[ba] 5 cylinder now idles - but still not making the grade smog-wise

[Michael Heth]

On Sep 14, 2011, at 5:06 PM, Steven B wrote:

> NOx is usually a result of high compression or high combustion temps.  Have you noticed pre-ignition at all?

Yes, pinging has come back over the last little bit at 4K and above. Was gone for a long time when I had switched up to Chevron Premium.

> It would be worthwhile to run compression numbers on all cylinders, perhaps you have excessive deposits on the combustion surfaces.  What can cause high combustion temps?  How warm are the engine coolant and oil getting during the test?  

Probably do have deposits, as it is the original top end. Had plans to obtain a later version head with the hotter cam and swap it over but they faded away a few years ago.

Might still pursue it since a new cat is probably $300 with tax and shipping.

>  
> I'm not sure I agree with the comments about the newer cats ... 3-way cats require the injection of air into the exhaust for the third catalytic reaction.  I'm sure the high price of cats in California now is a direct result of the new laws this state has enacted regarding catalytic converters ... they have to be somehow certified for the specific application, and installed by a certified smog technician.  "certified" = $$$$  I'd bet all that a "certified" cat is for a car as old as we're talking about is would be a new part from Audi.  There is little doubt that a new cat would help, but it is always best to see if you can make it without having to spend too much ...


Thanks that is excellent advice, much appreciated.


On Sep 15, 2011, at 1:01 PM, Brian Devlin wrote:

> Post your complete smog results and it will be easier to find the problem. Timing will affect the NO2 production, but I wouldn't start there. 

Okay they are below.

> How's the mixture since you put in the O2 sensor? If it's lean then NO2 goes way up, if rich then CO goes up. If the cat is working, I'd try to get it bit richer and let the cat clean it up.

As I remember the only adjustment available is a recessed set screw in aluminum throttle body(?).

As I remember it was just for adjusting the idle.

But still haven't found my manuals so I'm guessing here.

> If the mixture is good, retard the timing a couple degrees - you should have some wiggle room on that spec.
> If you do need a cat, Napa sells CA approved universal cats that are fairly priced, but you'll probably have to go through a shop to get one. If you failed an official test, then only a CA licensed smog tech can legally work on it for money (of course you and anybody else can donate their time).
> -Brian

If I could get by with mucking with adjustments then I would be motivated to get it to pass smog and then spend the $$ on another head and cam.

I can install it myself and as I remember it wasn't going to be over the cost of a new cat.

With some new rubber it would again be a car that turns as well as the Ferrari of the same year - 

(if you don't remember in '82 the only car that did better on the skidpad for Car&Driver than the Coupe was a Ferrari).

Here's the test data, although I can set the desmodromic valves on my Ducati to be right on the money I never learned how to interpret these types of readings

15 MPH -

1st test specs

RPM=1562 | %CO2=13.9 | %O2=0. 4|

HC (PPM) - Max=148, AVE=45, MEAS=60 |

CO % - Max=1.03, AVE=.016, MEAS=0.51 |

NO (PPM) - MAX=1175, AVE=434, MEAS=1374

2nd test specs

RPM=1561 | %CO2=14.1 | %O2=0.6 |

HC (PPM) - Max=148, AVE=45, MEAS=91 |

CO % - Max=1.03, AVE=.016, MEAS=0.54 |

NO (PPM) - MAX=1175, AVE=434, MEAS=1142

I passed the above after the tuneup and replace oxygen sensor.

After the tuneup but before I installed the new sensor the car was actually "peppier" in acceleration, so maybe the sensor sent things richer?

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25 MPH -

1st test specs -

RPM=2561 | %CO2=14.0 | %O2=0.3 |

HC (PPM) - Max=120, AVE=33, MEAS=36 |

CO % - Max=0.83, AVE=.014, MEAS=0.47 |

NO (PPM) - MAX=1005, AVE=357, MEAS=1276

2nd test specs

RPM=2576 | %CO2=14.2 | %O2=0.4 |

HC (PPM) - Max=120, AVE=33, MEAS=55 |

CO % - Max=0.83, AVE=.014, MEAS=0.50 |

NO (PPM) - MAX=1005, AVE=357, MEAS=1186

So I have to drop about 15% off the NO to get by.

Printout shows that timing is 6 BTDC which I assume is a measured value and not just the spec from the manual.

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Again, much thanks for the really high quality support I get from this list, you should see what passes for "fellow owner feedback" on a couple of MC lists I'm on.

I don't actually ever have any issues I need help with on my bikes but when others do the comments are often somewhat pathetic.

On this list, you guys actually know what you're talking about.

So your time and expertise is much appreciated.

M./

Michael Heth
classic_coupe at serversmiths.com