03 Cobra Air/Fuel Ratio Adjustments

[black03SVT]

I have really enjoyed the Air/Fuel ratio information provided by mjchip and others who have dynoed their vehicles. Quite a few unanswered questions remain however.

If a pulley and exhaust lean out the mixture a bit too much then is it necessary to change the injectors and fuel pump to get the necessary fuel into the motor?

Will a chip alone fix this problem? Or will a chip only cause a further lean?

I have been really interested in this topic and have never known so much about Air/Fuel ratios. Any additional information would be greatly appreciated.

Gabe

 

[black03SVT]

Anyone?

 

[mike69440]

A/F

In general ang engine, even a boosted enging will have best power around 13 to 13.5 to 1 A/F. There are variations as fuel density, oxygen content of the fuel and fuel composition have a lot to do with it. Gas today is just not a mix of octane and heptane. Hell, they blend any hydrocarbon almost and still call it gasoline.

Running a supercharged engine at 13 to one is very dangerous as suvivability dictates you need excess fuel beyond best power to cool the burn.

12,2 to 11.4 is about wher you want to be under full boogie. You may be down 25 hp, but you get to play another day.

Much below 11 to 1 an engine really starts to bog down and feel sluggish.

Even lower air fuel ratios are dangerous long term as the excess fuel cleans the cylinder wall and you wear the engine quickly.

The fuel curve on a Cobra is open loop at WOT.

My stock Cobra is running very rich and down on power.

If all Cobras are on the rich side, Ford has assummed that we will all be doing mods.

Some like mine are too rich stock.

Ford did put enoght injector and fuel pump to take the car over 500 hp. A recalibrated chip will change A/F among other things.

Best thing to do is get a dyno run with wide band A/F reading and work from there.

Hope this helps.

Mike