High Altitude Tuning

[Ridin'GMC]

Has anyone done high altitude tuning? Since I live at a low altitude area (1300' above sea level) I basically did my tuning at low altitude and left the medium and high altitude alone. Now I will be going back and forth to Flagstaff from my home, the elevation in Flagstaff is 8k above sea level. I noticed it slowly went back to stock power as I cruised into higher elevation. Can you tune it the same way as low elevation level except for using less fuel but same timing and boost?

I need to know what to avoid in high altitude (medium as well) because I won't be able to hear the engine ping.

My egts were almost similar to my low altitude but the boost are slightly different. The highest it got was 1150* going 75 mph on a grade 7 hill (believe it is a grade 7, it was pretty steep, Brian might know the grade lol).

 

[SSchmi5519]

Your stock tune will scale properly and you wont have to worry about ping.

Other than that hard to explain tuning in one post..

 

[Ridin'GMC]

I figured it would be hard to explain. I noticed my timing base and fuel pulse are the same, just the boost level that are different. So if I change the boost to make it similar to the low altitude, it should change the fueling and timing to similar as low altitude correct?

 

[SSchmi5519]

changing the desired boost will only affect vane position, not timing/pulse

 

[Ridin'GMC]

Alright. I'm a bit puzzled that it didn't smoke at full throttle in Flagstaff. In low altitude, whenever I hammer it, it would puff some smoke until the turbo spools up then it's clean after that. But up here, it barely smoked at all. I figured it should have bellowed smoke when I hammer on it due to thin air, at least that's what Brian told me.

 

[THEFERMANATOR]

You will need to spend some time dialing in your max torque to barometric pressure table to get fueling at altitude. Also keep in mind teh boost tables are set in absolute pressure, meaning 14.7 is 0 at sea level, but at 8,000 feet it will be like 10-11 for 0 boost. So you will have to decide do you want a certain amount of boost, or do you want an absolute amount of intake pressure for your altitude based tuning. And at altitude you will tend to run higher timing at low to medium amounts of power as the lower air density will have mor lag to it at altitude. You can always max out your torque to baro fueling, and make all of your timing tables and such the same, but this WILL give smoke at altitude if you stomp it.

 

[Ridin'GMC]

Thanks for the tip. I was trying to understand how it works in high altitude. When I do the tuning, I try to keep it clean as possible. I don't like it when it gets smoky. Clean, efficient burn is my goal since that's where the power and fuel economy is at.

 

[JoshH]

You need to do some datalogs at altitude. There are some baro limiting tables that could be pulling fuel quantity.

Also, you can't have the same boost tables as low altitude because they are absolute boost, not gauge boost. You could copy the high altitude tables and subtract the difference between barometric pressures for each table, but then you could get into problems with too much pressure ratio, especially at higher altitude.

 

[malibu795]

when i went to wyoming i pulled 2-3* out accross the table vs the timing i was running between 100-4,000ft here in east of the big muddy..

took care of the ping/timing rattle at part throttle.
since i dont run there much i didnt bother "optomising" the timing table, once i got back to low land i put my normal timing back in..

 

[Alliance1289]

Having driven my truck from Wyoming down (over 5300 ft elevation) to sea level and back several times... I guess I never really thought about making a change in tuning. It definitely felt like a rocket ship down at sea level with the tune that's in it. I've also driven my truck up to around 10,000 ft elevation and noticed it felt a little sluggish. Didn't really think much of it though as I was just cruising down the interstate on cruise control.

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