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Thread: DPI headers and starter wiring

  1. #21
    One of those purists you keep hearing about. sdg3205's Avatar
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    New 02 sensor would likely have an effect on your dwell. You should at the very least see if you're in the ball park. If you're mixture screw is still factory sealed, thats a good thing in some regards.
    Dave

    Here, somewhere.


  2. #22
    Senior Member DMCVegas's Avatar
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    Quote Originally Posted by sdg3205 View Post
    New 02 sensor would likely have an effect on your dwell.
    Which is precisely why you shouldn't set your fuel mixture based upon dwell. O2 sensors, in particular narrow band units w/o heater wires like ours, have a much shorter lifespan than modern wide band units. Which is why you're supposed to replace them every 30K miles; their ability to accurately measure oxygen content greatly decreases and results in false readings. Not to mention that you could technically even have manufacturing variations that could affect the performance of the unit.

    All of those things are variables factors which you do not have control over. That is why you should set your fuel mixture by analyzing the pre-catalyst exhaust gasses via the method described in the workshop manual that eliminates all variables such as combustion chamber temps, timing, enrichment circuits, etc.

  3. #23
    Senior Member Bitsyncmaster's Avatar
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    Quote Originally Posted by DMCVegas View Post
    Which is precisely why you shouldn't set your fuel mixture based upon dwell. O2 sensors, in particular narrow band units w/o heater wires like ours, have a much shorter lifespan than modern wide band units. Which is why you're supposed to replace them every 30K miles; their ability to accurately measure oxygen content greatly decreases and results in false readings. Not to mention that you could technically even have manufacturing variations that could affect the performance of the unit.

    All of those things are variables factors which you do not have control over. That is why you should set your fuel mixture by analyzing the pre-catalyst exhaust gasses via the method described in the workshop manual that eliminates all variables such as combustion chamber temps, timing, enrichment circuits, etc.
    Your not setting the mixture with a working lambda system. Your centering the lambda control (FV). Now you are setting the mixture when the lambda is open loop (cold engine) but that is designed to be correct with a centered lambda system.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  4. #24
    Senior Member Grover's Avatar
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    Probably late to the party here, but this is what I used to surround my wires with near the UK Stainless Exhaust Headers.

    Spark-Resistant Wrap-Around Sleeving

    Silicone rubber coats this fiberglass sleeving to shed sparks and molten metal splash. It also resists hydraulic fuels and lubricating oils. Install without disconnecting wire and cable; the hook-and-loop allows you to maintain access along the length of the sleeving. All you do is wrap it around and velco it together. Been keeping the wires burn-free since 2013.

    McMaster-Carr
    Fiberglass with Silicone Rubber Coating
    ID Thick Temp
    7/8" 5/32" -65 to 500 Orange 8266K11 $12.60
    -----------------------------------------------------------------------
    Steve Cosgrove, Vin. 1494
    "I'm Kicking Through The Walls In My Mind..." - Goo Goo Dolls
    On-going Engine and Car Modifications: http://dmctalk.org/showthread.php?50...Engine-Upgrade

  5. #25
    Senior Member DMCVegas's Avatar
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    Quote Originally Posted by Bitsyncmaster View Post
    Your not setting the mixture with a working lambda system. Your centering the lambda control (FV). Now you are setting the mixture when the lambda is open loop (cold engine) but that is designed to be correct with a centered lambda system.

    You're not setting the mixture with LAMBDA using the factory method either. In fact, you're not supposed to because you wouldn't want to center anything with LAMBDA because it is a bolt-on system which creates purposeful variants based upon adaptability to variable conditions. Setting a baseline with zero variables is critical to the proper operation of the system. LAMBDA does NOT control the Air:Fuel Ratio. Rather, it simply makes subtle tweaks to it. When properly working of course.

    What controls the AFR is the Air Mixture Unit itself. It adjusts fuel flow based upon air flow. From there we simply have bolt-on equipment that performs the fine-tuning of the AFR as it relates to the operating variables of the engine itself. This includes vacuum, and the all important temperature. You cannot control how colt an engine gets, let alone how fast it heats up. Which is why once you have your radiator fans running, you bypass the Otterstat to leave them on; this leaves combustion chamber temperatures in the control of the Thermostat which keeps said temperature constant. Thus the variables are removed.

    I get what you're trying to do here. It's pretty much just a crude way of substituting the O2 sensor for an Exhaust Gas Analyzer to adjust the AFR. It's noble enough, but there are still way too many variables at play here. You need a set fast idle for more accurate, yet static volume of fuel burned. You need a static engine coolant temperature to ensure a consistent burn...the list goes on.

    You need to remove all the variables to set a proper baseline. Otherwise, just plugging into an engine that's at stock idle with a fluctuating coolant temperature isn't going to properly set the AFR, no matter what method is used, is not going to work. You'll keep on chasing after that point, but you may catch it in the wrong area.

  6. #26
    Stuck in the 80s John U's Avatar
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    Quote Originally Posted by sdg3205 View Post
    New 02 sensor would likely have an effect on your dwell. You should at the very least see if you're in the ball park. If you're mixture screw is still factory sealed, thats a good thing in some regards.
    It is still sealed and I plan to keep it that way if I can

  7. #27
    President, DeLorean Industries
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    CO adjustment mandatory after exhaust install.

  8. #28
    Senior Member Bitsyncmaster's Avatar
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    Quote Originally Posted by John U View Post
    It is still sealed and I plan to keep it that way if I can
    You can still check the "dwell" without removing the seal. Then you can decide if you want to adjust it if needed.
    Dave M vin 03572
    http://dm-eng.weebly.com/

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