E34 520i Non-KAT/S199A Emission Test Failed

[93Siro]

Hi Guys,

Latley a friend of mine got a mint E34 520i M50B20. His HC numbers though are 30% higher than what is allowed in yearly inspection tests. To our surprise this car did not seem to come with o2 sensor. I VIN checked and it seems it’s a “leaded fuel kit” which probably means no o2 sensor. I have never seen something like this before.

Now my question is, how can i reduce the HC in this occasion? Or more correctly, in a open loop car like this what can cause high precentage of unburnt hydrocarbons? The other parameters, O2, CO and NOx were all in order. Lastly, I quickly checked and it seems this car shares the same ECU part number as a catted car, can i rig up the whole cat shebang to this car?

Thanks in advance

[whiskychaser]

Your yearly inspections are probably based on a car with a cat. Find out what the regulations for your country were before cats were introduced and compare them to your current emissions. You may well find that they are within the old specs. As a rough guide, our old HC limit was 1200ppm without a cat but with a cat it is only 200ppm .

So depending on your local regulations, you may not need to do anything to the car. But to get a 'pass' your authorities may need confirmation from BMW that the car left the factory like that.

[moroza]

HC is either unburned fuel or partially-burned oil. Short of modifications such as adding O2 sensors and cats, or messing with fuel/ignition tuning, the first things that come to mind that may help are: good spark plugs (NGK BKR6EK), clean injectors, and if you suspect oil burning, it may help to use oil that's heavier or higher-quality (synthetic typically burns less than conventional, though you risk oil leaks if the car's been using conventional for a long time).

[93Siro]

Your yearly inspections are probably based on a car with a cat. Find out what the regulations for your country were before cats were introduced and compare them to your current emissions. You may well find that they are within the old specs. As a rough guide, our old HC limit was 1200ppm without a cat but with a cat it is only 200ppm .

So depending on your local regulations, you may not need to do anything to the car. But to get a 'pass' your authorities may need confirmation from BMW that the car left the factory like that.

I have two options here. Either declare the car is carbureted and have 400 ppm HC limit, or EFI with only 250 ppm HC limit (my test showed 333 ppm). Carbureted option is risky because the city council may restrict high polluting cars access to different parts of the city, so i rather get this car fixed for good.

HC is either unburned fuel or partially-burned oil. Short of modifications such as adding O2 sensors and cats, or messing with fuel/ignition tuning, the first things that come to mind that may help are: good spark plugs (NGK BKR6EK), clean injectors, and if you suspect oil burning, it may help to use oil that's heavier or higher-quality (synthetic typically burns less than conventional, though you risk oil leaks if the car's been using conventional for a long time).

Yep i figured those routes. Someone mentioned leaky vacuum lines could be the reason too. I ultimately want to try convert this car to a KAT spec though.

[whiskychaser]

The Euro HC standard for the E34 520i with a cat is 200ppm and that dates from around July 1992. Presumably, your car is not a Euro market car? My 525i was not and it left the factory without a cat. IIRC, the HC was about 300ppm and I never had any problem passing the emissions test. However, I don't live in a city with local emission restrictions. If you compare your car to a Euro spec car on realoem, you will see what you need. I imagine that you will need to replace the front box with a cat, fit an O2 sensor and wiring and get the appropriate DME. That should not be too difficult as most of the cars on the market are probably like that anyway

[93Siro]

The Euro HC standard for the E34 520i with a cat is 200ppm and that dates from around July 1992. Presumably, your car is not a Euro market car? My 525i was not and it left the factory without a cat. IIRC, the HC was about 300ppm and I never had any problem passing the emissions test. However, I don't live in a city with local emission restrictions. If you compare your car to a Euro spec car on realoem, you will see what you need. I imagine that you will need to replace the front box with a cat, fit an O2 sensor and wiring and get the appropriate DME. That should not be too difficult as most of the cars on the market are probably like that anyway

S199a indicates Saudi Arabian market which at the time had leaded gas therefore a catted/o2 monitored car would not work there.
I'm looking to converting this into a catted car, at least a lambda car, to be frank i don't know how a open loop car would work fine with just maf sensor as it's primary mixture optimizing sensor. I think i should start looking into German forums.

[shogun]

we had a no cat car in the E32 forum, read the comments https://www.bimmerforums.com/forum/s...ghlight=no+cat

[93Siro]

we had a no cat car in the E32 forum, read the comments https://www.bimmerforums.com/forum/s...ghlight=no+cat

Thanks
I'm slowly getting the parts for a 520i catted to wire up the car.