Macster

yesterday, on I-80 somewhere between Salt Lake City and whereever I stopped for the night. Holiday Inn Express here in oh yeah, Rock Springs WY.

I glanced at the NAV unit's elevation reading and it was IIRC around 7800 feet. I should remember but I'm still not 100% rested up.

Had my foot smashed down climbing a pretty steep grade on I-80 and left it smashed down for as long as I could, which was until I reached the top of the grade. That 0.8 bar boost appeared and stayed for a few seconds. It was not just a transistory reading.

Anyhow, the point of this is to confirm to some extent what I was told and these engines are set up to deliver a specific amount of torque/power. Under most conditions the max. torque demand can be met with 0.7 bar boost, as I'm sure many have experienced.

But under some conditions -- higher elevations for one -- the engine controller can allow more boost to satisfy the torque demand of the driver.

And I saw this was occurring yesterday as I described above.

Just another amazing (to me anyhow) tidbit of the inner workings about these cars.

Sincerely,

Macster.

Macster

And now make that a solid 0.9 bar boost at over 8K feet. Left Rock Springs and headed east and encountered even higher elevations on I-80. Had a nice long grade to climb and floored the gas pedal in 6th at just under 3K rpms. Rpms climbed and boost climbed and I saw 0.7, then 0.8 and finally 0.9 bar and it stayed at that boost level for a few counts. I ran out of mountain to climb.

I love a Turbo in the mountans. Ain't bad going across I-80 and the flat ground just after leaving Wendover either.

Sincerely,

Macster.

earl3

The way I figured it, the engine is targeting an absolute pressure (or some target torque), and the gauge is displaying gauge pressure. I would see 1.3 bar with a 1.0 flash in Santa Fe, then 1.0 near sea level. My IATs would shoot up at high elevation from working the turbos to make up for the lack of air

Macster

Yes, you are right. That is what I was told. The engine is attempting to satisfy a torque demand by the driver and if it has to go to a higher boost it will, if it can. And based on what I saw it can.

I'm tempted on the way west to go the I-70 route and go over some of the higher passes on I-70 (one's 11,000 feet or so IIRC) and see if the boost gage will read 1.0 bar.

Don't know about the intake air temp. I have no way of checking that with me. (Left my OBD2 code reader/data viewer at home.)

Temps mild, though in the low to barely mid-70s through WY. Later yesterday it got up to 90 through NE.

Noticed an odd thing though about the car. I was running the car at highway speeds (75mph and maybe (ahem) higher) and things were just fine. I'd need a rest break and gas for the car so I'd do my coast down/off the exit ramp and then drive easy to the gas station.

But when I got to the station and the pump island the engine rpms were elevated. 1K or a bit higher. No other signs of trouble or distress. Oil pressure good (at 1K oil pressure hot was over 2.0 bar) and the temp gage needle was barely off the center of the hash mark (which given these gages may mean nothing or everything).

Oh, I was trying to save a bit of gas so I was running with the A/C off. Thankfully with the mild temps I was able to do this.

Anyhow, I just sat with the transmission in neutral and the clutch pedal released and let the engine idle at 1K until it dropped to its normal idle speed, maybe after a minute or so.

The only thing that I would think of was the engine was warm and due to the high altitude needed some extra and higher speed idling time to cool down.

I've run in hot temps before, 119F from Kingman to Needles and thereabouts but the elevation across there is not that high. Once through Kingman I don't think the elevation climbs above 4K feet anywhere the rest of the way to Livermore.

But of course, in 119F heat I had the A/C on, 72F and in automode.

But on I-80 through WY not once did I see the elevation on I-80 drop below 5K feet until near the NE state line. Before that though the elevation reached 6000, 7000 and even over 8000 feet in places.

I just wonder if the high speed (?) running and elevation worked to cause the engine controller to speed up the idle a bit until the coolant temp dropped? I wish I had my code reader handy to check the cooloant temp. I have a data recorder installed in the car which beams engine telemetry (which I think includes coolant temperature) back to a web site via a cell phone connection but I have no way of checking that on the road.

Sincerely,

Macster.

PAULUNM

I noticed the same thing yesterday at 7,500 feet on the Angeles Crest Hwy. Hit 0.8 pretty easily, and saw 0.9 a couple of times.

Dock

I believe (everything else being equal) the engine temperature will be lower if you run the A/C.

Dock

If you get a tune you could be seeing that kind of boost (or higher) at sea level.

Kevinmacd

Running your AC has no noticeale negative affect on gas mileage. Yes the car can runs a little cooler since the fans go into high speed. Compressors today being of a rotary or scroll type use very little energy.

Fastboy

With Kevin's first level flash you can get 1.3bar in central Ontario

larry47us

I have a Softronics flash, and can easily hit 1.0 of boost. I think that there was once when I cracked 1.1 boost and I think that it even rose to 1.2, but that was the limit, and it was only for a moment.

I was surprised to note, though, that I can watch the boost climb from 0.0 to 6.0 and more when I am accelerating from 30 mph or so, and the car really winds out. But if I am going 60 or 70 and hit the throttle hard, I see the boost gauge start at 0.6 and barely climbs at all. I guess that I don't really understand how the turbos work.

larry

Macster

Yes. The Turbo is pretty good (better than my 02 Boxster) at maintaining a more stable coolant temp even with the A/C off (and the radiator fans working only in demand mode) but with both cars I've noticed that with the A/C running the coolant temp is nearly a flat line over a wide variation in ambient air temperatures and driving situations.

Sincerely,

Macster.

Macster

You are right. I learned long ago these cars have superior A/C systems and the variable displacement compressors are very efficient.

My running sans the A/C was more a psychological thing.

Sincerely,

Macster.

Quinlan

Hmm - according to my dash display, I consistently get approx 2mpg better without the a/c - this is basically at sea level.

TheBucketOfTruth

I got a steady 0.8 BAR on the 101 last night, but I've got an X50 so it's not a fair comparison. You guys are saying the stock ECU bumps up the boost to compensate for the thinner air at higher altitude? Nice.

* Edit: I hit 0.9 recently.

sweanders

Could it be because MAF is used and not MAP?

MAF sensor is perhaps cooled less efficiently by intake air flow at higher altitude,

Just guessing here...