altitude and turbos

bubba

Well-known member
I know at a high altitude (driving up in the mountains) a naturally asperated engine doesn't perform as well as at lower altitudes, but what about turbo and surper charged angines? is there any differance in the way these engines perform in differant altitudes. in class today one of my engineering teachers claimed a turbo's performance doesn't change depending on the elevation. But i thought every engine lost power at a high altitudes.
 
Going by a little logic, common sense and a spattering of knowledge...
The turbo shouldnt have problems, unless its underpowered.
Reason being, that the turbo will be keeping the manifold at a constant pressure, and the NA cant do that, so has to use the thinner air, where the turbo pressurises it in the manifold, and so the air will be denser...
Thats my understanding of it.
But, I'd say the turbo's gonna be working a little harder, probably less efficent too, because its gonna be working harder to get more of the thin air in to bring up the pressure and density to what it is at a lower altitude.

There will be alot more to it thatn that, just think with logic, common sense, abit of knowledge about turbo's, and a bit more knowledge about physics, science and chemistry, they play a big part in understanding most of the world. :wink:
 
8) engine power does drop at higher altitudes, even turbo engine. the difference is like luke said, intake manifild pressure remains constant and thus engine power drops off less than it would without the turbo. the reason for that is the coolder intake charge. for every 10 degrees reduction in air temp, power goes up 1%. at that altitude, the power increase from the temp drop helps overcome the loss of power from the thinner air.
 
if the wastegate is dumping, then there will be no difference.

if the waste gate is closed and you've got full turbo into the intake, altitude will have an effect very similar to a NA engine.
 
As mentioned previously, a turbo engine won't care as long as the turbo has 'room' to spool.

A supercharged engine on the other hand will have all kinds of problems; less boost, a need to be leaned out some, and if the whole deal isn't electronically controlled, the carb tuning can get really messy...
 
A turbo engine can maintain boost and performance at higher altitudes without the loss of power associated with normally aspirated engines.

If designed for that environment a turbo can either provide boost or "normalizing", which maintains seal level performance.
 
We can thank the military for development of supercharging and 'turbo-supercharging' for use on aircraft prior to WW2. The Germans used a two-speed, two-stage, mechanically driven supercharger on the Daimler-Benz 605 inverted V-12 aircraft engine that worked to a ceiling of about 45,000 feet. We Americans used turbo-surperchargers on the Allison V-12's and various radial engines. Much of the metalurgical research and development necessary for this stuff was funded by the various governments (top secret stuff, ya know :wink: ) As long as a supercharger can maintain manifold pressure it will also maintain power, but there is a limit, after which power will drop. As Jack mentioned, some aircraft use a turbo in a system known as "turbo-normalizing" that simply maintains sea level power output. These work ok up to around 15,000 feet or so.
Joe
 
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