abrush

Sorry about the double post. This computer is acting up today. I hope that doesn't speak for how this day is going to go.

matyellott

Thanks guys, I had a procharger system put in my car and the guy shop that put it in was telling mw once you go FI, tuning gets a lot more percise.

Goldenpony

Years ago I had a '97 GT. Drove it on a western vacation. While out west I drove it to the top of Pikes Peak, no problems at all.

GidyupGo

Only thing about that drive is the catalytic converter gets red hot and sticks to high heaven. My first trip up there was in a 69 Fastback. Thing kept over heating, and I stopped at the water stops along the way to hose down the radiator. At tree line, no more water so had to pull over and head the nose into the wind to let it cool down.

matyellott

Thanks for the insight just seems a bit odd.

.boB

You're right, high altitude requires a differant tune. Mostly because of the decreased O2 per cube, but also because of decreased air pressure.

Modern EFI systems don't have any trouble compensating for this. There's a special fuel map in the computer to make the adjustment based on the reading from the MAP sensor. Less pressure=less fuel. The problem is that most computers read the MAP sensor once at start up, and then use the map point based on that single reading. Of course, as you make the rapid climb up the mountain, that single map point is no longer valid.

That's where the O2 sensors in the exhaust come in to play. All the modern systems use a wide band sensor. It will read the exhaust gases and adjust the map accordingly.

My Mustang has a V6/5 speed. At high altitude I get pretty good gas mileage. 22 on my daily commutes, and 32 on the highway cruising at 80mph. A couple of months ago I went to Texas. I noticed the lower in altitude I went, the more the mileage dropped. Across Texas I was only getting 26-28 at 80mph. Once I got back above about 4,000', mileage went back up.