View Full Version : Anyone have an RS6 (C5) at high altitude?
p3u
April 30th, 2009, 23:59
I live at around 6500ft, and to boost isn't on all the way till about 3500 RPM. Does this sound right for my elevation?
If I remember correctly at sea level full boost is supposed to be at 1750? Just seems like the car is a dog till boost hits, wanted to verify this is normal for where I live.
Thanks!
hahnmgh63
May 1st, 2009, 01:23
At Sea level I obviously get full boost at over 1000 rpm sooner. I don't know if Audi's Turbo's are still mapped the same but back in the 90's they claimed full HP up to 5000' altitude so at 6500' you wouldn't be loosing too much but probably at least 5% if you use the 3% per 1000' rule used on normally aspirated but start it at 5K?
vinny
May 1st, 2009, 20:06
hey p3u, we in joburg are also at 6500ft over sea level - the rs6's ive driven seem to start boosting at around 3500rpm....
best person to comment tho, would be garbi :)
BLITZEN
May 1st, 2009, 22:25
Where are you P3U? I'm in Salt Lake which is a mile high and I frequently drive in the mountains. But I've never felt like I had a problem getting turbo boost.
Don't our cars boost identically no matter where we are? Turbos spin up and run off the pressure of the exhaust correct? So why would there be less exhaust at 6500ft. than at 100ft. if the RPM's are the same? There's just less Oxygen, so maybe you're just not feeling it as much.
If our turbos are not run off the exhaust (or if boost is regulated by a computer) then engineering sense would say that since we know there's less O2 in the air at high altitudes, we should have the computer boost it a little more (not less).
Can any knowledgeable guys out there explain it differently?
Im in CO.
My understanding is that less oxygen means less power. Less power off the line means it takes longer for the cars initial acceleration, and longer to get to the RPM needed to make the turbos spool. Also air the density is less, therefore not as much mass in the exhaust gas to spin the hot side of the turbo, meaning it takes longer to spool.
When do you get full boost out in Utah, and what elevation are you at?
Bigglezworth
May 4th, 2009, 01:21
Some good reading here guys that should answer some of your questions:
http://twoguysrally.com/2008/04/28/turbochargers-part-1/
http://twoguysrally.com/2008/05/06/turbochargers-part-2/
http://twoguysrally.com/2008/06/20/turbochargers-part-3/[/URL]
http://twoguysrally.com/2008/07/03/turbochargers-part-4/ (http://twoguysrally.com/2008/07/03/turbochargers-part-3/)
[URL]http://twoguysrally.com/2009/01/08/turbochargers-part-5/
DHall1
May 4th, 2009, 02:11
That will keep em busy
Some good reading here guys that should answer some of your questions: