EGR tuning $8D S_AUJP

American Delco GM ECUs and PCMs, ALDL, OBD 1.5.
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34blazer
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cars: '85 S10 Blazer-GT3582R;7730 swap *in progress*
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Location: LasVegastan

EGR tuning $8D S_AUJP

Post by 34blazer »

Over my last weekend I was able to finally fix the EGR tube on the fiero. Last night I spent some time patching DC values and qualifiers from $24(fiero bin) and other $8D bins. The EGR DC table was propagated using values from $24, along with TPS threshold values. I cant open TP at work but iirc, $24 uses engine load in kpa for its qualifiers to enable EGR DC, also uses a qualifier for MAX threshold(higher loads). $8D uses TPS. On my way into work this morning the EGR looked like it was functioning normally, which is good. I did spot a possible issue, though. Let me start with the 3D EGR DC table, $24 uses a higher resolution table, but doesnt command and EGR DC above 50kpa, and max DC is ~44%. $8D commands 100% DC(which I didnt use those values) upto 80-90kpa, which I didnt use either just zeroed the table above 50kpa. Now in theory there wouldnt be any EGR DC commanded above 50kpa(in my mind) but I noticed EGR DC was 44%(at times) in the 60-90kpa areas. Thats weird to me because the table is zeroed out in those cells? If I dont want any EGR DC above 50kpa, theres nothing in the XDF to disable that. Or am I not understanding that right? There is only the TPS qualifiers, oh and the coolant temp V. EGR DC multiplier table. Im also going to assume that since the EGR DC table only reaches to 2000rpm that the values are interpolated above that? I didnt see a max rpm for EGR DC in the XDF either, possibly not found in hac? Or does it continue to operate no matter what RPM?


I will try to remind myself to get a datalog on the way home today.

Thanks!
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34blazer
Posts: 107
Joined: Mon Dec 31, 2012 4:54 am
cars: '85 S10 Blazer-GT3582R;7730 swap *in progress*
'86 Fiero SE-7730/S_AUJPV4
'87 Mustang GT-7703?S_AUJPV4
'97 Ram SS/T
Location: LasVegastan

Re: EGR tuning $8D S_AUJP

Post by 34blazer »

Scratch that. EGR is functioning properly and my questions have been answered. This morning I observed effects of the EGR and found that it provides no increase in fuel milage. Depending on the duty cycle, the impact negatively affected fuel milage. As soon as DC rose above 30% I noticed an increase in BLM counts. Not satisfied with that observation I toggled EGR on and off while highway mode was active, watching NBO2 readings similtaneously. With EGR DC at or above 30%, the A/F mixture would lean out, ~30-50mV. While it helps with emissions, it doesnt help fuel milage at all, at least in my case. Toggled off, the BLM counts fell back down to where im used to observing them, some cells fell by 6 counts. So I have no use for EGR anymore.
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vlad01
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Re: EGR tuning $8D S_AUJP

Post by vlad01 »

The idea of EGR is to reduce pumping loss. it allows the engine to breath more when cruising without actually making more power. The reduced pumping loss mean the engine can push the car with less power produced as power is recovered by reducing that loss.

make sense?


The EGR also reduces combustion temps so less NOx is produced in turn means you can even leaner = more fuel saving.

http://en.wikipedia.org/wiki/Exhaust_gas_recirculation
I'm the director of VSH (Vlad's Spec Holden), because HSV were doing it ass about.
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