NO power at higher altitudes

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

I dunno

Carl

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.

85 degrees. > > Any info that can help out here is much appreciated!

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

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

I was just hoping someone could verify my suspicion... I just won't say what that is yet.

snipped-for-privacy@gmail-dot-com.no-spam.invalid (taz77) wrote: > > > > 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... > > > David wrote: > > > 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.

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...

>

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

Care to share your suspicion?

~Brian

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.

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.

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.

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 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.

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 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.

Is your Forester XT M/T or auto?

Boris

-snip-

difference in the world. My

lot, a turbo charged

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.

snipped-for-privacy@gmail-dot-com.no-spam.invalid (taz77) wrote: > > > > 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)! > > > QX wrote: >

South Shore Motors, Authorized Subaru Dealer > 530-541-4070 > 1875 Lake Tahoe Blvd > South Lake Tahoe, CA >

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. Whenever we're up in Tahoe, it'll only be on the weekends. I might have to just give them a call and see if they've encountered my type of situation.

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

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

Not true: Van Bortel Subaru in Victor, NY

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!!

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

MAP)? > >

Typical AF ratio sensor readings at idle at stoichiometry? (I'm used to Toyota's being approximately 3.3v... according to my scanner, my AF sensors are showing

4.* volts. Is this normal?)? > > > > I was thinking I should call a dealer up in Tahoe to see if they have commonly seen issues like this. > > > >

taz77 wrote: > > > > 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 > > > Rick Courtright wrote: > > > 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?

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

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