EGR Tuning

[RobertISaar]

EGR fuel and spark changes are VERY mask dependant... the sheer number of styles of EGR that came out in the mid 80s to 1995 also played a part in it. pretty much everything i play with uses the 3 solenoid "digital" setup. there's also a 2 solenoid digital setup, only ever seen it on a couple of 4 cylinder applications. then there is EVRV, positive backpressure, negative backpressure and linear. there's probably more, but those are the ones i can think of off-hand.

Anyways, some masks are more "intelligent" than others... some, if you change the amount of desired EGR, fueling and spark are also changed. some, if you change desired EGR, fueling and spark are still the same as if you're running the original amount of EGR. in those situations, if you're reducing EGR and running the amount of advance that you were, expect knock and a lean condition. some are mixed... some masks support a combination of all of them.... it can get confusing.

[sherlock9c1]

I was thinking about this - what other tuning would I do with EGR not enabled? Unless you're implying that you don't want to take the part-throttle timing with EGR on and propagate it forward into PE or WOT mode?

[RobertISaar]

anything and everything engine related. when EGR is on, the MAF/speed-density calculation now has to account for something that is not as consistent as a MAP or MAF sensor.

i've never seen a calibration where both PE and EGR will be on at the same time... not that it's impossible, but some masks will disable EGR if PE mode is entered.

[helo]

post #4 is very true; I'll attest to EGR on my TBI-L31 (it's worth using). Hard to say mileage increase is "substantial" or even real, but I'd say it's totally plausible. My motor pulls way harder with EGR open at light throttle. This is from extra timing; with less fuel at the same time, the motor is operating more efficiently. Doing more timing and less fuel without the EGR open is playing with fire; I did get pinging when I tried this for shats and giggles (went away when I plugged the valve back in).

Toying with EGR can be amazing, you'll feel it if you get aggressive in the tables. I find it's safe to have 38*-39* total timing, or more (L31-tbi). Safest to simply set this limit with the 'max timing' constant. I had some evil noises with 41* and 20% fuel reduction, YMMV. Leaning out by much more than 15% noticeably reduced power, so I stay around 15% max and I have no problems maintaining speed up slight hills without going into PE. The vortec heads seem to love the extra timing when EGR is open. If I set EGR to come on only above 60mph, it's a world of difference on the highway when I cross that threshold.

In $0d, you can tune it to come on/off based on many parameters, you just have to use good judgement. I don't recall a flag that disables it explicitly for PE, it was based on MAP values and TPS.

I patched $0d_maf to include EGR functions, but I haven't extensively tested it yet. I kept having unrelated issues using MAF at low rpm under load in 4th gear. I suspect I need an intake 'reservoir' like on the factory vortec intakes. PM if you want $0d_maf_egr.asm, I'll share if I happen to notice your PM.. (i'm also on FSC)

[Playtoy_18]

I always delete and zero tables out,clutters up the engine compartment :)
I really like the idea of repurposing the tables though,like maybe water/meth activation and tuning? :)

The intake reservoir is only there to quiet the intake buffeting I was pretty sure,on Fords that is what class taught us about the reservoirs inline with intake. NVH was only reason in those cases.
I've had excellent luck capping it off (skoal can lid fits perfect) and cutting it out to hide nitrous solenoids :)