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Lambda value too high?
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wgsouter Offline
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Post: #1
Lambda value too high?
I fitted a HHO Generator to my 1998 BMW 728 some months ago and coupled it to a MAF Adjuster. My BMW has 4 wires going to the MAF Sensor and I believe that I spliced into the correct wire. Despite the HHO unit producing gas and the MAF adjuster seemingly behaving as it should (signal voltage much lower than led to expect), I have not realised any fuel savings Sad

Last week, my car failed its emissions ... actual %CO and HC ppm very much lower than prescribed limits (I think that this is good) but the Lambda value is higher than prescribed (1.165 versus max allowable 1.030) and therefore a fail. I don't understand what I am seeing here - why is the Lambda value too high and therefore an emissions fail?

Grateful if somebody out there might be able to explain in laymans terms what is happening here. TVM.

Wolfie Souter
Westbury, UK
08-14-2009 11:36 AM
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colchiro Offline
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Post: #2
RE: Lambda value too high?
Maybe this will clear things up: http://www.petercoopercarrepairs.co.uk/new_page_3.htm

Lambda refers to the air fuel ratio, it is a reading which is calculated from the other emission readings (lambda (l) comes from the Greek word for balance). When faced with a car that has failed the emission test on lambda reading the most common response is to condemn the lambda sensor. This guesswork will sometimes pay dividends but more often than not you will have made an expensive mistake. The lambda reading on a gas tester is, to repeat, an indication of the air to fuel ratio, too high a lambda reading relates to too much oxygen. Too low a reading relates to too much fuel. Check the other readings before condemning the lambda sensor.
Sounds like you need to get your mixture under control to achieve any mileage gains and pass emissions.

How many miles on your front oxygen sensors? We always like to replace them no later than 100k miles.

Using just a MAF sensor mod doesn't work that well. You might also check into Mike's digital efie. The oxygen sensor is the king of sensors and has the final word. Wink

Rick

Links: Documents / Tuning for Mileage | Toyota Sensors | Autoshop Sensor Tutorials
(This post was last modified: 08-15-2009 06:22 AM by colchiro.)
08-15-2009 06:14 AM
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wgsouter Offline
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RE: Lambda value too high?
(08-15-2009 06:14 AM)colchiro Wrote:  Sounds like you need to get your mixture under control to achieve any mileage gains and pass emissions.

How many miles on your front oxygen sensors? We always like to replace them no later than 100k miles.

Using just a MAF sensor mod doesn't work that well. You might also check into Mike's digital efie. The oxygen sensor is the king of sensors and has the final word. Wink

Thanks, sounds as if I might have leaned out my mixture too much and its become counter-productive. My O2 sensors are probably original and will have therefore covered 150k miles - I will change both and purchase one of Mike's digital efie's ... might end up getting a fuel saving after all.

I've also read about adding a few fluid ounces of acetone to a tank of fuel: any tips or comments?

Wolfie Souter
Westbury, UK
1998 BMW 728
08-16-2009 06:39 AM
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colchiro Offline
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Post: #4
RE: Lambda value too high?
Too lean can mean open loop or just a loss of efficiency and power.

I'm surprised you can go that lean with just a MAF w/o throwing codes at low speed.

Sorry, I have no experience with acetone.

Rick

Links: Documents / Tuning for Mileage | Toyota Sensors | Autoshop Sensor Tutorials
08-16-2009 03:52 PM
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wgsouter Offline
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Post: #5
RE: Lambda value too high?
Yes, the O2 sensors are disconnected; however, I assume that the Lambda reading was taken by the MOT station using an exhaust sniffer device, therefore surprised that a car could fail for having too much O2 in the exhaust. As previously indicated, %CO and HC ppm very much lower than prescribed limits and not a fail.
08-19-2009 10:10 AM
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colchiro Offline
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RE: Lambda value too high?
Disconnecting pre-cat o2's and expecting to pass emissions is a stretch IMO.

W/O a working o2 sensor, you should go into open loop where the ecu falls back on known values (usually rich) to try to limp home.

One reason that newer vehicles get better mileage than in the 80's is because of fuel injection and o2 sensors.

Rick

Links: Documents / Tuning for Mileage | Toyota Sensors | Autoshop Sensor Tutorials
08-19-2009 01:58 PM
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