Background info, running megasquirt 2 on a 4.8 ls engine with 70mm turbo. Going down the track I kept loosing traction which required me to lift the throttle then get back in it several times during the run. Looking at the logs, I am showing lean spike immediately after I lift/get back in, and a super lean spike on decel after the whole run. I know that some sensors may lag some so what's going on here and should I try to tune it out? Here's a pic of my datalog?

TPS is Top row GREEN
KPA is Top row RED (map sensor)
AFR is Second row RED
Timing advance is Bottom row GREEN

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Perfectly normal, to be lean on decel. No worries.

 

Just fyi you have decel leaning options in the ms. It is an expected behavior.

 

Thanks! There is no decel leaning enabled right now. Do you think what is really happening is an extreme rich condition when throttle closes abruptly causing a false lean spike? Reason I'm asking is i had a great 10 runs then as the track cooled started loosing traction. I had to blip in and out of the throttle several times throughout the run and I smelled burnt oil when decelerating. No loss in performance or anything, but wondering what would be causing the oil burning smell. I'm running e85 btw.

 

Have you messed with your accel tables at all? Looks like you are going a tiny bit lean when you stab the throttle.

Oil smell could be normal, unless it's like a cloud.

 

I played with it a little on gas but not since switching to e85. I know I neeed to adjust them.

Well I ran a compression check and appears I cracked a piston. It was 90psi while the others were 180.

Could this be caused by the lean spike getting back in it after I let out?

 

this is sorta a long explanation to get thourothly, but in a nut shell fuel sticks or "puddles" in the walls of the head and intake ports making them wet with fuel. when the throttle is lifted the engine is no longer in a steady state or near steady state so the fuel stuck to the walls gets sucked in along with metered fuel causing rich mixture, explanation for rich spike. the opposite is tru for a throttle hit there is less fuel on the walls and some of the metered fuel gets applied to the walls and dosent make it into the cylinder the first few cycles. that is the reason for accel enrichment. all of this ae stuff is the main reason why car manufactures have went to direct injection, to avoid transient fueling adjustments.

now to address your issues, trust me they are not horrible but could use some tweaking. the rich spike you cannot get rid of without using eae it would also dramatically help out tip in but it is a royal bitch to get right and is a trouble maker if you have a cam that is anything but smooth.
so what i would do in your situation is go to the accel enrichement setting tab and up the high and low threshold. a brief explanation of these is at or past the high trheashold there is no ae, at the low threshold is the beginning point of tapering off (below it gets full ae). i would probably set the high to 5500 and the low to 4000. then goto the accel wizard and add some ae past 500tpsdot.

another thing i saw is some low timing, on your engine i would probably run 16-18 degrees at 12psi if using e85 and that would be a safe number. on a 6.0 on e85 i have been running 20@15psi but that is a 4 inch bore. i think i was running 18 on a 5.3 and had a whole season on it and it survived.

a good example would be my race car 351w, i tuned it on race gas then switched to e85, it was only running 10 lbs boost and high 9's but i noticed egts wre really high up to 1800, i added more fuel and it helped out but then i looked at timing i was running 16 or so i slowly upped the timing to 24 egt's dropped almost 200 degrees and power was up considerably i was running mid 9's.