all the way. Then it measures the change in boost and if that stays between 80 and 200mbar, it's set up right.
I tried simulating this test with my brother keeping the revs at 1400 and me sucking the vacuum pipe to the turbo - before shortening the stop screw the difference was barely 15mbar, after it was about 60mbar so definitely better but not yet dialled :rolleyes:

Share this post


Link to post
Share on other sites
6 hours ago, martinlink said:

Ugh, I knew I've forgotten something with all this information crammed in one thread :P

The car only has one stat and I swapped it in june. Temperature reaches 93 degrees C after about 5 miles, so usually right when I get to the destination to park it.

Your MPG sounds about right then. You'd probably be better off with a petrol model. (or even a bicycle ?)

Share this post


Link to post
Share on other sites
7 hours ago, Rob- said:

Your MPG sounds about right then. You'd probably be better off with a petrol model. (or even a bicycle ?)

I like the idea of biking, except that we tend to get knee-deep snow from time to time. Need the car just in case :P

One quick question: is it normal that when the car is about half way to warm and I then turn the heat from 16C to 18C on full blast, it falls back almost into the blue zone? Seems logical as the aux pump stirs up the colder water to the temperature sensor, but just checking...

Oh and my electrical flow heater is fried since I got it - would getting this fixed give me any boost in mileage on my short trips, or is the impact on the alternator so big that it negates any gains from the faster warm-up?

Edited by martinlink

Share this post


Link to post
Share on other sites

I've never seen my temp needle drop, be it from relatively cold to fully warm. The electric heater should definitely help.

Share this post


Link to post
Share on other sites

Well, if I start off with the heater on 18C or more, it takes about 15-20 minutes for it to get to 93 degrees C, where it will stay, rock solid, no matter what.
With the heater set to 16C (no heat), it takes roughly 10 minutes and also stays totally steady at 93C.

It's only when starting off with the heater on 16C and then half way turn it up to 18C or more, the temperature plummets.
Wouldn't want to believe it's the thermostat since it's pretty new, made by Gates; and also it reaches 93C so can't be totally broken.

Share this post


Link to post
Share on other sites
On 24/11/2015, 14:41:30, martinlink said:

I do ~90% of my driving in the city, about 10 miles a day and 40 mile trips about once a month........................

......... 3rd gear 1700rpm @ 30mph constantly during commutes...........

 

On 25/11/2015, 16:34:22, martinlink said:

Temperature reaches 93 degrees C after about 5 miles, so usually right when I get to the destination to park it................

I suspect these 3 are the root of your "issues".  Under these circumstances I'd be reasonably happy with 34mpg.  5 miles to get to 93deg seems to be par for this particular course.  You're rarely driving the car anything other then "cold".

Edited by StuBeeDoo

Share this post


Link to post
Share on other sites

It's true that these short trips aren't doing the car justice, but the reason I'm after better mileage is that absolutely everyone that drives a 2.0 diesel (be it BMW or other) is getting better results. Also the discrepancy between the OBC and real consumption - just doesn't seem right.

For example a friend asked me to read his codes last week. He drives a 2004 320d automatic. OBC showed 36mpg, he said later that the calculated consumption was 37mpg. He does exactly the same commute I do :( Only difference I noticed when we went for a spin was his boost spiked at 2.9bar and settled at 2.5bar, faster than mine can rise to 2.4bar. Car was massively faster than mine on that test run, too.

Share this post


Link to post
Share on other sites
17 minutes ago, martinlink said:

Also the discrepancy between the OBC and real consumption - just doesn't seem right.

Dude, as above - you need to disregard the OBC.  You aren't the only person to have reported huge discrepancies.  How sure are you that you're not being fed "duff gen" by "absolutely everyone that drives a 2.0 diesel (be it BMW or other)"?  The only way of comparing cars 100% is to test them on exactly the same run under exactly the same conditions.  I'm not saying you don't have a problem, just that you could be focusing on the wrong stuff.

Edited by StuBeeDoo

Share this post


Link to post
Share on other sites

The difference between OBC and real consumption is just one thing I noticed. Not too bothered about it on its own, but rather about the whole "package".

The thing with comparing the consumptions is, nobody local is getting a high consumption like mine. 3 people that I know wouldn't "bluff" about their consumption run e46 diesels, two 320d and one 330d. Now, I know they might not be doing 100% the same trips, but no matter how hard I try (or no matter how high my motorway driving % is), I can't get the consumption under 40mpg... meanwhile the 330d (manual) guy is tracking around 43mpg every tank, doing even less motorway driving than me on my best tank.

Share this post


Link to post
Share on other sites
4 minutes ago, martinlink said:

meanwhile the 330d (manual) guy is tracking around 43mpg every tank, doing even less motorway driving than me on my best tank.

Running a 330d manual myself, I find that hard to believe.  The only times I get better than 40mpg is if I use at least half the tank on a decent run.

Share this post


Link to post
Share on other sites

Well when I last did 60% in town and 40% on a long motorway cruise, I averaged ~39mpg. Last tank he did was similar % wise and did exactly 42mpg.
I ran that tank in summer, his tankful was in late October, so way colder, too :mad:

Share this post


Link to post
Share on other sites

.I have to say I empthasise with you on this. I see my OBC dropping from 37mpg on a motorway run (real life 530ish miles to a tank from brimmed to red - 41ish mpg) down now to 35.8 and still dropping no matter how sensible I drive. I do a journey of approx 17 miles to work, going to work the first 5 miles is town with a bit of stop and start. After that its moorland generally doing 50+mph. I know someone with a very similar 330cd who is doing similar journeys who gets 600+ miles. Frustrates the hell out of me!

So far Ive changed both 'stats (although I find that it takes longer than my old 320cd to get to temp and temp needle wont move when just idling) increased tyre pressures to 35 psi front and 37 psi rear, oil service, air and pollen filter changed, brake service so they arnt dragging, decat, swirl flap delete and using better quality diesel (Texaco Supreme)

Next up is fuel filter and injector test through my local Indie garage. I drive like miss daisy but every once in awhile put my foot down across the moors. Last owner didnt look after it very well, was only getting to the first line temp wise full stop. I suspect running rich all the time has pushed a few injectors out of tolerance.

Were the new injectors you put in tested and within tolerance? Cleaned the VNT? That was a big thing on the PD lumps, more so on the PD100 and PD115. Only other thing I can think of is have you got a vacuum operated actuator or is it the electronic one? Duff actuator?

Edited by dooge

Share this post


Link to post
Share on other sites

The injectors I put in were from a parted out 330d which didn't have any consumption or running issues. They are +-1.2 in the selective mass adjustment screen in INPA so should be good... 

 

VNT is clean and moves smoothly. Actuator is a vacuum one and the whole vacuum system has been overhauled already.

 

Let me know how you get along after the injector refurb. Might try that if nothing else works.

Share this post


Link to post
Share on other sites
Temp will fall again when the thermostat opens

Yes the temp will drop, but the temp needle is damped so once the car is started it should never drop - 'perceived quality'.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...

×
×
  • Create New...