ok, just got back from Las Vegas's Centennial - red hot chilli peppers & Weezer...woo hoo!!! very nice concert. anyway, on my way to vegas from LA area, my car began bogging really bad when i hit 4000ft elevation near the state line of cali and nevada. The bogging was so bad i had to stop the car on the side of the road. There was no problem before that. Well, i checked for leaks and stuff, but nothing visible was wrong with the car. So i sat in my car on the side of the road letting the engine cool off. I then start engine and proceed to vegas, and arrive with no problem. Well on my way home, from vegas to again the same exact area where there is 4000ft elevation, the car again starts to bog down really bad, had to stop again, and let the engine cool before i proceeded. So then i start her up and go, and no more problems. i figured it was the elevation since the distance from my home to 4000ft is much further than the distance from vegas to 4000ft. The car bogged at the exact place. Does elevation restrict air from entering the intake or something that it caused this? i don't really know if it's the elevation, but the car didnt have any problems after passing 4000ft

excerpt from "how stuff works"

Turbos on High
A turbocharger helps at high altitudes, where the air is less dense. Normal engines will experience reduced power at high altitudes because for each stroke of the piston, the engine will get a smaller mass of air. A turbocharged engine may also have reduced power, but the reduction will be less dramatic because the thinner air is easier for the turbocharger to pump.

my turbo seemed to get the more dramatic effect out of this elevation. Damn car couldnt even keep going, it was so bad.

I had the same problem in Tahoe at about 7000 feet, the car was bogging so badly it nearly stalled several times, and I too ended up on the side of the road scratching my head.

My solution at the time was to lean out the SAFC and lower the fuel pressures on my SFMU. Since the air is considerably less dense, you're running super rich.

Unfortunately the SFMU was already set at the lower limits of its range just for sea-level driving so it couldn't go much lower without completely stalling at idle.

Factory turbo cars typically have a MAF sensor, and use the intake air temp much more effectively. This is one of the main reasons I gave up on turboing a MAP-based nonturbo car. If you start really getting into tuning you'll notice the same problems on cold and/or humid days, or worse... at a high-elevation track like Palmdale or Willow.

The megasquirt has a lot of potential in this department, but I gave up before the megasquirt was available.

Originally posted by thedawg
I gave up.

That is so sad, Dan. x(

You were probably experiencing vapor lock. "an obstruction to the flow of fuel to a gasoline engine, caused by the formation of bubbles in the gasoline as a result of overheating or higher elevations."

I drive to Mt. Evans in colorado all the time. The drive starts at 5500 feet and goes to 14,000 feet. I have gotten vapor lock twice driving up there and its the same symptoms your describing. Pulling over and letting the car cool down has always fixed it. So it has nothing to do with your turbo.

While I do notice a performance loss at palmdale...I never bog. It lovs the cold and foggy days too.

QUIT! WTH!

nah ... just likes to break other ppls toys...jerk :P

Quick question: Would you have to let it cool off? The bogging is the result of the ECU not being able to adjust to the altitude, but if you turned it off for a minute or two and turned it back on, the ECU should adjust. am I right on this?

i don't really know, but when I did turn the car off, I turned it back on after 10mins and it was still bogging, so I decided to let it cool off for 20-25mins, and then it was ok. Next time, I will lean out the SFMU a bit, and see if that fixes it quickly.