Alright I'm a tad bit lost. Exactly what would be done to alter high-altitude performance? What happens to the mixture and timing as a general rule when adjusting for altitude? And what constitutes "high-altitude"? How far above sea level?

 

I don't know what exactly consititutes high altitiude but over here in Albuquerque we are just over a mile high above sea level. I think we are about 6500 feet above. I don't know what effects this might cause to the power. I 'll see if I can get some answers when I take my truck in today. I'll let everyone know what happens when I get the truck back. Hopefully it will be good!

 

BLUBEAST01 you may be right about the high altitude thing. My situation, I live in Texas and the hills I where referring to where the ones around Austin. Not much altitude there.

JW

 

do the firestone bags help soften the stiff suspension

 

>do the firestone bags help soften the stiff suspension


lol, where did that come from???


i would think that the lower altitude trucks would run better becuse they get more air. thats always good. i wonder if there is anything that could be done fer the 5.4's? i think ill call my dealer also.


-nathan

 

>do the firestone bags help soften the stiff suspension


I'm with redranger. Where'd THAT come from. Anyhow...Bags help keep the truck even when loaded (amongst other things.). The only thing that will "soften" stiff springs is new springs.

 

The effect would likely be an offset to the fuel mixture setting range to the lean side, or at least the startup mixture ratio would be different. If you are going for performance "low lander", a slightly richer mixture is probably better than too lean. That might burn valves. Unless you changes other things, or the standard setting is somthing other than optimal, changing the computer setting will either do nothing or will hurt performance.

Rich

 

I assume everything out of the box is set to run at sea-level. At higher altitudes, the air is thinner... thus resulting in a richer mixture.

To properly adjust your mixture for higher altitudes, you are effectively leaning out the mixture. The problem is, if you get a 'high altitude' setup for a sea-level truck, you will be running too lean.

Setting everything up to run at sea-level is safe for everywhere... unless you get way, way below sea-level... which isn't going to happen. There are places that are below sea-level like death valley and parts of Arizona (I believe), but they are not low enough to matter.

But, if a high-altitude setup is run at sea-level, you will be running lean.

How lean? It depends on how high of an altitude correction was made and at what level you are running the vehicle.

Personally, I think the computer should utilize a barometer so it can correct the mixture automatically no matter where you drive. This sounds crazy... but with all of the other computerizations (is that a word?) on these vehicles, it sounds feasible. It could default to a sea-level setting if it fails.

 

Actually, the computer don't measure baro pressure (I don't believe), but it does measure mass flow, so it can compensate for density variation somewhat. But I think it either don't have enough control range, or it don't seem smart enough to set it right untill the airflow has been measured a while. I think (I don't know for sure, someone here may be much more knowledgable about specifics), that the adjustment moves the entire auto adjustment range and sets the "static" setting. If it don't work like that, I don't know why there is an available "program" adjustment at all. You wouldn't need one.

Rich

 

I know it doesn't use a barometric pressure device. That is why I suggested that it would be a good idea.

 

Just got back from the dealer to have a door latch problem taken care of. I asked the service adviser about the re-flash, and he said they would check as sometimes an update is available. He also said that he believed that changes were mostly emissions related. After checking, he told me there were no updates for mine, at least for the Excursions. Maybe the 'performance octane' update is just for the trucks?

 

The deal with high altitude is that the vehicles use a LOT more ignition advance, and have to run leaner. When I first moved to Colorado almost 20 years ago, I advanced the timing on my truck's distributor maybe 6 degrees just to get it to work halfway right (no EFI back then).

The lean part is obvious- The air is a lot thinner, so you lean out the fuel to maintain the correct air-fuel ratio.

This is the exact opposite of having a turbo or supercharger.

Regular unleaded in Colorado is 85 octane, mid-grade is 87. No problem, because your effective compression is less.

You DON'T want to run a vehicle set with high altitude ignition advance and lean at lower altitudes, you'd be pinging and wouldn't have power because it was too lean- eventually nasty stuff would happen like burned valves. The computer is supposed to properly adjust the timing and mixture for your altitude, apparently the situation is there's a bug at the high altitude settings requiring the reprogramming to properly set the mixture and timing--but ONLY in high altitude areas. This modification wouldn't help anyone at or near sea level so I wouldn't get excited about it, folks.

In the carb days, you had to re-jet vehicles if you moved to a high altitude area or vice-versa. Expensive, a real pain. Mt bro-in-law bought a used Ford E-350 460 inch van here in Denver, took it back to Ohio and it cost him $1,200 for a new carb and retuning.
EFI is a wonderful thing.