Re: S.P.E.A.R.C.O.intercooler guys??

[DeWitt Harrison <de@aztek.com>]

Engine power testing is a topic related to this intercooler thread because
dyno power measurements are subject to local ambient temperature and
pressure conditions in the same way as they are subject to intercooler
efficiency, etc.

The "Getting Technical" column in the new ec magazine (August 1997,
Vol. 28, No. 8) discusses SAE standard J1349 which provides engine
power measurement correction factors for air temperature, altitude
(atmospheric pressure) and humidity.  The correction tables are provided.
It would appear, for example, that we Mile High folk take about a 20%
power hit compared to the Surf and Sand crowd, at least for N/A motors.
Turbo motors do better, presumably, but there is no free lunch. At boost,
we would expect to see significantly hotter air in the IM up here than at
sea level; poorer air D.

There is some discussion of the physics but important ideas such as
absolute temperature are omitted. They do succeed in making a good
point, though. It is noted that any benefit from "ram air" intake
ducting comes from bringing cool air into the engine, not from
increased inlet pressure. They cite standard aftermarket air filters for
the VR6 which draw under hood air that is easily 100 deg.F hotter
than outside air. Not cool.

DeWitt Harrison    de@aztek.com
Boulder, CO
88 5kcstq