Subject: New Vanos rings- increased fuel consumption? Author: webhorn4477 : member since November, 2009 : 45 posts Posted on: 2010-01-24 18:39:24

Hi Rajaie and forum,

as i posted already, i very sucessfully changed the vanos seals on my ´01 530i touring almost two months and 2000 miles ago. Car is still running strong, has lots of low end torque. But one thing bothers me: from the moment the new seals were installed, i noticed increased fuel consumption. At first i thought it was because of my spirited driving for seals break-in, and because it was just very much fun to use the engine´s newly found horses under the hood.
In the meantime, my driving style has returned to normal, which is rather calm- but the car continues to use siginificantly more fuel than before the seals change.
I have a longer trip that i drive frequently, always with the same circumstances (same route, same car load, same speed) which is a 150 km stretch of autobahn. I usually use cruise control, at 130 km/h- which equals about 3100 engine rpm (manual gearbox)- so this is great for fuel consumption comparison because of the similar conditions and engine loads.
On this "test" stretch, the average consumption since the seals change has increased by about 10%, which means one litre per 100 km more or 2,6 mpg less than before. I observed the same increase of consumption in my normal, daily driving.
So, since i´m convinced that a correctly working vanos should actually DEcrease the fuel consumption, maybe you have an idea what could be the reason for the increase? DME fault memory is, of cause, empty.

In the past two years and 50,000 kilometres i replaced, fixed and cleaned:
-fuel filter
-CCV system and hoses
-MAF sensor
-pre-cat O2 sensors
-Disa Valve (improved version)
-Idle controller
-re-welded close-to-engine catalytic converters. Housings were cracked (common fault on german cars with constantly high autobahn speeds/engine loads) and replaced exhaust manifold gaskets
-intake boot
-intake manifold gaskets

My engine, beeing an ´01 M54B30 ECE-version, does not have a secondary air system.

The fuel trim adaption values are almost perfect: The DME (ECU) has to lean out on idle: additive mixture -0,09 (Bank 1) / -0,07 (Bank 2) milliseconds injection time.
Due to this, i can rule out every sort of vacuum/air leak (because the engine-created vacuum is the greatest at idle), a leak in the cat´s or exhaust manifold/gasket (because especially at idle, the exhaust gas pulses can suck ambient air/oxygen in the manifold and thus corrupt sensor readings) and broken/aged O2-Sensors, because all of this would cause the idle adaption to rise significally into positive values or even throw a code. These values have stayed the same before/after the seals change.
Not-so-perfect are the values of the multiplicative active mixture, which covers the area between idle and full throttle. These values are ~ +8% for both banks, which might point to a fuel starvation issue at higher loads (it´s Pinging!!! fuel pump?!?)- but still well in the green. The DME maxes out and throws a code at +/-20%, afaik.
These values also stayed the same before/after the seals change, which makes me think that i didn´t break anything and assembled everything correctly.

Every idea of what could be the reason for the increased fuel consumption, is greatly appreciated! Maybe already fixed parts are broken again?

Thank you all in advance,

webhorn

• New Vanos rings- increased fuel consumption? - webhorn4477 2010-01-24 18:39:24 (1137 views)
  • Re: New Vanos rings- increased fuel consumption? - Rajaie 2010-01-24 22:00:24 (627 views)
    • Re: New Vanos rings- increased fuel consumption? - webhorn4477 2010-01-25 08:20:37 (684 views)
      • Re: New Vanos rings- increased fuel consumption? - Rajaie 2010-01-26 16:55:10 (578 views)
        • Re: New Vanos rings- increased fuel consumption? - webhorn4477 2010-01-27 08:55:18 (621 views)
          • Re: New Vanos rings- increased fuel consumption? - Rajaie 2010-01-27 16:22:50 (428 views)
            • Re: New Vanos rings- increased fuel consumption? - webhorn4477 2010-01-27 19:52:45 (424 views)
              • Re: New Vanos rings- increased fuel consumption? - koveras 2010-03-17 12:55:32 (416 views)
                • Yes, i did. See... - webhorn4477 2010-03-17 18:11:01 (392 views)
              • Ok. Let us know how things go (nt) - Rajaie 2010-01-28 20:16:58 (454 views)
  • Re: New Vanos rings- increased fuel consumption? - poolman 2010-01-24 19:06:05 (521 views)
    • reply@poolman - webhorn4477 2010-01-24 19:34:16 (461 views)
      • Re: reply@poolman - poolman 2010-01-24 20:26:06 (427 views)
        • Re: reply@poolman - webhorn4477 2010-01-24 20:43:17 (785 views)
          • Re: reply@poolman - Rajaie 2010-01-24 21:54:39 (457 views)
            • Re: reply@poolman - webhorn4477 2010-01-25 07:11:21 (461 views)
              • Re: reply@poolman - poolman 2010-01-26 19:36:01 (393 views)
                • Technically not... (pic) - ZetaTre 2010-01-27 17:26:42 (472 views)
                  • Great shot - poolman 2010-01-27 22:02:54 (410 views)
                    • Yea, but that's with the head off... - ZetaTre 2010-01-28 16:34:50 (379 views)
              • Re: reply@poolman (pic) - ZetaTre 2010-01-26 17:18:06 (458 views)
              • Thanks for the super info! (nt) - Rajaie 2010-01-26 15:41:51 (423 views)
              • Re: reply@poolman - poolman 2010-01-25 08:01:51 (396 views)