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  •  » EGR question

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    4/08/2020 12:37 PM  #1

    Nos681
    Senior 24-7 FYI Addict

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    From: Atlantic Mine, Michigan
    Registered: 7/14/2016
    Posts: 3,337

    EGR question

    I understand the purpose of EGR.
    Especially the reason back in the day.

    EFI can control and monitor via feedback with multiple wideband O2 sensors.
    Depending on exhaust, it can tweak it until it’s clean.

    Why still have the system?

     

    4/08/2020 2:37 PM  #2

    Bullet Bob
    Senior 24-7 FYI Addict

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    From: Montrose, Colorado
    Registered: 4/01/2013
    Posts: 4,888

    Re: EGR question

    Well...even if the engine tune is perfect and reduces emissions to the minimum, there is still some.  So, by using EGR during steady state cruise the effective size of the engine is reduced by inserting inert gasses into the cyl.  So that further reduces the amount of emissions for any given engine size.  Also, and I have proven this for myself, EGR increases MPG by making the engine "smaller".  When I had EGR on the stock engine, the MPG was easily 24-25.  Then I went to the Explorer intake and removed EGR.  MPG dropped to 22.  And, according to Probst,EGR does not affect performance since it is not allowed by the computer during WOT operation, and he wrote the book....literally!  It is ugly though so if you decide to remove it I'll send you the simple skizzy for the EGR Position Sensor eliminator to keep the PCM happy.  EGR Vac Reg. gets a 75 ohm resistor like the Secondary Air valves or Canister Purge if removed.

    BB1

    Last edited by Bullet Bob (4/08/2020 2:38 PM)

    "you get what you pay for, good work isn't cheap, and there are NO free lunches...PERIOD!"
     

    4/08/2020 3:35 PM  #3

    TKOPerformance
    Hyper FYIFORD ADDICT

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    From: Newark, DE
    Registered: 12/15/2014
    Posts: 7,511

    Re: EGR question

    The actual purpose of EGR is mostly misunderstood.  Its an emissions device, but its actually so much more than that.  The primary goal of EGR was to reduce NOx emissions.  NOx are worse the higher the compression ratio a vehicle has, and EFI vehicles with typically wide LSA cams have a higher dynamic compression than typical carbed engines, so NOx went up on them even as other emissions went down. 

    What people don't understand is how it does this, and this plays into what BB is noting about mileage.  By introducing exhaust gas, which is for all intents and purposes chemically inert, into the chamber the cylinder becomes effectively smaller.  This allows the use of what would otherwise be impossibly lean AF ratios. 

    Again, people think mileage went up, power must be down, or this somehow hurts performance.  Dead wrong.  Thing is, EGR only works during a steady state engine operation, basically, while cruising.  During throttling, idle, etc. it doesn't work, because it can't.  Trying to use EGR under those conditions would stall the engine or prevent acceleration.  This is why the early systems used vacuum.

    There's zero downside to running EGR on a gas engine (I'll spare you my tirade about what it can do to Diesels), and in fact you will likely see a modest MPG increase. 

     

    4/09/2020 8:15 AM  #4

    TremendousWand
    I FYI 24-7

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    Registered: 5/16/2013
    Posts: 657

    Re: EGR question

    Most people will tell you to just delete the entire EGR system.  They sell EGR delete kits.  These cars are way past the age of having to pass emission inspections so it's fine to remove it. 
    However, keep in mind the engineers who designed these cars didn't thrown in extra components for no reason.  All the systems in your car are designed to work together and efficiently from the factory.  I don't have the EGR system in my 5.0 MAF, EFI setup.  Likewise, there will be a permanent code but the effect would be very hard to measure regardless.

     

     

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