High Altitude Boost

RichB · Postby **RichB** » Wed Nov 17, 2010 9:14

I'm new to the area and I wondering how different boost level are here at altitude. At sea level i'd see 17 psi easy on a stock tune but up here I see it in the mid 15s.

Also, my AFRs at WOT are in the low 12s when I used to see them mid to low11s. Am I loosing my mind or is this normal?

erod550 · Postby **erod550** » Wed Nov 17, 2010 9:14

You're seeing AFRs at WOT in the low 12s on a stock tune?

RichB · Postby **RichB** » Wed Nov 17, 2010 9:14

erod550 wrote:You're seeing AFRs at WOT in the low 12s on a stock tune?

Yup, should I be worried?

mOOsE · Postby **mOOsE** » Wed Nov 17, 2010 9:14

boost numbers are normal. Higher alt = less atmospheric pressure = less overall PSI

tbot · Postby **tbot** » Wed Nov 17, 2010 9:14

how much have u driven up here since you moved? if not long, then there's a chance the ecu needs to learn the altitude difference for less atmospheric pressure. aslo, what are your mods, cause stock these cars were set to 15.5 psi (at sea level btw)

RichB · Postby **RichB** » Wed Nov 17, 2010 9:14

Well, I re-set my ECU and am showing the numbers stated above. I've been here a few months. BTW I have a CAI, CBE, and FMIC.

erod550 · Postby **erod550** » Wed Nov 17, 2010 9:14

I don't know if you should be worried but I don't think you have a stock tune. Stock runs pig rich and puts you in the low 10s to the 9s by like 5k rpms. Did you buy the car used? Maybe someone else had flashed the ECU before you got it and never put it back to stock before trading it in.

RichB · Postby **RichB** » Wed Nov 17, 2010 9:14

Nope, I'm the original owner. I was seeing between 9s and 10s at sea level. Here I see low 12s but sometimes get in the 11s.

tbot · Postby **tbot** » Wed Nov 17, 2010 9:14

I would say pull the battery for 10 minutes, reconnect, and then do the "MAF calibration" instructions from cobb, or MSF, or online somewhere. Doesn't sound like your ECU is compensating for the altitude...or the cold we're dealing with now

RichB · Postby **RichB** » Wed Nov 17, 2010 9:14

Don't have an AP so it'd be kinda hard to pull that one off. I'm wondering if it is either my mods on the stock tune or the gauge I am using. Right now I have an Aeroforce Interceptor but back when I was at sea level I had an AP. Sounds like I will have to confirm with an AP when I gather some funds to get one again. Everything seems fine though because my exhaust has a bunch of soot on it as always.

tbot · Postby **tbot** » Wed Nov 17, 2010 9:14

MAF calibration i guess was the wrong terminology...you need to get the ecu to relearn the maf for this altitude and temperature...you do so by the maf calibration instructions.

RichB · Postby **RichB** » Wed Nov 17, 2010 9:14

Oh, so you mean perform the steps (i.e. drive at various speeds for a set amount of time)?

speedjunkie · Postby **speedjunkie** » Wed Nov 17, 2010 9:14

As far as boost goes, you lose 4% for every 1000 feet, so I know in C Springs it's about 27% loss, or so the tuner told me anyway.

RichB · Postby **RichB** » Wed Nov 17, 2010 9:14

That kinda makes sense, I heard about 1psi per 1K feet. Workes out to be about the same.

I didn't loose that much boost though.

mOOsE · Postby **mOOsE** » Wed Nov 17, 2010 9:14

RichB wrote:I didn't loose that much boost though.

Due to the FMIC

High Altitude Boost

High Altitude Boost

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