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I have a feeling its my MAFs but am not sure. What else can cause the beast to be slowww? I already ordered new spark plugs will be putting them in tomorrow. When I did the MAFs test my readings were pretty off. At idle it reads 0 liters, at WOT in 2nd gear I can't get it past 105 anymore. I have already replaced the air filters. I had read that there is a group buy on MAFs, can someone please point me in the right direction. If anyone has any suggestion as to why my beast is slow, your help would be greatly appreciated. Would really like for my beast to be doing this :M5launch:!
 

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I replaced my MAFs only a day ago and it made a world of difference. And the MAFs I got were not even new.

Smoother acceleration and loads more power. Hope it lasts :wroom:
 

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If there is any hesitation, flat spots or stumbing, then it is probably the MAFs. Is the car throwing any codes?
:cheers:
 

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i wonder if you're doing the right test though. It's not possible to have a fuel flow of 0L/hr if the engine is running.
Mike
 

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mottati said:
i wonder if you're doing the right test though. It's not possible to have a fuel flow of 0L/hr if the engine is running.
Mike

...unless the car is moving and you use the engine to slow it down, only then the fuel flow can go down to 0.

Mike is right, you have probably selected L/100 km instead of L/h.

Have a look at:

How to test the MAFs yourself and How MAFs work
http://www.m5board.com/vbulletin/showthread.php?t=54788

David
 

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Discussion Starter #7
Yes there are stumbling points, and it deffinitely does not feel like 400 horsepower. I just when out to the car and got a chance to do some testing again. Apprantely I was in the wrong menu, the figures I quoted earlier were from L/100km, I appologize for my ignorance. This time I did choose the L/H and could not get it to past 105 liters per hour. So its the MAFs huh?

Thanks again for all the help, this trully is a great board!

:cheers:
 

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IMMMPRESSED said:
Yes there are stumbling points, and it deffinitely does not feel like 400 horsepower. I just when out to the car and got a chance to do some testing again. Apprantely I was in the wrong menu, the figures I quoted earlier were from L/100km, I appologize for my ignorance. This time I did choose the L/H and could not get it to past 105 liters per hour. So its the MAFs huh?

Thanks again for all the help, this trully is a great board!

:cheers:
It is most likely the MAFs. It could also be low fuel pressure, but that is far less common. Anyway, you will need new MAFs every 50k miles, or so.

There are still a few MAFs left in the Group Buy, which can be mailed to you on Friday.

Have a look at the GB tread (link posted above.)

David
 

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Have you installed the IATS relocation kit? This makes a big difference in the summer heat.

:cheers:
 

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It is the relocation of the IATS so it would not be effected by the heat created from the engine bay.

Mucho Loadso discussed on this topic.
 

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Exactly. The position of the stock intake air temp sensor (IATS) is integrated with one of the MAFS. This gets heat soaked and sends false data to the DME that results in a loss of power due to retarded timing, etc. An after market IATS relocation kit is available that relocates the IATS to a more suitable location that provides more correct IAT data to the DME. The difference can be dramatic. I tested and found at least a 30 degree F difference in the stock and relocated sensors.

:cheers:
 

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i've just had my car (UK - Jan '01) dynoed for exactly the same reason - 336bhp!!! ouch!!!

the power curve seems to suggest the engine hitting a "wall" at approx 4500-4750 rpm but no fault codes are showing.

MAFs replaced 1,000 miles ago

VANOS units replaced 6,000 miles ago

all suggestions welcome before i torch my dealer.

NB: torque reading was 386lbs
car is still under extended warranty

cheers

lore
 

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lore said:
i've just had my car (UK - Jan '01) dynoed for exactly the same reason - 336bhp!!! ouch!!!


cheers

lore

it that's hp at the wheels it sounds pretty normal.
 

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lore said:
i've just had my car (UK - Jan '01) dynoed for exactly the same reason - 336bhp!!! ouch!!!

the power curve seems to suggest the engine hitting a "wall" at approx 4500-4750 rpm but no fault codes are showing.

MAFs replaced 1,000 miles ago

VANOS units replaced 6,000 miles ago

all suggestions welcome before i torch my dealer.

NB: torque reading was 386lbs
car is still under extended warranty

cheers

lore

Did you pull the fuses 17 & 30 to switch the ABS/DSC completely off? If not it will not allow the engine to rev above 5 k RPM with the front wheels standing still.

the ABS interprets the rolling rear wheel and still front wheels as two broken ABS sensors on the front wheels, and therfore limit the engine power to that obtainable at 5k RPM.

After dyno testing you without removing fuses you will have a ABS sensor fault code stored, and an illuminated ABS lamp. The lamp goes away after a little driving.

David
 

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i took it to a reputable specialist who i assume knew what he was doing so i'm taking his findings at face value.

regards

lore
 

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Why not check if the dyno shop removed the fuses mentioned before giving the dealer a hard time? What you describe very accurately match what happens when dynoing with the fuses still in place. There are so many different cars, and even the best dyno shops cannot know everything about every car model.

It would not be good for your relationship with the dealer if you were barking up the wrong tree...

David
 

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Ever since I got my car a few months ago, I thought it was slower then its should be. I put in IATS Relocation Kit and the AA CAI, still felt mostly the same. Last weekend I put in some new air filters (OEM). The ones in the car were 7k miles old and very black. After those, I did notice some improvements in performance. I then put in new MAFS Monday night and noticed even more improvements. (Car has 46k miles roughly, so I figured it was about time)

My MAFS tests were only about 15L/H under what I should be seeing while using my original MAFS. I haven't done new tests yet.

For the inexpensive price of the GB, I felt it was worth the money, even if they weren't the problem. I have CPO, which would cover MAFS, but getting the dealer to proactively replace them because "the car is slow" would have been a nightmare.
 

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If your car is still under the maintenance plan, I believe they will replace the MAFS at no cost to you.
 

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MEnthusiast said:
If your car is still under the maintenance plan, I believe they will replace the MAFS at no cost to you.
Problem with that is most dealers trust the service computer far too much. If it does not report broken MAFs, most dealers will not replace the MAFs.

The service computer tests the MAFs at increased idle at 2k RPM, which is very far from 7k RPM WOT which is where MAF performance is most compromised when the MAFs get contaminated.

Most dealers are just part changers without too much understanding of the systems on the car. Ther are however also many extremely good SAs and Techs. Let´s treasure those people!

David
 
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