EGR on effects on fueling for late CRD engines

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EGR on effects on fueling for late CRD engines

Postby Biggvl » Fri Oct 06, 2017 6:44 pm

Soooo, been trying to find info on what happens to diesel fueling when EGR is active. The assumption that I make is that it would add more fuel to counter the extra air/gasses when the valve is open? More fuel in a diesel means higher EGTs. So when an EGR block off is fitted the ECU ads fuel when the EGR is operated but because the extra air/gasses aren’t there the EGTs would rise with potential for issues?.. if this is correct the best method would be to delete EGR operation in the software?

Thoughts?
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Re: EGR on effects on fueling for late CRD engines

Postby vlad01 » Fri Oct 06, 2017 7:22 pm

EGR reduces available oxygen since exhaust gas has its oxygen already spent but increases total available gas volume, allowing less fuel to be injected with the remaining reduced atmospheric air without raising combustion temps as it effectively allows "leaning out" without actually leaning out.

In other words its like running the engine on a low VE and load and fueling and filling the rest of the volume with inert filler to take up the space so it mechanically runs like a high VE condition. Basically its a cheats way of getting the best of all combustion conditions, less fuel, stoich, less emissions, lower temps and less pumping losses.

Only down side is carbon build up, which applies to all engines with EGR.
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Re: EGR on effects on fueling for late CRD engines

Postby pman92 » Fri Oct 06, 2017 8:54 pm

On a diesel the fueling may remain largely unchanged?
Since the already ubundant oxygen avaliable under normal operation (diesels always run lean).
Essentially reducing EGT/cylinder temp (and emmisions) for a given fuel delivery without actually reducing fuel and power output?

Or you may be correct that fuel delivery may actually be increased, creating more power without increasing emmisions

Hence why EGR is so effective for emmisions on diesel vehicles and so often used

I doubt fuel would be reduced like kn a petrol engine.

Definitely agree software delete is better than blank off though. Most late model stuff will detect the blanking plate from MAF flow and turn on the engine light anyway
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Re: EGR on effects on fueling for late CRD engines

Postby VX L67 Getrag » Fri Oct 06, 2017 9:19 pm

I've never looked into the effects especially with Diesel as the fuelling is so different to what I'm used to with petrol, so yeah I only block off when the code is deleted in software(plenty of good sources for EGR, DPF, Lambda, Hot start, etc... delete software now).

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Re: EGR on effects on fueling for late CRD engines

Postby Charlescrown » Sat Oct 07, 2017 7:47 am

I was playing around with a Rodeo. It had the check engine light EGR code and as I closed it off the engine really started to hammer with diesel knock and as I moved the setting back to where is should be it got nice and quiet. I don't know if I wouldn't play with the software but rather use better fuel to stop the system blocking up.

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