Posted for BILL HANNAHAN <wfhannahan@yahoo.com>:

 Lorn
 
 Thanks for the data points.
 
 My rocky mountain engine monitor display only goes up to 19 deg C. pulling
 carb heat pegs it unless the initial carb temp is below -5 C indicating a
 change of 24 C, 43 F. when I built it in 1991 the only sensor was an
 expensive certified probe with a brass thermowell that screws into the
 carb body near the venturi (possibly above the venturi and below the
 butterfly) and extends about a quarter inch into the airstream. Since
 brass is a good heat conductor, it is measuring some ratio of air
 temperature and carb body temperature. I don’t know how this correlates to
 inlet air temperature. The Tiger may have a similar probe. A sensor would
 have to be upstream of the carb for an accurate assessment of the
 induction heat system.
 
 What are folks using for probes these days?
 
 My heat muff is flat wrapped aluminum sheet around the two crossover
 exhaust pipes in front of the sump, bent into an oval cross section and
 secured with spacers and hose clamps to provide a 1/8 to 3/8 inch gap
 between the pipes and muff. Both ends are open and a flange for 2 inch
 scat is welded on the bottom center of the muff. Air can flow in from both
 ends. The gap on top is larger than at the bottom so most air flows in
 from the top and wafts down around the exhaust pipes to the scat. The air
 is preheated by the cylinder fins.
 
 ////
"""
 Bill,
 
 I flew in a Tiger last year. The Tiger had a carb air temp (CAT)
 gauge. When I pulled the carb heat, the CAT increased by about 10°F.
 In my Lancair with an O-320-D1F, and the heat muff stuffed with
 stainless steel Brillo pads, the CAT only increases by about 8°F. I
 know that this is not enough but I would be happy with a 15°F increase.
 
 The new CAT increase requirements must be much more stringent than in
 the past.
 
 Lorn
"""
 
 
 BILL HANNAHAN
 WFHANNAHAN@YAHOO.COM