Bro u have been more than helpfull with these questions i have asked. i want the light i just dont really like the look of it u know. people will think its a shift light(not that i really care what others think) when its a lot mroe than that.the gauge looks a lot better but we will see. i also found the aem uego for like 220 or something cheap like that, i just dont have an arc welder or mig welder so that would have to be done for me.

 

Hey guys, I'm trying to get into and understand the readings I get from my air fuel gauge. I've searched and this post is the best one I''ve found so I want to bring it back to life.

I have all basic bolts on along with kelfords 272s, my air fuel at idle is between 14.5 to 15.5 and then about 10.5 at WOT.

I'm trying to understand its meaning and whats too rich or too lean. I'm assuming Im running rich because I do smell the fuel when I first start her up.

Any help would be appreciated, thanks in advance guys!

 

Easiest way to think about it is higher numbers mean its leaner lower numbers mean its richer.

14.7 is the number where the fuel and air are at a ratio where no extra fuel or air is left over.

 

First off I hope you didn't read too much of this thread because its cluttered with misinformation.

AFR which most gauges use and is usually the easiest to understand has a broad scale from 7:1 all the way up to 26:1. Obviously neither one are good for using in a engine.

14.7:1 is the optimal AFR for best emissions and fuel economy.

This is why your car idles where it does, for the lowest emissions and fuel consumption.

The better range for fuel economy comes form 15.2-15.7, this in turn though will affect your emissions(greater output).

In terms of performance the best power is achieved at the 12.5 +/- .2 AFR. Now keep in mind gas is a temperature control. So while running this "lean" generates more heat then is desired in high boost applications it can also create detonation(knock). Both can lead to part failures in the motor as well as the turbo itself.
In this instance depending on air cooling mods and efficiency we target a richer AFR anywhere between 11.8-10.9 AFR. This allows the excess gas to cool the exhaust temperatures down and prevent things from melting or detonating.

Now if your seeing 10.5 in boost that would be a little overly rich. Now depending on your type of enviroment, IC efficiency, and driving conditions you'll want to richen it up a bit. At least a full half point. Of course if this were e85 or race gas fueling is done a little differently.

As far as smelling gas well that will happen when you first start the car up and its cold.

 

Thanks alot guys! And thank you project your little essay there taught me something today.

 

Thank you, thank you so much for writting all of this so I didn't have to, saved me a lot of time

There is a lot of misunderstood info in this thread, this is basically spot on....
There is such things as too rich, just the same as too lean. Motor to motor is different, some will allow leaner burns than others, the key is the fuel mixture that makes the most power and keeps you safe. keep in mind, alcohols do not have the same stoich as gasoline, so using gasoline 02 sensors are not suitable... you'll need to understand lambda.

Klaus explains too rich pretty well...
http://www.034motorsport.com/article...rticles_id=130

 

something that i haven't seen noticed in this thread is timing.
if you add more fuel (running rich) you have to run more timing because the flame front moves slower through the mixture.
If you run it "lean" (say 12.5:1) then you can make the same, if not more power, with less timing because the flame front moves faster.
obviously the design of the combustion chamber makes a difference too, squish areas etc.

 

Before I get a re-tune, how bad is it to run a low 10.x at WOT?

 

it's not bad, but it's not necessary. 11.5 to 12.0 is about right for these engines on gasoline.

 

Not necessarily bad, but detrimental to power. I have never seen a car wash down cylinders but I have seen them sputter and cough and smoke (I assume its doing the same thing).

Some helpful data to clarify alot of comments in this thread-

Stoich is related to efficiency and should NEVER be confused with what makes best power.

You have max power rich and max power lean (aka RBT and LBT), see attached links:

http://en.wikipedia.org/wiki/Air-fuel_ratio

http://www.bristoldyno.com/tech/airfuel.htm

http://www.max-boost.co.uk/max-boost...20metering.htm

Keep in mind we can use these values for Ethanol with a gasoline calibrated WB (this is common practice in fact) so you can judge for yourself what RBT / LBT relationship you want to run. Keep in mind EGT follows AFR as well.

 

so in plain english, 10.5 at WOT is not bad but not good?

 

english with as little technical in it as I can

10.5 at WOT is not bad but not good

 

lol thanks man that what I meant.

Well I was at 10 flat at WOT for about 2 weeks after I installed my gauge then one day out the blue it went up to 10.5. Strange?

 

This is correct, but I want to clarify what you said for other people... Flame speed is highly dependant upon AFR and timing..... and you CAN make more power running leaner...however the best way to find out what is best to change your afr and then adjust timing. I just did this AFR and timing sweep on an FP Red Evo8.... It made more power 7-10whp @ 11.2:1 than it did at 11.8:1.

However... my old turbo Neon (2.4L) made more power at 11.8:1 than it did at 11.2:1.

Our FSAE car loved it at 13.5:1... that's a whole other topic

So I won't say that there is a garuanteed success with going leaner...or richer. It really depends on the engine and the components. The best way to determine what the best AFR is.... is to actually tune the car and use the dyno as the tool it is.

 

It also depends on the octane of the gas you are using. If you are stuck in CA, where we get 91 octane, you will need to be more conservative with your A/F ratio or timing.