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#1
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American Aviation Intercoolers
Richard,
American Aviation's intercoolers are no longer available but they still service the product and have spare parts available, such as the induction boot, etc. The units are built pretty tough, and all you're dealing with is a heat exchanger, much like the way an oild cooler is constructed, only instead of oil moving through it, it's hot air. About your only choice at this point is to buy a bird with the units already installed, or contact Riley/Tule Aero for a new install. I'd be interested in knowing what today's 'ticket price' is for admission. I'll bet it's sky high. As far as specs, max placarded power setting for ISA at sea-level for takeoff is 35.3" hg. The engine produces basically the same horsepower, but it does so more efficiently and with lower power settings, since the heated induction air from the impeller (Turbo Discharge Temperature) is reduced from about 220 degrees F down to about 80 degrees. Without intercoolers, the compressed induction air can get as hot as 300 degrees F even though the outside air temperature may be at or below zero. Since hot air is less dense and contains fewer oxygen molecules than cold air -- as much as 40% less -- much of the power that could be produced by the turbocharger is lost. The intercoolers are a great benefit during hotter than normal conditions and at high density altitude airports. Other advantages include better engine detonation protection, improved climb rates and higher cruising speeds. Typical power settings, fuel flow in PPH, TAS (Knots) and Servo Inlet Temp: 10,000 @ 75% = 33" Hg @ 2400 RPM, 88 PPH, 195 Kts & 57 F 10,000 @ 65% = 30" Hg @ 2400 RPM, 76 PPH, 184 Kts & 52 F 10,000 @ 55% = 27" Hg @ 2300 RPM, 64 PPH, 170 Kts & 46 F 16,000 @ 75% = 33" Hg @ 2400 RPM, 88 PPH, 210 Kts & 65 F 16,000 @ 65% = 30" Hg @ 2400 RPM, 76 PPH, 198 Kts & 56 F 16,000 @ 55% = 26" Hg @ 2400 RPM, 64 PPH, 182 Kts & 48 F The above figures are 'Best Power' Fuel Flow settings, but by using the 'Best Economy' Fuel Flow for 65% and 55% power, you can shave the fuel flow down to 67 PPH and 57 PPH respectively (running at or near peak EGT). It would almost be cost prohibitive to add intercoolers because of Mr. Alan GreenSPAM's thing called 'inflation'... as I recall, the American Aviation intercoolers were installed on our bird back in '86 and at that time the total price was around $10K, including the paint. Best to look for a bird with these units already installed. SkyKing 
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#2
11-29-19, 10:42 AM
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I have a 1974 P337 with air conditioning, Horton STOL, no wing de-ice boots, and the Riley intercoolers. I mention all these things because each impacts performance, though none of the mods actually say how much they impact performance!
I used to use 33"/2500RPM at 17,500 and obtain about 202kts on 34GPH (204pph). Lately, I've been at 31"/2500RPM at 17,500 and obtain 196kts on 26.6gph (160pph). Note that this is "slower than book", but "book" doesn't account for the STOL kit or the air conditioning scoops (or the intercooler scoop/venturi). My POH calls the 33"/2500 "75% power", but calls for 80pph per engine (13.3gph), which I cannot obtain without overheating the engine. The Riley STC instructs to reduce MP by an amount between 0" and 2" depending on altitude, and it's essentially a straight line with 0" at sea level and 2" at FL200. So my theory is that if I run 33"/2500 at 17,500', I'm at more like 85% power, based on fuel stoichiometry. Reducing MP down to 31" brings fuel usage back in line with book, implying a return to 75% power. And of course, temperatures are much easier to control. QUESTION: Nothing about the intercooler installation should increase the rated power output of the engine, should it? Sure, the engine will produce more power if I let it, but presumably the main everyday benefit of the intercooler is better thermal control (if MP is reduced to account for the colder/denser air bring introduced into the engine). A secondary benefit is that in emergencies, slightly more power than stock, is available. Does this sound like a good way to think about aftermarket intercoolers? BTW, my rear engine actually runs cooler than my front engine. But during climb out on hot summer days (33"/2500rpm/140mph/cowl-flaps-open/full rich), I still have to watch the temperatures on both engines. Thanks -- Dan Quote:
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