Added timing or leaner fuel - Which adds more power?

[Joe6pt0]

This is kind of a general question. Lets say:

Scenario 1
You add 3degress advance to the high octane table in the general WOT ranges (say somewhere in 0.68g/cyl-->0.88g/cyl @ 4k rpm-->6500rpm). I don't have the table in front of me, so bear with me as I'm going off memory.

Lets say that with the 3 degrees addition of timing you are getting ~11.5 AFR and NO knock retard. One would expect a power increase due to increased timing and no KR correct? Even though you are running a tad rich.

Scenario 2
You decide to lean PE to get the values near 13.0 AFR in the above ranges. Leaning the AFR however creates some KR so you have to take out lets say all 3 degrees of timing in the above areas. (for sake of arguement, see scenario 3 for the mix of both) You are now running leaner ~13.0AFRs in those ranges. One would expect a power increase due to the AFRs being closer to the lean/best power range correct? Even with stock timing values.

Scenario 3
Kind of a mixture of the above. 1-2 degree advanced with AFRs in 12.5 no KR.


Which scenario produces more power? Obviously KR in any of the 3 is bad because it could pull timing more than necessary to compensate. Lets focus simply on the AFRs/timing here and negate the obvious changes due to different gas, hotter air/fuel, etc...just something I was trying to figure out.

[tech]

Leaner mixture and less timing.

[jimmyblue]

Been wanting to get to the dyno and do some "shotgun"
tune testing to prove out this very thing. Basically go in
prepared with a rack o' tunes, varying AFR by maybe 0.5
and spark by a couple of degrees, and just map out the
results and pick the best.

I saw on LS1Tech a post from Katech where they were
running a LS2 motor at 13.4ish, and big differences seen
from mixture deviation. That AFR surprised me, way more
air than people usually aim for.

[Joe6pt0]

Well I can tell you that the SOTP feel seems to go with scenario 1. But, we know how accurate the SOTP can be.

[MeentSS02]

I've added timing at richer mixtures, and my car still felt sluggish. Things didn't start feeling better until I leaned it out. I think once you get to a point (13.0-ish), adding timing with a little richening versus less timing with a leaner mixture starts splitting hairs. Never verified any of this on a dyno though...

[oztrack]

I just spent some time on a dyno and found that with my car
(ls1 mafless otrcai 216 220 114lsa 1.8 rockers 555 lift ported heads 10.7:1) that it responded well to more timing - leaning out more than 12.6 didnt help much and added knock.

Here are some figures
timing is specified at 6000rpm (with slightly less at 5000rpm)

26 deg AFRs 12.2-11.9 was 245rwkw unlocked
26 deg AFRs 12.4-12.7 was 251rwkw
28 deg AFRs 12.5 was 255rwkw (261rwkw locked) this is what i have in the car now.
29 deg AFRs 12.9 was 257rwkw (263 locked) but there was knock and would be no good other than a drag tune.
23 deg AFRS 12.6 was 249rwkw (255 locked)

Richer than 12.0 was definitely a downer.
My theme now is more timing at whatever AFR can help it.

The car has done 11.768 and 115mph when it only had 235rwkw unlocked. At a race weight of 3650lbs.

[TheDastardlyDuo]

In my experience with dyno's, I've seen the highest horsepower results with the AF between 12.6:1 and 13.1:1, and timing between 27 and 31 degrees. Different cars have liked different combinations, just gotta play around and see what your car likes.

Mike

[WS6FirebirdTA00]

added timing does not mean more power. you can add timing, run richer and get no knock and loose power. timing doesnt make power, an efficent burn of the charge is what makes power. leaving fuel alone, change timing and see which makes the car run the leanest, of course make sure the afr is in a safe range. generally a leaner mixture will make more power but you run the risk of killing a motor lol

[EC_Tune]

Yes and no. More timing on a less efficient setup can help. It will definitely hurt a more effiecient setup. Rich on a less efficient setup will have the same effect as not enough timing on a less efficient setup.

Test & tune. It's the only way.

EC

[S2H]

also..it all varies depending on torque or HP...
at peak torque you richen up teh fuel and loose a little spark..
at peak HP you lean it out a little and add a little spark...
then you richen it back up and leave spark alone out to rev limit

[benno25]

Think i heard somewhere that you generally run the AFR that makes the power with the least amount of timing, really need access to a dyno though to really check what afr's and timing works.
Cheers
Benno

[WS6FirebirdTA00]

i used a MAF table doing my buddys car, didnt use the airflow jsut the Hz from it. with 23* of timing the frequency was 200 Hz higher than at 29*, which means more airflow which means its more efficent at filling cyls, which makes more power lol

[Joe6pt0]

i used a MAF table doing my buddys car, didnt use the airflow jsut the Hz from it. with 23* of timing the frequency was 200 Hz higher than at 29*, which means more airflow which means its more efficent at filling cyls, which makes more power lol

I thought about this, but lovely indiana mornings at 45 degrees will show different values than afternoons at 75 degrees like today. I'd have to do them back to back at the same time of day, same air temp, same IAT sensor value to be really accurate.

[WS6FirebirdTA00]

yeah thats what we did, like you said cooler air will read more. when we did it the cooler air was actually trying to help the higher timing but it still made it lower. i did thsi on my car today but its a little harder with the MAF off the car lol.