Air fuel ratio

[Adamvr93]

hi guys,
what would be the leanest afr that would be safe to run on light throttle to get maximum fuel economy? What should the afr be under heavy load? ive been trying to keep it around 13:1... and what load range should it start to go down to 13 (or whatever optimum afr is)?

Thanks

 

[delcowizzid]

15:1 is safe enough at light load 30-50kpa could go to 16:1 start to richen at about 70-80 kpa obviousy using a wideband so when doing load tuning match the wideband reading to the commanded A/F ratio in the bin using the VE table then when its all matching you should be able to just adjust the commanded A/F ratio to what ever you want and it should match on the wideband.each engine will be different as to what ratio's it likes so get it all set then change the commanded ratio and see how it responds.

 

[Adamvr93]

thanks for the reply man you're a champ:thumbsup:

 

[delcowizzid]

having fun with the wideband and burner by the sounds of it

 

[greenfoam]

16.5:1 is the ideal ratio at light loads. Most new cars run well above 17:1, Hondas are at more like 20:1 but they have been designed for those lean mixtures. Any old school engine will go 17:1 but you reach a point where you start loosing more power than you are gaining in less fual so then you have to boot it more and you ned up the same. This is why they say 16.5:1 is often the sweet spot. Under decel it can go right up over 20:1. Under medium load you want to go into the 14's and full throttle about 12.8-13:1 for NA cars (anywhere from 12.2-13:1 makes about the same power) down to 11:1 for boosted cars. But yeah at cruise you don't want to see anything under 16:1, aim for 16.5-17

 

[Adamvr93]

having fun with the wideband and burner by the sounds of it

I'm actually using a haltech e6gmx ecu... when i first found an interest in tuning i didnt research enough and just went all out and got the haltech thinking that the standard ecu wasnt very tuneable... i now know otherwise since ive been a member of this forum lol.. but i quite like the haltech.. the software is nice and easy to use and really the main reason i bought it wasnt because my car needed to be tuned... a greenfoam memcal would have been more than enough.. i just wanted to get into it and muck around teaching myself how to tune an engine.. and i must say ive learnt alot.. when i was talking to a guy at a dyno tuning shop about getting it and he ask whos tuning it and i said i am doing it myself... he had the look of horror on his face and told me to start looking for another engine to buy with it.. well i proved that **** wrong! lol

16.5:1 is the ideal ratio at light loads. Most new cars run well above 17:1, Hondas are at more like 20:1 but they have been designed for those lean mixtures. Any old school engine will go 17:1 but you reach a point where you start loosing more power than you are gaining in less fual so then you have to boot it more and you ned up the same. This is why they say 16.5:1 is often the sweet spot. Under decel it can go right up over 20:1. Under medium load you want to go into the 14's and full throttle about 12.8-13:1 for NA cars (anywhere from 12.2-13:1 makes about the same power) down to 11:1 for boosted cars. But yeah at cruise you don't want to see anything under 16:1, aim for 16.5-17

haha ive been wondering why my fuel economy is so **** now... wow ive got it way off lol... i should have know by all the black **** all over my rear bumper around my exhaust tip :whistling
my afr is around 14.5 at light throttle, medium throttle was around 13.5-13.8... and heavy loads are around 13... i have been trying to keep idle as close as i can to 14.7... thats normally where it should be right?

Thanks guys thats helped alot

 

[delcowizzid]

idle around 13.5 ish will make it nice and snappy when you snap open the throttle from idle but if it doesnt mind being at 14.7 its all good whatever works.

 

[greenfoam]

If it will still idle smooth at 14.7 then 14.7 is ok, mid 13's usally makes a smoother idle. And maybe high 12's for cars with a decent cam in them. But by all means if it idles smooth at 14.7 run 14.7 less fuel is allway for the win