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Anyone with LM-1 Gas Analizer Experience

Discussion in 'Technical Q&A' started by msouza, Feb 7, 2006.

  1. msouza

    msouza Formula Junior

    Mar 14, 2005
    291
    Tennessee
    Full Name:
    Milton Souza
    I finally got around to try my LM-1, but have one problem. There is no room to install/weld the supplied exhaust bung. All I'm trying to do is adjust the idle A/F mixture, since my engine is running very rich.

    I know that proper procedure to adjust the fuel mixture, is to disconnect the O2 sensor, so not to fight the O2 sensor trying to compensate the mixture while you are trying to adjust at the same time.

    Would it be correct to remove the car's O2 sensor and install the LM-1 sensor in its place while adjusting the mixture?

    Regards,

    Milton
     
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  3. Llenroc

    Llenroc F1 Rookie
    Rossa Subscribed Consultant

    Jun 9, 2004
    3,343
    Colorado
    Full Name:
    Vern
    Milton, If you remove the 02 sensor it will give you an inaccurate mixture reading because you have changed a parameter the ECU uses to set its injection pulse time there by giving you an incorrect reading for you to adjust to. The 02 sensor is the sensor the ECU uses to fine tune the mixture and then signals the injectors pulse time(lean or rich) at idle after full warm up of the engine, it is trying to keep the mixture at 14:7. Anyway if you remove it you will be in open loop mode and then you would be tuning to that OL situation. Then when you reconnect the 02 sensor you are changing the parameters and you are out of adjustment again ie; right back where you started. There should be somewhere on the exhaust that you could weld the extra fitting. On my 355 I installed them(2) near the existing 02 units. You also want to be as close to the source as possible. I also thought I should be as close to the factory position to duplicate the reading as best I could. Hope that helps. Regards, Vern

    Edit: Milton it didn't dawn on me what kind of car you are adjusting until after a wrote the above, my frame of reference is based on the 2.7 motronic which is not what you are working on. Is your 02 sensor the single wire type? If so you are probably OK to remove the factory sensor and plug and play. Sorry for all of the above it may or may not apply. Regards, Vern
     
  4. Rifledriver

    Rifledriver Two Time F1 World Champ

    Apr 29, 2004
    27,124
    Austin TX
    Full Name:
    Brian Crall
    There are 2 correct procedures for the cis system according to Ferrari.
    One is to disconnect the O2 (at that point it really doesn't matter if it is screwed in the pipe or not) and make an adjustment measuring up stream to the correct CO level, making sure the other gasses stay within limits.

    The other and more common is to use a duty cycle meter hooked in line with the frequency valve and to adjust that to 50% at a hot 1000 RPM idle with everything hooked up.
    If you dont have a duty cycle meter a dwell meter is the same thing with a different scale. 60 degree scale, 30 degrees = 50%.

    CIS mixtures change quite a bit with RPM so make sure the idle speed is right.

    I also ALWAYS retest after the O2 is reattached to be sure the 02 system is working correctly. At that time it should drop below .6% CO with a good balance of all the other gasses on a US car.

    BTW Late 328's have an upstream analyzing tube built into the car. It's behind the R/R wheel sticking out to the side.
     
  5. msouza

    msouza Formula Junior

    Mar 14, 2005
    291
    Tennessee
    Full Name:
    Milton Souza
    Vern and Brian, thank you for your assistance. Please accept my apologies for totally forgetting to state the car model (87/328) in my post.

    I'm at work right now, and unfortunately can't remember the scale range on my dwell meter, but I will check it tonight when I get home. I do remember that it was displaying a lot more then 50% of the range. Another issue, is that I always undestood that the dwell meter would display a small amount o variation, something like 45% - 55% of the scale range, when the mixture is properly adjusted. Well, mine is steady with no variation at all. Does that indicates a problem (like a bad frequency valve) or is it normal?

    I'll post the scale range late tonight.

    Regards,

    Milton
     
  6. Rifledriver

    Rifledriver Two Time F1 World Champ

    Apr 29, 2004
    27,124
    Austin TX
    Full Name:
    Brian Crall
    The dwell meter should show a sweep of about 10% of the range. That indicates normal functioning of the O2 in a K lambda system. No sweep but proper setting (50%) suggests that the sensor is not functioning at all and may just be unplugged. Pull the boot on the large green wire for the sensor back to expose the metal terminal to be sure it is connected. I have seen them inside the rubber but disconnected or taped off to fool a visual inspection when the o2 system was malfunctioning and no one wanted to repair it.
     
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  8. msouza

    msouza Formula Junior

    Mar 14, 2005
    291
    Tennessee
    Full Name:
    Milton Souza
    Hi Brian, just got home.

    My dwell meter has a scale from 0 to 45 degrees. When I was testing the duty cycle, my meter was showing 35 degrees. This equals to approximately 77.8% duty cycle. Very high as I suspected. By the way, the engine was hot and RPM were set at 1000 correctly.

    On your previous post, you mentioned that the dwell meter should be connected "in line" with the frequency valve. Just to ensure I am doing this correctly, by "in line" you mean each wire of the dwell meter connected to each wire of the frequency valve, corrrect?

    Regards,

    Milton
     

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