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Thread: Could blanking egr effect injection timing at all?

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    Default Could blanking egr effect injection timing at all?

    I know most people who blank their egr valves report good results, and as far as im aware egr flow is detected between the maf and map sensors, my question is if no egr flow is detected(followed by eml usually) would the ecu alter the injection timing at any point or at certain revs, load or speed to compensate at all?

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    you have PM.

    plus a cheeky bump :-}

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    I have a DAMOS file for the Z19DTH (Fiat variant), and couldn't see any maps relating to injection timing (SOI) correction by EGR flow. So probably not. There are SOI correction maps for air temp, coolant temp, etc but can't see one for EGR.

    I believe the SOI maps are calibrated assuming 'normal' egr operation. But the effect of EGR on the required SOI is so small its not worth worrying about.

    In fact, the standard SOI maps are actually retarded a little from the ideal value under light-load cruising conditions as a measure to further reduce NOx emission. Therefore once egr has been disabled thus increasing the burn rate of the injected fuel, the standard SOI map is probably closer to being ideal for economy. This may explain why I've seen better fuel economy on long journeys after disabling EGR.
    Last edited by Teapot; 6th January 2013 at 23:20.

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    Quote Originally Posted by littleteapot View Post
    I have a DAMOS file for the Z19DTH (Fiat variant), and couldn't see any maps relating to injection timing (SOI) correction by EGR flow. So probably not. There are SOI correction maps for air temp, coolant temp, etc but can't see one for EGR.

    I believe the SOI maps are calibrated assuming 'normal' egr operation. But the effect of EGR on the required SOI is so small its not worth worrying about.

    In fact, the standard SOI maps are actually retarded a little from the ideal value under light-load cruising conditions as a measure to further reduce NOx emission. Therefore once egr has been disabled thus increasing the burn rate of the injected fuel, the standard SOI map is probably closer to being ideal for economy. This may explain why I've seen better fuel economy on long journeys after disabling EGR.
    Nice bit of info there mate, another question for your motor mad mind lol, as you said the soi maps are set up for normal/functioning egr, when you blank or unplug the egr the ecu expects a certain amount of exhaust gas in with the air fuel mixture that is not there and is replaced with more oxygen/air so would that at certain egr operation upset the air/fuel mixture or are diesels not bothered so much, like a petrol running lean if you know what i mean?

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    Regular Member Teapot's Avatar
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    that is correct, the effective oxygen-fuel ratio will be leaner after egr disablement. however this is no problem on a diesel engine. the fuel may just burn slightly faster in the presence of more oxygen. this results in higher nox emission but less particulate matter, and possibly better fuel economy.

    To reduce the amount of surplus oxygen in the intake charge and so slow down the burn rate, one can open the turbo vanes more, and reduce the requested boost pressure in the rpm/iq range in which egr would have previously been active. this has the added benefit of reducing pumping losses and hence another small increase in fuel economy.

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    Quote Originally Posted by littleteapot View Post
    that is correct, the effective oxygen-fuel ratio will be leaner after egr disablement. however this is no problem on a diesel engine. the fuel may just burn slightly faster in the presence of more oxygen. this results in higher nox emission but less particulate matter, and possibly better fuel economy.

    To reduce the amount of surplus oxygen in the intake charge and so slow down the burn rate, one can open the turbo vanes more, and reduce the requested boost pressure in the rpm/iq range in which egr would have previously been active. this has the added benefit of reducing pumping losses and hence another small increase in fuel economy.
    Cheers mate your knowledge is second to none, i have to ask another lol, whats your input on glueing the swirl flaps open, ive run with 1,3+4 glued open for a little while now and at first seemed no different but the longer time has gone on the more i think i am loosing a bit of grunt low down, for instance if i accelerate by feathering the the throttle in it pulls really well but sometimes if i stamp it from low down it seems sluggish through the whole rev range but sometimes stamping it low down it will pull well aswel?

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    Regular Member Teapot's Avatar
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    sticking the open should be fine. it makes a slight reduction in torque and efficiency at low rpm, possibly increases soot emissions slightly but not enough to worry about.

    The lost torque can easily be recovered and more through remapping, at the expense of soot emission or course. but the current UK mot is more than generous enought to allow for that.

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