I think that the actual boost is decreased (even though it's just relative to atmospheric)... why*? or by how much I don't know. I'm getting spike to 15 psi and steady state psi of like 13psi w/ no check engine light
*I guess the turbo would have to be spinning a lot faster in the thin air...I guess the ecm takes atmospheric pressure into account and reduces boost accordingly to save the turbo.
Earlier this year I took my car from about 200 feet above sea level to over 7000 feet above sea level when I drove from my home near San Francisco to Reno. Around the SF Bay Area my boost was spiking around 21PSI and settling on 18PSI. Above 4000 feet above sea level my boost was spiking around 30 PSI and sustained was 24 PSI. At 7000 feet above sea level, well, I was keeping my boost below 16PSI after I noticed what was happening.
Well according to the TDI tech document for the motor in the A3 jettas boost increases as you go from sea level to ~5,000 (1,500 meters IIRC) feet, then boost is slowly decreased to prevent turbo overspeed as altitude increases.
At my house in Idaho (6,200 feet) my boost was 14 PSI with WETT and at sea level it is 12 PSI with WETT. I have never taken note at 5,000 to see if that it's maximum potential boost.
Jack, thanks for sharing that info. Where can I find that source? The previous replies still seem consistent with the spec. But I wonder if the SF to Reno guy had to keep his boost down or if the computer was 'helping' him do it. I was hoping for an absolute max cyl pressure instead of just a relative one. Sort of like gage vs absolute pressure...
[ QUOTE ]
PC: Were your numbers with a chipped car?
[/ QUOTE ] Upsolute.
At about 4500 feet above sea level I decided that the high boost pressures surely were not good for my turbo (especially since the air was thinner, meaning that my turbo was working really hard at this point) and I was hundreds of miles from home so I backed off and never allowed it to go above 16 PSI until I was back down to about 3500 feet.