I checked "other".....
Ya'll check me. I see only three sources. There's conduction from the engine case and engine oil, hot air downstream of the cylinders, and radiated heat from the exhaust system.
I marked "other". The cooling issue is when the aircraft are on the ground and the fuel system heat soaks leading to vapor lock. Unfortunately, a blast tube isn't going to help in that situation because it ain't blasting until you get the engine started, and at that point you don't need it...
I believe there are two different issues that folks have. The first is a true vapor lock where it is nearly impossible to get the engine started. The second is an inconsistent fuel flow to the fuel injection nozzles causing a very rough running engine. My Superior IO-360 exhibits the second during very hot ambient conditions with a fuel stop of around 20 minutes. It starts normally but is very rough at low power settings. There was a post about this in the recent past that discussed the problem of a combination of fuel being heated by the mechanical fuel pump and very low pressure (approx 1/2 psi) at idle in the fuel lines downstream of the fuel servo. I purchased a shroud for the mechanical fuel pump and intend on installing it with a blast tube and additionally insulating the lines from the spider to the individual nozzles to alleviate some of the heat soaking. My problem disappears when power is applied for takeoff and the fuel pressure from the servo is increased. BTW I have gotten some interesting looks when I tell people the engine will run fine when we takeoff.
I'd add one more, forced convection from the oil cooler, which, if baffle mounted, puts the fuel pump directly between the oil cooler exit and the cowl exit. I would suspect that this is one *might* be the worst offender?
For the simple reason that a mechanical fuel pump in the first place is a hydraulically poor solution.
If I HAD to live with a mechanical pump then forced cooling is an absolute essential in my opinion.
Frank
Falls in the "hot air from the cylinders" category, although oil cooler air should be lower temperature than cylinder air. Better heat exchanger efficiency, but roughly half the delta-T.
I'm guessing the worst offender to be radiant heat from the pipes. I suspect a heat shield below the pump might be as effective as forced air cooling and without cooling penalty. The "problem" doesn't seem to be a hot pump in normal flight, but rather, heating during ground operation.
Besides, it is possible to kill two birds with one stone, maybe lowering cooling drag even further
Kent,
What temperatures did you see?