2005 Silver Bullet

At higher altitude, all cars will lose power. Thinner air = less power. But turbo cars will lose less power than N/A cars.

As altitude increases, air density decreases. The turbo will offset some of that density (and resulting power) loss.

BigHatch

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BigHatch

I actually traded in an '06 STi i had for the RDX...our kids were growing and we needed more room for all their football gear that was also increasing in size.

We miss the STi, but this was the only alternative I considered. Nothing else would have gotten me to give up the STi. We still get to have fun in a turbocharged, ultra-reliable daily driver with a GREAT (SH-)AWD system, but have more than enough room. I like to actually DRIVE cars down the street, not pilot a boat. I would never buy a ginormous Barge like a QX..so unnecessary IMO. But my wife actually drives this car all the time.

And no, not an SUV.. this is a unibody hatch at 120% ...thats why it drives the way it does, and why we love it.

Is it big, sure....could it use more power? ...what couldn't? Is it an STI? ...of course not...but it sure does let me have my fun when I drive it and actually lets you feel the road...like a real car should...so you can actually be IN control and not just have the illusion of control when you need to push it.

...and I still have my '02 WRX wagon if I want a smaller hatch.

So yes, two different beasts from two different worlds for two different tastes.

analogkid

Anyone have any empirical data on cars power loss vs altitude for turbo cars and n/a cars? My understanding is the factory waste gate is set to an upper limit of boost at an absolute pressure relative to the atmospheric pressure.

Just asking.

mrgold35

From What I can tell from the internet (and the internet never would lie to us) about power loss for a naturally aspirated engine at higher altitudes is (about 3%-6% per 1000feet depending on NA engine):

HP Loss = (elevation X 0.03 X horsepower @ sea level) / 1000 (TQ loss seems to follow the same formula)

2013 RDX 3.5L 273HP and 251 TQ at sea level

265 HP/243 TQ: 8.20 hp/tq loss = (1000ft X 0.03 X 273HP)/1000
257 HP/235 TQ: 16.4 hp/tq loss = (2000ft X 0.03 X 273HP)/1000
248 HP/226 TQ: 24.6 hp/tq loss = (3000ft X 0.03 X 273HP)/1000
240 HP/218 TQ: 32.7 hp/tq loss = (4000ft X 0.03 X 273HP)/1000
232 HP/210 TQ: 41.0 hp/tq loss = (5000ft X 0.03 X 273HP)/1000
224 HP/202 TQ: 49.0 hp/tq loss = (6000ft X 0.03 X 273HP)/1000
216 HP/194 TQ: 57.0 hp/tq loss = (7000ft X 0.03 X 273HP)/1000
208 HP/186 TQ: 65.5 hp/tq loss = (8000ft X 0.03 X 273HP)/1000
199 HP/177 TQ: 73.7 hp/tq loss = (9000ft X 0.03 X 273HP)/1000
191 HP/169 TQ: 82.0 hp/tq loss = (10,000ft X 0.03 X 273HP)/1000
183 HP/161 TQ: 90.0 hp/tq loss = (11,000ft X 0.03 X 273HP)/1000


It depends on how much reserve power you have at altitude if you feel the drop in power. I imagine the 2013 has plenty of reserve power to maintain the desired speed at altitude without having to slow down or go WOT or downshift +2 gears.

There doesn’t seem to be a lot of information on power loss on automotive Turbo engines at high altitudes (mostly piston WWII aircraft links). I think because there are so many variables with a turbo (single or twin-turbo, twin scroll, variable geometry, Inter cooling, water injection, wastegate, blow off valves, programming, etc…) and not to mention all the different engine types a turbo can be used on; it might be very hard to find a formula to cover all turbo engines.