has anyone played with the timing to increase milage. I have read that changing a few degrees from TDC can have some effects for better milage. Any thoughts

 

What year is your truck? The 2005 and up Super Duty 5.4L 3V and 6.8L 3V have variable valve timing that adjusts for additional torque and supposedly better mileage due to requiring less power to push the truck with the higher torque it can produce at lower RPM's. I have a Diablo PredatorSport programmer and I can actually adjust my timing with it in addition to the variable valve timing that the newer 3v engines come with. I haven't custom tuned it over and above the programmer 91 octane tune which adjusts the timing and air fuel mixture to accomodate the premium fuel, but plan on getting it dyno'd once the new intake and exhaust are added.

I you have an older 2v, I am not sure what your options are, but someone else may know. I'm pretty sure you can find a programmer that can alter your timing, but most are designed for more power and without letting the engine inhale and exhale better you might not find the increased mileage you are looking for.

Someone will correct me if I'm wrong, but I think if you retard your timing enough you can lean out your air fuel mixture and get better mileage, but this can be very hard on your engine (more heat). Most programmers advance the timing and increase the fuel air fuel mixture so that it is richer which provides more power, but this will not improve your mileage when under load.

 

I have an 01 E250 5.4. I have also read that "leaning" the mix will get better milage. Do you know if I can install better header or if a better exhaust sys will help if there is heat build up. I am getting around 14-15 mpg hwy right now and I do so much driving its killin me.

thnx

 

3V 6.8L's do not have VCT,only the 3V 5.4L.
And you're totally lost on how timing and air fuel are related.
JL

 

Maybe you could explain it to us then?

 

Altering air/fuel has no effect on cam or ignition timing.
Altering cam or ignition ting has no effect on air/fuel ratio.
They're three totally seperate tuning paramters,and none depends on the others.
JL

 

No one said it did. I think you need to go back and reread the post from WildWildWest.

Here he stated (correctly) that retarding your ignition timing will allow you to run a leaner mixture, but at the risk of much higher combustion chamber temps, and that most programmers will make the mixture rich and advance the timing to make more power. These are correct statements.

 

I did read his post,and it's wrong.
The most heat you'll have in the combustion chamber is at 14.64:1 air fuel. Leaning the mixture will yeild a COOLER combustion chamber,as will richening it. Tuners make power in 2 ways on gasoline engines.
Setting up the air fuel ratio to a LEANER mixture than stock on most applications,and advancing ignition timing beyond stock. V10's are the only applications where the air fuel is richened for more power
5.4L 3V's have VCT for one reason-to create internal EGR for emissions and economy. The benefits for power/torque by chaging cam timing are just a plus that comes along with it.
There is no reason whatsoever for there to be a need to richen the fuel mixture because you're advancing ignition timing. There's also no need to retard ignition timing because you're leaning the fuel mixture.
JL

 

Leaning the mixture does not necessarily drop temperature combustion temps. On an aircraft (License Private Pilot speaking) as you lean the mixture in flight the EGTs initially spike, this is because there is less fuel being injected, fuel actually cools the combustion chamber slightly when it enters the cylinder. However if the mixture is set lean enough EGTs drop down slightly because there is overall less fuel being burned. Much past this point and it'll start to run rough. From my experienced rough running engines at 5000 ft aren't fun, and rough running engines in trucks aren't great. Usually aircraft are run "lean of peak" meaning just after the EGTs peak, this seems to be where you get the most power, howeverp is still debated. I would assume that since both are internal combustion p istonengines, that principle would apply to your truck too.

 

What air/fual ratio is that airplane engine running at?
I'll be it's richer than 14.64:1,so leaning it up to 14.64:1 will yeild a hotter combustion chamber-leaner than 14.64:1 will net a cooler combustion chamber.
JL

 

No, sorry, you've got it all wrong.

As mentioned, a lean mixture charge doesn't cool the combustion chamber as well, leading to elevated temps.

From http://www.matraclub.com/04mecanica/...acts/facts.htm

• Air/fuel mixture: Lean air/fuel ratios raise cylinder-head temperatures, requiring a colder plug. Rich air/fuel ratios require a hotter plug to prevent fouling. Mixtures that cause the plugs to read lean may contribute to pre-ignition or detonation. If not running an electronic engine management system, it pays to tune slightly on the rich side to avoid detonation.

 

someone let me know when we decide if changing timing mechanically by adjusting the cams is beneficial or not.

 

Yes! Advancing and retarding the cam can move the power band up or down a few hundred rpm. Advance for more bottom end and retard for more top end. More bottom end power will result in better fuel mileage, unless you spend all day driving around above 3500 RPM.

 

cool. i had a twin dual overhead cam v6 in a past car, and a few guys on my forums retarded the exhaust cams 13* for some top end with decent results.

is there any documentation of this being done on a 2v 5.4? i'm very interested.

 

You're looking at this wrong.
It's physically impossible for combustion chamber temps to be higher with leaner than stoich(14.64:1)air fuel ratio. The stoich air/fuel ratio for gasoline(14.64:1) is it's highest BTU thermal point-in other words-it makes the highest amount of heat and does the most work at that ratio.
Internal combustion engines are not 100% efficient,so they unfortunately do not make the max power at gasoline's most efficient air fuel ratio-it's somewhere between 12.8-13.1:1 air fuel for most engines-Modulars typically make the most power at 13:1. When someone(like your reference above) refers to a "lean" mixture-they're simply referring to a mixture that's leaner than the air/fuel that makes max power for a given engine. They are NOT referring to mixtures leaner than stoich for gasoline.
JL