Hey I dont know much when it comes to afr's regarding out car so i was wondering if someone could elaborate. I was asking in another thread what afr's people are running with a 2.9 and gm stage 2 tune and someone replid 10 which is rich. I thought 10 was lean for an engine. the higher the richer right? Can someone explain.

 

on our cars 10s are rich. im running that now i need a tune. 11.8s alot of people like running and its good. getting into the 12.5s or so is a bit risky as far as i have read. so 11.8s and what not is good. but ill let some of the other people that know better than me elaborate on that just trying to help

 

The lower the number, the richer you will be. The higher the number, you are running leaner. There is less fuel to air when running leaner. LSJ's like to run a little rich, and my guess is because of the heat issue. Right now I'm running an 11.6:1 AFR. and have no issues with it.

 

11.8-12.2 seems to be the MONEY spot for these cars!

I ran a 12.0 on my LSJ all day long with a 2.7 ring on the blower!

 

12's skeer me.

Although on race tune I'm gonna pull 12.2 and hopefully run 22-24* of timing.

 

On my 2.8 meth tune I was 12.2 with 25-26* of timing (Area47 tune)

On my 2.7 meth tune I was 12.0-12.1 with 25* of timing (Area47 and myself tuned)

 

i atleast wan to run 12 with meth

 

I ran a 12.2 and 26* on my 3.1" Tvs pulley and that ****** moved out

 

well, it's a ratio

parts of air to parts fuel

10:1 would be 10 parts air for every one part fuel

14:1 would be 14 parts air for every one part fuel

So the higher the number the leaner the mixture.

 

ok great. Thanks guys. I just had it completely reversed. EVen though its common sense air to fuel i was thinking fuel to air. So the lower the number the richer and the higher the leaner. Got it. I was just wondering because i was wondering what people were running with a 2.9 and gm stage 2 tune and someone said 10 and since i was uneducated I was nervous since im having mine installed friday. Thanks guys.

Who wants to explain timing now?? Ha

 

goin in a little deeper, every fuel has its own stoichiometric ratio. this is were the mixture is neither rich or lean, its the theoretical "perfect" ratio. also, every fuel tends to make more power when its richer or leaner then stoich. gasoline for example has a stoichiometric ratio of 14.7:1, however best power is usualy between 11.5-13:1, so it makes best power when its rich. this property of gasoline can make tuning safer as you usualy notice a drop in power before you cause any engine damage. methanol alcohol on the other hand has a stoichiometric ratio of 6.4:1 but makes best power when its leaner. with a blown alcohol motor, the most power is made when the motor is litterally melting itself, its a very fine line between making max power and hurting a motor, wich is why the phrase "lean is mean, but its hard to richen it after the bang" came about.

 

^ Ok interesting. But even while running on gasoline you can still lose power while being too rich right? FOr instance ill be running a 2.9" pulley on a gm stage 2 tune and i heard that ill probably be running in the 10's afr. I would make more power if i were to go leaner right? such as 11.8? So richer isn't always more powerful right? like in this case. Gm stage 2 tune is a little too rich?

 

yup thats correct. abit of math/science involved but its quite easy. I'm running 11.9 on my TVS right now...seems like the best spot. Also if u r 10.0 now and u change it to 11.8-12.5 or so...your fuel range will be better...since im canadian its in L/100km....i went from a avg. of 8.1L/100km in the city to 7.7L/100km

 

if you get it tuned by someone other than gm youll gain power and gas milage