Why does my WOT AFR always dip @ 4,900RPMs?

[dale_gribble]

From as long as I have been logging with my AP and during my time with Lex e-tuning, I have always seen my AFRs dip from ~11.0:1 to ~10.5:1 between 4800-5200. The AFR always stabilizes after 5200 back to the previous levels.

I have stacked every logged variable against the dip across multiple logs and there isn't a single event that happens that coincides with the dip. I have checked every single log field against the dip. No KR, no boost changes, nothing.

I see others' WOT runs where the AFR is a perfectly straight line past 4,000.

Maybe this is inline with others' experiences. It doesn't seem to impact power; my power/torque curves are always very smooth. I am just curious as to why I see this dip.

[dale_gribble]

Actually, I did find one thing that coincides with each dip. The calculated load appears to spike very slightly during the AFR dip. Is that what does it?

The calculated load changed during this dip on each run:

1.81-1.85
1.77-1.81
1.62-1.66
1.68-1.71

[dale_gribble]

I can't find anything in the load tables that would command this little load bump at these RPMs...

[Keko]

Do you have a speed6? I was reading a post earlier today that was talking exactly about this. I think it had to do with VVT changing to 0 at this load or something?

[dale_gribble]

I do have a speed6... Interesting...

[Keko]

Graph your VVT on that also, it should intersect where the load peak/afr dip is

[Keko]

Finally found it. That was bugging me. This is quoted directly from Phate:

You also have a spike in calc'd load when VVT -> 0°. It's an MS6 thing that started with one of the last few releases of ATR. If you keep VVT just above 0 through the top end rev range, it won't spike. Ghetto work around, but it works and you won't lose power. That (the spike) will put you in higher load cells, where you will run less timing = less power.

his post has an image

[speedms6]

dale_gribble i have been having the absolute same exact problem, only started happening a couple atr releases ago, what vvt are you gonna run to red line, is 2 good enough to keep it from spiking?

[dale_gribble]

I am literally about to make a run with 1 degree vvt and will report back soon.

[dale_gribble]

I still see the dip with +1 on VVT FYI. Plus, now I have KR and my power dipped a bit...

[speedms6]

i made up a map with 2* last night, havent had a chance to run it yet, but drove ti to work this morning, also retarded the timing a bit, gonna figure this out first then get back to tuning the timing

[rfinkle2]

Lex would probably want to know about this, as I know he is particular and thorough.

[Joe Isuzu]

vvt kickin in bro

[speedms6]

just went out and took some logs, i dont have a screen print of my vvt table but from where it would usually be 0 i had 3 for a coupl columns then down to 2 deg for the last few, its seemed like it may have worked, felt smoother, but when i get home and have atr i'll post some logs

[speedms6]

it worked. thank god now i can get my afr's back in order, btw the reason the afrs are so low is because i have the 2150 psi rail valve and im trying to see if i can get the pressure to not hit 2073 and give me fuel cut, no luck yet though, always happens around 6000 rpm

anyway, attached first is a print screen of my vvt table, second a random old log that shows the dip and spike in load when the vvt goes to zero, and third is the log from today showing no dip and spike in load, i retarded my timing alot, gonna get my afr's all straight then up the timing some more, may also check out if i get any increases with vvt increase before i do timing, in know its been found on small turbos you dont, but i do have the reworked k04 so maybe a little up top could help
dale_gribble rfinkle2

[dale_gribble]

speedms6 - hows your work been going with this? Any updates? I would love to know where your VVT and timing tables ended up relative to when you started.

I still haven't decided to trade my AFR dip with another set of problems until I got your feedback.

[speedms6]

dale_gribble well i pretty much have the same vvt table i believe, i played around a little bit, but i really dont have time to get logs at consistent temps and where i live i have to drive like 10 mins to find a perfectly flat road thats good for a solid 4th gear pull

that being said i really dont think vvt adjustments up top will net much gain on a k04, i barely saw any differences that would lead me to think otherwise.

i think i ran 8 vvt out to 5000 rpms like the cobb maps(or maybe 5 i cant remember) and then two from there on out, the main thing is it cured the load dip and spike, no more of that, feels much smoother.

i also upped ignition i tihnk maybe a degree or 2 and the only kr i ever get is like .35 on spool up, so i tihnk i still have some more room, last vd i took, was consistent 290's for hp, no eth. so i dont think thats too bad, temps were somewhere between 60-65 degs.

ohhh and forgot to mention, i havent been on atr, since last thursday, and my comp at home is dead and i have no power. so until i get power back from this storm(which i dont think will be till friday the 9th, probably wont be doing much tuning.

[86azms3]

Load is calculated off of airflow....so you're getting a bit of an anomaly at that certain rpm in the maf tube. Me thinks.

[phate]

you should be able to move where vvt goes to zero, and watch a corresponding shift in the load spike. VVT is definitely in the calc.

[speedms6]

its 100% by vvt, when my vvt previously went to zero there was a spike, at the exact point in the log where it went to 0, changed it to two across the board, zero dip or spike and only thing i changed was vvt

[djuosnteisn]

Very weird VVT is affecting the ecu perceived load. I haven't looked at any of the maps, but is it safe to assume the spark advance simply drops a bit due to the higher calc load, not just mysteriously on it's own, right?

[phate]

Originally Posted by djuosnteisn Very weird VVT is affecting the ecu perceived load. I haven't looked at any of the maps, but is it safe to assume the spark advance simply drops a bit due to the higher calc load, not just mysteriously on it's own, right?

Yep, totally correct. It just seems to change the load calc and everything else follows the new load curve at that point.

Sent from my Galaxy Nexus using Tapatalk 2

[speedms6]

Originally Posted by djuosnteisn Very weird VVT is affecting the ecu perceived load. I haven't looked at any of the maps, but is it safe to assume the spark advance simply drops a bit due to the higher calc load, not just mysteriously on it's own, right?

Originally Posted by phate Yep, totally correct. It just seems to change the load calc and everything else follows the new load curve at that point. Sent from my Galaxy Nexus using Tapatalk 2

in my log(the first one before i changed the vvt) the only thing that changes is the vvt, the ign adv. stays exactly the same, well not the same but it just continues rising steadily as it should via my tune, i can post my tune from that if you would like, just gotta do some searching, but as soon as i changed the vvt just to target 2 instead of zero it completely fixed it

[phate]

Originally Posted by speedms6 in my log(the first one before i changed the vvt) the only thing that changes is the vvt, the ign adv. stays exactly the same, well not the same but it just continues rising steadily as it should via my tune, i can post my tune from that if you would like, just gotta do some searching, but as soon as i changed the vvt just to target 2 instead of zero it completely fixed it

It depends on how you have the timing tables set up and what the conditions were like. I've now seen a few cars do this and the ignition tables follow the altered load curve. Would be interesting to see yours.

[speedms6]

phate; now that i think about it you're right, i have my timing the same for the bottom 5-ish rows, since in the upper rpms im not going over 2.0 load i didnt want variations in timing due to different temps since im running a boost tune, one sec let me find an older map and a corresponding log

[speedms6]

attached are an old log and the map i was running and a newer log from a couple days ago and my most recent map, still working on upper rpm timing i think i had a loose bracket on the intake mani that was giving me a little false kr, before i did that most recent log so i lowered timing there and now i get none, also have the ptp hprv so i get fuel cut around 6000k so i cant rev real high, still lose power anyway past there, and my ap(old dongle) logs slow as shit, still good for 290 on the VD with no e85

[phate]

Originally Posted by speedms6 phate now that i think about it you're right, i have my timing the same for the bottom 5-ish rows, since in the upper rpms im not going over 2.0 load i didnt want variations in timing due to different temps since im running a boost tune, one sec let me find an older map and a corresponding log

Originally Posted by speedms6 attached are an old log and the map i was running and a newer log from a couple days ago and my most recent map, still working on upper rpm timing i think i had a loose bracket on the intake mani that was giving me a little false kr, before i did that most recent log so i lowered timing there and now i get none, also have the ptp hprv so i get fuel cut around 6000k so i cant rev real high, still lose power anyway past there, and my ap(old dongle) logs slow as shit, still good for 290 on the VD with no e85

Thanks for posting those. Yours is a bit tough to see with the slow logging rate, but I think we still get a good idea of what's occurring. If you look at calc'd load vs MAF, you can see the load increases pretty dramatically whereas MAF is just a steady increase in the same region (just north of 4500 rpm). You're also well above the load level where you have static ignition values.

PS - Since you're hitting such high loads, why not scale the load axis?

[speedms6]

Originally Posted by phate Thanks for posting those. Yours is a bit tough to see with the slow logging rate, but I think we still get a good idea of what's occurring. If you look at calc'd load vs MAF, you can see the load increases pretty dramatically whereas MAF is just a steady increase in the same region (just north of 4500 rpm). You're also well above the load level where you have static ignition values. PS - Since you're hitting such high loads, why not scale the load axis?

you can scale the load axis in atr? must have missed the boat on that one, if i'm getting this right, you mean i can scale the load axis like you scale a maf, just so say when i get 2.5 load i can scale it to read 1.8 in atr or something?

also once xmas is over and i presents and shit im gonna call cobb and see about getting a replacement ap the log rate is absurdly slow on mine

[phate]

Originally Posted by speedms6 you can scale the load axis in atr? must have missed the boat on that one, if i'm getting this right, you mean i can scale the load axis like you scale a maf, just so say when i get 2.5 load i can scale it to read 1.8 in atr or something? also once xmas is over and i presents and shit im gonna call cobb and see about getting a replacement ap the log rate is absurdly slow on mine

Yes, scaling the load axis in the ATR tables. Beware the Ign 'max' tables don't automatically change like the rest of them...just go play with it and check it out, it's one of the best features we've gotten recently

[dale_gribble]

speedms6, have you scaled your load axis yet? That makes perfect sense. I would love to get your feedback on this.

[speedms6]

Originally Posted by dale_gribble speedms6, have you scaled your load axis yet? That makes perfect sense. I would love to get your feedback on this.

nope havent been in atr for a while, had a lot going on with thanksgiving and stuff, i am also not really sure how to 100% go about the scaling, like i get the idea of it and all, but the only time i go over 2.0 load is really when i go wot, and things are running find now, i'lll have to take some time and look into it and see what works