Despite the fact that 14.64:1 AFR is stoich for gasoline, this is NOT where peak torque is made. Under full load, peak torque occurs around 11.8:1 and peak HP is closer to about 12.6:1. Cruise conditions are quite a bit different and can run upwards of 15.0:1 without technically being "lean", although again this doesn't necessarily equate to the best fuel economy or performance.
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Thanks, Bill - makes perfect sense to me. And, I can see how your A/F curves smoothly adopt that strategy, rather than having the sharp "bump" at 4500 rpm.
But, now I've started "thinking" again (which I know is dangerous). The stock curve seems to hold the A/F ratio near 14.08 (the ideal for E10). And, I have to imagine the older trucks like my 2005 and earlier tried to hold it at 14.64 (for REAL gas ;) ), so did Ford put out a flash to the PCM to "adapt" them to E10 when it sort of became the "standard"? As I recall from the f150 forums, the 2004-2005s were already lean running when they came out. E10 would just make things worse, right? - Jack |
To some degree. Keep in mind that the vehicle tested was a FlexFuel vehicle and had the ethanol sensor. Also, don't forget that those are WOT runs. The fuel strategies are a little bit different at WOT than at cruise where 15+ AFR is not uncommon.
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That is pretty Fricken sweet.nice job.
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At cruise, there's very little load on the engine. I imagine that's how you get away with a lean A/F setting.
- Jack |
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Ok, so it's Lean + Load conditions that can cause issues.
thanks for the clarification! |
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Bill,
I do not have a Gryphon yet, hopefully soon...that being said, because of the air intake mod I have, do you think it would be detrimental to my engine (stock 5.4 3v with stock air filter) to make WOT runs? Should I cap off the ram air section and just let it breathe through the fenderwell until I get a Gryphon? I haven't made any WOT runs yet, and based upon your explanation of A/F ratios it's probably a good thing I haven't. Thanks for any guidance. |
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