: The heating of the intake and the consequent reduction in density is the
: reason that I think it will take more MP to produce the same HP at higher
: altitudes with a turbocharged engine. At the same MP/RPM a tubocharged
: engine is effectively running at a higher density altitude than a normally
: aspirated one. The turbocharged engine is also running at a higher density
: altitude as altitude increases at the same PM becasue there is more
: compression required, therefore more heating. The intake air is heated
: *substantially* and its density is reduced substantially. Natually, the
: effect is strongest at high manifold pressures and high altitudes. I agree
: that reduced pressure at the exhaust helps and an intercooler certainly
: helps too.

: I don't have a flight manual for a turbocharged airplane here but hopefully
: somebody here does.

I agree completely. The heating can be quite substantial from what I've read.
If there's no intercooler, I suspect that you probably always lose the added
scavanging HP to lower density incoming air at the elevated temperature as you
suggest. If there's an intercooler, things might trade off differently and equiv
MP/RPM combination at altitude might be less than, more than, or equal sea-level power
at the same MP/RPM combination.

Between the (substantially) higher inlet air temperature, decreased cooling
due to thinner air flow over the cylinders, and the ability to maintain very long,
high-power climbs, it's no wonder turbo'd engines eat cylinders routinely. The stock
turbo Arrow system is particularly bad... throttling full boost at the inlet? Pretty
stupid to compress the intake only to throw away most of it.

-Cory

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* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
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