I'm currently @ 5,312' above sea level.
My boost gauge is now reading -14hg as opposed to -18hg when I was at sea level.
Are there any adjustments that can be made to compensate for the deficiency in air at this altitude?
Thanks.

 

Your loss in boost is greater than I saw at 5k' at my former home (now at 7.4k' in easternmost AZ). Negative 2.5 psi correlates with the chart I found online (see pdf attachment) when understanding my own boost numbers (displayed on Android tablet from bluetooth OBD2 port dongle). I'd suggest rechecking your gauge against a similar method. In any case, no way known (by me) to counteract the effects of elevation.

 

@MCS4FUN , looks like a bit too little loss. Should be ~1 inHg/1k ft, so should be 5 inHg less instead of 4. Though, @Here2Go , are you referencing your boost at sea level or where you were before in Atlanta? Most of Atlanta is at ~1k feet of altitude.

All the normal methods of cramming more air mass into the cylinders still apply.

Or are you concerned about the tune at idle since you’re referencing vacuum? It’s not like the old days where you had to re-jet. The DME will compensate for the altitude during closed-loop operation as it calculates air mass.

 

@deepgrey Did you view the chart pdf attachment? If so, my own results seemed to match that boost loss at 5k' elev...

 

Yeah. It matches what I just said… You should see ~1 inHg loss in vacuum per 1k feet, all other things (like ambient temp) being equal, of course.

Note that he’s working in inHg, and vacuum, not boost. So a loss in vacuum is a positive number.

 

Hey guys Thanks for responding with your inputs @MCS4FUN - yeah I had also noticed a slight decrease in boost. As you said - about 2psi lost in boost. Although a bit difficult to tell = 5k elevation, 40º ambient, snowing and constant undulating mountainous (crappy) roads.
@deepgrey Yes. while I was in ATL my -inhg at idle was about -18inhg. In FL it was about -19-20inhg. Up here on the border of NM/AZ I'm seeing a variance between -13 --14inhg at idle.
I do have a custom "wide mouth" CAI I modded which had shown to make a fair amount of difference in air intake compared to stock. I'm thinking about mounting a 6" high speed spindle fan under the cowl. I forget what cfm it produces but it's a relatively cheap and quick mod just to see if iit makes even the slightest difference.

BTW: I like that you referenced the "old days" with regards to simply re-jetting. Early in my life I was contracted from FL to do some design work in ABQ/NM.
I drove my hybrid 914 powered Beetle up there. Totally ran like crap and had to buy/re-jet it so it would actually be able to ascend the mountain roads at more than 50mph. Ahh; the good ole days..

 

Curious what you are trying to accomplish? Yes, the air is thinner at altitude, and not much can be done about it. Maybe switch to a turbocharger with boost control to absolute (instead of gauge) pressure reference in the manifold? Then you'll actually be boosting to an absolute number, instead of a differential pressure. But, I'm sure you weren't asking about rebuilding your car... A bigger displacement supercharger would help some.

 

Initally It wasn't really a question to accomplish anything.
Other than to rule out a possible vacuum leak or was the altitude having the affect due to the increase in -hg.
However I was also wondering (to myself), if moving to a higher elevation might require a re- tune. I've pretty much resided in the fact that it is a cost of performance above sea level.

 

Gotcha. Yeah, if you've never driven to a higher altitude, I guess you wouldn't expect the power and vacuum loss. Modern cars can re-adjust as needed.