[MidnightAuto]

I finally got my RPM hooked up to my LM-2. Much easier to analyze. Car runs well, but the plugs are reading a bit rich with black soot. Assuming I get to tan coloring would represent optimal mixture. I've never stared at one of these charts so curious to hear any feedback of what is here. Purple line is AFR, Black is RPM - matches Y legend. X Axis is time. The first chart is when I was idling and then feather launched and got to WOT quickly. The second chart is cruising around. It's a Tripower car with a 5 speed.

[shaker455]

What's your engine combo and how are your trips jetted?
Looking at your cruise chart looks like your fat on idle so how many turns from seated is your mix screws?

[MidnightAuto]

Thanks shaker. Center large carb at 68. Ends at 72. 461, 290 kre heads and 60919. Rare manifolds to 2.25.

I am not sure on adjustment would have to check. Is 2.5 turns right place to start?

[Formulajones]

There is no real setting for idle mixture screws. Every engine is different.

This is where you'll use that wideband to find a happy AFR for idle tuning. This will overall change the fuel curve throughout so I'd start there first.

Experiment to see what your engine likes. It might idle fine with 14.0 AFR, or it may want 13.5. Either way that's a bunch leaner that what you are currently showing. So that will lean out the curve everywhere. Test drive and see, change and repeat.

[25stevem]

All the experts will tell you that you can only determine two things when tuning on a sound / good motor by looking at the plugs!

1) if the heat range is good at full throttle for the level of hp being made.

) if the motor is detonating.

Blackish looking plugs on only one side of them assuming it's not oil , is from wet flow issues that no changes in tuning will cure.

Flat out just do it the way you are doing it now by means of the AFR reading and forget about plug color.

Heck, even running different brands of pump gas with the same octane rating will show differences at full throttle with the AFR meter if you really want to get crazy with it.

[ta man]

Originally Posted by 25stevem

All the experts will tell you that you can only determine two things when tuning on a sound / good motor by looking at the plugs!

1) if the heat range is good at full throttle for the level of hp being made.

) if the motor is detonating.

Blackish looking plugs on only one side of them assuming it's not oil , is from wet flow issues that no changes in tuning will cure.

Flat out just do it the way you are doing it now by means of the AFR reading and forget about plug color.

Heck, even running different brands of pump gas with the same octane rating will show differences at full throttle with the AFR meter if you really want to get crazy with it.

The plugs will tell you if the motor has a rich cruise condition.

[shaker455]

Originally Posted by MidnightAuto

Thanks shaker. Center large carb at 68. Ends at 72. 461, 290 kre heads and 60919. Rare manifolds to 2.25.

I am not sure on adjustment would have to check. Is 2.5 turns right place to start?

Ok, start buy having both mix screws even amount turns out from seated and your idle AFR about 13.2

[MidnightAuto]

well ive made some tweaks to my set up and want to revisit this. Since this posting, Ive added 1 inch spacers and ditched the air filters. Ive also played around with center carb jets (currently 67) and I feel like I ahve the idle now dialied in at about 13 when warm. Lets skip my annoying fast idle problem sticking that i ahve to goose the pedal all the time and get right to my question - when cruising my afr jumps all over the map - in the 2500 range you can see if go from 11 to 16. When it starts to get up into the 16ish - the car hesitates/surges a tiny bit every now ang again. I used to have 68 in the center, but it was running richer. that was before i added the spacers though that definitely changed some things - crisper throttle response for one.

So based on this zig zag of insanity in the video - what would you do? drop 68 back in? or something else with any of the circuits?


https://www.youtube.com/watch?v=Q72lScRUsyE

[mgarblik]

Where do you have your O2 sensor located? Are you in a taillpipe or up in the exhaust system in a weld bung near the exhaust manifolds. You can't have any stray oxygen screwing with your sensor readings. Any exhaust leak or outside O2 getting in the mix will give you those scattered readings.

[MidnightAuto]

hmmm. the bung has not changed since those earlier readings. its up about a foot or so after the manifolds. let me look around for leak. thanks for the tip. those readings do seem crazy