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      02-08-2009, 04:37 PM   #67
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Originally Posted by jinjur View Post
OK.............so say for example that i unplug the MAF or the EGR........i know they will throw a code but would the car be faster/more fuel efficient if either is not operating at 100%?

How does the car know the air flow?

Does it just run of a set of pre programmed figures on the ECU?




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Andy
The MAF (Mass Airflow Meter or German equivalent) does exactly that - measures the airflow and affects fueling. The EGR (Exhaust Gas Recurculation valve) is an emissions control device, not related to economy - not sure how you would 'disconnect' or bypass this, even if you wanted to.

The car shouldn't be faster/more fuel efficient with either disconnected/bypassed. Both are integral to the engine running as it should. Faults with either would end up with the engine running badly (you'd notice it if either were faulty) and/or fault codes.
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      02-08-2009, 05:11 PM   #68
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there is something far wrong with your car if thats the mpg your getting.iv had my 320d 163 for 18months and it has never been below 40mpg.thats all town running and the cold weather the most iv had is 54mpg on a long drive good luck.
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      02-08-2009, 05:22 PM   #69
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FFS well my average is 30 and I've seen it down to 19!!!!!!!!! On a very spirited run...


Its got FSH and nothing close needed. Could book it into early service but would rather not give away money knowing that it hasn't helped with the above.

Interested to know what the problem is for sure..
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      02-08-2009, 05:25 PM   #70
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There simply has to be a problem with some of these cars...........

This cant be right at all. Not with some people reporting some bloody respectable figurs and those of us with horrific ones, notable....all pretty similar might i add.




I mean, i tried as hard as i could today (town). Driving like Miss Daisy and i COULD NOT get above 30mpg..........

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      02-08-2009, 05:32 PM   #71
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Too right. I averaged 47mp on my earlier E46 oner 45,000miles and the E90s are more fuel efficient. Something very wrong. Have you checked the OBC accuracy? My E46 was accurate to within a few %; my E90 shows 50mpg, I am getting 45mpg.
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      02-08-2009, 05:35 PM   #72
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Quote:
Originally Posted by J4MES View Post
The MAF (Mass Airflow Meter or German equivalent) does exactly that - measures the airflow and affects fueling. The EGR (Exhaust Gas Recurculation valve) is an emissions control device, not related to economy - not sure how you would 'disconnect' or bypass this, even if you wanted to.

The car shouldn't be faster/more fuel efficient with either disconnected/bypassed. Both are integral to the engine running as it should. Faults with either would end up with the engine running badly (you'd notice it if either were faulty) and/or fault codes.
Guys, the MAF senses what comes in after the air filter. The EGR it is way beyond that, you can interfere with it, and it does affect economy. Pull off the hose of the actuator, stick a proper sized bolt in the hose to avoid it keeps sucking a vacuum, and there you go. Works well on E46 (no feedback sensor). On E90 it has a feedback (if you have an electric connector above the valve body that's it). I don't know why but disconnecting it will take forever before the engine throws up a faultcode.
But also this doesn't achieve anything if you have the throttle valve on your diesel. Look at the piping from intercooler to engine, if at the end of the black piping you have an alu body with a shaft in it, what do you think that is?
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      02-09-2009, 03:44 PM   #73
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F104, i have attached a pic showing what i cleaned.......

And after having had most of the intake off dude....there is no butterfly.

I reckon you are talking about the EGR.



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      02-09-2009, 04:45 PM   #74
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so is there problem with mine then?
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      02-09-2009, 05:21 PM   #75
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so is there problem with mine then?
Well, if yours is an E90 320D returning 23MPG under moderate driving then yes.

Otherwise, probably not




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      02-09-2009, 05:52 PM   #76
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Jinjur, the E92 320D is more complicated then wat you have. Yours looks more like my E46. There's no feedback sensor shown, thus pull of the hose (in the bit you circled), plug the hose with something (a bolt will do) and see if that changes things. I've been driving E46's for over 300 kmls with this disconnected. If that doesn't show improvement your problem is somewhere else.

Carlos, I believe you have the same system as on mine. A motorized butterfly valve. Only i have only the motorized shaft left :-)

cheers,

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      02-09-2009, 05:57 PM   #77
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Quote:
Originally Posted by tisme View Post
Too right. I averaged 47mp on my earlier E46 oner 45,000miles and the E90s are more fuel efficient. Something very wrong. Have you checked the OBC accuracy? My E46 was accurate to within a few %; my E90 shows 50mpg, I am getting 45mpg.
iirc the E46 320d had 125/150bhp, the early E90 320d has 163bhp (and more on later models - 177/204) and as such, pre-eD, are less economical (the E90 is heavier too).

However, if some E90/E91 320d drivers (pre-eD, 163bhp) are getting well over 40 and into the 50's, then clearly a batch of them doing <30mpg may (?) indicate a problem in a number of variants/model years??

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      02-10-2009, 02:32 AM   #78
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Jinjur, the E92 320D is more complicated then wat you have. Yours looks more like my E46. There's no feedback sensor shown, thus pull of the hose (in the bit you circled), plug the hose with something (a bolt will do) and see if that changes things. I've been driving E46's for over 300 kmls with this disconnected. If that doesn't show improvement your problem is somewhere else.

Carlos, I believe you have the same system as on mine. A motorized butterfly valve. Only i have only the motorized shaft left :-)

cheers,

Martin
Martin mate,

Mine does have a feedback sensor etc as well as all the gubbins in the pic you posted. But none of that needs cleaned, just the EGR valve.

Not sure i have ever seen a diesel with a butterfly valve to be honest.....


J4MES,

That is excatly my reckoning. ED cars aside, there are 163 E90's chrning out figures that i could only dream of having......never mind the fact that older cars with older tech engines wipe us out economy wise.

JJ

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      02-10-2009, 08:47 AM   #79
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Martin mate,

That is excatly my reckoning. ED cars aside, there are 163 E90's chrning out figures that i could only dream of having......never mind the fact that older cars with older tech engines wipe us out economy wise.

JJ

JJ,

What build is your car? Mine is 12/2005, perhaps there is a connection with some engines?

I appreciate you trying to get to the bottom of this, my mechanical ineptness won't be of much help i'm afraid but i can make all the observations you might need.

cheers
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      02-10-2009, 01:28 PM   #80
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Martin mate,

Mine does have a feedback sensor etc as well as all the gubbins in the pic you posted. But none of that needs cleaned, just the EGR valve.

Not sure i have ever seen a diesel with a butterfly valve to be honest.....

J4MES,

That is excatly my reckoning. ED cars aside, there are 163 E90's chrning out figures that i could only dream of having......never mind the fact that older cars with older tech engines wipe us out economy wise.

JJ

JJ
I tried disconnecting my EGR vaccuum hose (with the feedback sensor) and it does take some time to generate a fault code. After that I reconnected it and the fault disappeared. I don't know what the problem on your car is, but the point i tried to make is not about a sticking EGR valve. I was thinking if something causes the EGR valve to be open more often then normal. If you have the feedback sensor , then I assume you also have another part as well which modulates the valve position (rather than just open/closed). On mine it's whithin inches of the valve. If your EGR valve is clean now, and moves "freely", pull the hose of which should ensure the thing stays closed (remember to block off the hose though). If that doesn't resolve the economy, then the problem is elsewhere. If your dealer found out what you did just be honest about it. EGR is good for the environment, but if someone wants to claim disabling it hurts the engine they are on very weak grounds..

Re throttle valves on diesels that's what i thought too... But this thing is under the hood on mine, at the end of the intercooler piping to engine. It's an about 3" dia valve. Those torx bolts were not easy to get out..

If you want to know more about EGR do a search on "Pierburg" and "pdf", and you should find the PDF from which this was taken

Martin
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      02-12-2009, 04:11 AM   #81
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A couple of points. On the spider tuning thread there's a comment from TiRich

"Bosch MAF's in my opinion should be a service item. The effect they have on performance and MPG is very significant. A lot of people with cars over 40k miles don't realise that the MAF has gone out of spec as it, in general, happens so slowly so goes unnoticed. I discovered that cleaning the MAF as often as every 3k miles made a significant difference., it shows how sensitive they are - especially in the winter when there is a lot of road spray. A lot of the contamination in the spray ends up on the MAF."

http://www.e90post.com/forums/showth...106924&page=10

I did a fairly big run yesterday and got 41 mpg which isn't so bad but i noticed a few things.

6am in the morning, doing 70 (yes really) in 6th was giving around 30mpg on a flat surface. Three hours later the same situation was getting me 50mpg. So i assume that engine and outside temp has a big effect. With it being generally so cold at the moment, perhaps this is a bigger factor then we think.

I found it slightly better to floor it up to speed than slowly reach speed.

Doing the same in my 120d would give me over 50mpg easily but my 120 would have been on 10k and the 320 is on 60k.

So the comment about the MAF above interests me because it would make sense in my (and perhaps your) situation.

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      02-12-2009, 05:58 AM   #82
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Hi Jinjur, paul and everyone on this thread. I have been following this thread for some time as I have a 320d E90 (18k miles) too which isn't fuel efficient in my opinion.

My car is still under warranty and I took it to BMW last week and after inspecting the car they said the air intake system is all good but the valves needed some adjustment. The car has improved a little after that but in town I still get around 32mpg and on motorways around 50. The guy also mentioned that the average will improve in warm weather.

I am not happy with town mileage as my previous car (2006 Passat 2.0tdi) never went below 37 in town.
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      02-12-2009, 07:20 AM   #83
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Hi Jinjur, paul and everyone on this thread. I have been following this thread for some time as I have a 320d E90 (18k miles) too which isn't fuel efficient in my opinion.

I am not happy with town mileage as my previous car (2006 Passat 2.0tdi) never went below 37 in town.
I'd be happy with 50 on the motorway, that's around a 20% difference. When i get a moment i'm going to take it in and get them to have a look at the MAF and anything around that area.

I look forward to seeing Jinjurs rolling road and other tests

I would consider a tuning box as well, in time once i know that the base engine is as 'clean' as it can be.

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      02-12-2009, 07:28 AM   #84
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I too have been watching this with interest. I've been driving my car very carefully since buying it and it's not as good as I had hoped. Average consumption for my normal commute is about 38-40mpg which sounds good but when you consider that 90% is dual carriageway it aint that good. Out of interest what transmission are you all using? Mines an Auto so that has some negative effect
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      02-12-2009, 07:57 AM   #85
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This sounds exactly like a MAF problem, hesitation, no urgency in acceleration and poor MPG.

Swap that out before going any further.


What I will say is I used to only get 27mpg from our 120d auto round town, a combinded of 33.6mpg over 18 months and 38mpg on a run at best.

The ED 320d was far better, 39 average.
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      02-12-2009, 08:10 AM   #86
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This sounds exactly like a MAF problem, hesitation, no urgency in acceleration and poor MPG.

Swap that out before going any further.

What I will say is I used to only get 27mpg from our 120d auto round town, a combinded of 33.6mpg over 18 months and 38mpg on a run at best.

The ED 320d was far better, 39 average.
I would say those figures were bad. Certainly the 120d, mine was 43 average with a lot of that around town and 50+ on a long run.

I wonder how much of this is driving style vs actual different tolerances in the engines. Perhaps we're all worrying about nothing but then a 20% saving in fuel costs does add up these days.

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      02-12-2009, 08:18 AM   #87
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tagging thread as coming upto 50k and want to check the maf myself.
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      02-12-2009, 08:21 AM   #88
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tagging thread as coming upto 50k and want to check the maf myself.
Does beg the question whether the MAF is checkable without taking to a dealer? (for someone with inept mechanical skills like myself...)
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