AFR vs. octane vs. pinging

[SilverXJ]

Yesterday I did a WOT run and recorded the current AFRs. I have been running midgrade gas for a week and no pinging including on this run.


As seen there it was running rich. So, I dialed it back a bit and it is closer to 12.8:1. However I noticed some pinging on the run today with the adjustments. It looks like it was pinging where it was just about at 12.6:1. It is still too rich after that.

1) Since it is pinging should I richen it up, or do I need to run premium?

2) What AFR should I be going for? I was planning on 12.5-13:1, but maybe I should just stay at 12.5:1.

[lafrad]

hmm.. that is a great AFR line.

Where is the wideband sensor drilled into the pipe?

In the HEMI world, they like the afrs to start at 12.8, but drop quickly right before torque peak then fall to about 11.8 for a "safe" torquey tune.

[SilverXJ]

Its right after the header. And its not a great AFR curve. Too rich.

[Cheromaniac]

A WOT A/F of 12.5-13.0 is what you should be aiming for across the whole rev range. In your case it looks like you're only in that band over a narrow rev range. Too lean at low revs and too rich above 3000rpm.
If you have an Apexi SAFC, you should be able to dial in more fuel at lower revs and pull fuel out at higher revs.

[SilverXJ]

A WOT A/F of 12.5-13.0 is what you should be aiming for across the whole rev range. In your case it looks like you're only in that band over a narrow rev range. Too lean at low revs and too rich above 3000rpm.
If you have an Apexi SAFC, you should be able to dial in more fuel at lower revs and pull fuel out at higher revs.

What we are looking at is the pre tuning curve. Around time mark 485 to about 497. Prior to 485 it is on closed loop, which can not be adjusted. Now, the period that it pings (after slight tuning) is 488-491. It is nearly 12.6:1 AFR. 3200 to about 4000 RPM. BTW, that horizontal black line is at 12.5, so in that graph I am nowhere close.

The curve you see, which is sloppy rich, I didn't notice pinging, however after adjusting to around 12.6:1 I noticed pinging. What I am asking is if I need to be running premium or if it is too lean. Being 12.6:1 I'm thinking that I need to run premium instead of midgrade.

I'll post the version with the pinging later.

[SilverXJ]

Here is the current AFR graph. The horizontal dashed line is 12.5:1. The vertical is the snap shot you see at the top. 12.6:1 @ 3605 rpm



That was teh first set of changes I made. I know I need to adjust it after 4000 RPM or so.. I haven't gone any further then this because I need to figure out if I need to go back to premium or not.

[SilverXJ]

btt

[TurboTom]

If your running a 12.5 and pinging..You need premium.
Or take a little timing out

[gradon]

So have you tried 93 yet? I haven't tried reinstalling the psc1 in mine(waterlogged it ). On mine, I get slight pinging from part throttle 2.5K-3.0K rpms right before it goes into open loop, where it doesn't ping at all(didn't always do this). This is with 93 octane and 25.5# lt1s. As you know, you can tweak the apexi as much as you want in closed loop, but the pcm will pull the fuel back out. I feel mine would not ping at all if I could get that range into the mid 13's. What plugs and injectors are you using? For sure, there should be no reason to dip below 12 on a NA app, but if the higher octane doesn't help and adjusting the apexi does. . .

[lafrad]

If you don't ping at 12.2 AFR on regular grade gasolene, and need premium to run 12.5 AFR WOT... I would ask "what is this being used for"

If you need the extra 10 hp from a 12.5 AFR and premium fuel... then, by all means, do it. Otherwise, a Daily driver and even *EXTREME* trail rig would be FINE at the 11.8 - 12.2 AFR without ping.

You will NOT hurt anything with 11.8-12.3 AFR's... just be a bit lighter on the wallet when it comes time to fill up.

[gradon]

So today I tried reconnecting the psc1 and it's still a no go. I checked the rc9s and all looked similar--not white, not sooty, but there was a reddish tint to them. I closed the gap to .030" and the light pinging is now about 2700-3000rpms(on light-med accel, not when you hold it or heavy accel) instead of the previous 2500-3000(maybe try .025"?). I'll have to drive it around more to confirm that closing the gap helped. I still have yet to try the normal rc12s, so I'll buy a set and if they don't help, then I'll use them on a future project Jeep or give them to my bros or dad.

[SilverXJ]

I can run two different correction files on the Apexi... so one will be for premium, and the other for regular if I can make it work there. First I need to fix my thrust bearing issue.

[gradon]

So closing the gap made WOT feel like it was hesitating/holding back a bit(like 50hp), so tomorrow I'm gonna try the rc12s, and if that don't cut it then I'll see what .040" does on the rc9s.

[gradon]

I must've not snapped the #4 wire on the plug good, so last night it was running on 5(my butt meter was close, huh). I changed out the rc9s for rc12s and just got done a datalog session. Anybody monitor spark advance with a scanner before? I was ranging 14-20* advance at idle. I'll check to see what it is in the 2.5-3K area.

[SilverXJ]

I hadn't had time to datalog the timing yet.