Turbos Rule at Altitude, Fact or Fiction

[MtnSub]

I had the impression that turbo enhanced cars did not lose as much power at high elevations as normal, fuel injected cars. Years ago, the same thing was said about fuel injection vs normal carborators. Yet, on this site, I have read a number of comments about significant loss of Booost/HP at high elevation for turbos. What are the facts? Is this a case of all cars lose power, but some lose less or what?

[7stars]

You lose the same amount of power as N/A, but with turbos, you can up the boost to make up for it. This won't hurt your engine, but it will make the turbo run very hot. 1-2psi above would be ideal. For long term turbo reliability, this may not be a good idea.

[SUBE555]

[url=http://forums.nasioc.com/forums/showthread/t-544211.html]HERE[/url] is a good explanation.

[Deer Killer]

[quote name='SUBE555'][url=http://forums.nasioc.com/forums/showthread/t-544211.html]HERE[/url] is a good explanation.[/quote] It's not that good. That applies when boost is controlled in an open-loop environment, and perhaps full-on always at WOT. However in a closed-loop computer controlled environment - especially where the system is designed not to be full-on all the time, the computer can make up the additional 2 psi by spinning the turbo faster, leaving you with the same total cylinder charge. I don't know if the 05 GT applies, but when you get an audi where they run way under what the turbo can really do in order to deliver a completely FLAT torque curve, this will happen. This is actually one of the reasons thought as to why the B5 S4 turbo's fail so often, a boot fails leading to a small boost leak, the computer requests more boost, and eventually *BAM*.

[MtnSub]

Once again, this site always produces higher quality info than other sites I have visited. Must admit that it is not easy to read all data and come to a general conclusion. Without tinkering with boost, it appears that it is not easy to conclude that turbo cars have any consisstant, quantifiable advantage over std fuel injection cars. Am I off base? I have no intention of playing with boost during my weeks/months above 6,000 ft.

[SUBE555]

Perhaps ths link offers more insight into the variance into natural aspiration and forced induction per altitude changes along with the use of altitude compensation systems for naturally aspirated engines. [url]http://www.turbochargersnz.com/about.html[/url]

[Yamagacy]

FWIW- Pretty much any turbo system with a wastegate is a closed-loop system. An example of an open-loop system would be a supercharger; pulley spins, s/c impeller/screws spin, boost is made and is limited only by max engine speed and the max volumetric capacity of the s/c. The difference between various turbo systems stems from what pressure the controller closes the loop on, i.e. relative manifold pressure or absolute manifold pressure. Relative controllers will suffer an altitude loss in accordance with the lower ambient pressure. Absolute will, if the turbo can safely spin fast enough, not suffer a loss at altitude as it seeks to build the same pressure in the manifold regardless of ambient. Assuming an adibatic system, that is. There will be some loss of acceleration however, due to the increased time it takes a turbo to produce full boost at altitude, regardless of whether it's an absolute or relative controller.[/quote]

[Drift Monkey]

Power loss is less apparent with a turbo car than a NA car. That's really all you need to know.