Fred,
Don't forget that at 16000 feet the OAT is maybe minus 30 degrees, so the
inlet air is that temp, then raised by compression in the turbo, and cooled
by the intercooler to about 30 degrees warmer than ambient, so it goes into
the cylinder at around 0 degrees, not 110 degrees F. Maybe a bit more HP
than you figured.
Add to that the effect on true airspeed at altitude and you might convert
145 knots normal cruise to 220 mph cruise at altitude, especially if the
wind was in your favor to boot!
Peter
>In rereading the archives too, the only concern was questioning 220
>MPH top speed, impliedly due to only an intercooler. No question re
>some fuel efficiency, engine wear, and climb, but not cruise. There
>are intercooler "tech" papers all over the web. Claims vary (mostly
>auto enthusiasts but with access to dynamometers), but best I found
>was (for 100HP engine) 1.5HP per 10F degrees reduction in induction
>air temp. Assuming 50F drop, the math works out to about 4 MPH at
>100% throttle cruise, minus effect of add'l cooling drag. Suspect
>you get a bit more above the magic 16,000 ft., with controllable-
>pitch prop, but altitudes much above that are not practical
>unpressurized, except now and then for the fun of it!
>
>I just read a cool (no pun!) way to look at it. Engine efficiency
>goes up with the spread between induction air temp and EGT: If you
>ingest 1600F air, same as EGT, the engine would produce no power. So
>reduce induction air from from 160F to 110F, and do the math, that's
>only a 3% increase in power and fuel efficiency, not 7.5% per above.
>
>Regards,
>Fred F., A063
>
>KarkelB@aol.com wrote:
> >
> > Hi Folks,
> > read an article in the forum archive about intercoolers where
> > someone expressed concern about installing one.I spoke to someone at the
> > rotax factory who actually said that rotax do recommended the fitting of an
> > intercooler to the 914 as it enhances its efficiency/performance and
> reduces
> > the wear and tear on the cylinder heads. In addition to that one can
> have the
> > maximum 115bhp for more than the stated five minutes at full throttle.
> > However he went on to say that should an intercooler be fitted it must have
> > the flow rate as recomended in the 914 installation manual. And to cap it
> > all, your warranty should not be affected by the installation. Thought i
> > should share this with all those with 914's craving better performance. If
> > you are in england demon tweeks on 01978664468 have all sizes of
> intercoolers
> > and can custom build some if you want infact they have one that is
> similar to
> > Denis Vories,just seen it in their catalogue. Denis Vories installation
> is a
> > real clean one folks!
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