Can the AFRP (actual fuel rail press.) be adjusted to control the amount of fuel going to the engine, which would give me the ability to lean/rich my engine?

06, Flareside, 4.6L, Evo, KN 77, Gibson superflow

 

Custom tunes would have to be used to do this.

 

In case 88's reply wasn't clear, there is no user control over A/F ratio. The tuner sets it through the program when the engine is in open loop. I closed loop, the feedback system simply tries to maintain a lambda of 1.0.

- Jack

 

Thanx Jack!
I knew you could explain it better!

 

Thanks Jack, but what's a lambda of 1.0? Also, is the closed/open loop the result of a good/bad 02 sensor?

 

Details on A/F Ratio, Lambda, and Stoichiometry
http://en.wikipedia.org/wiki/Air-fuel_ratio

Closed and Open Loop are states that the ECU utilizes for differing fuel ratio table utilization - IIRC Closed loop is when the engine is up to temp and operating normally, Open loop is during initial startup and warmup periods.

 

No. A Change in desired fuel rail pressure drop across injectors changes the pulse width.

 

Ideally, from a pollution standpoint, you want all carbon in fuel to be converted to Carbon Dioxide, all Hydrogen to H2O (water) and all Sulfur to Sulfur Dioxide. If there are any of these elements that are not properly converted, such as Carbon being converted to Carbon Monoxide, combustion is incomplete. With a "reference" blend of gasoline, you get complete combustion (called Stoichiometric) at an Air/Fuel ratio (A/F ratio) of about 14.7. A/F ratios higher than 14.7 are lean and those below the "Stoich" value are rich. You get more power with somewhat rich mixtures, and, you can get improved economy with slightly leaner mixtures (as long as the load on the engine is low).

Different fuel grades, such as E85, have different "Stoich" A/F ratios, so, it's helpful to have a different way to express the "ideal". That way is known as "Lambda" and is simply the current A/F ratio divided by the "ideal" A/F ratio for the fuel used.

Obviously, if they're the same, Lambda = 1.0. But, if the engine is running lean, Lambda will be greater than 1.0 and if rich, Lambda is less than 1.0.

I'll add to Jax_F150's comment that you also are in Open Loop any time you are operating at WOT, even if the engine is fully warmed up. You are probably at WOT anytime you have the throttle more than about 90% open.

If you have a bad O2 sensor, you will probably have a code that tells you this. The O2 sensors ARE the feedback sensors in Closed Loop.

- Jack