Cali smog - Failed NO and HC

[xcx4x]

EDIT: Passed smog after changing o2 sensor. Results drastically improved. See 3rd post down for results.




Hi Everyone,
Finally got my first e30 after ~6 months of lurking and searching.

I've got questions on getting a new catalytic converter. First, details below:

1990 BMW 325i
I have changed:
-oil
-spark plugs
-air filter
-battery

Odometer: 177107

Test Results:
________________%CO2____%O2__HC(PPM)
Test_______RPM__MEAS____MEAS__MAX___AVE___MEAS
15mph_____1813__14.7_____0.1____108____37____115
25mph_____1938__14.9_____0.1____83_____28_____44

_________________CO(%)
Test_______RPM___MAX___AVE___MEAS
15mph_____1813___0.71___0.14___0.41
25mph_____1938___0.40___0.11___0.26

_________________NO(PPM)
Test_______RPM___MAX___AVE___MEAS
15mph_____1813___767___238___1044
25mph_____1938___706___188___210


So I am currently changing the O2 sensor then going to smog again and hope to pass.

If I fail again, my plan of action is:

1. Change the catalytic converter.
I know the OEM cat converter is $$$, so I am looking for an aftermarket one. However, there's one for about 200$:
Magnaflow Cat:

http://www.autopartswarehouse.com/sku/BMW/325i/Magnaflow/Catalytic_Converter/1990/M6636037.html

OR

http://www.oreillyauto.com/site/c/detail/MGFC/336037/02404.oap?year=1990&make=BMW&model=325i&vi=1011700&ck=Search_02404_1011700_2558&pt=02404&ppt=C0022

QUESTION1: What mods are necessary for this aftermarket cat?
QUESTION2: What is the difference between this cat and the cat posted below?


or there is one for 533$ on turner motorsport

http://www.turnermotorsport.com/p-3278-catalytic-converter-e30-325i-325is-1987-91-50-state-legal.aspx

QUESTION3: Are there any cheaper catalytic converters available? I am on a tight budget right now and I still have to change the timing belt.

QUESTION4: I used the lambda calculator found here:

http://www.smogsite.com/calculators.html#lambda

But I don't really know how to interpret the results...Can anyone give me a hand here?

Thanks for your help! :):p

[jalopi]

Looks like that Magnaflow cat is a slip fit, though even if it isn't you can get a pipe expander for about $40.

The cat from turner looks like it's more of a mid-pipe than just a cat.




Not sure what the stock inlet/outlet is, but I saw some 'universal' cats on summit for about $100:

http://www.summitracing.com/search/part-type/catalytic-converters/outlet-quantity/two/inlet-quantity/one?SortBy=BestKeywordMatch&SortOrder=Ascending&page=2

[jlevie]

The problem is only at low engine speeds and the numbers are quite good at higher engine speeds. That suggests that the cause could be intake leaks causing lean misfires, which will will drive up both HC and NOX. So before contemplating a replacement catalytic converter, have a smoke test run and fix the leaks it reveals. The engine may also benefit from new ignition wires, plugs (NGK ZGR5A's), & distributor.

[xcx4x]

jalopi - thanks for the awesome MSpaint job. I didn't know that.
jlevie - thanks for your input and reasoning, your post led me down a few other alleys that proved fruitful in my overall understanding of cars.

After changing the o2 sensor, I passed.


Test Results:
________________%CO2____%O2__HC(PPM)
Test_______RPM__MEAS____MEAS__MAX___AVE___MEAS
15mph_____1901__15.0_____0.0____108____37____35
25mph_____1964__15.0_____0.0____83_____28_____17

_________________CO(%)
Test_______RPM___MAX___AVE___MEAS
15mph_____1901___0.71___0.14___0.15
25mph_____1964___0.40___0.11___0.07

_________________NO(PPM)
Test_______RPM___MAX___AVE___MEAS
15mph_____1901___767___238___192
25mph_____1964___706___188___106


Once again, thank you all for your input. I know this thread has been done to death but I am sure you all can identify with the feeling of passing smog after not passing smog.

[jalopi]

I am sure you all can identify with the feeling of passing smog after not passing smog.

Definitely man, definitely... oh wait, I don't live in Cali, don't have to pass smog ;)

In any case, good to hear bro. Much cheaper than doing a cat. How often is the smog test in Cali anyway? 2 years for non-historic/street rod cars in MD.

[xcx4x]

Every 2 years I believe.


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