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krohelm

Idle with accessories

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4age 20v engine, alpha-n:  I'm having troubles stabilizing idle with headlights, fan, engine fan and AC (or even just AC).  Any tips would be greatly appreciated, pclr is attached.

I've tried turning up my target idle speed to 1000rpm, increasing my base IAC position, feathering the throttle - it just dies due to unexpectedly high load at 0% throttle.  Seems like MAP would be more ideal, but ITBs make it fairly impractical.

idle_question.pclr

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Thanks for the reply Ducie54!  I wired up the "AC Request" digital input, but it's more of a "yo, I just engaged the AC clutch so you know - think fast" semantic from the factory.

I got it to idle without insta-death via a 4D fuel map adding 32.5% fuel to idle cells while DI-2 is on.  Seems like there should be a better way to accomplish this same thing, as I see 

G4+ ECU Tuning Functions > Fuel > Fuel Corrections > Idle Load Trims > Air Con Trim

in the help menu.  However it appears to only show up with traditional fueling.  I need it in modeled!  Added a feature request:  http://forums.linkecu.com/index.php?/topic/7099-ac-load-compensation-in-modeled-fueling/

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An engines VE should not change bases on load. There's another issue IMO. Where did you get the base map from?

For starters i would be turning off your idle ignition control as those setting will not be helping. 

post a log of idling with ac off then on then off

Edited by Ducie54

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1.6 liter engine running at 900-1k rpm, if you turn AC on it kills it very quickly (log says <2.5 seconds).  You have to give it more air and more fuel to maintain 900rpm (hence different VE at the same idle cell).  If I had e-throttle idle it'd be a different story, as the map would contain the load cell.  Or if I were MAP/MGP tuning it would also work ok.  But alpha-n it's just an otherwise unaccounted for change in load which requires both air and fuel compensation, or physics compensate with reducing engine speed to 0. :-p  This map is mine.  Originally I referenced some details from another map but this doesn't resemble it at all anymore.

Idle ignition is fine, it's holding my idle steady while my IAC adjusts to suit the base 10 degrees btdc target.  Without it, idle bounces around in an unseemly fashion.

I need to test this with more normal conditions, i.e., not in my garage, but this map with the 4d fuel table allows me to toggle AC on and off with almost no blip in rpms.  It's pretty smooth now!  I'll grab a log another day if you're interested!

idle_question_4d_ac.pclr

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This is really a limit of using modeled mode with TP as the load reference - it simply cant account for extra air entering the engine from any source but the TP.  If you have a reasonably stable MAP at idle then you will probably get a better result by connecting that, otherwise it will need a change to traditional mode to allow use of the extra compensation tables.

The reason these tables arent available in modeled mode is the whole idea is to base fuel delivery on calculated/predicted airflow.  If you have no way for the ECU to "see" this increased airflow (such as MAP) then modeled mode isnt going to work.

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Yeah that makes total sense.  Can I actually use MAP at idle and above 100kpa?  I'm planning to add a supercharger and I expect to still need alpha-n at low rpms.

I really believe MAP/maf at idle is ideal.  For the moment this 4d adder table is working OK, but it's quite a bit like traditional fueling.  I expect to have problems with it when it's cold or when I'm up in the mountains.

Any recommendations for a good MAF sensor that works great with g4+?  Ideally one that would utilize my last remaining digital input...  I could ditch alpha-n entirely with a decent maf.  I wonder how Toyota got it so smooth with TPS+MAP.

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I would do it the same way we do itb GTR's.  You need to set fuel load source to MAP, have MAP sensor connected to manifold, leave fuel table axis as TP.  You then have compensation for the idle valve and boost when you add it later. You then use the openloop lambda table spanned with MAP/MGP to take care of the fact you want different AFRs at different boost pressures since TP is locked at 100.  

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I would do it the same way we do itb GTR's.  You need to set fuel load source to MAP, have MAP sensor connected to manifold, leave fuel table axis as TP.  You then have compensation for the idle valve and boost when you add it later. You then use the openloop lambda table spanned with MAP/MGP to take care of the fact you want different AFRs at different boost pressures since TP is locked at 100.  

Ahhhh I forgot I had my equation load source set to BAP.  I did that initially to get it running in modeled mode, always intended to work out the MAP mode separately.  If I remap on MAP it will probably work itself out and I can remove the AC compensation table.  Thanks for digging in deeper, I'll work on remodeling my fueling (after stashing my current configuration away safely)!

 

edit:  Yup, I spent about 45 minutes dialing in my idle in MAP fueling and it's much more solid now.  I deleted the 4d fuel map and it reacts to change in load very quickly.  This will be much easier to tune I think.

Edited by krohelm

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