nAst1: Progress and Concepts Thread

[robertisaar]

this is being read off of a wideband too, IIRC...

i know i've asked this a lot before, but headwork? especially anything done to the chamber itself?

[Mars]

I'm anxious to see what the fuel pres. drop does... I think it may help.

[caffeine]

this is being read off of a wideband too, IIRC...

i know i've asked this a lot before, but headwork? especially anything done to the chamber itself?

No headwork at all

[caffeine]

Well today I ran in open loop again and didn't get the constant misfire even around 14.5 AFR. I'll leave it in open loop for now but I don't understand why closed loop causes misfiring...

Another thing I'm having issues with is when I give it throttle suddenly it stumbles and bogs for a bit, then catches here and there before finally going. Is this something to do with AE? If I gradually give it more throttle it accelerates fairly smooth in comparison.

[robertisaar]

sounds like AE.

the values that work for a LH0 are bound to be pretty different than what works for the 3500s. stumble/bog sounds like too much fuel, but feel free to confirm which direction it's going on the wideband. be certain to have your main VE right before messing with AE, otherwise one will cover the other and will cause you to run circles around why it works one day, but not the next.



as for why no misfire in open loop.... i wouldn't think it would be, but it's possible that your engine is just that sensitive to AFR... or with injectors as large as you're running, you'll need to turn down the O2 prop gains to keep the AFR swings a lot closer to the commanded AFR.

[caffeine]

I've now dialed back AE quite a bit, but still go extra rich when PE and AE overlap. Is a PE/AE overlap supposed to happen or should AE end once PE kicks in? It doesn't make sense to me why they would overlap at all.

Another thing I've noticed is that when I start the car warm, it struggles to idle at first, but then after driving for a minute or two the idle goes back to normal. Does this have anything to do with startup coolant temp? What tables/scalars does startup coolant temp affect?

Oh also, when's the spark-cut limiter gonna be ready? I'm hoping to be doing 1/16th mile on the 5th of May so it will be important for such a short track.

[robertisaar]

i suck at life.... that being said, full refund offered upon request.

AE and PE at the same time.... if it's happening, it's allowed in the code somewhere. i could always add in a bit to allow/disallow them from both being active at the same time, obviously with PE being the priority. normally, by the time you would get into PE(in regards to throttle), AE would never really be needed, but due to the way AE code works with the 60V6 masks, it can still happen. an "oversight" by GM.

startup coolant temp effects a LOT of things.... from the sounds of it, you're running into issues with the "choke" values, perhaps you could see what coolant temps this is happening at and

1. richen the AFR immediately after cranking
2. make the time it takes to get out of choke fueling and into open loop fueling longer
3. both of the above

if it is a fueling issue, that's your fix.

[caffeine]

Ok I got the AE-PE transition smooth by zeroing the 7-8 AE 'pulse' I think it's called.

But I'm still having issues when the startup coolant temp is high. It drives like a dream when started from cold or 160ish *F but I I start it hot/fully warmed up I get low-load/ part throttle bucking even when driving for a long time. I'm just not sure what values to look at to fix this.

[robertisaar]

so the issue is still present long after choke fueling would no longer be needed when started above that temp?

there aren't a lot of variables that are still active for more than a minute or two after starting based on startup coolant temp.

[caffeine]

Ya it's present after choke fuelling should be long gone. Would intake runner temp have anything to do with it? It runs leaner when started fully warmed up I've noticed but only at very light load. At medium-full load AFRs are pretty much the same as when started cold.

Is there anything that affects spark advance that could cause this behaviour?

[robertisaar]

IRT is a good thought since coolant temp does effect it, i would think it would go away pretty quickly though after any significant amount of throttle for more than a few seconds... IRT is initialized to coolant temp before startup.

your IAT sensor doesn't get heatsoaked does it? it shouldn't be very far off of ambient temps.

F104, F105, F106, F55, F50, F81, KAFTCLOW, KAFTCHI, KADSUCTA(with stock BFUZ values, this is RIGHT at the 160 threshold) are all effected by startup coolant temp and suspect to being the cause. that's ALMOST the entire list of stuff that startup coolant temp is compared against. does INT/BLM do anything odd during these events?

[caffeine]

I'm still running open loop so correct me if I'm wrong but BLM and INT can't be affecting anything.

[robertisaar]

i tend to forget little details like that.... so yes, BLM and INT should be locked to 128 at all times then. how about Closed Loop Correction? it should also be stuck at 128.

[caffeine]

The IRT in the logs appears to pretty much always be around 100 *F higher than the MAT reading in cruise situations. Is that normal? MAT is usually between 70 and 90 *F, sometimes reaches 100* in slow moving traffic or when starting the car hot.

At WOT the IRT is about 60-70* higher than the MAT.

[robertisaar]

might be normal, might not. the intake design of the 3500 is noticably different compared to the LH0 intake that the calibration was made for. a good place to start estimating what would be correct would be to see if any GM info could be dug up on what it calculates IRT out to be on it's native PCM.

removing/adding the throttle body heater coolant loop would actually change the values needed as well, along with anything else that might change the temperature of the intake manifolds, heads and TB.

i'm not saying it's the best resource, but i have a 2002 monte carlo 3400 BIN open in tinytuner, in the Fuel->MAF section, there are two interesting tables(speed density MAF compensation vs ECT and vs IAT), unfortunately neither looks very finely tuned. those look like what would be used to compensate the airmass based on intake runner temp, but the values in the IAT table are useless and the ECT table aren't completely done either. i checked from 96-05 and couldn't find any 60V6 applications that had a usable table. checked a 05 monte carlo L67 BIN and for some reason the IAT table there seems to be inverted?