Best Air/Fuel ratio??

[iceman1214]

Hey guys just wanted to hear what you think is a safe/good Air fuel ratio is for my set up.

D16y8 Edelbrock kit (Garrett T28R) 7-7.5 Psi
Test pipe 2.5 back
Walbro 255
Piggyback ecu controller (came with kit)

Had Dyno done today tuner said it was just a little lean!! so it will sit until that gets fixed.. 190.1 whp@7250 137 torque. 12.9 A/F

Plan to get fuel pressure regulator and add a little bit of pressure to stock injectors (Kit comes with four Additional injectors so 8 total)

What you guys think?
(I know I'm a noob sorry I will punish myself with hours of searching soon)

[AllmotorD]

12.5

[alt]

The best AFR is the one that makes the most power for you, its not a solid number across the board. Once you can dial your AFR in, change it around some richen it up across the board for a couple of runs and then do the same with a different AFR, overlay the dyno graphs and find out which AFR makes the most power for you.

[skibee1000]

well the best air fuel you can have is 14.7... thats why you add fuel system upgrades to compensate for your boost. so that you can mantain that 14.7 its efficient and powerful

[alt]

Originally Posted by skibee1000

well the best air fuel you can have is 14.7... thats why you add fuel system upgrades to compensate for your boost. so that you can mantain that 14.7 its efficient and powerful

No, thats just stoich on 100% gasoline, which you can't seem to get at the pump anymore, keep finding 90% gas 10% ethanol or higher which in turn has decreased the "perfect" stoich number for combustion.

[crazymx6]

Originally Posted by alt

No, thats just stoich on 100% gasoline, which you can't seem to get at the pump anymore, keep finding 90% gas 10% ethanol or higher which in turn has decreased the "perfect" stoich number for combustion.

so then by that comment what is the perfect stoich # for our 90/10 gas?

like 13.7?

[alt]

Let me see if I can find my info for E85, stoich for that is like 9 something, its all a ratio in between. But to the OP you don't want to run a vehicle on the brink of being lean at WOT, unless you enjoy detonation and don't mind building motors.

[crazymx6]

ya i got ya was just wondering why my tuner had my car idlesing @ 13.7 and if this is the case then i wont b so madd!

ya by no means under boost do you want to be any where near stoich

good rule

no boost=14.7 stoich
0-2 psi= 13.5
2-7= 12.5
7-15= 11.5

mind you these are ROUGH estimates to go by and you should have a professional tune you car on a dyno..

[crazymx6]

to the op why not see if you can find a set of 440's that will hold you plenty with room to spare @ 7 psi you can find a set for under 100 if you look aroind then have them flowed and tested, install, retune, no more lean= fun time!


btw you can still drive your car just dont boost it...if need be

[alt]

Why are you idling there? Shit I idle my LS1 at 15, its like 0 MPG just sitting there, I don't like to use as much gas if I can help it.

[crazymx6]

nah im not ne more im at roughly 14.7-15.1.....................at idle

and boost is set to roughly stated # above ............in post above

[AllmotorD]

you are at 14.7-15.1 at WOT... You guys crazy or am I missing something here.. AFR like that at WOT will make an engine casserole.

[crazymx6]

no no

14.7 idle then change a/f accordingly to the other post i made

no boost=14.7 stoich
0-2 psi= 13.5
2-7= 12.5
7-15= 11.5

[B20BbenN]

14.7 is where the engine still have good power and have the lowest level of pollution(idle and steady speed driving). If I remember well, if you go leaner than 14.7, the co2 decrease but the NOX increase.

If you check a a/f ratio VS exhaust gas graph(co2, nox, oxigen....) you will see right at 13:1 there is no more oxigen coming out of the combustion. If you run richer than 13:1, there is no more oxygen molecule to burn with fuel....no more power to gain.
This is theorie, but in practice, some boosted engine gain a litte power going from 13:1 to 12,5:1 cause the extra fuel help to cool the combustion.
NO need at all to go richer than 12:1 a/f ratio.......except if you want ton of black smoke coming out of your exhaust!

[crazymx6]

Originally Posted by B20BbenN

14.7 is where the engine still have good power and have the lowest level of pollution(idle and steady speed driving). If I remember well, if you go leaner than 14.7, the co2 decrease but the NOX increase.

If you check a a/f ratio VS exhaust gas graph(co2, nox, oxigen....) you will see right at 13:1 there is no more oxigen coming out of the combustion. If you run richer than 13:1, there is no more oxygen molecule to burn with fuel....no more power to gain.
This is theorie, but in practice, some boosted engine gain a litte power going from 13:1 to 12,5:1 cause the extra fuel help to cool the combustion.
NO need at all to go richer than 12:1 a/f ratio.......except if you want ton of black smoke coming out of your exhaust!

really even at higher boost levels? like say 17psi? or 20

[AllmotorD]

Originally Posted by B20BbenN

14.7 is where the engine still have good power and have the lowest level of pollution(idle and steady speed driving). If I remember well, if you go leaner than 14.7, the co2 decrease but the NOX increase.

If you check a a/f ratio VS exhaust gas graph(co2, nox, oxigen....) you will see right at 13:1 there is no more oxigen coming out of the combustion. If you run richer than 13:1, there is no more oxygen molecule to burn with fuel....no more power to gain.
This is theorie, but in practice, some boosted engine gain a litte power going from 13:1 to 12,5:1 cause the extra fuel help to cool the combustion.
NO need at all to go richer than 12:1 a/f ratio.......except if you want ton of black smoke coming out of your exhaust!

Good info!

[whipbak]

keep in mind a/f on the dyno is still different from street a/f
whatever reading you have on the dyno is usally leaner on the street due to load/wind resistance and a bunch of factors,

i usally shoot for 11.9's WOT on the dyno and on the streets it reads around 12.4 - 12.6
idle a/f 14.7 - 15.5 and cruising light throttle 13.6 - 14.2

[OneCam]

lean doesn't necessarily make you prone to detonation. it makes EGTs get high and your motor will run hot. THEN you will start to detonate. My rule of thumb for AFRs on a boosted car is to stay between 11.5 and 12.5; the leaner you get the more power but you will run into many problems.
Theres a tuning think on Hondatas site, PGMFI.org hit up the Wiki, Xenocron.com, phearable.net, theres many sites on the net. Most will tell the same thing. ~12.5 for boost at WOT.

[crazymx6]

ya there is also a sticky in forced indution on tuning - great info one cam
edit:^first link in my sig

[alt]

Originally Posted by whipbak

keep in mind a/f on the dyno is still different from street a/f
whatever reading you have on the dyno is usally leaner on the street due to load/wind resistance and a bunch of factors,

i usally shoot for 11.9's WOT on the dyno and on the streets it reads around 12.4 - 12.6
idle a/f 14.7 - 15.5 and cruising light throttle 13.6 - 14.2

Turbo vehicles are meant to be run on a load bearing dyno, preferably a mustang dyno. Then once they're tuned for that, ran on a dynojet for e-penis hp numbers.