Air/Fuel Ratios

[SledFreak]

Hey Guys.. Who ever is running a Wide band PCIII/Ignition Controller or just in general what is the optimal air/fuel ratio for the Apex. How lean can you go and for how long can you run them at that ratio...

Thanks

 

[SledFreak]

no body knows?

 

[FLYBYU]

i believe in the area of 13.5 at idle

 

[Iceman57]

14.7:1 is the ideal ratio for lowest emissions, but this isn't the best ratio for power. It used to be that 12.5:1 was considered the best power ratio, but with improved combustion chambers and hotter ignition systems, the ideal now is around 12.8:1 to 13.2:1. This is roughly 13 parts of air to one part fuel. It's what combustion engineers call an excess fuel ratio and is intended to ensure that all the air is used to support the combustion process. This is because air is the oxidizer in combustion. Too many enthusiasts think that adding additional fuel beyond the ideal to create a richer mixture will make more power. This doesn't work because you can only burn the fuel when you have enough air to support combustion. That's why engines make more power when you add a supercharger or nitrous--you're shoving more air in the cylinder so that you can burn more fuel. Regardless of the amount of air in the cylinder, it still requires a given ratio of fuel to burn. Add too much extra fuel, and power will decrease. The lower the number the richer the mixture. When it comes to fuel mileage and increased fuel efficiency, this ratio changes again. All new cars run at 14.7:1 air-fuel ratio at part throttle because this is the lowest emission point. But depending upon the engine, it's possible to run an engine at leaner mixtures like 16:1 or more at part throttle to gain mileage. The difficulty with this is that driveability and throttle response suffers at these ratios. Engine response is lazy and stumbles are commonplace. Each engine will be different, but there is fuel mileage to be gained by fine-tuning your carburetor. Don't be intimidated by these lean mixtures at part throttle. You won't burn the engine up since it is making very little horsepower at part throttle cruise, often less than 30 hp.

 

[SledFreak]

14.7:1 is the ideal ratio for lowest emissions, but this isn't the best ratio for power. It used to be that 12.5:1 was considered the best power ratio, but with improved combustion chambers and hotter ignition systems, the ideal now is around 12.8:1 to 13.2:1. This is roughly 13 parts of air to one part fuel. It's what combustion engineers call an excess fuel ratio and is intended to ensure that all the air is used to support the combustion process. This is because air is the oxidizer in combustion. Too many enthusiasts think that adding additional fuel beyond the ideal to create a richer mixture will make more power. This doesn't work because you can only burn the fuel when you have enough air to support combustion. That's why engines make more power when you add a supercharger or nitrous--you're shoving more air in the cylinder so that you can burn more fuel. Regardless of the amount of air in the cylinder, it still requires a given ratio of fuel to burn. Add too much extra fuel, and power will decrease. The lower the number the richer the mixture.

So mark, what is the best scenerio for WOT runs for a 1-3 miles in distance without letting off? I have some rivers around here where you don't really have to let off and you can cruise at 100mph to top end.

 

[SledFreak]

14.7:1 is the ideal ratio for lowest emissions, but this isn't the best ratio for power. It used to be that 12.5:1 was considered the best power ratio, but with improved combustion chambers and hotter ignition systems, the ideal now is around 12.8:1 to 13.2:1. This is roughly 13 parts of air to one part fuel. It's what combustion engineers call an excess fuel ratio and is intended to ensure that all the air is used to support the combustion process. This is because air is the oxidizer in combustion. Too many enthusiasts think that adding additional fuel beyond the ideal to create a richer mixture will make more power. This doesn't work because you can only burn the fuel when you have enough air to support combustion. That's why engines make more power when you add a supercharger or nitrous--you're shoving more air in the cylinder so that you can burn more fuel. Regardless of the amount of air in the cylinder, it still requires a given ratio of fuel to burn. Add too much extra fuel, and power will decrease. The lower the number the richer the mixture.

Duplicate post..

 

[Srxspec]

There is not much difference between 12.0 to 13.0 on the Apex.

B (Green in color) 12.1

F (Red in color) 12.6

G (Blue in color) 13.1

I try to shoot for 12.5 to 12.8 usually.

 

[Iceman57]

The answer will vary from person to person slightly, but you will get an answer of below 13 being as the high acceptible number, but I would go 12.5:1 for a safer ratio. Much lower and you will be runing too rich.

 

[**sj**]

now if we could get a map for our apex's pc3's setup by a wideband!

 

[race24x]

My buddy has a wide band O2 (I think thats what it is like 350 bucks) on his Apex but is only running the Hauck Fuel processor. I wish I could get one to install the PCIII I really like that setup.

 

[SledFreak]

Dynajet sells them for the PCIII.... Look on there website...

 

[87gtNOS]

14.7:1 is the ideal ratio for lowest emissions, but this isn't the best ratio for power. It used to be that 12.5:1 was considered the best power ratio, but with improved combustion chambers and hotter ignition systems, the ideal now is around 12.8:1 to 13.2:1. This is roughly 13 parts of air to one part fuel. It's what combustion engineers call an excess fuel ratio and is intended to ensure that all the air is used to support the combustion process. This is because air is the oxidizer in combustion. Too many enthusiasts think that adding additional fuel beyond the ideal to create a richer mixture will make more power. This doesn't work because you can only burn the fuel when you have enough air to support combustion. That's why engines make more power when you add a supercharger or nitrous--you're shoving more air in the cylinder so that you can burn more fuel. Regardless of the amount of air in the cylinder, it still requires a given ratio of fuel to burn. Add too much extra fuel, and power will decrease. The lower the number the richer the mixture. When it comes to fuel mileage and increased fuel efficiency, this ratio changes again. All new cars run at 14.7:1 air-fuel ratio at part throttle because this is the lowest emission point. But depending upon the engine, it's possible to run an engine at leaner mixtures like 16:1 or more at part throttle to gain mileage. The difficulty with this is that driveability and throttle response suffers at these ratios. Engine response is lazy and stumbles are commonplace. Each engine will be different, but there is fuel mileage to be gained by fine-tuning your carburetor. Don't be intimidated by these lean mixtures at part throttle. You won't burn the engine up since it is making very little horsepower at part throttle cruise, often less than 30 hp.

Don't forget to quote the website you got that from!

Let me add, (and it's not from a website) that in many instances, more fuel makes more power. More fuel is often used to cool the combustion chambers. Often in Turbo/SC/big bore applications. NOS on the other hand doesn't have the extreme cylinder temps due to it being cold to begin with! Turbos are hot air, hence the extra fuel for cooling. Big bores have added chamber area and piston surface, hence the need for extra fuel for added cooling.
All this throws the A/F ratio theory's out the door. Now fuel economy really comes into play. Safe A/F mix vs. economy!!

 

[1badattack]

I have a koso a/f gauge on my attak, I found at idle it was around 11 and as lean as 18 at wot.

I have a boondocker and adjusted the fuel between 12.5 to 13 throughout the rpm now. That is with the stock airbox, no mods.

 

[87gtNOS]

Don't be intimidated by these lean mixtures at part throttle. You won't burn the engine up since it is making very little horsepower at part throttle cruise, often less than 30 hp.

Again, 350 Chev tuning, not Sled tuning.

I would be very scared of lean PART THROTTLE A/F mixtures on a 2 stroke also. Piston wash and/vs. EGT's is what I'd watch long before an A/F gauge.

 

[Iceman57]

You don’t have to get your panties all up in a knot I was just posting information about air/fuel mixtures. That same information is posted all over the internet and is very accurate info and I never claimed to be the author. What is written in that article is referring to 4 strokes and is very accurate information according to my resources at the GM Milford Proving Grounds here in Michigan. I was directed to that article from someone that works in the powetrain division. My experience is with auto engines but what we are talking about here is a naturally aspirated 4 stroke engine and not 2 strokes, or big bores or turbo. You may need more fuel for cooling in certain circumstances for what we are talking about here is a near stock apex engine. 1badattack ran his sled at 18:1 at WOT until he installed a wideband and I am pretty sure he would still be running that ratio if he hadn’t. That 18:1 is way lean and I would bet that a lean condition is pretty common on our sleds and you don’t see Apex engines failing often. In most circumstances running too rich will hurt performance. Allens dyno results show that a rich 12.1:1 mixture reduces HP over the 12.6:1 mixture. With the Genesis 150 in the naturally aspirated state you don’t need to use piston wash for your air fuel settings, that is over kill, nothing more then an o2 sensor is needed. The 2009 GM LS7 puts out 505 HP and is set to run at 14.7:1 air fuel mixture at the factory settings don’t tell me that the Genesis 150 is a more high performance engine then the LS7.