NO power at higher altitudes

[taz77]

I drove my 04 wrx to South Lake Tahoe for the first time since
bought my car a few weeks ago. I'm in San Francisco at sea level, th
area of Tahoe I was at was about 5000+ feet above sea level. As soo
as I get to Tahoe, I notice a serious lack of power when I'
accelerating from a stop. I understand that due to the thinner air a
higher altitudes, performance will decrease to a certain extent... BU
my 4 year old nephew will out run me across an intersection (not tha
I tried... but he could have)! :shock: It can take about 4 second
just to make it halfway through the intersection. Once I build u
speed, It'll be ok, but there is a SERIOUS lack of acceleration fro
a stop

First, I thought maybe my wastegate might be stuck open or somethin
from running 3000rpm for 2 hours, but when I drove home and got bac
down to Placerville, my car accelerated near normal speeds... an
back in the nice, cold, dense foggy air of San Francisco, boy does i
accelerate

I'm no expert in Subarus, or in turbos for that matter, but I though
the ecu would use either the MAP sensor, or a baro sensor if it'
equipt with one to read atmospheric pressure and compensate

I'm hoping someone can shed some light here on what might be going on
I haven't found anyone else with the same problem online... and
couldn't find any TSBs in this matter. For reference, I'm runnin
stock everything except for a SPT intake and exhaust... an
temperature is not the cause. It the same at 50 degrees, as it is a
85 degrees

Any info that can help out here is much appreciated

 

[Carl 1 Lucky Texan]

I drove my 04 wrx to South Lake Tahoe for the first time since I
bought my car a few weeks ago. I'm in San Francisco at sea level, the
area of Tahoe I was at was about 5000+ feet above sea level. As soon
as I get to Tahoe, I notice a serious lack of power when I'm
accelerating from a stop. I understand that due to the thinner air at
higher altitudes, performance will decrease to a certain extent... BUT
my 4 year old nephew will out run me across an intersection (not that
I tried... but he could have)! :shock: It can take about 4 seconds
just to make it halfway through the intersection. Once I build up
speed, It'll be ok, but there is a SERIOUS lack of acceleration from
a stop.

First, I thought maybe my wastegate might be stuck open or something
from running 3000rpm for 2 hours, but when I drove home and got back
down to Placerville, my car accelerated near normal speeds... and
back in the nice, cold, dense foggy air of San Francisco, boy does it
accelerate.

I'm no expert in Subarus, or in turbos for that matter, but I thought
the ecu would use either the MAP sensor, or a baro sensor if it's
equipt with one to read atmospheric pressure and compensate.

I'm hoping someone can shed some light here on what might be going on.
I haven't found anyone else with the same problem online... and I
couldn't find any TSBs in this matter. For reference, I'm running
stock everything except for a SPT intake and exhaust... and
temperature is not the cause. It the same at 50 degrees, as it is at
85 degrees.

Any info that can help out here is much appreciated!

I suppose it could take a few drive cycles - or resetting the ECU? -
before the system 'learns' the thinner air.


I dunno


Carl

 

[David]

On Wed, 22 Aug 2007 22:04:12 -0500,

I drove my 04 wrx to South Lake Tahoe for the first time since I
bought my car a few weeks ago. I'm in San Francisco at sea level, the
area of Tahoe I was at was about 5000+ feet above sea level. As soon
as I get to Tahoe, I notice a serious lack of power when I'm
accelerating from a stop. I understand that due to the thinner air at
higher altitudes, performance will decrease to a certain extent...

I live in greater Los Angeles and go from close to MSL to 5,000' AMSL
a lot. I have noticed no performance issues at that moderately high
altitude. I have an NA '07 Forester MT.

 

[taz77]

taz77 wrote
I drove my 04 wrx to South Lake Tahoe for the first time since

bought my car a few weeks ago. I'm in San Francisco at sea level, th
area of Tahoe I was at was about 5000+ feet above sea level. As soo
as I get to Tahoe, I notice a serious lack of power when I'
accelerating from a stop. I understand that due to the thinner air a
higher altitudes, performance will decrease to a certain extent... BU
my 4 year old nephew will out run me across an intersection (not tha
I tried... but he could have)! :shock: It can take about 4 second
just to make it halfway through the intersection. Once I build u
speed, It'll be ok, but there is a SERIOUS lack of acceleration fro
a stop

First, I thought maybe my wastegate might be stuck open o

something from running 3000rpm for 2 hours, but when I drove home an
got back down to Placerville, my car accelerated near normal speeds..
and back in the nice, cold, dense foggy air of San Francisco, boy doe
it accelerate

I'm no expert in Subarus, or in turbos for that matter, but

thought the ecu would use either the MAP sensor, or a baro sensor i
it's equipt with one to read atmospheric pressure and compensate

I'm hoping someone can shed some light here on what might be goin

on. I haven't found anyone else with the same problem online... and
couldn't find any TSBs in this matter. For reference, I'm runnin
stock everything except for a SPT intake and exhaust... an
temperature is not the cause. It the same at 50 degrees, as it is a
85 degrees

Any info that can help out here is much appreciated

Well,
know it is not normal for any car to accelerate like that... Subaru o
not. Turbo cars would probably notice a little more of a performanc
decrease due to the turbo lag... but not that much. There were plent
of WRX's there that out accelerated mine.

And resetting the ecu won't help. For one thing, most people won'
have the resources to know how to reset their ecu. Manufacturer
would have programmed some way for the ecu to updated while th
person is driving. I've heard going WOT at a low rpm should hav
updated the ecu. Second thing, I already tried that. :wink: Trie
resetting the ecu in a couple ways, neither of which helped

I was just hoping someone could verify my suspicion... I just won'
say what that is yet

 

[taz77]

David wrote


I live in greater Los Angeles and go from close to MSL to 5,000 AMS
a lot. I have noticed no performance issues at that moderatel hig
altitude. I have an NA '07 Forester MT

Oh yeah, I'm not familiar with the terms MSL and AMSL. Could you tel
me where the altitudes are 5000'? I might be heading down to LA, an
I'd like to test out a sensor at high altitudes

 

[Porgy Tirebiter]

Oh yeah, I'm not familiar with the terms MSL and AMSL. Could you tell
me where the altitudes are 5000'? I might be heading down to LA, and
I'd like to test out a sensor at high altitudes.

Mt. Wilson(5800), Angeles Crest Highway, Mt. High, Blueridge.Fraiser
Mountain(8000)
Lots more....but I dont buy this "it needs to learn the drive" stuff
either...

 

[strchild]

Sure your MAF is compensating for the SPT intake at the higher altitude?

Care to share your suspicion?

~Brian

 

[QX]

Oh yeah, I'm not familiar with the terms MSL and AMSL. Could you tell
me where the altitudes are 5000'? I might be heading down to LA, and
I'd like to test out a sensor at high altitudes.

Here is a great place to check out a Subie at altitude, if you are
going to be anywhere near Big Pine, CA (US-395).
Just a few miles north of Big Pine, turn east on CA 168.
When you get to "White Mountain Road" turn north. The signage will
also say "Great Bristlecone Pine National Forest". The turn off is
about 13 miles off 395. The road constantly rises till you get to the
Visitor Center, which is at about 10,000 ft, At that point the paved
road ends, and turns into a good quality dirt road. It ends at a
closed gate which is about 12,000 ft. The road is only open from May
to November, depending on snowfall. Also, depending on when you go,
there may be an entry fee from the Forest Service.
Once a year you can go farther up the dirt road when UC Davis opens
the high altitude animal research station to visitors.

 

[David]

On Thu, 23 Aug 2007 21:36:14 -0500,

Oh yeah, I'm not familiar with the terms MSL and AMSL. Could you tell
me where the altitudes are 5000'? I might be heading down to LA, and
I'd like to test out a sensor at high altitudes.

Mean Sea Level and Above Mean Sea Level

State Route 2 between Glendale and Red Box Rd (goes to Mt. Wilson).
Santa Clara Divide Rd. between Angeles Forest and Little Tujunga is
right around 5,000'. Most of the highways in the San Bernardino
Mountains. And like that.

 

[taz77]

intake, the MAF somehow wasn't detecting all the air entering th
engine, but I know there are plenty of people out there that have th
same intake. Probably cause they're afraid of voiding warranty. S
far, I have not heard of anyone with the same problem. I guess I ca
compare the stock intake air flow volume compared to the SPT.the MAF readings are at idle, and at 2000 rpm, I can compare it t
mine, and see if my MAF is reading the same.

 

[Scott Nevin]

[snip]
Any info that can help out here is much appreciated!

I had the same concern. We had an '04 XS and drove it several times to high altitudes in the Sierra
and in Oregon. The performance at altitude was bothersome. Last year we upgraded to an '07 XT and
the first trip was to Wuksachi Lodge in Sequoia up at 7,000'+. All I can say is the performance
difference was night and day. We had power to spare hauling a RocketBox full of our stuff and the
back loaded up with more stuff.

The turbo charger is going to hold sea level pressure and makes all the difference in the world. My
suggestion is that if you live in the high country or plan on going there a lot, a turbo charged
Suby is the way to go.

 

[taz77]

Problem is... mine is a turbo

taz77 wrote
[snip
Any info that can help out here is much appreciated

Scott Nevin wrote


I had the same concern. We had an '04 XS and drove it severa

times to high altitudes in the Sierra

and in Oregon. The performance at altitude was bothersome. Las

year we upgraded to an '07 XT and

the first trip was to Wuksachi Lodge in Sequoia up at 7,000'+. Al I can say is the performance
difference was night and day. We had power to spare hauling

RocketBox full of our stuff and the

back loaded up with more stuff

The turbo charger is going to hold sea level pressure and makes al

the difference in the world. My

 

[QX]

On Wed, 22 Aug 2007 22:04:12 -0500,

I drove my 04 wrx to South Lake Tahoe for the first time since I
bought my car a few weeks ago. I'm in San Francisco at sea level, the
area of Tahoe I was at was about 5000+ feet above sea level. As soon
as I get to Tahoe, I notice a serious lack of power when I'm
accelerating from a stop. I understand that due to the thinner air at
higher altitudes, performance will decrease to a certain extent... BUT
my 4 year old nephew will out run me across an intersection (not that
I tried... but he could have)!

The next time you are up to Tahoe you may want to stop in at

South Shore Motors, Authorized Subaru Dealer
530-541-4070
1875 Lake Tahoe Blvd
South Lake Tahoe, CA
http://www.south-shore.subaru.com/en_US/

That is just west of the "Y" (50/89) away from the main tourist
area. If the vehicle continues to act up and the SF dealers can't fix
it, the car will be at altitude and possibly malfunctioning when you
take it in to the SLT Subaru dealer. They should be able to pick right
up on it.

 

[boris]

[snip]
Any info that can help out here is much appreciated!

I had the same concern. We had an '04 XS and drove it several times to
high altitudes in the Sierra and in Oregon. The performance at altitude
was bothersome. Last year we upgraded to an '07 XT and the first trip was
to Wuksachi Lodge in Sequoia up at 7,000'+. All I can say is the
performance difference was night and day. We had power to spare hauling a
RocketBox full of our stuff and the back loaded up with more stuff.

The turbo charger is going to hold sea level pressure and makes all the
difference in the world. My suggestion is that if you live in the high
country or plan on going there a lot, a turbo charged Suby is the way to
go.

Is your Forester XT M/T or auto?

Boris

 

[b]

taz77 wrote: -snip-
The turbo charger is going to hold sea level pressure and makes all the difference in the world. My
suggestion is that if you live in the high country or plan on going there a lot, a turbo charged
Suby is the way to go.

This is not really true in most automotive turbo applications (unlike in
aircraft). I'm gonna glaze over a lot of boring details, but basically
the auto turbo has to work harder (spin faster = more lag) at higher
altitudes to produce the same amount of boost as at sea level...it may
actually get outside of its most efficient operating range, making less
boost than at sea level. As power output is related to boost +
atmospheric pressure (which also decreases w/ altitude), power is less
at altitude than at sea level. FWIW, my WRX is much more fun in the
cool/dense air while visiting my SoCal friends than at home in Prescott,
AZ (mile high).

I'd hazard that your experiences are more due to the XT starting off
with about 70 more ft-lb of torque (~30% more) than the XS.

Brent.

 

[taz77]

QX wrote


The next time you are up to Tahoe you may want to stop in at

South Shore Motors, Authorized Subaru Dealer
530-541-407
1875 Lake Tahoe Blv
South Lake Tahoe, C
http://www.south-shore.subaru.com/en_US

That is just west of the "Y" (50/89) away from the mai tourist
area. If the vehicle continues to act up and the SF dealers can' fi
it, the car will be at altitude and possibly malfunctioning whe yo
take it in to the SLT Subaru dealer. They should be able to pic righ
up on it

Damn... I was only 3 miles away from there. You know what the proble
is with Subaru dealers is though? They're not open on the weekends
Whenever we're up in Tahoe, it'll only be on the weekends. I migh
have to just give them a call and see if they've encountered my typ
of situation

Is there anyone here on this board that works at a dealership? Righ
now, all I really need is access to some specs for the MAF, and MA
sensors. Or see if there are any TSBs related to this issue.

boris and b: I actually have an Impreza WRX... auto..

 

[KLS]

On Sun, 26 Aug 2007 00:19:55 -0500,

Damn... I was only 3 miles away from there. You know what the problem
is with Subaru dealers is though? They're not open on the weekends.

Not true: Van Bortel Subaru in Victor, NY (www.vanbortelsubaru.com),
is open Saturdays, which is a huge help in scheduling maintenance and
repairs for us. And the Saturday hours are 7:30 am-9 pm!!

 

[Rick Courtright]

bought my car a few weeks ago. I'm in San Francisco at sea level, the
area of Tahoe I was at was about 5000+ feet above sea level. As soon

Hi,

Couple of thoughts and possible red flags to consider:

You say the car's an '04 and new to you. WHY did the previous owner sell
it? Perhaps you've just discovered why?

Lake Tahoe's around 5000 ft? (I thought it was higher, but it matters
not.) I know the books call that "high altitude", but IME that ain't
"high altitude" enough w/ today's computerized cars to cause the kinds
of power loss we used to see w/ carbed engines (or like you've
described.) Sure, you'll lose a little, but, judging by all the various
NON-turbo'd cars I've driven regularly at "high altitude" (I live at
2700 ft in the SoCal foothills, regularly hit 5000-8000 ft on local
roads), your car should barely know you've climbed a hill (I've talked
to local guys up in Big Bear--6000 ft--who've run both turbo'd and
non-turbo'd Subies "up the hill" and most of 'em would never go back
from a turbo.) Did you reset the ECU by disconnecting the battery cable?
Maybe it needs a complete reboot. I doubt you're going to "drive it
smart" if it's as bad as it sounds.

It's an auto? How's the trans feel--any indication of slippage?
Especially when hot after running up the hill for a couple of hours?

There's a modified/aftermarket component in the turbo system? Again, the
ECU may need a total reboot to figure out what the "new" part's doing. I
know, "everybody" has a better idea than the factory when it comes to
these things, BUT, the factory boys calibrated the computer for THEIR
components. Could be it doesn't actually know what to do w/ its new
parts. Did you do the installation and keep the OEM parts that you could
swap back for a control if necessary?

How's the installation? Everything's tight, no air/vacuum leaks, no
vacuum line lying about someone forgot to hook up, no sensor wiring
still unplugged, that sort of thing? Any fault codes stored in the ECU?

Air cleaner's in good shape? Plugs are in good shape? Oil and coolant
are clean and full, with no overheating? Conversely, it's running warm
enough, w/ a FACTORY thermostat? (Around here, where it's likely to hit
108 or so before I finish the day, people love to put in lower temp
t-stats, then can't figure why their engines run WORSE--back to the
computer being confused by "non-standard" parameters.) Good fuel filter?
Can you do a compression test to rule out bad cylinders or possibly
leaky headgaskets? How about a bottle of Techron, Berryman's B-12, Sea
Foam or other pretty strong fuel system cleaner? Simple things, sure,
but they're important overall.

Methinks you do have a definite problem to diagnose, just don't have
more good ideas right now.

Good luck!

Rick

 

[taz77]

remember seeing was a sign at the CA/NV border on 50 that had 5*** f
elevation. I just couldn't remember the other 3 numbers... could hav
been 5800.dealer, so the car could have been there for several reasons. Ca
could have been a repo, trade-in because of this particular problem
trade-in because they no longer wanted the car, etc. I do have a
extended warranty, but I'm wondering if I'm just wasting my tim
leaving it to a local dealer, because they're not going to be able t
"duplicate the customer's complaint". I should know..battery... I left my hand tools at home, even though I was suppose
to bring it with me. I used my scan tool on my pda, created a MI
code by disconnecting the MAF, and cleared the code that I hope
would have cleared the memory. I believe the short term/long ter
fuel trims did reset to 0.decide to stick with Subaru parts in the hopes something like thi
wouldn't have happened. Installation did go smoothly. I broke one o
the exhaust bolt, but the SPT intake came with new ones. No exhaus
leaks. Intake and heatshield went in easily, though I did have t
"space" the snorkel back away from the intake filter t
keep it from rubbing. I still do have the stock parts, and sooner o
later, I will swap them back as a control test.Vacuum leaks? I believe not. From what I've noticed, a vacuum lea
after the MAF would cause the long term fuel trim to jump up to +30
throwing a p0171 code. My short term and long term fuel trims are i
the -4% to -9% ranges.yet cause they weren't as easy to check like in my Civic. I believ
the t-stat is OE. The temp at normal operation temp at idle i
approximately 196 degrees F. I will try the fuel system cleane
though. I hear Chevron's got a new highly concentrated cleaner...
might give that one a tryfew cars here and there... Is there an
chance you have access to technical specifications to the MAF or MA
sensors? Or if you have the followingused to Toyota's being approximately 3.3v... according to my scanner
my AF sensors are showing 4.* volts. Is this normal?)

 

[QX]

Lake Tahoe's around 5000 ft?

FWIW, Lake Tahoe Airport (TVL) Elevation 6,264' MSL