EGR/DPF Delete - Page 2
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Thread: EGR/DPF Delete

  1. #11
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    @firehawk618 sez defeating the EGR will lower MPG or not change it.

    I say it'll improve MPG if it changes it at all.

    Who's right?
    Both of us?
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  3. #12
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    I'm thinking it will change for the better due to the enrichment that occurs to raise EGTs required for burn off....
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  4. #13
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    Just deleting EGR by itself will most likely result in increased fuel consumption(worse mpg) {or no change}

    Getting rid of EGR means the engine ingests more clean metered air while running. More clean air means it will require more fuel to maintain desired cylinder pressures, and temperatures and power output at any given throttle input.

    The engine has the "potential" to make more power at any given throttle opening, so you may require the use of less throttle to go any given speed, which seems to indicate an equilibrium of sorts...But it doesn't work quite that way due to the throttle body, turbo pressure, and enignes pumping losses. Additionally exhaust gas in the form of EGR is a little bit "magic" as it doesn't react to combustion in the same way as clean air. The introduction of additional gases and water vapor changes how much pressure can be generated by a given amount of heat(fuel) in the cylinder.
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  6. #14
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    In my 2015 Cruze Diesel simply disabling EGR gave a big boost in fuel mileage and the oil was squeaky clean by comparison to oil with EGR. EGR is the Devil to diesel vehicles. No joke.
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  7. #15
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    Quote Originally Posted by Ma v e n View Post
    More clean air means it will require more fuel to maintain desired cylinder pressures, and temperatures and power output at any given throttle input.
    EGR lowers cylinder temperatures and pressures. That's why it's used to reduce NOx output. Eliminating EGR on a diesel engine increases efficiency.
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  8. #16
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    Quote Originally Posted by Barry Allen View Post

    EGR lowers cylinder temperatures and pressures. That's why it's used to reduce NOx output. Eliminating EGR on a diesel engine increases efficiency.
    It's not that straight forward on the gen2 and many computer controlled common rail diesels.

    NOx is reduced because there's lower temperatures, yes. But there's a very direct correlation between oxygen level in the charge air, and NOx production. Reduce O2, reduce NOx , it's that simple.

    Temperature (and indirectly, pressures) come into play of course, but the oxygen content in the cylinder is the biggest indicator of NOx output. And even though temps are lower, the charge air composition with EGR dilution is notably different than clean air.

    And it's constituent parts such as water and carbon dioxide offer significantly different(higher) expansion rates at combustion chamber temps than that of clean atmospheric air. So you take a combustion chamber of clean air and provide it with a given amount of heat, and it will expand a certain amount and create a certain amount of pressure to push the piston down. A similar amount of diluted charge air can create those same pressures with less heat.

    Also of note is that typical diesels are completely fuel throttle, not air throttled like a gasoline engine, so they don't suffer pumping losses from sucking through a throttle body like a gas engine does. However the gen2 engine DOES have a throttle body, that is used to induce those same pumping losses a gas engine sees in order to make sure the EGR works as designed in this engine. (And for other reasons like DPF regents and catalyst light off..) So turning off the EGR isn't just getting rid of the charge air dilution, it's getting rid of the pumping loss from throttle body function. Leaving EGR on and turning off the throttle body would probably yield economy improvements. But that's not what this is about.

    Can you tune a diesel to be more fuel efficient with no EGR, of course. Will just turning off EGR on the 1.6 make it more fuel efficient? It's really hard to say across the board, especially when you add in the fact that deleting EGR typically involves disabling DPF regens as well.(because EGR and throttle body function are tied into Regen as well) Lack of DPF regeneration will without a doubt make fuel mileage better.

    I think it's really a moot point either way, because there's no way I would delete EGR and leave functioning DPF.
    Last edited by Ma v e n; 04-11-2019 at 09:50 AM.
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  9. #17
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    Long caffeine free ramble...Sorry.

    The DPF and regens are the biggest fuel consumer.
    The EGR definitely has its own problems such as intake tract coking reducing volumetric efficiency over time and the detriment of running soot through the engine.

    Turning off both will improve engine longevity and fuel economy. I wouldn't ever consider only disabling one or the other. A tune should also include disabling the throttle body in my opinion, unless I can be shown otherwise.
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  10. #18
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    Quote Originally Posted by Ma v e n View Post
    huge wall of text
    You're right, EGR on modern diesel engines is far more complex that most people (including myself) think.

    I do agree with you that a delete tune will get rid of EGR and also block that throttle plate wide open. Depending on where it is in the engine intake, I wonder how difficult it would be to remove the throttle plate?
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  11. #19
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    Does the computer use the throttle plate like an engine brake? I live in Florida so there are no hills here for me to try, but when the cruise is enabled, does the car maintain its set speed when going down a hill?
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  12. #20
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    Quote Originally Posted by coalminer View Post
    Does the computer use the throttle plate like an engine brake? I live in Florida so there are no hills here for me to try, but when the cruise is enabled, does the car maintain its set speed when going down a hill?
    I don't know definitively what's going on under the hood, but I can tell you there's almost zero engine braking.
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