Limits?? (A/F ratio)

[White Devil]

Hey guys, I was wondering, what are the limits that I should stay between on my a/f ratio?? Idle reads 14.7 and I went out for a drive and gave it WOT for 400 yards and it was reading 12.5+/-
with VP fuel I think they should go up a little bit right?

[sprayedenali]

Is that 12.5 with or without the spray?

12.5 is slightly rich fir NA, but slightly lean for nitrous

13.1 is generally about where you wana be NA and between 10.0-13.0 for nitrous, peoples opinions vary alot on AFR for nitrous, so that's why I said such a large range...

[White Devil]

It was without spray bud.. I hope the standalone & VP Race fuel will help me a bit..

[sprayedenali]

ok, i figured... itll be fine, but maybe not ''optimum''

but since you spray it, it wont hurt anything to have the tune slightly rich on motor just to give you some extra room for error with the nitrous.

[farmtruc]

actually, you're not going to get any more power with 12.5 to a 13.1 and have it be worth it, you'll get more power with more timing though.
12.5 is right on for an NA engine.
I would much rather to run the hell out of my truck with a 12.5 a/f ratio than a 13.1. If a customer calls and says their truck is at a 12.5 and says it's too rich, i typically won't send a retune out to lean this truck out. i tune for the masses, not individuals I can cater to and continously adjust their tune. that is nice to do and all, but there needs to be some cushion in the tune.
no tune will be right on either, a/f ratio changes with all the different elements, so it's best to keep it safe and leave it there, it's just like chasing ltrims, get them pretty close and leave them alone.

Why is 12.5 better? Most say some of the cylinders run lean, right? Well, nobody runs 8 wideband sensors to keep tabs on things, we always read a/f ratio from the left or right side, or a collective reading of all eight cylinders, which would be at the end of the ypipe.
So, if we're reading a collective reading, and your truck is at a 13.1, what's to say one cylinder isn't running 14.0 and one is running 12.0, averaging the a/f ratio out to be 13.0, which is what you're seeing on the wideband.
just an example that's all.
12.5 is not considered rich for an NA setup. some heavy head and cammed engine setups make more power at 12.1 than 13.1. that's been proven on my dyno.
so for his setup, it may be optimum, his truck may make more power at 12.5 than at 13.1. You will never know though , until you get it on the dyno and prove it.

you are right about toooo many opinions though. just like my reply is my opinion, lol.

i would say if he posted "my truck is at 11.5", that is too rich, but not 12.5.
his truck could have a lean cylinder that requires the collective reading to be 12.5, so that the one or two lean cylinders are rich enough to make good power.

most do shoot for an average of 13.1 though, but some vehicles make good power at 13.8. IMO, that is too lean, but GM doesn't think so, they hold 14.5 or so at wot for several seconds and below 5000rpms.
Just measure the a/f ratio on an HD truck with an 8.1 or 6L, watch how long GM's calibration holds 14.5 or so, it goes against everything suggested, but they are the experts and have longevity to think about.
Take the cobalt turbocharged engine for example, GM holds that sob at 12.8 or so at wot through 1-4 gears and only lets it get to 12.4 after 100mph or so, that is a big no no for us, but they do it.
After tuning this cobalt, it made more power at 11.4 than GM's 12.5 and was much smoother through the gears.
So, lean, rich, ehhhh, it's up to the engine, where it likes to be, and what internals it has, etc, etc, etc.

I'm just trying to elaborate on this because don't get stuck on one number that the internet says is correct. do your own homework and come up with your own decision and opinion on what's correct. it won't come easy or fast, it's going to take dozens and dozens of tunes and various vehicles.

by no means is this towards you mitch, it's towards the entire internet that says one way is the only way. hopefully this will spark some conversation and other opinions.

later,
allen

[ChevyLee]

Sounds perfect to me, 14.7 is PERFECT for idle and cruzing, 12.5 is also PERFECT for WOT.

Good write up Allen, hopefully that will learn some people about A/F

Lean is mean

actually, you're not going to get any more power with 12.5 to a 13.1 and have it be worth it, you'll get more power with more timing though.
12.5 is right on for an NA engine.
I would much rather to run the hell out of my truck with a 12.5 a/f ratio than a 13.1. If a customer calls and says their truck is at a 12.5 and says it's too rich, i typically won't send a retune out to lean this truck out. i tune for the masses, not individuals I can cater to and continously adjust their tune. that is nice to do and all, but there needs to be some cushion in the tune.
no tune will be right on either, a/f ratio changes with all the different elements, so it's best to keep it safe and leave it there, it's just like chasing ltrims, get them pretty close and leave them alone.

Why is 12.5 better? Most say some of the cylinders run lean, right? Well, nobody runs 8 wideband sensors to keep tabs on things, we always read a/f ratio from the left or right side, or a collective reading of all eight cylinders, which would be at the end of the ypipe.
So, if we're reading a collective reading, and your truck is at a 13.1, what's to say one cylinder isn't running 14.0 and one is running 12.0, averaging the a/f ratio out to be 13.0, which is what you're seeing on the wideband.
just an example that's all.
12.5 is not considered rich for an NA setup. some heavy head and cammed engine setups make more power at 12.1 than 13.1. that's been proven on my dyno.
so for his setup, it may be optimum, his truck may make more power at 12.5 than at 13.1. You will never know though , until you get it on the dyno and prove it.

you are right about toooo many opinions though. just like my reply is my opinion, lol.

i would say if he posted "my truck is at 11.5", that is too rich, but not 12.5.
his truck could have a lean cylinder that requires the collective reading to be 12.5, so that the one or two lean cylinders are rich enough to make good power.

most do shoot for an average of 13.1 though, but some vehicles make good power at 13.8. IMO, that is too lean, but GM doesn't think so, they hold 14.5 or so at wot for several seconds and below 5000rpms.
Just measure the a/f ratio on an HD truck with an 8.1 or 6L, watch how long GM's calibration holds 14.5 or so, it goes against everything suggested, but they are the experts and have longevity to think about.
Take the cobalt turbocharged engine for example, GM holds that sob at 12.8 or so at wot through 1-4 gears and only lets it get to 12.4 after 100mph or so, that is a big no no for us, but they do it.
After tuning this cobalt, it made more power at 11.4 than GM's 12.5 and was much smoother through the gears.
So, lean, rich, ehhhh, it's up to the engine, where it likes to be, and what internals it has, etc, etc, etc.

I'm just trying to elaborate on this because don't get stuck on one number that the internet says is correct. do your own homework and come up with your own decision and opinion on what's correct. it won't come easy or fast, it's going to take dozens and dozens of tunes and various vehicles.

by no means is this towards you mitch, it's towards the entire internet that says one way is the only way. hopefully this will spark some conversation and other opinions.

later,
allen

[DBRODS]

Nothing like some good plug reading to tell you what the engine likes...

[George C]

its amazing what those little 4bangers that are boosted run at. i seen a tegra make its best power at 13.8 thats crazy lean but it liked it and has been there for over a year now.

most import guys here with big boost setups like mid 12s for boost which is crazy as well.


Allen pretty much sum'd it up. Youll gain power leaning it out however to some ppl every single ounce of power isnt worth it to most and is a liability [depending on owner]


old saying tho is lean is mean and on ragged edge is strongest but youre also sitting on that edge


as for AFR for N20 read plugs, to rich on n20 will cause that motor to die faster then you will believe. 12.2 is good starting point for juice

[bluecajun5.3]

16's for cruising and 12.5 on spray is no problem. all in timing and fueling.

[Frenchy]

Nothing like some good plug reading to tell you what the engine likes...

Agreed. You guys are getting spoiled with your Widebands and scanners and blah blah blah.