2009 F-150 5.4L Preliminary Dyno Results!

[Jackpine]

Originally Posted by secondarychaos

That's a nice improvement...
but that AFR graph of stock is a bit scary...

Kind of like falling off a cliff, isn't it? But wouldn't everything be better if all the A/F curves stayed closer to the ideal 14.08 value (for E10) throughout the envelope? Or, does the engine really HAVE to run rich under load to prevent damage?

I remember a certain brand of model airplane engine I had when I was a kid that was very good at destroying itself as the fuel in the tank ran out. It would suddenly start running quite lean, the RPMs would increase then drop slightly and it would sound "weak". Then, the crankshaft would fracture! I learned the only way to prevent this from happening was to run the thing at a richer than full-power setting for the entire flight.

- Jack

[secondarychaos]

LOL that's an interesting design...
run out of fuel? Bang LOL

I'm thinking this was ford's engineer's idea to help fuel economy...

[Power Hungry]

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.

[Jackpine]

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

[Power Hungry]

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.

[secondarychaos]

Originally Posted by Power Hungry

at cruise where 15+ AFR is not uncommon.

Really? I thought this was a recipe for disaster. I always heard how leaning a motor out could wreck any number of parts, most notably the pistons. is there any truth to this? is it only under certain conditions?

[Jackpine]

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

[Power Hungry]

Originally Posted by JackandJanet

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

Exactly. Running a tad lean (lean being a relative term here) during light cruise (minimum load) is not uncommon for most auto manufacturers. In fact, I've seen as high as 15.8:1 under light cruise. Under acceleration or load, fuel curves will richen up as necessary to keep things safe.

[chappy]

That is pretty Fricken sweet.nice job.